GroupDIY

Project Specific Discussions => Filters/Equalizers => Topic started by: daveee on February 17, 2010, 07:18:04 PM

Title: G-PULTEC problems, please help!
Post by: daveee on February 17, 2010, 07:18:04 PM
just finished building my first eq, a gyraf pultec :)

i paid quite a bit of attention to detail with the construction (e.g. double-checking all wiring and component values)... but sadly it doesn't work as intended on first test, and i'm wondering if anyone could suggest where i should begin in terms of fault finding...

basically the controls work pretty much as expected, although with all pots at 0 (and even in bypass mode) there is a lack of bottom end (as if it's rolled off). the signal is also a little distorted. when i turn up the low boost pot the bottom end is boosted but the signal becomes more distorted (with low boost at around 2 or 3 the bottom end is roughly where it should be when bypassed, if you see what i mean).

a slightly odd thing i've found is the +250V HT rail is actually at around 275V (i guess because the first power trafo is outputting a slightly high 15V) but i assumed this would be within the tolerated range... maybe a mistake?

any ideas? (thanks in advance!)
Title: Re: G-PULTEC problems, please help!
Post by: substitute on February 17, 2010, 09:51:17 PM
Did you use an input xfrm or just the output?  I'm not sure whether bypass bypasses the transformers or not, but sounds like it may be one legged output.  Double check all the polarities on your xlr's and make sure you have the transformers hooked up right. 
Title: Re: G-PULTEC problems, please help!
Post by: buschfsu on February 17, 2010, 10:00:23 PM
i had to change the value for  the B+ resistor to get 250v. mine was high at first too.
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on February 18, 2010, 04:44:20 AM
Check the polarity of your wiring from the PSU / Amp to the filter boards.

Title: Re: G-PULTEC problems, please help!
Post by: daveee on February 18, 2010, 08:26:03 AM
thanks for the quick replies!

- yes i'm using LL5402 for input and output transformers, they're mounted on the PCB so can't be hooked up wrong i think...
- all polarities are correct (to/from XLRs, and between amp and filter boards).

i think i'm going to try running a low freq sine wave through it and tracing with the scope and see what i can find...

if there's any more suggestions i'm all ears :)
Title: Re: G-PULTEC problems, please help!
Post by: daveee on February 18, 2010, 09:20:22 AM
ok this is really strange...

i've just realised that the unit works perfectly when first switched on... then after a few minutes this happens: (i'm really not an expert on circuit design so you'll have to forgive me if this is obvious!)

- +6.3V heater voltage slowly decreases to around 2.5V
- +250V HT slowly increases to around +275V
- sound becomes quieter, distorted, with less bottom end.
- if i switch the unit off and on, it works ok again.

i didn't realise this initially because i was waiting for the tube to warm up before running audio through it.

anyone know what this could be?
Title: Re: G-PULTEC problems, please help!
Post by: jackies on February 18, 2010, 09:36:58 AM
- +6.3V heater voltage slowly decreases to around 2.5V

That's a big problem, your psu doesn't work...
Bad power transformer?
Maybe too small?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on February 18, 2010, 09:38:29 AM
This is most probably because of too little cooling on the heater regulator - it gets too hot and powers down. Try a (much) bigger heat sink.

Lets make this the one and only "Official" GPultec help thread...

Attached a .JPG image with a simplified explanation of the filter workings - if you need to figure out what parts do what job.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: loopermc5 on February 18, 2010, 10:32:42 AM
Jakob is right (of course)mine did a very similar thing regulator was shutting down bigger sink and it's all better
Good luck
Title: Re: G-PULTEC problems, please help!
Post by: daveee on February 18, 2010, 11:42:47 AM
thanks jakob, i was hoping you'd see this thread :)

i'm using a fairly standard TO220 heatsink, a C-shaped one about the size indicated on the PCB silkscreen, with thermal paste... but it does seem to be giving off a rather large amount of heat... i'll try and find a bigger one and see if that helps...
Title: Re: G-PULTEC problems, please help!
Post by: daveee on February 18, 2010, 12:20:31 PM
yes!! that's fixed it.

so for future reference...
i used this heatsink to start with:

(http://www.binbin.net/photos/trusemi/to2/to220-bolt-on-heat-sink-rc.jpg)

and replaced it with one like this:

(http://canada.newark.com/productimages/nio/standard/4465963.jpg)
(although black and without those pins)

do you think i could be even better off with using one with more fins? like this:

(http://www.apexjr.com/images/HSink220TN.jpg)

don't have any to hand so would have to order.

had it running for about 30 mins now with no problems so it seems like the other one will suffice.

thanks everyone!
Title: Re: G-PULTEC problems, please help!
Post by: Matthew Jacobs on February 18, 2010, 07:21:30 PM
Lets make this the one and only "Official" GPultec help thread...

I agree, there's been a lot of threads about G-Pultecs recently, although they has never been a "official" thread. I myself have a few questions about my G-Pultec but have been holding off because I didn't want to create more threads.

This is a excellent idea...

Thanks

J
Title: Re: G-PULTEC problems, please help!
Post by: benlindell on February 18, 2010, 07:34:55 PM
I'm cool with an "official" thread finally.

Any idea how to change around the gain. I have one unit that is -3dB and another that is -4dB, how can I at least make them the same?
Title: Re: G-PULTEC problems, please help!
Post by: loopermc5 on February 18, 2010, 10:08:04 PM
yes!! that's fixed it.

so for future reference...
i used this heatsink to start with:

(http://www.binbin.net/photos/trusemi/to2/to220-bolt-on-heat-sink-rc.jpg)

and replaced it with one like this:

(http://canada.newark.com/productimages/nio/standard/4465963.jpg)
(although black and without those pins)

I used a chunky black one like that and ran it for almost 18 hrs straight no problem. Glad that was an easy fix!

do you think i could be even better off with using one with more fins? like this:

(http://www.apexjr.com/images/HSink220TN.jpg)

don't have any to hand so would have to order.

had it running for about 30 mins now with no problems so it seems like the other one will suffice.

thanks everyone!

I used a chunky black one like that and ran it for almost 18 hrs straight no problem. Glad that was an easy fix!
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on February 19, 2010, 02:52:35 AM
I'm cool with an "official" thread finally.

Any idea how to change around the gain. I have one unit that is -3dB and another that is -4dB, how can I at least make them the same?

Try some other/more tubes - stage gain depends on exact tube data. Filter loss varies with the actual end-to-end resistance of your 10K Hi-boost potentiometer (and pots are often +/-20%)

Jakob E.
Title: G-Pultec Inductors
Post by: envelope on February 20, 2010, 10:24:16 AM
Can anyone let me know what they used for the inductors, and offer sonic opinions?
20mH, 47mH, 100mH, 100mH

I am also wondering what these values should be for the G-Pultec
 
(I am not yet well-informed in inductors technology, still learning)

Max DC Resistance:
DC Current Rating:
Title: Re: G-PULTEC problems, please help!
Post by: envelope on February 23, 2010, 12:13:09 PM
just finished building my first eq, a gyraf pultec :)
Hi, I was wondering if you would let me know where you sourced your inductors and the part numbers if possible. thank you kindly

Can anyone help me with this?
Title: Re: G-PULTEC problems, please help!
Post by: benlindell on February 23, 2010, 01:13:10 PM
I used faston inductors from mouser

Mouser:
434-03-223J
434-03-473J
434-03-104J
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on February 23, 2010, 05:45:00 PM
i used the sowter choke. theyve got one for this project.

Jake
Title: Re: G-PULTEC problems, please help!
Post by: benlindell on March 01, 2010, 07:53:28 PM
Is there anyway to add a trimmer and tweak the levels? prehaps the 470K before the gainstage?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on March 01, 2010, 11:38:24 PM
Is there anyway to add a trimmer and tweak the levels? prehaps the 470K before the gainstage?

No, not in any good and simple way, I think. We need all the ECC88 gain we can get, and any trim would cost some gain.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: Kingston on March 02, 2010, 12:36:07 AM
Is there anyway to add a trimmer and tweak the levels? prehaps the 470K before the gainstage?

If you absolutely must, you have two somewhat easy options but both have drawbacks.

1. you can replace the 10k load resistor just before the SRPP stage with a trimmer (like 22k) and tweak to equalise gain. You can only tweak down the channel that has more gain. Drawback is you lost some gain.

2. measure your 10KA high boost pot end-to-end resistances, and add a trimmer (say, 1-2k) to the one that has lesser value. This is probably the lesser of two evils, as pots will be slightly uneven (then again, they are most of the time anyway).
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on March 05, 2010, 08:31:54 AM
Hi Guys,

I have 2 GPultecs fully stuffed, including filter boards and Amp / PSU boards.

I did this before understanding that 1 PSU was sufficient to drive 2 channels.

Im not too bothered about the additional cost of stuffing the boards now its done, but would like to power the pair off 1 pair of toroids. they are rated 15v at 1.7A so I think this should be plenty.

Im guessing I can just take the 15v from the first transformer, then take the 220v from the second transformer and use these 2 feed the 2nd PSU. But would I need to do anything to the section of the 2nd PSU baord that is allocated for the secondary of the 2nd transformer? Or is it OK to just skip that if you already have the stepped up voltage from elsewhere?

Would I need to change the fuse on the 1st PSU at all? On the schemo it seems to suggest its breaking 220, but on the board it looks like its breaking the 15 / 12v line, so Im a bit confused about its role. I assume its there as a failsafe if one of the toroids fails, but I dont really understand much more than that.

As you can probably tell, Im quite far from expert when it comes to PSU stuff, even though I know it should be quite simple!

Thanks a lot
Jake
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on March 08, 2010, 05:02:24 AM
Sorry to bump this, but just wondering if anyone out there can help me?

Thanks
Jake
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on March 08, 2010, 07:39:15 AM
In general it's not a good idea to power two G-Pultec units from one PSU, as the circuit is not made with this in mind. I'm not saying that it is not possible, but it is hard to tell what sort of problems you may run into regarding grounding and such. There has been quite a few builders that had problems with this.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on March 08, 2010, 09:20:05 AM
Thanks Jakob, I'll just run it like 2 totally seperate channels in one box then. Just trying to save a few ££


Cheers
Title: Re: G-PULTEC problems, please help!
Post by: benlindell on March 09, 2010, 12:40:36 AM
Just about done with these, just need to do the final mounting, thought I'd share how they're lookin:

(http://blog.benlindell.com/wp-content/uploads/2010/03/PultecMock1-150x150.jpg) (http://blog.benlindell.com/wp-content/uploads/2010/03/PultecMock1.jpg)

(http://blog.benlindell.com/wp-content/uploads/2010/03/PultecMock2-150x150.jpg) (http://blog.benlindell.com/wp-content/uploads/2010/03/PultecMock2.jpg)
Title: Re: G-PULTEC problems, please help!
Post by: JoleFIN on March 23, 2010, 09:28:21 PM
Looks good :)

I'm going for both input + output Lundahls and Sowter inductors.. would be great to have all parts top notch but at least now I need to settle for some compromises. Can I use two 2,2uF in parallel to replace the 4,7uF on the main board or is this combination sufficient?

What is the asterisk mark about on the 75 ohm resistor on the filter board? On the 10k resistor it's about the bypass unity gain, it's the same with the 75R ?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on March 29, 2010, 09:01:32 AM
the 75R is the correct value - the * was some left-over note for myself...

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: JoleFIN on March 29, 2010, 01:24:17 PM
Ahh ok, thanks Jacob! Found a shop in home town which actually had one piece of the 4,7uF poly cap left on the shelf, so everything's great :)
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on April 01, 2010, 05:11:28 PM
Hi All,
       I see that there is an " Optional "  transformer balanced input which I plan to use, could I also put a 1/4" jack on back panel for unbalanced input and be able to use either ?

   also would anyone have the Sowter inductor part numbers ? ..  and what is the voltage requirement for the small film caps ?
         
  sorry for all the newb questions   :-[
   Thanks,
              Chip
 
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on April 01, 2010, 05:29:55 PM
yeah you can use both balance and unbalanced output. Theres a molex header for each if i remember rightly.

The sowter inductor you want is  9930.

Jake

Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on April 01, 2010, 05:39:18 PM
 Thanks  for the quick reply  :)
     ... just to be sure.. that's the Input, correct ?
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on April 01, 2010, 06:48:57 PM
oh, i read output. my bad.

im not sure. i think the transformer does more than just balane on the input.

i'll let someone else answer that one

jake
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on April 02, 2010, 12:26:18 AM
   snipsnip , Thanks so much.

       Has anyone used the Sowter input or output transformers in this project instead of the Lundahls ?

  EDIT :  snipsnip  - that Sowter inductor, in the description on the Sowter page it states that this one piece replaces the " Individual " inductors spec'd in the schematic / PCB layout with the leads or taps off of it ... how exactly is that wired ?  - the numerical values of the " taps " listed don't match up except the 22uh , but I see that all the " tapped " values add up to the same 269uh as the 100uh,100uh,47uh,22uh in the circuit layout

.. sorry I'm such a newb  :-[
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on April 02, 2010, 02:54:50 PM
The values in the 9930 are equivilent to the ones specified on the PCB, but they are connected in series. its just a drop in replacement for individual inductors.

22mH = 22mH
22 + 47 = 69mH
22 + 47 + 100 = 169mH
22 + 47 + 100 + 100 = 269mH

Using the colour code provide by sowter, you wire it up as per the diagram in the thread below:

http://www.groupdiy.com/index.php?topic=29972.msg363411#msg363411

Dont know anything about alternative transformers Im afraid.

Jake
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on April 02, 2010, 06:41:12 PM
   Thanks Jake ! 

                      I think I have everything else figured out... at least for now  ;D

,, very much appreciated,
                                   Chip
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on April 03, 2010, 12:19:18 PM
...o.k., another question  ::)

              a little confused on the power trans set up... in the documents from Gyafs page it shows T1 and T2 as 12v secondaries, but the PCB overlay states 15v for T1.

   so is it T1=15v , T2=12v like the G9 set up ? , or is it T1=12v , T2=12v.  

     alternatively, could I also just use on old tube amp PT that has a 115v pri and a 250v and 6.3 volt secondary?

  Thanks,
             Chip
Title: Re: G-PULTEC problems, please help!
Post by: fallout on April 03, 2010, 01:34:24 PM
Chip, you can use 2 transformers like Digikey PN: TE62062 (12v). Wire T1's primary for 120v (parallel) and secondary for 12v (parallel). Install the 2nd transformer in reverse for 12v (parallel) and wire the primary side for 240v (series). I hope this makes sense..

-jay
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on April 03, 2010, 09:56:59 PM

Thanks Jay, cleared that up for me  ;D
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on April 04, 2010, 06:46:20 AM
Yeah, it can be either  2x15v or  2x12v wired back to front. Dont get one 15 and one 12 or it wont work properly.
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on April 04, 2010, 10:56:50 AM

 Thanks Jake,
                          I've been looking around, the cost of two Torroids is approx $50 US , so i found these - http://www.hammondmfg.com/pdf/5c0030.pdf - the 261G6 seems to be the one to use for this project, and I've found it new for $35 US. 

    Have you or anyone else ever used this style PT for this or similar DIY projects ?  Physically it will fit in a 2U rack case but not sure about noise / shielding etc .
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on April 06, 2010, 03:03:25 PM

.. O.K.... another question....I was planning on using a DPDT toggle for the " Bypass " in/out, and just noticed the three through holes marked " Out , GND , In "  under the rotary switch for bypass...

   Could someone shed a little light on this ? 

    Thanks,
              Chip
Title: Re: G-PULTEC problems, please help!
Post by: pacemaker on April 11, 2010, 05:51:35 PM
hi guys,
i have built a G-pultec
with edcor XS100 input/output,
i would like to put a cinemag CML-150t
to replace my cheap inductors
i have the following values 27mH, 33,47,68,82 and 150mH
the g-pultec values are 22mH, 69,169 and 269mH
22-27mH is pretty close but for the next values ,
i can reach 60mH (27+33) or 74mH ( 27+47mH )
and after it began worse ,
i can have 142mH (27+33+82) or 156mH ( 27+47+82)
and finally 292mH (27+33+82+150) or 306mH (27+47+82+150)
am i missing something about inductor wiring
or do i need to recalculate caps values to match g-pultec frequencies ?
I've searched and read a lot
but coudn't find any post
about a CML-150T wired in a g-pultec,
so if anybody has done it,
any help would be greatly appreciated
Regards,
Francois
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on April 13, 2010, 11:32:13 PM
Hello again,
               I've been looking for inductors for this project, I found these at Mouser -  http://au.mouser.com/ProductDetail/Bourns/RL622-104K-RC/?qs=Lkb%2fp%252bsDSFEmY0jX5iG7pA%3d%3d - I guess they're cheap enough to try, but should I go through the trouble? Any thoughts....anyone ?
        One of the threads said TOKO inductors were good, but cant find any.  I saw that someone used Cinemag inductors, on their web page, they list one for a Pultec EQ, but the values seem to be different, I spoke to them and they suggested changing cap values to compensate.
              I little over my head, any help or guidance is greatly appreciated.

  Thanks,
             Chip
Title: Re: G-PULTEC problems, please help!
Post by: benlindell on April 14, 2010, 04:40:41 PM
I remember somewhere someone had said that the TOKO inductors work just fine. I used them and I think they sound great (without comparing them to any others of course).

I actually just finished up my pair today. Here's some pics:
(http://blog.benlindell.com/wp-content/uploads/2010/04/IMG_1159-150x150.jpg) (http://blog.benlindell.com/wp-content/uploads/2010/04/IMG_1159.jpg)(http://blog.benlindell.com/wp-content/uploads/2010/04/IMG_1150-150x150.jpg) (http://blog.benlindell.com/wp-content/uploads/2010/04/IMG_1150.jpg)(http://blog.benlindell.com/wp-content/uploads/2010/04/IMG_1152-150x150.jpg) (http://blog.benlindell.com/wp-content/uploads/2010/04/IMG_1152.jpg)
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on April 14, 2010, 11:32:10 PM
beautiful units benlindell , may I ask where you got the Toko's, I cant seem to locate them.
Title: Re: G-PULTEC problems, please help!
Post by: benlindell on April 15, 2010, 03:07:30 AM
Sorry, I mis-spoke, I used fastron inductors from mouser part number (22uh): 434-03-223J
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on April 15, 2010, 05:56:29 AM
..you want mH, not uH...
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on April 15, 2010, 08:52:56 AM
Thank you both, I will try those.    :)
Title: Re: G-PULTEC problems, please help!
Post by: JoleFIN on April 19, 2010, 04:27:11 PM
Okay guys, question: I have two of these transformers. They're a bit overkill for the project (1.5A needed?) and I came to thinking can I use the 1st transformer's other secondary output for feeding the 2nd transformer in reverse, or will I be having some sort of phase problems with the power side? Would be easier and more tidy to wire them up this way than having the secondaries in parallel.

(http://www.joelkalsi.com/diy/gpultec/IMG_5755.jpg)
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on April 19, 2010, 11:57:24 PM
with that much power, you can pretty much do what you want. no problem.

but watch out for induced hum from power- to audio-transformers.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on April 20, 2010, 05:35:56 AM
Hi Jakob,

I have a pretty big induced him in my dual gpultec unit.

I havent been in the studio much of late, so havent tried much to fix it so far.

Anything you can recomend other than taking the torroids to an external PSU?
Title: Re: G-PULTEC problems, please help!
Post by: briomusic on June 27, 2010, 07:05:32 AM
In general it's not a good idea to power two G-Pultec units from one PSU, as the circuit is not made with this in mind. I'm not saying that it is not possible, but it is hard to tell what sort of problems you may run into regarding grounding and such. There has been quite a few builders that had problems with this.

Jakob E.

After reading this conversation you had with snipsnip, I am still a little confused...

If I want to build a two channel g-pultec in one case, I understand I need to stuff both PSU's, i.e. double up on all the rectifiers/caps etc.

But...can I get away with just two transformers to power this (connecting the secondaries to both PSU boards) or will I actually need a total of four transformers? (I hope not...)

thanks briomusic

ETA found answer elsewhere, apparently 2 transformers are enough if they are rated 3A.
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on June 28, 2010, 05:37:38 AM
I wouldn't recommend making dual units - too many people has had trouble getting them hum-free...

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on June 28, 2010, 05:48:09 AM
Yes, I have had no joy resolving my hum issues with a dual unit, and have my Gpultecs in pieces again.

I will be building them in seperate cases when I have some money.

Thanks for the advice jakob.

Jake
Title: Re: G-PULTEC problems, please help!
Post by: briomusic on June 28, 2010, 11:43:45 AM
Is this hum due to the proximity of the power transformers (which are twice the size/hum for a dual unit)? wouldn't it make more sense to have the transformers in a separate case then?
Title: Re: G-PULTEC problems, please help!
Post by: telefunk on July 01, 2010, 07:52:10 PM
Hi!

this must probably be really stupid question but i have to ask because i cant find any proper answer anywhere...

so, i´m building a g-pultec unit and i cant find a 2.2k pot that is high enough quality. But Alpha has 2k pot that feels good. Can i just add a 200R resistor to make it 2.2k and it will be exactly the same results?

R
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on July 02, 2010, 05:23:20 AM
I would just use a 2k pot, or 2k5 is probably better.
Title: Re: G-PULTEC problems, please help!
Post by: telefunk on July 06, 2010, 07:17:46 PM
hi,

people: you´ve heard this one before, but i just cant find a decent answer:

I have 30VA 2x12v (parallel) secondary for the first trafo and I want to put the lamp to it. If I want to use a led, what volt value for the led & what resistor values should I use?!?! Dont want to boil the trafo...

Title: Re: G-PULTEC problems, please help!
Post by: telefunk on July 09, 2010, 10:12:47 AM
ok, my g-pultecs are up and running (and sounding REALLY smooth!) but one slight little problem i seem to have.

This only happens when BOTH of my pultecs are inserted to my Soundcraft 6000 input channels: when I put full HI-boost of 18Khz with both of them with "q"-range in zero, it starts to oscillate. Both of them. And it gets less when I make some extra grounding to the case.
Has it  something to do with impedance??!
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on July 10, 2010, 06:14:37 AM
There's no way to get the pultec to oscillate by itself (it's a passive eq), so you must have a wireing or setup problem (some output signal making it's way back to input)

Error is probably in the soundcraft and/or in the ground wireing

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: mamiti on July 15, 2010, 05:03:03 AM
Hi,

would anyone be willing to share gerber files for GPultec pcb as I couldn't find them at gyraf.dk?

Thanks,

MT
Title: Re: G-PULTEC problems, please help!
Post by: skal1 on July 15, 2010, 01:19:32 PM
Hey mamiti 

here is the pdf , you can make a pcb from the files


http://gyraf.dk/gy_pd/pultec/gy_pd.pdf

skal1
Title: Re: G-PULTEC problems, please help!
Post by: mamiti on July 15, 2010, 01:49:39 PM
Hey mamiti 

here is the pdf , you can make a pcb from the files


http://gyraf.dk/gy_pd/pultec/gy_pd.pdf

skal1

Thanks, I've got the pdf already. Thing is that the pcb drill really likes gerber or some other common design file format. PDF is better suited for home-etching. I'm not going to produce these for sale but I just happen to have an access to a great drill so etching is too much of a hassle if there is an alternative.

Anyone?

Cheers,

MT
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on July 15, 2010, 11:27:41 PM
I don't think we ever made Gerbers for the GPultec...

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: mamiti on July 16, 2010, 02:44:40 AM
I don't think we ever made Gerbers for the GPultec...

Jakob E.

Ok, thanks for the info. I'll try to find a way to import pdf.

Cheers,

MT
Title: Re: G-PULTEC problems, please help!
Post by: mrcase on July 26, 2010, 05:21:51 PM
hey!

I just finished my first pultec, sounding really nice so far - but I just wanted to clarify how to measure the voltage for the tube correctly.
I´m measuring 290V without the tube in the socket - is this okay or is this way to high? Or do I have to measure this with the tube in the circuit?

thank you all

Title: Re: G-PULTEC problems, please help!
Post by: alexc on July 26, 2010, 07:24:59 PM
Can anyone explain the effect of using an SRPP with unequal cathode resistances ?
(1K and 470R in the gpultec)

I'm finding on mine I have 250V at the plate of the top tube and around 85V on the
cathode of the top tube. It seems like it should be more like 125V as indicated on the diagram.

Using an ECC88

Thanks
Title: Bridge rectifier?
Post by: danielb on August 09, 2010, 05:33:15 PM
Can I use this bridge rectifier 1000VAC(700V RMS)/1.5A?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on August 10, 2010, 06:16:52 AM
mrcase: Always measure voltages with tube in place and heated up.

alexc:  The unbalance is on purpose, giving a bit lower output impedance. Only drawback is reduced maximum swing into high-Z, but is outside what we want anyway.

danielb: 700V/1.5A is just fine for the rectifier bridges.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: alexc on August 10, 2010, 06:44:42 AM
Thx Jakob.
Title: Re: G-PULTEC problems, please help!
Post by: danielb on August 10, 2010, 03:43:45 PM
Thanks Jacob

Can I i use one of these capacitors for the "4,7uF 250V":

http://elektronik-lavpris.dk/product_info.php?products_id=85892
http://elektronik-lavpris.dk/product_info.php?products_id=102760
http://elektronik-lavpris.dk/product_info.php?products_id=85565
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on August 11, 2010, 07:23:12 AM
nope, first one is electrolytic, the two next are physically too bit to fit (37mm - we do only have 27½mm spacing - check the pcb).

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on August 20, 2010, 06:01:46 AM
Hi All,
    I purchased two of these - http://www.hammondmfg.com/pdf/5c0030.pdf - the 261G6, and was wondering if i can just hook up the 250vac and the 6.3vac to the appropriate power input pads on the PSU PCB ?  I think the 250vac would work fine, but the 6.3vac when rectified would bring it to maybe 9.2vdc ?   is that enough " differential "  for the LM317 to regulate ?  and would I need to change the " adj. leg " resistor ? 

  any help is always appreciated,
                                             Thanks,
                                                         Chip
Title: Re: G-PULTEC problems, please help!
Post by: Kingston on August 20, 2010, 06:20:58 AM
is that enough " differential "  for the LM317 to regulate ?  and would I need to change the " adj. leg " resistor ?

It's not enough, or just barely. Realistically when the tubes start pulling current that 9.2VDC drops to maybe 8-8.5VDC. Regulator will drop that 3V more. But you don't really need the regulator in the first place. Replace it with a simple resistor and you will have enough passive filtering for decent DC stability.

Or you can just take the 6.3VAC directly to tubes with carefully planned (or well shielded) wiring.
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on August 20, 2010, 12:28:04 PM
Thanks so much Kingston !
      ... so bypass LM317 and add maybe a 1w or 2w dropping resistor after bridge rectifier for 6.3vDC heater ?  
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on September 17, 2010, 10:40:55 PM
Hi All,
   
     Got some Questions   ;D

   I am attempting a dual G-Pultec in a 2U case, have used this PT - http://www.hammondmfg.com/pdf/5c0030.pdf - the 261G6 - this PT has a 250vac/ 130ma secondary and a 6.3vac/2.0A secondary. Secondaries are split from terminal block to each PSU-I/O board.  I replaced the 3k3 2w resistor with a 33k 5w and am getting +247vdc after rectifier ( under load ).  Swapped out LM317 with a TL1086 a 1.5A Low Dropout Positive Adjustable Regulator, changed the 1k8 adjustor with a 1k86 and got  +6.26vdc ( under load ) .  so I think I'm good powerwise.

  I've mounted and stacked the control boards to the case floor about an inch behind the front panel. The PSU boards are on the left side towards back of case, so the ( In / GND / Out ) connecting PSU- I/O board to Contolboards, using shielded cable is 6-8 inches long - will that cable length cause a problem ?

  I've read this thread and am searching now, but what is the grounding scheame for this ?  is it just earth ground from IEC connector to case - and thats  it ?   Input shield to XLR ground tab to  " Star Ground " do I run GND shield on output from I/O to XLR ground tab to " Star ground "  ? 

  also, does anyone have the actual frequencies for front panel labeling ?   I seem to remember seeing them somewhere, but not sure where. also I seem to recall some thing about a " enhanced Pultec EQ "  is that  a mod for this project ? or is that a whole other project.

  as always, any and all help appreciated

   Thanks   :)
 

 
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on September 18, 2010, 05:13:52 AM
Hi,

I had issued with mine as a dual build, and its currently in bits waiting to be made as 2 standalone units... so this is just from memory.

I didnt have a star ground on my build. I think the connection on pin 1 will mean it will be grounded to the next piece of kit its plugged in to. I dont think you need to the the audio ground to chassis in this build... but appreciate others opinion here. IEC to chassis is obviously for safety reasons.

Regarding cable length, shouldnt be a problem... I dont think you even need to use shielded wire in this build if you dont want too (again, I appreciate others input here)
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on September 18, 2010, 05:40:44 PM

 Thanks snipsnip !   :)

  I seem to recall a thread where someone said if their Dual unit didnt work out they would just put them in separate cases. I plan on doing the same if I end up with problems I cant figure out. I feel that if the noise or hum ( wont know till I fire it up ) is induced by having two large PTs in the case, I may have found a solution with the PT I'm using, and because its all in one PT, I have room in the case to shield it if shielding it is the solution, or mount outside case.
 
 If grounding scheme is just IEC earth ground to case, I cant see how a " ground loop " can occur , but then again I am still soooo much a newbe  ;D

  I found some pics of other units in the metameta, so I have written down the frequencies , I'm sure they're close enough.
  An Interesting read here - PULTEC - Input Options -Buffers- Imp - TX - JLM Hybrid opamp - does this apply to this tube version ?  and if so , has anyone done it ?  also, is it just a case of adding caps and inductor values to add/increace  frequency selections ?
 
 I do appologies if any of this has been covered, I've just finihed reading the G-Pultec threads from the metameta and my eyes/brains are I little fuzzy  ;D

Thanks again snipsnip and to All
Title: Re: G-PULTEC problems, please help!
Post by: south2577 on September 19, 2010, 10:32:06 PM
Is there a BOM for the G Pultec project?
Or is it a bit loose to have one?

Thanks
Ben
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on September 19, 2010, 11:01:38 PM
I just put together a list from the the PCB layout and the Component placement  pdf-file on the Gyraf web page, not very many parts,  I got the WIMAs from TAW, found Bourns and Fastron inductors from Mouser they were inexpensive enough so I got both to try.
 
 Hope this helps

EDIT :  found this thread - http://www.groupdiy.com/index.php?topic=7704.0  - on inductors, Sowter and Cinemag also make inductors that I see have been used, but expensive, and I wanted to build it " stock " first " kind of thing....although I have veered a little   ;D
Title: Re: G-PULTEC problems, please help!
Post by: south2577 on September 19, 2010, 11:26:58 PM
Thanks Audiophreak

More questions to come.  :)
Title: Re: G-PULTEC problems, please help!
Post by: south2577 on September 20, 2010, 01:57:45 AM
Ok so I'm just getting my head around some things on this build. Newb alert!! :D
Is this right for pots?
low boost- 10K log not 10K lin?
Low cut - 100K log
High boost - 10K Lin
High Cut - 1K Lin
Q - 2K2 Lin


cheers
Ben
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on September 20, 2010, 09:29:34 AM
I believe that is correct, I'm at that point now myself, couldn't find the post that states the correction, but remember that it said the schematic on Gyrafs page was correct and the PCB overlay was not - I also read over the weekend that in Europe the "A" is Lin and "B" is Log - and in US the "A" is for Audio/Log and "B" is Lin _ ( confusing ) so according to the Schematic the Low Boost and Low Cut are Log and the rest are Lin. 

  ... at least that's the way I see it  ;D

 someone please correct me if I'm wrong

 
Title: Re: G-PULTEC problems, please help!
Post by: south2577 on September 20, 2010, 03:25:45 PM
I also read over the weekend that in Europe the "A" is Lin and "B" is Log - and in US the "A" is for Audio/Log and "B" is Lin _ ( confusing )
 

Ahh just another example of the world working together. Ha  :D
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on September 21, 2010, 04:08:55 AM
Common pot notation:

10KA=10K Linear (european tradition)
A10K=10K Log (japanese/far-eastern tradition)

10KB=10K Log (european tradition)
B10K=10K Linear (japanese/far-eastern tradition)

And yes, use 10KB (log) for low boost

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on September 21, 2010, 09:11:39 AM
 
  Well put  ... Thanks Jakob  :)

  Found this thread through search  ;D  on the actual Boost / Cut frequencies, very informative and shows the math,  thought I would post a link here in the help thread.

http://www.groupdiy.com/index.php?topic=32839.0
Title: Re: G-PULTEC problems, please help!
Post by: daveee on October 12, 2010, 09:42:11 AM
well i got the g-pultec working and i've been using it in the studio for a while now...

one thing i've found - it doesn't sound completely amazing, and i'm wondering why :)
especially on bass - i seem to lose some of the low bottom end and it seems to be quite 'flabby' if that's even a word.
other instruments like guitars and vocals can sound quite harsh when EQ'd.

i've heard great things about the g-pultec so i'm sure it's something that needs changing in mine - i'm wondering where to start?

i've used llundahl trannys, wima caps and a mullard nos valve. should i maybe try a different valve? any suggestions?
thanks in advance!
Title: Re: G-PULTEC problems, please help!
Post by: Nick Franklin on October 13, 2010, 01:54:16 AM
well i got the g-pultec working and i've been using it in the studio for a while now...

one thing i've found - it doesn't sound completely amazing, and i'm wondering why :)
especially on bass - i seem to lose some of the low bottom end and it seems to be quite 'flabby' if that's even a word.
other instruments like guitars and vocals can sound quite harsh when EQ'd.

i've heard great things about the g-pultec so i'm sure it's something that needs changing in mine - i'm wondering where to start?

i've used llundahl trannys, wima caps and a mullard nos valve. should i maybe try a different valve? any suggestions?
thanks in advance!

Would you like to send me an audio file and I'll run it through my G-pultec, then you can compare it with yours and see if you think yours is behaving correctly?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on October 13, 2010, 03:56:04 AM
"flabby" could possibly be from too high a output level?

GPultec will do something like +12dBm happily, but not much higher (and NOT the +28dBm that some soundcards has as default for 0dBFS-digital)

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: kazper on November 11, 2010, 02:54:31 PM
Just wanted to post some notes from my recent build.

I had way to low of voltage for the heaters using the 470R and 1.8K near the LM317. I ended up getting usable loaded down voltages by changing the 470R to an 240R and using a 1K in place of the 1.8K. A 2.5K trimmer could be used inplace of the 1.8K to dial in the 6.3. I think you could just change out the 1.8K to a 1.9K and your there too, http://www.electro-tech-online.com/tools-lm317-calculator.html

That LM317 gets HOT.....

I'm also getting 280-290V on the High Voltage supply that I need to knock down a bit.
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on November 11, 2010, 02:59:58 PM

That LM317 gets HOT.....


Sure does!

Did you find a good sink for yours? I still need to replace mine.

Title: Re: G-PULTEC problems, please help!
Post by: kazper on November 11, 2010, 03:07:24 PM
I've been using the first one that was pictured a couple pages back, that was replaced... I have larger ones here but I was going to let it run a bit and take a look at the outside temp before making another move.

Does the higher voltages for the HV+ matter?  I'm trying to understand what it does and why the 30-40V difference would matter.


I need to go listen to them now...

BTW I'm using the 120-120/12V-12V Antek branded transformers, with mixed VA's for the primary (50VA) and secondary (25VA). I can't imagine how that would cause any issues.
Title: Re: G-PULTEC problems, please help!
Post by: kazper on November 11, 2010, 08:22:04 PM
Sounds fantastic, but I think your going to want MBB switches on everything but the bypass...
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on November 12, 2010, 04:35:04 AM

Does the higher voltages for the HV+ matter?  I'm trying to understand what it does and why the 30-40V difference would matter.


It matters - because we're already stretching the ECC88's voltage capability to the edge (it's anode voltage is rated some 90-120V depending on what datasheet you consult)

Ca. half of our HT voltage appears across each half of the ECC88 - so the suggested 250V HT shouldn't be exceeded by too much.

On very-high-overvoltage units, there is a tendency of premature burn out of the tube.

Adjust voltage by trying different value resistors between resevoir caps - circuit sounds good between 200 and 250V.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: kazper on November 12, 2010, 03:42:03 PM
Thanks Jakob... I'll bump it down before putting the lid on it....
I had read up on the tube specs and ended up with more questions so I just posted here.


I posted this stuff over at another thread but since this is the META I thought I would post it here as well.


Front $46 using a Par-Metal plate (just a edited copy of the original one found on Franks site) Thanks to FRANK or someone!
Price is no frills no fills you provide the material ... so the engravings show raw Aluminum which looks great in person!
Holes for the pots are for the low cost Alpha's.
3mm LED ON indicator located in the center of the O in ON, feed off the Regulator 6.3V DC with a 350R resistor in series to the LED +.

(http://twin-x.com/groupdiy/albums/userpics/428/Front_Pultec.jpg)

Rear $43 using a Par-Metal Back plate (Check Hole Sizes to your parts!!!!!!)
Price is no frills no fills you provide the material ... so the engravings show raw Aluminum which looks great in person!
(http://twin-x.com/groupdiy/albums/userpics/428/Rear_Pultec.jpg)

FPE Files:
http://twin-x.com/groupdiy/albums/userpics/428/GpultecFPE.zip

Delete or customize to your taste. I believe I have a lower cost back unit somewhere but I can't find it at the moment.
Title: Re: G-PULTEC problems, please help!
Post by: kazper on November 13, 2010, 10:21:32 PM
I ended up pulling the adjustment resistor in the 6.3V section and installing a pot so I could dial it in a little more. An 2.5K-5K pot will work nicely in place of the 1.8K in the SRPP/PSU board for future builders.

I also ended up with 15K total of 3W resistors to get me to 225V in the HV section replacing the 3.3K-2W. I had a 10K and it wasn't low enough to get my 310V after the rectifier down to under 250V. It was close, but no cigar..

Using 120/12V to 12V/220-240 Antek's like I did I would suggest about 12K 2-3W for getting the voltage to 250V, 15K for 225V and 20K for 200V. As Jacob had put it somewhere between 200-250V sounds good in this circuit. I'd order a few values of resistors from 3-20K and experiment. Another word of advise is give it a few min after power up to let the caps fill up and the PSU to line out before taking measurements.

Kaz..
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on November 26, 2010, 11:12:38 PM
Hi All,
         Just wanted to post an update, Preliminary results are good with my Dual G-Pultec !    :) :)

  waiting to install correct shaft dia. pots - Collin at AML now carries 1/4 inch shaft 20mm pots for the G-Pultec.

 so with pots and switches just hanging off control boards, everything works and no humm or buzz !   :)

have only run a 58 through a G-9 and also a CD player - but so far it sounds great !   :)

  will post  documentation and pix in a few days.

  Thanks to all !


 EDIT -  wanted to also post that I just have the IEC Earth ground to Chassis - circuit is not grounded to chassis and input pin 1 is not grounded to chassis, -   so is this whats called a " Floating Ground " ? 
Title: Re: G-PULTEC problems, please help!
Post by: EHOFFA007 on December 10, 2010, 02:36:23 PM
Getting a Bom together for my 2x single Gpultecs.
Just want to make sure these power traffo's will be ok.

http://www.mouser.com/Search/ProductDetail.aspx?R=VPT24-1040virtualkey55310000virtualkey553-VPT24-1040

24.0V CT @ 1.04A 12V @ 2.08A Parallel
Power Rating:   25 VA   
Primary Voltage Rating:   115 V to 230 V   
Secondary Voltage Rating:   12 V to 24 V

On the Gyraf PDF it calls for 12v 1.5A.
Thanks
Title: Re: G-PULTEC problems, please help!
Post by: kazper on December 10, 2010, 02:54:41 PM
Getting a Bom together for my 2x single Gpultecs.
Just want to make sure these power traffo's will be ok.

http://www.mouser.com/Search/ProductDetail.aspx?R=VPT24-1040virtualkey55310000virtualkey553-VPT24-1040

24.0V CT @ 1.04A 12V @ 2.08A Parallel
Power Rating:   25 VA   
Primary Voltage Rating:   115 V to 230 V   
Secondary Voltage Rating:   12 V to 24 V

On the Gyraf PDF it calls for 12v 1.5A.
Thanks

I used Antek transformers (www.antekinc.com)
AN-0512 (50VA) + AN-0212 (25VA)

The 50VA is the first transformer that feeds the heater, and the 25VA is used on the step up.

So your $24 per unit in transformers this route.

You may also look at there new AS-0512 as a alternative for $3.50 more.

The units I built are surprisingly dead quite with the IEC grounded to the chassis.

Kaz
 
Title: Re: G-PULTEC problems, please help!
Post by: EHOFFA007 on December 10, 2010, 03:00:40 PM
Thanks for the info. The beefier traffo1 makes sense.
Beefier is better   ;D
Title: Re: G-PULTEC problems, please help!
Post by: kazper on December 10, 2010, 03:18:49 PM
The regular one is probably more than enough.
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on December 20, 2010, 07:28:49 PM
Hi All,
       Finally got some pix of my Dual G-Pultec !!!   :)

    I used the Hammond 261G6 power trans, it has a 250V C.T. @ 130 ma secondary 6.3V @ 2A secondary. I replaced the 3k3 2w resistor with a 33k 5w resistor to bring the rectified 380vdc down to 240vdc.  I replaced the LM317 with a TL1086, its a low voltage drop out regulator and a drop in replacement, although Kingston mentioned that just a dropping resistor could be used as after rectification its about 7.8vdc.
     The front panel was done at Prodigy Engineering, I think I may have crowded the left side as I wanted to keep as much room as possible between filter boards and power switch. Collin at AML now carries all the pots for this all in 1/4 inch shafts.
    I haven't done extensive testing yet, but so far it sounds Fantastic !  - clean, fat, big bottom end ... and Smoooooooth   ;D
    no hum or buzz or grounding issues - I only have IEC ground to chassis, I have a ground wire in place to connect to pin1 XLR inputs, but haven't tried it yet

  Here is a link to some pix - https://goo.gl/photos/dDLHy9yr2zdCZAUH7

  If anyone wants the panel graphic, I have it in Illustrator , just email me.

  All questions / comments welcome

  Big THANKS to Jakob E. / Gyraf , Kingston , snipsnip , benlindell ,  and to this great forum.


   
Title: Re: G-PULTEC problems, please help!
Post by: creal on December 20, 2010, 08:17:59 PM
wow very nice eq audiophreak. i like your frontpanel.
very good post about the gainstage here. i think, i'll start my dual gpultect soon.
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on December 21, 2010, 09:04:35 AM
Thanks Creal !
           
        Not really sure how I got it to not have grounding problems... maybe Newbee luck  ;D

But even Jakob stated that a number of people have tried a dual G-Pultec and have had problems. Thats why I posted the link with detailed pix of what I did. That Hammond PT only has 115v primary mains, I see your from France, so that PT would not be an option for you, I don't even know if that is the reason it worked for me or not, but good luck with it, and I'll help as much as I can.

   Snipsnip ...  you there ?  - maybe this could help with yours ?

  Thanks again,
                       Chip
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on December 21, 2010, 09:36:44 AM
Hi Chip,

Good work, looking really nice.

Im also in europe so need the 230 primary. Im currently waiting for grandmasteraudio to get better so I can order some front panels and rebuild mine as 2 separate units. Glad yours is working though, everyone needs a bit of good luck from time to time :)

Im with you on the sound, the bottom end on this thing is wild, but never gets flabby. I also tend to pass mine through my ez1290 pres (with a pad) and this gives massive 3D tight lows.

I have smallish sinks on my voltage regs like you, and they overloaded from time to time when mine was up and running. If you do see any strange behaviour in future, take a look at those.

Congratulations, and enjoy!
Title: Re: G-PULTEC problems, please help!
Post by: sonicwarrior on December 21, 2010, 12:39:05 PM
Finally got some pix of my Dual G-Pultec !!!   :)

Nice idea to secure the power switch.  :)
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on December 21, 2010, 02:50:54 PM
Thanks sonicwarrior  !
     I've always installed the handles on the cases because I'd like to think they would protect the knobs and switches. This is my first panel layout, and I got a little too close the the left side, made adjusting the low boost and cut knobs a little difficult, so I removed the handles and put studs in with the acorn nuts. The knobs are pretty beefy, but left the switch exposed  :o   had a couple of those switch guards left over from another build.

  Thanks snipsnip !
       The ez1290s are on my list  ;D  .. for the heat sinks, the PT I used has a 6.3v secondary, although I could just use a dropping resistor, I went with a TL1086, its a low voltage drop out regulator, so its regulating from about 8vdc or so, so it doesn't get very warm.
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on December 21, 2010, 06:08:23 PM
oh yeah! Should have read your post in more detail.

Title: Re: G-PULTEC problems, please help!
Post by: muffy1975 on January 23, 2011, 07:56:03 PM
Hey guys,

can anyone detail how to bypass the ouptut ( yes output ) transformer on this build? Where do you connect the output xlr/jack and are there any parts that need to be added?

Many thanks in advance

Michael

ps, I've already built one unit with the OEP trannie output! Not a bad sound at all but would like to build a second without the transformer
Title: Re: G-PULTEC problems, please help!
Post by: JW on February 02, 2011, 02:03:15 PM
Bumping this one to ask about inductor shielding

I have a ringing going on with my G Pultec. I usually don't hear it but it occasionally comes on.
I have switches that terminate the outputs with 600 ohm resistors. Those don't make a difference so I don't think it's transformer ringing. (I have 600:600 Tamura/Yamaha PM1K transformers on the input, and the recommended Edcor on the output)

If I had to guess I'd say the ringing was up around 16K or so. Pretty high.

Does this sound like a possible symptom of the Torroids getting into the inductor? Or would that manifest itself generally at a lower frequency?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on February 03, 2011, 02:01:30 AM
..probably a unhappy tube - have you limited supply voltage to ca. 250V? That is relatively important.

Try changing tube...

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: JW on February 04, 2011, 06:54:01 PM
Okay,

Looks like about an 8.5K resistor instead of the 3.3K 2 watt will get the high voltage down to 250V. I had it up around 267V.
Also, the 125V was down around 98V or so. I did some testing with a pot, and it looks like about 470R instead of the 1K resistor beside the 4.7uF cap should get it close to 125V.

As for the heater, I'm getting 6.03V. How important is it to get it all the way up to 6.3V?

Title: Re: G-PULTEC problems, please help!
Post by: EHOFFA007 on February 06, 2011, 09:08:52 PM
Just finishing up a pair of these bad boys :)
first test seems as if the HF board is not acting properly.
I used these bournes inductors from mouser. Are these acceptable?

http://www.mouser.com/Search/ProductDetail.aspx?R=RL622-104K-RCvirtualkey65210000virtualkey652-RL622-104K-RC

LF board working fine.
polarity of I/O is correct
I have tied the filter boards together.
Took a chance with these inductors. Newbie so may have missed something in the specs :P
Title: Re: G-PULTEC problems, please help!
Post by: kazper on February 06, 2011, 10:29:22 PM
Just finishing up a pair of these bad boys :)
first test seems as if the HF board is not acting properly.
I used these bournes inductors from mouser. Are these acceptable?

http://www.mouser.com/Search/ProductDetail.aspx?R=RL622-104K-RCvirtualkey65210000virtualkey652-RL622-104K-RC

LF board working fine.
polarity of I/O is correct
I have tied the filter boards together.
Took a chance with these inductors. Newbie so may have missed something in the specs :P



Those look ok..
Title: Re: G-PULTEC problems, please help!
Post by: EHOFFA007 on February 07, 2011, 04:18:08 AM
Just finishing up a pair of these bad boys :)
first test seems as if the HF board is not acting properly.
I used these bournes inductors from mouser. Are these acceptable?

http://www.mouser.com/Search/ProductDetail.aspx?R=RL622-104K-RCvirtualkey65210000virtualkey652-RL622-104K-RC

LF board working fine.
polarity of I/O is correct
Took a chance with these inductors. Newbie so may have missed something in the specs :P
I have tied the filter boards together.



Those look ok..


Thanks for the reply man
I didn't see any polarity markings on the inductors. My first time dealing with these. There aren't +/- poles, correct?
I'll have to look deeper.
Reading a lot of threads about input signal and loading properly. I'm using the recommended lundhal Tx's. I'm pushing it with a balanced out on a PS audio DAC for testing.
would this keep the HF section from not responding at all?
Flipped the boards and tested continuity against the schematics and all the inter-pcb jumps are good.

Any other insight would be great.


Title: Re: G-PULTEC problems, please help!
Post by: EHOFFA007 on February 09, 2011, 12:40:32 AM
Just finishing up a pair of these bad boys :)
first test seems as if the HF board is not acting properly.
I used these bournes inductors from mouser. Are these acceptable?

http://www.mouser.com/Search/ProductDetail.aspx?R=RL622-104K-RCvirtualkey65210000virtualkey652-RL622-104K-RC

LF board working fine.
polarity of I/O is correct
Took a chance with these inductors. Newbie so may have missed something in the specs :P
I have tied the filter boards together.



Those look ok..


Thanks for the reply man
I didn't see any polarity markings on the inductors. My first time dealing with these. There aren't +/- poles, correct?
I'll have to look deeper.
Reading a lot of threads about input signal and loading properly. I'm using the recommended lundhal Tx's. I'm pushing it with a balanced out on a PS audio DAC for testing.
would this keep the HF section from not responding at all?
Flipped the boards and tested continuity against the schematics and all the inter-pcb jumps are good.

Any other insight would be great.



I had the High Cut and High Q pots mixed up!
I'm Finding on my first couple of builds not to trust myself too much :-)
Sounds great! Thanks for this great project!
Title: Re: G-PULTEC problems, please help!
Post by: JW on February 09, 2011, 04:37:15 PM
Okay,
Voltages now are:
222V at the HT
120V at the 4.7uF poly cap,
and 6.31 at the heater.

Seem good?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on February 10, 2011, 06:42:26 AM
yes..
Title: Re: G-PULTEC problems, please help!
Post by: scott_humphrey on February 10, 2011, 11:52:10 PM
Hi All,
       Finally got some pix of my Dual G-Pultec !!!   :)

    I used the Hammond 261G6 power trans, it has a 250V C.T. @ 130 ma secondary 6.3V @ 2A secondary. I replaced the 3k3 2w resistor with a 33k 5w resistor to bring the rectified 380vdc down to 240vdc.  I replaced the LM317 with a TL1086, its a low voltage drop out regulator and a drop in replacement, although Kingston mentioned that just a dropping resistor could be used as after rectification its about 7.8vdc.
     The front panel was done at Prodigy Engineering, I think I may have crowded the left side as I wanted to keep as much room as possible between filter boards and power switch. Collin at AML now carries all the pots for this all in 1/4 inch shafts.
    I haven't done extensive testing yet, but so far it sounds Fantastic !  - clean, fat, big bottom end ... and Smoooooooth   ;D
    no hum or buzz or grounding issues - I only have IEC ground to chassis, I have a ground wire in place to connect to pin1 XLR inputs, but haven't tried it yet

  Here is a link to some pix - http://picasaweb.google.com/audiophreeek/DualGPultec?feat=directlink

  If anyone wants the panel graphic, I have it in Illustrator , just email me.
  All questions / comments welcome


  Big THANKS to Jakob E. / Gyraf , Kingston , snipsnip , benlindell ,  and to this great forum.


   

(http://www.pinballreviews.com/cousin%20eddie.jpg)
She's a real beaut, Clark!
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on February 11, 2011, 09:42:51 AM

 Thanks Scott !
                      I love the sound of this thing so much, as soon as I finish my current project ( a quad of NewYorkDave One Bottles ) ....  I'm gonna build another one  :)
Title: Re: G-PULTEC problems, please help!
Post by: ncoak on February 12, 2011, 12:52:45 PM
just wrapping up sourcing everything for my g-pultec - last item on the list is a socket for the tube. i've scouted around online, all the 9-pin sockets i've seen look like the pins are too large for the holes on the gyraf board. can anyone point me to an appropriate socket? unfortunately my local stores don't carry them so i can't just take a quick look...the wonders of the internet age :P
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on February 12, 2011, 04:22:17 PM
I couldn't find ones either. I drilled out the pcb holes a bit.
Title: Re: G-PULTEC problems, please help!
Post by: ncoak on February 12, 2011, 06:06:44 PM
curses!

came across this thread for anyone in the same boat...will post results when they arrive.

http://www.groupdiy.com/index.php?topic=7392.0

edit: received the sockets and the pins were indeed too big; trimmed them down to size no problem.
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on February 12, 2011, 08:25:34 PM
Hi,
  I've used these - http://cgi.ebay.com/tube-sockets-9-pin-pc-gold-ceramic-25-pc-bag-wholesale-/330528394271?pt=Vintage_Electronics_R2&hash=item4cf5070c1f#ht_500wt_1156

   I've built a lot of tube gear so I got the bag of 25, at that price , even with shipping it comes out to just over $2 a socket.
  Not sure if its the same seller , but havent had any problems ... yet  ;D
Title: Re: G-PULTEC problems, please help!
Post by: leadbreath on February 21, 2011, 07:02:25 PM
hi

could someone please tell me the current drawn for the g-pultec circuit??

cheers
mick
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on February 21, 2011, 09:18:16 PM
Look up the Tube Data sheet, I think the heaters are about 400ma and the B+ is around 15-20ma  then of course LED or lamp  
Title: Re: G-PULTEC problems, please help!
Post by: ncoak on February 28, 2011, 09:53:54 PM
where exactly should i be taking the various voltage measurements - black probe to ground, red probe to ?

Title: Re: G-PULTEC problems, please help!
Post by: ncoak on March 01, 2011, 04:52:27 PM
if i'm interpreting the overlay correctly, i should be able to measure ~250v at pin 4 and 6.3v at pin 6 - just want to verify that i'm measuring with respect to ground here...and that touching a probe to these pins with the other probe to ground (case/star ground) won't leave me cooked like a thanksgiving turkey  ;D
Title: Re: G-PULTEC problems, please help!
Post by: kazper on March 01, 2011, 07:53:30 PM
You want to take your voltage readings across the 2 wires... IE the black and red wires from your T2 Antek transformer. With using the 6v secondaries you should be very hot on your T2 primaries (actaual transformer, not as in use/backwards. I'd recommend taking your readings with the tube out, get voltages close then try with a tube in it.

Kaz
Title: Re: G-PULTEC problems, please help!
Post by: ncoak on March 12, 2011, 03:30:04 PM
ok...so i've got the transformers sorted, getting a nice 236v going into the board - led attached to the 470r by LM317 lights up as it should, lovely.

...until i plug the tube into the socket, at which point i get no LED action, and the tube doesn't heat up. i've tried 2 different tubes so i'm pretty sure that's not the issue. any ideas of what i should look for to get this going? learning as i go here so i'm not exactly sure between which two points i should be taking voltage measurements around the tube - if anyone could shed some light it'd be greatly appreciated.

please excuse my noobness!



Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on March 12, 2011, 03:56:45 PM
Hi,
    I'm still a Noob too.  I wouldn't take the feed for the LED from the 470r as thats part of the ADJ. circuit to set heater voltage. I soldered a wire to the heater + tube socket pin on the bottom of the PCB with a 420r in-line to the LED.

  Look at the PCB Layout on Gyrafs Web page and just follow the traces to the tube socket pins to check heater and B+ voltages, black meter lead to star ground or heater ground, red meter lead to heater+ or B+ pin on tube socket - BE CAREFUL  !!!
Title: Re: G-PULTEC problems, please help!
Post by: ncoak on March 16, 2011, 02:09:42 PM
thanks audiophreak - i've been mulling this over and studying the circuit, definitely going to take your advice on the LED.

edit: noob alert
Title: Re: G-PULTEC problems, please help!
Post by: ncoak on March 16, 2011, 06:08:29 PM
got this guy up and running, sounds great! 226v between tube pins 4 & 5, 6.3v between 5 & 6. moving the led made all the difference of course - learned quite a bit in the process of this build. thanks to everybody for the help, and of course to jakob for making it all possible.
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on March 16, 2011, 07:15:17 PM
Congrats   :)  Glad to hear it .... Enjoy !!!
Title: Re: G-PULTEC problems, please help!
Post by: muffy1975 on March 17, 2011, 06:10:11 AM
Guys,

The first 2 low frequencies don't work in boost mode on my g pultec? has anyone got his or fixed this problem? i believe these two frequencies are covered by a 2u2 cap and a 1u cap.

help please

michael de A ???
Title: Re: G-PULTEC problems, please help!
Post by: funkymonksf on March 17, 2011, 03:22:53 PM
Does anyone have a bom for this project?

Oh pretty please!

-Brice
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on March 18, 2011, 09:51:20 AM
The first 2 low frequencies don't work in boost mode on my g pultec? has anyone got his or fixed this problem? i believe these two frequencies are covered by a 2u2 cap and a 1u cap.

..make sure (with ohm-meter) there's connection through the frequency switch and into the capacitors - that's the only thing that can go wrong there, I think..

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: muffy1975 on March 21, 2011, 03:04:51 PM
With Regards B.O.M,

for the filter section, most people are using polypropylene capacitors for the LF sections ( Wima MKP4 or MKP10 ) or other boutique polyprops etc.

For the high section they are using polystyrene caps, sometimes in series to build up the value required. made by xicon from Mouser these are cheap and rock. Some people are using silver mica caps but they are 10 times the price.

The switches are 2 pole 6 positions switches MBB. The pots I believe are 10k lin, 100k log, 10k log, 2k2 lin and 1k lin.

The resistors are 1/4 watt metal film etc.

The PCB with the tube......all the values that you need are stated in the PDF. Actually so are all the values for the filter section.

Go for F&T caps for the big 220uf caps and the 4700uf cap. They are great PSU caps.

Michael

Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on April 02, 2011, 03:20:44 PM
Hi guys,

just finished up a couple of Gpultecs, front and back by grandmasteraudio. Sowter chokes, Mullard tubes. Needless to say they sound hella dope. Big thanks to jakob and all the usual heads.

Ive made a couple of mistakes with my cap value selection and am having a bit of trouble figuring out which ones on the schemo. Does anyone have a table of cap values and associated freq's to hand?

(http://i96.photobucket.com/albums/l163/irisone/photo.jpg)

(http://i96.photobucket.com/albums/l163/irisone/photo-1.jpg)

(http://i96.photobucket.com/albums/l163/irisone/photo-2.jpg)
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on April 03, 2011, 09:10:12 AM
Hi guys, bit more time to test now it's not so late at night.

It's only the first position on the boost sections that are incorrect; 20hz (it's letting almost all freqs through), and 2khz (the freq boosted is too high).

Any ideas what caps I need to change? I have real trouble reading multi pos switches on schemos.

Thanks a lot
Jake
Title: Re: G-PULTEC problems, please help!
Post by: Ptownkid on April 03, 2011, 09:35:09 AM
The first position is the 100mH/18nF combo on the high boost switch. Is that what you would like to know? From the looks of it on Gyraf's schematic, the dot indicates the final position in a clockwise rotaion.
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on April 03, 2011, 09:43:17 AM
Thanks, that's what I figured for the high, but I got confused with the first position on the low boost as the schemo seems to show 2 switches. If the dot indicates the last position (I thought it might be first position) then I guess my problem is either with the 100n or 2u2.

Cheers
Title: Re: G-PULTEC problems, please help!
Post by: Ptownkid on April 03, 2011, 09:48:26 AM
I thought the same thing at first, about dot = position 1, but then I looked at the pcb to make sure instead of giving you a guess. The low boost is a double pole switch. If you look at the naming, it's SW3a and SW3b.

Cheers

PS - be careful with the switch names, it looks like Gyraf's numbering of the switches on his schem is diffrerent than on the pcb drawings.
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on April 03, 2011, 11:17:09 AM
thanks a lot
Title: Re: G-PULTEC problems, please help!
Post by: Ptownkid on April 03, 2011, 11:27:29 AM
My pleasure, hopefully you get it sorted out.
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on April 03, 2011, 02:18:54 PM
Hey snipsnip ,
                       Congratulations !!   
                                                   Looks Great !! 
                                                                           ... and dont they sound Awesome  ;D

Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on April 05, 2011, 05:19:43 AM
they do sound wicked. Love them.

I do have a bit of an issue with one of the voltage regs shutting down now and then even though ive got a pretty big sink on it. The other channel, using the same brand LM317 is fine.

Anyone think its worth swapping it out for one that may be more reliable. Any brand with more tolerance?

Cheers, and thanks again Jakob, these sound so 3 dimensional.
Title: Re: G-PULTEC problems, please help!
Post by: ncoak on April 11, 2011, 01:19:22 PM
meet the twins

just tracked some test vocals with them and am pretty floored - great sounding units.
Title: Re: G-PULTEC problems, please help!
Post by: funkymonksf on April 12, 2011, 03:29:03 PM
Does anyone know how to wire in the edcor XS1000 transformer instead of the Lundahl 5402? I heard there was a PCB out there to make it simple..

Thanks,
Brice
Title: Re: G-PULTEC problems, please help!
Post by: mitsos on April 12, 2011, 04:12:11 PM
I've never used it, but I think this is the one people have used it, so I guess it should work.
Title: Re: G-PULTEC problems, please help!
Post by: who on April 28, 2011, 06:09:44 AM
fat sound and masterclass noisefloor > -100db. I will put some audio samples in here later :)

(http://img6.imageshack.us/img6/8016/p1020470z.jpg) (http://img6.imageshack.us/i/p1020470z.jpg/)

(http://img808.imageshack.us/img808/2350/p1020457g.jpg) (http://img808.imageshack.us/i/p1020457g.jpg/)

Title: Re: G-PULTEC problems, please help!
Post by: gyraf on April 28, 2011, 07:28:36 AM
VERY good looking!
Title: Re: G-PULTEC problems, please help!
Post by: who on April 28, 2011, 11:54:42 AM
the panel is just in awe of your great circuit pcbs.

you can use the heel of hand to boost atten the hard positions by a fly and hear the clacks of the frequency knobs...
awesome sound on guitars, vocals,... everything. I love it!!

thank you very much
Title: Re: G-PULTEC problems, please help!
Post by: ChrisPbass on April 28, 2011, 01:46:53 PM
meet the twins

just tracked some test vocals with them and am pretty floored - great sounding units.

Nice looking build there, congrats!
Title: Re: G-PULTEC problems, please help!
Post by: Neily on May 06, 2011, 01:49:00 AM
That looks amazing....

Could someone explain to me how this can be built using only 1 toroidal? I see some gpultecs with 1, some with 2 and I'm confused. Sorry if it's a stupid question, I'm new....

I'm going to be building mine soon... I'd prefer to use only 1 if i could.
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on May 06, 2011, 07:04:18 AM
you use 2 wired back to back for a cheap off the shelf solution.

you use 1 if you can get a custom tranformer that gives you the secondaries you need, which may be a bit harder to find... or perhaps who is selling them in his shop?

If you go with one torroid it looks like some small changes are required to the PS board (at a glance i see only one recifier and an additional voltage reg)

IMO there is nothing wrong with using the 2 torroid solution. I mounted mine on the side of my case and have no noise despite the PS / Amp board being quite close. 
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on May 06, 2011, 08:58:03 AM
For a single-transformer you'll need two secondaries: A 8-12V 500mA and a 210-230V/50mA (or something around there), but as these are not easy to find off-the-shelf, we did the two-transformer-trick.

Actually, the later years it has become much easier to find ready-made heater/ht-voltage power transformers - some 15 years ago (when we made the GPultec) it was nearly impossible.

There are rectifiers on the pcb for both voltages, you can easily use the dual-secondaries trafo if you find it.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: mrcase on May 19, 2011, 07:13:31 AM
hey all!

Do you think it is possible with the gpultec to fry an input  on my AD (presonus firestation)??
because I experienced something strange:
I had my fine working pultec as an insert in my soundcard and all of a suddend it was quiet and my input was dead... ??? ???
Could it be that I had to much voltage on my gpultec`s out or something? or just a crazy coincidence?

thank you!
martin
Title: Re: G-PULTEC problems, please help!
Post by: who on May 20, 2011, 10:46:33 AM
That looks amazing....

Could someone explain to me how this can be built using only 1 toroidal? I see some gpultecs with 1, some with 2 and I'm confused. Sorry if it's a stupid question, I'm new....

I'm going to be building mine soon... I'd prefer to use only 1 if i could.

Hi Neily, thank you very much :)
the power trafo is a custom wounded trafo especially for the g-pultec project.
I tryed some different other trafos and came to the point to run a custom trafo production that fits perfect to this project.
You can get this trafo direct from me or at my lil online shop http://don-audio.com/g-pultec-power-trafo-sec-220v-9v-5V_2 (http://don-audio.com/g-pultec-power-trafo-sec-220v-9v-5V_2)
I build my third g-pultec now and with this trafo there are no noise or heat problems cause the 9v are better for the regulators than 12v. At the end you need 6,3v for the tube so 9v is the perfect match. 5v is a seperat winding for the led or 5v light bulb. This trafo can also be fixed horizontal and vertical in a 2HE case cause of its small size.
be careful with this high voltage project. But this is sounding awesome and worth all the work.
Title: rotary switches?
Post by: Songguy on May 21, 2011, 11:11:56 AM
hi all,

is there a preference over shorting vs. non shorting rotaries?

thanks for helping a noob.

chris
Title: Re: G-PULTEC problems, please help!
Post by: who on May 21, 2011, 04:13:58 PM
yes, there is  :)
http://www.groupdiy.com/index.php?topic=17938.0 (http://www.groupdiy.com/index.php?topic=17938.0)
Title: Re: G-PULTEC problems, please help!
Post by: Songguy on May 22, 2011, 11:30:40 AM
Does anyone have G-Pultec front panel measurements they can share?

chris
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on May 22, 2011, 12:23:09 PM
they are published, along with all other docs, on the Gyraf website.
Title: Re: G-PULTEC problems, please help!
Post by: frazzman on May 31, 2011, 07:49:16 PM
That looks amazing....

Could someone explain to me how this can be built using only 1 toroidal? I see some gpultecs with 1, some with 2 and I'm confused. Sorry if it's a stupid question, I'm new....

I'm going to be building mine soon... I'd prefer to use only 1 if i could.

Hi Neily, thank you very much :)
the power trafo is a custom wounded trafo especially for the g-pultec project.
I tryed some different other trafos and came to the point to run a custom trafo production that fits perfect to this project.
You can get this trafo direct from me or at my lil online shop http://don-audio.com/g-pultec-power-trafo-sec-220v-9v-5V_2 (http://don-audio.com/g-pultec-power-trafo-sec-220v-9v-5V_2)
I build my third g-pultec now and with this trafo there are no noise or heat problems cause the 9v are better for the regulators than 12v. At the end you need 6,3v for the tube so 9v is the perfect match. 5v is a seperat winding for the led or 5v light bulb. This trafo can also be fixed horizontal and vertical in a 2HE case cause of its small size.
be careful with this high voltage project. But this is sounding awesome and worth all the work.


This PSU looks great... currently gathering info and putting together BOM to start my own pultec project.... couple of questions... do you have a diagram for the PSU which describes which windings are which based on the colors, trying to work out the connections to the gpultec mainboard in my head.... also, any modifications need to be made to gpultec board to accomodate this PSU??? Thanks!
Title: Re: G-PULTEC problems, please help!
Post by: who on June 01, 2011, 05:04:59 AM
@frazzman
here is a diagram how to wire this trafo:
(http://img155.imageshack.us/img155/8075/gpultectrafoanschluss.jpg) (http://imageshack.us/photo/my-images/155/gpultectrafoanschluss.jpg/)

You can also wire it parallel for use in 110v countries.
(http://don-audio.com/bilder/produkte/gross/g-pultec-power-trafo-sec-220v-9v-5V_2_b4.jpg) (http://don-audio.com/bilder/produkte/gross/g-pultec-power-trafo-sec-220v-9v-5V_2_b4.jpg/)

I used a LED lamp with a 3k9 resistor. If you want to use the original fender 5v lamp bulbs you need no resistor.

(http://img194.imageshack.us/img194/8851/trafo220v9v5v.jpg) (http://imageshack.us/photo/my-images/194/trafo220v9v5v.jpg/)

all the best
"who"
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on June 01, 2011, 06:47:43 AM
Whats the additional offboard voltage reg in your pic? Is that required?
Title: Re: G-PULTEC problems, please help!
Post by: who on June 01, 2011, 07:43:31 AM
Hi snipsnip,
this is a 600v 6a rectifier (Vishay) that rectifies the ac current of those 220v wires more far away from the pcb to optimize the noisefloor. It replaces the onboard bridge-rectifier that rectifies your ac to dc. DC current does not radiate as much as AC does. So it is better putting +-220v dc into this pcb than rectifieing those 220~ ac on board near to the sensible parts. The 4u7 con and the xformers are very sensible to radiation. There are no problems with 9v ac - it can be rectified on board.
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on June 01, 2011, 09:13:29 AM
Interesting! Good Job.
Title: Re: G-PULTEC problems, please help!
Post by: Songguy on June 14, 2011, 11:27:08 PM
Hi all,

I'm having trouble finding the correct on/off rotary switch. Can someone suggest which one to get.

many thanks in advance!

Chris
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on June 15, 2011, 01:55:12 AM
Lorlin power switch, available from  e.g. RS
Title: Re: G-PULTEC problems, please help!
Post by: who on June 15, 2011, 10:18:59 AM
Product no is RMS1016  ;)


Title: Re: G-PULTEC problems, please help!
Post by: Songguy on June 15, 2011, 02:57:40 PM
Hi G and Who! Thanks for your replies.
Who, looking forward to that g-pultec torroidal.
Btw anyone have know where I can get that 5 volt pilot lamp assembly?
Thanks again,
Chris
Title: Re: G-PULTEC problems, please help!
Post by: MicDaddy on June 15, 2011, 03:37:09 PM
Where would be the best spot to stuff a VU (and if necessary a buffer)?

Just prior to output XLR?

I've an old Ampex VU that I'm thinking of repainting and adding to the G-pultec if only for some 'ooo aaaah'.

Also, I'm thinking of mounting the tube off of the pcb.  What are any things to be cautious about?
I'd like to mount it in a way to be viewable through a small window similar to how ART does the tube MP.
Title: Re: G-PULTEC problems, please help!
Post by: who on June 22, 2011, 10:49:25 AM
where I can get that 5 volt pilot lamp assembly?

you can get those Fender lamps from banzaimusic or if you like, i have a lot of them here too. Just give me a mail.
But be careful not to buy those chinese plastic fakes. They should be glass and metal.  :)
Title: Re: G-PULTEC problems, please help!
Post by: MicDaddy on June 29, 2011, 03:41:07 AM
after some time troubleshooting I have the g-pultec working great with no hums or other issues (so far through a brief vox/bass test) 

The thing is just amazing simply cranking a pre and listening to the noise floor while playing with the knobs.

Used the same power transformer as audiophreak but ended up using a pot to drop down to 6.3. 

I mounted the tube off of the pcb and cut some slits so that it can be viewed while glowing (you cannot really see it so it was kind of a dud idea)

Also, I do have the VU tied to the output XLR but the meter just does a funny dance near zero and only jumps up on loud transients, and then slowly releases back to zero.  If this needle would dance with the level out it would be friggin cool looking.  Anyone care to shed some light on how to configure a VU?

Did all the metal work myself with a 2mm steel Hammond 3RU very very shallow enclosure.  I ended up mounting the power transformer on the back of the exterior of the case.  The front panel is my first and turned out so so.  The VU was a pain in the ass, the metal work in general has been a learning experience.

The only issues I have are with my High Freq 2x6 and High Shelf Freq 2x6, since mounting the board to the front panel these two switches now want to go twice around the horn, so twelve positions.  It seems to still function in this configuration but to no benefit and only confused the hell out of me for awhile.  So that will need to be corrected.

Overall was a good build, would have been smooth sailing if I had just purchased a case.

Title: Re: G-PULTEC problems, please help!
Post by: gyraf on June 29, 2011, 05:13:34 AM
If it is a real VU-meter (AC-reading, internal rectifier), you simply connect it across your output, with a 3K9 resistor in series with the +side of the meter, and it will read 0VU for a +4dBu signal level.

If it's not a real VU-meter, but a DC-reading meter, you'll need to add a diode bridge of four low-forward-voltage Ge-diodes (and hope that sensitivity is somewhere around what you want).

BUT - both these solutions will add distortion to the unit, so better make it switchable.

(I really don't see the need for a VU-meter on a unit like this, other than the good looks)

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: MicDaddy on June 29, 2011, 10:47:20 AM

(I really don't see the need for a VU-meter on a unit like this, other than the good looks)


Absolutely,  thanks for the tips Jakob... I'm really not sure if this is an AC/DC reading meter, it was cannibalized from an Ampex 1260 reel.  I see no passive components internally, it simply looks like a needle and some coil windings. 

I shall try the 3K9 in series with the + side, I have assumed so far + terminates to pin 2 of the output, and the - side to tie to pin 3?  Thanks for the tip on the switch.

This was my first valve circuit and I cannot thank you guys in this thread enough.  I've learned a lot more about power-supplies during this build than I've ever had to know.

Seeing that GE start to glow amber was very satisfying thanks again to Jakob and everyone who has contributed to this thread.  And especially to audiophreak (I have been stalking your picasa for weeks) I liked what you did with one transformer and I ran with your idea.  Thanks to Kingston for the KISS principle on recommending the simple dropping resistor.

I still need to powder coat my front panel, and airbrush all the pad printing.
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on June 30, 2011, 10:19:38 AM
Micdaddy , Thanks for the kind words ,  Glad to hear of your success  :)
 
  .. on the  " View Window "  for the tube - I've seen a few units with this and found they " Back Light " the tube in the box so it can be seen through the " Window " -  maybe a little 6v incandescent or one of those " Warm " LEDs behind the tube opposite the window ? 

   Congrats !!    .. and lets see some pics   ;D   
Title: Re: G-PULTEC problems, please help!
Post by: MicDaddy on June 30, 2011, 06:49:38 PM
what color to paint this thing? 

My only complaint is the physical buzz from the power transformer.  bzzzzzzzzzzzz   I'll need to play around with how it is seated.

pretty ugly to look at now but it sounds very lovely, studio tests tonight..

First time for metal work, not sure if I'll be doing any more of that.  XLRs weren't too bad, it was cutting the round hole for the VU that drained my will.  2mm steel might have also been a factor, perhaps a more light-weight chassis and aluminum panel would have been a breeze?

Just need to dremel the high cut pot to match the others and get everything painted, and knobs, gotta have knobs.
Title: Re: G-PULTEC problems, please help!
Post by: shabtek on June 30, 2011, 09:50:46 PM
nice mic :P :P
Title: Re: G-PULTEC problems, please help!
Post by: MicDaddy on June 30, 2011, 09:57:39 PM
nice mic :P :P

it sounds so nice through the eq, wow
Title: Re: G-PULTEC problems, please help!
Post by: idylldon on July 14, 2011, 01:21:45 PM
Can someone tell me what the frequencies are for a Gyraf Pultec using ioaudio's inductor?  I've looked through all the threads and discussions about the math behind it all, but I never saw a final result.  A pic of someone's front panel would be fine as well.  I'm currently working on designing my panel and would like to get it right.

Also, I bought these as unfinished units and they've needed to be completely rewired.  The power transformers included are Triad FS12-1000 and Amveco 62062.  Unfortunately, both of these are rated at 1A @ 12 volts so I'm assuming I need to get some 1.5A 
transformers? 

Thanks,
--
Don
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on July 14, 2011, 05:34:39 PM
Hi Don,

   Check this link -  http://www.groupdiy.com/index.php?topic=32839.0

  also , if you're doing separate units - check the tube data sheet - but i think the heater draws about 400mA  and B+  is 15-25 mA   - so I think your good for a single channel  ,  a dual unit may be pushing it on the heater side of things. 

also , this forum member has some good info - http://blog.benlindell.com/
Title: Re: G-PULTEC problems, please help!
Post by: mitsos on July 14, 2011, 05:40:09 PM
Just stick the L and C values here:
http://circuitcalculator.com/lcfilter.htm

or here:
http://www.deephaven.co.uk/lc.html

there are others where you can plug any two of F, L and C and get the third.  Or you can do it the old fashioned way
F= 1 / [2pi * sqrt(LC)]

Also, I think Gyraf.dk has front panel designs for all the DIY projects.  Keep in mind that F doesn't change only because of L, it is also dependent on C.  So you can tweak them both to hit whatever frequencies you want.  I'm terrible at explanations, but it's really pretty simple. 

I don't know the power requirements of the gpultec amp though, sorry.

but hey, maybe you can ask this guy:
http://www.groupdiy.com/index.php?topic=44779.0
 ::)

good luck!
Title: Re: G-PULTEC problems, please help!
Post by: idylldon on July 14, 2011, 05:43:35 PM
Hi Don,

   Check this link -  http://www.groupdiy.com/index.php?topic=32839.0

Thanks!  I looked that over but kind of went cross-eyed.  I'll have another careful look at it.


Quote
also , if you're doing separate units - check the tube data sheet - but i think the heater draws about 400mA  and B+  is 15-25 mA   - so I think your good for a single channel  ,  a dual unit may be pushing it on the heater side of things. 

I'm building two separate units and I thought 1.5 seemed to be overkill for the tube requirements but I thought I'd double check with those who have already got theirs up and running. 

Quote
also , this forum member has some good info - http://blog.benlindell.com/

I will check that out as well.

Thanks!

Cheers,
--
Don
Title: Re: G-PULTEC problems, please help!
Post by: idylldon on July 14, 2011, 05:45:01 PM
Thanks, mitos!  I'll check that calculator out.  Seems like a good way to do it.

Cheers,
--
Don
Title: Re: G-PULTEC problems, please help!
Post by: Majestic12 on July 14, 2011, 06:31:06 PM
Does anybody know where I can get the original bypass switch that fits the collective case 3 HE frontpanel ? I'm looking for a while now.
Title: Re: G-PULTEC problems, please help!
Post by: MicDaddy on July 15, 2011, 02:02:19 AM
Just wanted to chime in and thank Chip for the help with some issues I've experienced this build.

Swapped out a faulty power transformer and this thing is very quiet now.  I was prepared to live with the hum, but this thing is 100x better, sounds so nice.  Played around with it just talk testing through a dynamic mic, for literally over an hour.  Can get tones from speakerphone all the way to voice of God with the gpultec.  I couldn't be more happy with it.

Also thanks to Jakob for helping with getting the VU set up properly.  This specific meter had no internal diodes or other circuitry.  I added one diode on the + side and now the meter works great.  The change in tone with/without meter is negligible.  What happens if I replace the diode with an LED and mount it in a hole to be drilled in the VU faceplate?   Would it light up as signal passes through it?
Title: Re: G-PULTEC problems, please help!
Post by: Majestic12 on July 20, 2011, 06:05:56 PM
Do I have to change anything in the power supply when using the Don Audio transformer with 9V output ?
Title: Re: G-PULTEC problems, please help!
Post by: who on July 21, 2011, 09:20:39 AM
Do I have to change anything in the power supply when using the Don Audio transformer with 9V output ?

nothing to change. just put both cables to the destined connectors.
(http://www.don-audio.com/bilder/produkte/gross/g-pultec-power-trafo-sec-220v-9v-5V_2_b3.jpg)
Title: Re: G-PULTEC problems, please help!
Post by: Majestic12 on August 03, 2011, 09:07:54 AM
I fired up one of my two builds today and realized that the 250V anode voltage was only 50 V. After tracing the voltage, I noticed that the mains transformer only provides 50V instead of 220V (I'm using the don audio transformer with 9V/5V/220V secondaries). 6,3V and 5V are both correct, so I guess that I have a faulty transformer.
I'm changing it for my second one I have, let's see if it works.


EDIT: The second transformer works as it should. 220V on the secondary side. But the anode voltage is 320V after the 3K3 2W resistor.. What am I doing wrong ?


EDIT2: Changed the 3K3 to 15K, but it's not enough. Will try to use a 30K to get the voltage down to 250V. Don't know why the voltage is that high.
Title: Re: G-PULTEC problems, please help!
Post by: Majestic12 on August 03, 2011, 03:53:03 PM
Even when it doesn't work properly yet, it already looks beautiful :)

(http://i55.tinypic.com/259lguv.jpg)
Title: Re: G-PULTEC problems, please help!
Post by: Majestic12 on August 04, 2011, 08:15:54 AM
Changed the 3K3 resistor to a 100K resistor and still having 300V HT voltage. What the heck is wrong? Can't seem to get the voltage down to around 250V. Could it be the tube?

Title: Re: G-PULTEC problems, please help!
Post by: MicDaddy on August 04, 2011, 11:00:45 AM
FWIW I used a 33K, and my secondary was showing 289VAC before rectification.

What AC voltage is your secondary showing before rectification, and after rectification?  What kind of tube are you using?

Your front panel is a lot prettier than mine  :'(
Title: Re: G-PULTEC problems, please help!
Post by: Majestic12 on August 04, 2011, 02:33:26 PM
I'm voltages (after 5 minutes warm-up)

AC Inputs rectifier:     240V (slightly high....transformer has 220V written on it)
AC Input to ground     125V

DC after rectifier:       330V
DC after resistor (now at 100K):  275V     
Heater Voltage:           6,03V

Voltage on 4u7 dc coupling cap:    101V

I'm using the don audio transformer and a JJ 12AX7 (ECC 83S) tube.
Title: Re: G-PULTEC problems, please help!
Post by: MicDaddy on August 04, 2011, 04:24:56 PM
I'm not familiar with the ECC 83S, I used ECC88  Could be the tube causing you problems??
Isn't that a 12AX7??   :o

I believe anode current is quite different on the ECC83?

I'm no tube guy, so I'm gonna sit this one out and let somebody else step up.
Title: Re: G-PULTEC problems, please help!
Post by: PeteC on August 04, 2011, 05:03:06 PM
No expert here - but if your not getting voltage drop with bigger power supply resistor then it sounds to me like there is not enough/no current being drawn by your tube stage - if there was then you would get the corresponding V=IR drop across this resistor.  Sounds like a problem with your tube or the cathode circuit maybe ?

measure round your tube circuit and report back - someone more experienced will step in ...

I am yet to build mine so cant measure typical voltages and calculate current draws.

Rgds
Pete



Title: Re: G-PULTEC problems, please help!
Post by: PeteC on August 04, 2011, 05:17:00 PM
just noticed you're using an Ecc83 - not 88 - a very different tube.

you need 6Dj8/Ecc88/E88CC/CV2943

Rgds
Pete


Title: Re: G-PULTEC problems, please help!
Post by: Majestic12 on August 04, 2011, 05:17:40 PM
That's it....I'm such a stupid guy. Used a ECC83 (12AX7) instead of an ECC88. Must have read the schematic wrong (it's hard to read the .gif files on Gustavs website). Confused 88 with 83.....


Changing the tube should fix it, thank you guys :)
Title: Re: G-PULTEC problems, please help!
Post by: PeteC on August 04, 2011, 05:35:13 PM
Let us know !!

hope it works out for you.

Pete
Title: Re: G-PULTEC problems, please help!
Post by: Majestic12 on August 05, 2011, 07:38:23 AM
Problem solved. After swapping the tube for an ECC88 and setting the resistor to 15K I got 252 V HT voltage.
Unit seems to work as it should, there is only a slight bass roll-off at around 40Hz even when turned to bypass and with attenuators turned down.


(http://i55.tinypic.com/23t4ins.jpg)
Title: Re: G-PULTEC problems, please help!
Post by: Songguy on August 05, 2011, 07:03:09 PM
Hi all,
Potentiometer question:
Will I have any problems if I use a 10k audio taper pot rated at 200v instead of 500v?

Many Thanks,
Chris

Title: Re: G-PULTEC problems, please help!
Post by: Majestic12 on August 06, 2011, 04:18:28 AM
No, shouldn't be a problem.
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on August 06, 2011, 08:25:49 AM
  Hey  Majestic12 ,  got this from a few pages back , thought you might benifit from it , I think I have my B+ sitting about 238vdc .



Does the higher voltages for the HV+ matter?  I'm trying to understand what it does and why the 30-40V difference would matter.


It matters - because we're already stretching the ECC88's voltage capability to the edge (it's anode voltage is rated some 90-120V depending on what datasheet you consult)

Ca. half of our HT voltage appears across each half of the ECC88 - so the suggested 250V HT shouldn't be exceeded by too much.

On very-high-overvoltage units, there is a tendency of premature burn out of the tube.

Adjust voltage by trying different value resistors between resevoir caps - circuit sounds good between 200 and 250V.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: keefaz on August 06, 2011, 08:32:41 AM

Unit seems to work as it should, there is only a slight bass roll-off at around 40Hz even when turned to bypass and with attenuators turned down.

Is there the same bass roll-off when you connect the output of your 1176 comp in the gpultec input (eg connect the 1176 between your sound source and gpultec) ?
Title: Re: G-PULTEC problems, please help!
Post by: PeteC on August 06, 2011, 09:20:57 AM
just curious .....

has anyone tried messing with LED cathode bias or a CCS in the tube stage of the G-Pultec ?
I've used these on my audio and guitar amps with success - just wondering really before I start to build my pair.

Rgds
Pete
Title: Re: G-PULTEC problems, please help!
Post by: benlindell on August 14, 2011, 03:38:58 PM
Where's the best spot to take power for a 6.3V lamp?
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on August 14, 2011, 05:05:43 PM
Hi Ben ,
          I used an LED for less current draw and soldered leads to the tube socket pins for the heater under the PCB. 
 
Title: Re: G-PULTEC problems, please help!
Post by: snipsnip on August 14, 2011, 05:38:46 PM
Where's the best spot to take power for a 6.3V lamp?

you can just take it straight from the secondary and drop it with a 2 watt resistor.
Title: Re: G-PULTEC problems, please help!
Post by: benlindell on August 14, 2011, 08:12:26 PM
Where's the best spot to take power for a 6.3V lamp?

you can just take it straight from the secondary and drop it with a 2 watt resistor.
What value resistor? I'm not so hip with my formulas.
Title: Re: G-PULTEC problems, please help!
Post by: idylldon on August 14, 2011, 09:56:05 PM
Where's the best spot to take power for a 6.3V lamp?

you can just take it straight from the secondary and drop it with a 2 watt resistor.
What value resistor? I'm not so hip with my formulas.

Use Ohm's law.  Piece of cake.

Cheers,
--
Don
Title: Re: G-PULTEC problems, please help!
Post by: benlindell on August 14, 2011, 11:00:02 PM
So 6.3v and .15amps means around 42ohms right?
Title: Re: G-PULTEC problems, please help!
Post by: Majestic12 on August 15, 2011, 08:02:04 AM
R=U/I

6,3V/0.15A = 42 Ohm

But 150mA current only for the lamp seems much. Don't know if the regulator can handle the current.
Title: Re: G-PULTEC problems, please help!
Post by: PeteC on August 19, 2011, 11:24:39 AM
quick question ...
I'm building 2 G-Pultecs,

I have all my parts ordered and in my stash except for the 4.7uF output coupling caps

I have some very nice 2.2uF caps surplus from a hifi project - could I sub these without loss of low freq signals on the output or will this be detrimental to the sound ??   ( I only have one for each EQ though otherwise I'd try to pair them up to get 4.4Uf.  )

Dont want to compromise the units as I'm using gold pin mullards for the SRPP stages.

Any advice very welcomed - especially help to understand how the cap value affects the freq - I'm not sure which resistance in the output circuit  is reacting with the cap for the RC value 

cheers
PeteC
Title: Re: G-PULTEC problems, please help!
Post by: PeteC on August 21, 2011, 05:06:42 AM
bump..sorry..... can anyone help me out on this ?

Cheers
PeteC
 
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on August 21, 2011, 09:58:56 AM
try this  -  http://www.muzique.com/schem/filter.htm

 
Title: Re: G-PULTEC problems, please help!
Post by: PeteC on August 22, 2011, 06:39:12 AM
thanks - I'll play around with that -

still not sure what the impedance of next stage is - ie the impedance looking into the Lundhal output TX and loading of next piece of kit.
Rgds
Pete

Title: Re: G-PULTEC problems, please help!
Post by: PeteC on August 22, 2011, 01:19:52 PM
Can anyone help me here ........
I'm building 2 G Pultecs at the moment from Gyraf's excellent resource.

today my neighbor helped me develop and etch all 4 boards for both units.

The 2 main boards ( PSU and tube stage ) went great - but we hit problems trying to get the filter boards to etch properly due to the position of 2 very close traces at the edges of the boards

His solution is for us to edit the layout so we have more space to play with ( and seing as he is doing all the helping out for me I cant really argue with that - so after a couple of aborted attempts we stopped using more photo resist board.

Question is - does anyone have an editable version of the pcb layout I could edit to move tracks around ?

I realise that many of you will have been able to etch the boards,  just as they are designed , quite successfully - but we had some problems with the closeness of these 2 tracks.

Can anyone advise on a way to overcome this or a way to convert and edit the pdf? Or is there an Eagle version etc somewhere ? 

All help much appreciated. - Cant wait to get these units built and running in my set up.

Rgds
PeteC
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on August 24, 2011, 09:16:22 AM
What I usually do with this type of problem is simply to cut the remaining unwanted copper with a sharp knife..?

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: Majestic12 on August 24, 2011, 10:09:58 AM
My second Pultec is ready. This one is for a friend of mine. Looks as beautiful as the first one :)

(http://i51.tinypic.com/2ladg7q.jpg)

(http://i51.tinypic.com/34ss5r6.jpg)
Title: Re: G-PULTEC problems, please help!
Post by: MicDaddy on August 24, 2011, 12:21:41 PM
 8)

Lookin' good, nice and clean Majestic
Title: Re: G-PULTEC problems, please help!
Post by: Majestic12 on August 24, 2011, 12:27:39 PM
BTW, is there a specific reason why the bypass circuitry is the way it is? Wouldn't it be much easier and better to use a switch to simply switch the Input directly to the output?
In the Gyraf circuit, the the bypass doesn't prevent the signal from going through the transformers and gainstage.
Title: Re: G-PULTEC problems, please help!
Post by: MicDaddy on August 24, 2011, 02:41:53 PM
I like the signal in bypass  :D
Title: Re: G-PULTEC problems, please help!
Post by: PeteC on August 24, 2011, 03:56:15 PM
Jakob,
thanks - you're right of course - redrawing the board is a rather extreme solution to the problem.

In the end as we botched up 1 of the filter boards I have hand re-drawn it and etched - its electrically sound even if it looks a little amateur.

BTW - thanks for putting such great projects in the hands of keen hobbyist engineers like myself who are really musicians. its much appreciated.  My GGSL is a great bit of kit - so I cant wait to complete the 2 G-Pultecs.

Thanks again
PeteC


 
Title: Re: G-PULTEC problems, please help!
Post by: Songguy on August 24, 2011, 08:46:39 PM
Hi guys,

If I wanted to add an unbalanced 1/4 input to my g-pultec is it really as simple as wiring it to the board and mounting the  jack?
Cheers,
Chris
Title: Re: G-PULTEC problems, please help!
Post by: Majestic12 on August 25, 2011, 03:21:53 AM
Yes, that's all you need to do.
Title: Re: G-PULTEC problems, please help!
Post by: PeteC on August 26, 2011, 03:39:45 PM
Just finished etching and drilling the last of my 4 boards for the G Pultec pair I am building - getting very excited - Like a big kid again .. ;D

Pete
Title: Re: G-PULTEC problems, please help!
Post by: karloff70 on September 07, 2011, 12:16:37 PM

Hi chaps....

I bought a diy Pultec off someone and it is rather 'ghetto'.....and has issues that I can not grasp. The main one at the moment is it powers up ok, works initially (valve glows, if not very much...) then gradually over the next minute or two it stops glowing and descends into thin distortion and out........any clues/ideas would be appreciated very much!
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on September 07, 2011, 02:31:00 PM
Hi,
     I'm still very much a newb , but I might put a DMM on the B+ ( could check it at the tube side leg of the 3k3 2w resistor )  to see if that stays stable ( should be around +245vdc ).  Then check the heater voltage if it satys stable  ( could be checked at the middle pin of the regulator - should be around 6.3vdc ). If all of that checks out, try swapping  in another tube .

  Hope this helps - BE CAREFUL  !!

 
Title: Re: G-PULTEC problems, please help!
Post by: ncoak on September 07, 2011, 03:37:08 PM

Hi chaps....

I bought a diy Pultec off someone and it is rather 'ghetto'.....and has issues that I can not grasp. The main one at the moment is it powers up ok, works initially (valve glows, if not very much...) then gradually over the next minute or two it stops glowing and descends into thin distortion and out........any clues/ideas would be appreciated very much!

possibly too small a heatsink on the regulator - someone had a similar issue on the first page of this thread.
Title: Re: G-PULTEC problems, please help!
Post by: karloff70 on September 07, 2011, 05:11:40 PM
Thanks guys!! I'll measure (carefully...) and get a bigger sink, as the one in there is indeed smaller than e.g. the one in the Pultec earlier on this page.........hmmm, makes me think the seller told me porkies, as if that is the case the thing would never have been happy as is.....
Title: Re: G-PULTEC problems, please help!
Post by: PeteC on September 18, 2011, 03:24:13 AM
Hi All,
Another one is born ....and its twin is nearly here too.....
I just completed the first of my pair of G-P's and its working fine first time  ;D

Just the artwork to do now.

Does anyone have any ready-made panel artwork that has the frequencies on it ?  I'm using Mac OSX


The second G-P just needs the case drilling now and final wiring.

So thanks to Jakob and this fantastic forum, I now have a GSSL  and 2 G-P's in my project studio, and have etched the boards for a Dual Green pre.  Also on the list is a DIY Tube Mic, but I may have to sell some gear to buy a good capsule i think.

Meanwhile any help on artwork much appreciated, I'm using Lazertran Injet on Black panels.

Cheers
PeteC
Title: Re: G-PULTEC problems, please help!
Post by: Nick Franklin on September 18, 2011, 04:51:42 AM
Hi Pete,

PM me your email and I'll send you the artwork. I've got tons of advice for using the lazertran product too.

Nick

Hi All,
Another one is born ....and its twin is nearly here too.....
I just completed the first of my pair of G-P's and its working fine first time  ;D

Just the artwork to do now.

Does anyone have any ready-made panel artwork that has the frequencies on it ?  I'm using Mac OSX


The second G-P just needs the case drilling now and final wiring.

So thanks to Jakob and this fantastic forum, I now have a GSSL  and 2 G-P's in my project studio, and have etched the boards for a Dual Green pre.  Also on the list is a DIY Tube Mic, but I may have to sell some gear to buy a good capsule i think.

Meanwhile any help on artwork much appreciated, I'm using Lazertran Injet on Black panels.

Cheers
PeteC
Title: Re: G-PULTEC problems, please help!
Post by: PeteC on September 19, 2011, 05:19:54 PM
Hi All,

a bit deflated tonight as I tested the first of my newly finished G-P's as an insert on some tracks in Mixbus.

I seem to be getting a lot of distortion when using the unit as an insert. Especially from the low boost. In fact the unit only seems to stay clean if the sends are quite low.

How do I go about testing to see if its my sends and return that are too hot - or whether I have a problem with my unit.
It sounds like blocking distortion so I'm wondering whether my caps are OK etc etc 

Not sure where to start so any advice on a methodical approach to tracking the issue down would be great.   I'm using allegedly good Mullard NOS ECC88's so I'm hoping the tube is good . I will try subs to see what gives.

Any help much appreciated - a lot of late nights have gone onto building these EQ's !!!

Rgds
Pete
 
Title: Re: G-PULTEC problems, please help!
Post by: Nick Franklin on September 19, 2011, 05:59:49 PM
Are the tubes you're using definitely good?
Title: Re: G-PULTEC problems, please help!
Post by: PeteC on September 19, 2011, 06:07:17 PM
I think so Nick ,

I just swapped one for an E88CC - and exactly same voltages and symptoms -

after a bit of testing I noticed that my HT is sitting at 279v and heaters at 6.23 v -   so I think I ned to drop another 30V or so across the power supply.

I'm reading 18v across the 3k3 resistor so reckon drawing 5.45ma , to drop another 30v i think i need another 5K5 or so resistance to get under 250V for the HT

I wonder whether this is the problem ? would a too hot HT show these issues ?

I just ran some tracks in mixbus, and found that with the sends all down low then the blocking distortion was gone, and the EQ sounded great - maybe I'm just to hot with te faders on my mixes usually !?

Still concerned that there is something wrong with a cap in my filter section though.

PS thanks Nick for the great help earlier on teh panel graphics - really really helpful - much appreciated.

Rgds
Pete


 
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on September 20, 2011, 02:55:01 AM
I'm pretty sure that you have a level problem.

What sort of levels are you feeding the eq with?

The GPultec output stage is happiest running the old-fashioned standard +4dB as in analogue tape recorders, which means some 10dB headroom above this before nasty sneaks in.

Try to output a 100Hz full-level sinewave from your system, and verify with a multimeter that it's not much more than +14dB - ca. 3.9V AC

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: PeteC on September 20, 2011, 03:14:42 AM
thanks Jakob,  I will try that

I forgot to add that I'm running unbalanced inputs at moment until i get more LL5402's for each unit

I'm sending out from MIxbus on my Mac into an Edirol FA-101 interface , and then using the send and returns on the interface.
I dont know what levels the signals are usually but will check the peak AC on the send leg to see what I'm feeding the EQ.  Its been fine with my GSSL.

meanwhile i will add some more resistance to the dropper between the two caps. At the input leg of the 3K3 I'm reading 297v and 279 at the output leg at the moment.

Rgds
Pete
 
Title: Re: G-PULTEC problems, please help!
Post by: PeteC on September 20, 2011, 04:57:21 AM
Jakob,

I downloaded a 100Hz sine wave test tone and normalised it in Mixbus

the send is measuring 2.27v AC on both the hot and cold legs of the balanced out.

seems well within the ac signal voltage.
maybe something else going on then ?

Rgds
Pete
 
Title: Re: G-PULTEC problems, please help!
Post by: PeteC on September 20, 2011, 06:06:15 AM
more....
with an incoming signal at c. 2.27v when the bass boost is up I'm getting an output signal over 4v ac from the EQ - this seems to be overdriving the return input of my audio interface.

maybe my HT is too high and I'm getting too much gain from the tube stage ?

Rgds
PeteC

 
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on September 20, 2011, 06:10:49 AM
..balanced AC voltage is measured between hot and cold (XLR pins 2&3) - is that how you measured it?

Also, remember that the unit will boost selected frequencies up to some 20dB at full-boost.

If it sounds right with no low-boost, but sounds ugly when boosting, it'll be a result of levels exceeding the working range of the unit (as the filters can't and won't add distortion).

Try measuring output level of the unit when it sounds bad?

Alter your operating levels till it sounds right?

Jakob E.

edit/ps: higher HT voltage won't affect unit gain, only potentially shorten tube life.
Title: Re: G-PULTEC problems, please help!
Post by: PeteC on September 20, 2011, 06:57:37 AM
Hi Jakob,   thanks for your help and advice so far...

I have unbalanced input at present - input voltage at 2.2v ac

measuring across the hot and cold of balanced output I'm seeing following voltages.

with low boost down and Low freq control down I see 1.73vac
with low boost full up and low freq still down i see 2.37vac

but when i turn up the low freq switch we quickly get gain .....

with low boost control fully on here are the voltages at the different low freq switch positions

1 : 2.37vac
2 : 3.94 vac
3 : 5.26 vac
4 : 6.39 vac
5 : 8.31vac
6 : 9.86vac

is this what you'd expect from a properly working unit ?

many thanks
PeteC

Title: Re: G-PULTEC problems, please help!
Post by: gyraf on September 20, 2011, 07:00:57 AM
figures seem to be in the right area

try setting up your system to lower output levels

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: PeteC on September 20, 2011, 07:09:19 AM
thank Jakob,

I just ran pink noise test out from mixbus at just under 1vac  and swept everything - sounds very good

i think it is a levels problem as you said right at the start
this is configurable in Harrison MIxbus so no problem to adjust send levels
thanks for helping me get there in the end, and getting confidence that my build is OK.

now to finish the other channel EQ !

Rgds
PeteC



Title: Re: G-PULTEC problems, please help!
Post by: PeteC on September 20, 2011, 08:06:57 AM
added a 4.7K 2watt resistor to the 3k3 dropper to get under 250v to prolong tube life

Rgds
PeteC
Title: Re: G-PULTEC problems, please help!
Post by: MicDaddy on September 20, 2011, 12:18:58 PM
hey PeteC, sounds like you're about to be rocking with your pair of eqp-1a.   Don't relish too much  8)

Something maybe worth noting, I've found my G-pultec does not like to drive certain other pieces in the chain specifically the 1176 shown in the photo.  If I stack them the other way around it sounds beautiful.  I've read of dropping a 600 across the output, but have not tried that or if that is even appropriate in this application.

Ended up commissioning Dan of collective cases for one of his 2RU chassis, and ever so glad I did.

Thanks again Dan,

Just waiting on the Jewel and the on/off switch
Title: Re: G-PULTEC problems, please help!
Post by: spase on September 20, 2011, 02:36:56 PM
where i can find that edcor adapter pcbs for this project?
Title: Re: G-PULTEC problems, please help!
Post by: PeteC on September 20, 2011, 02:50:31 PM
thanks MicDaddy

where do i find more info about strapping a 600 across the output ?  - I'm guessing you mean 600ohms ? sorry to be a bith thick as we say here in Yorkshire  ;D

cheers
PeteC

Title: Re: G-PULTEC problems, please help!
Post by: PeteC on September 20, 2011, 03:16:31 PM
one last question ( honest , .....at least for now )

embarrassingly I drilled an extra hole in my Gpultec faceplate when I was using the Gyraf template - to the left of the on/off switch

now I'm wondering whether I can use this to advantage - say for a phase switch or something - anyone care to make a suggestion ( apart from drill it right next time you fool.......) ?

cheers
Petec
Title: Re: G-PULTEC problems, please help!
Post by: sonicwarrior on September 20, 2011, 03:20:03 PM
where i can find that edcor adapter pcbs for this project?

I have 8 as I'm using the Lundahls now instead of the XS1100. But I'm from Germany so if you are not from Europe this wouldn't make much sense.
Title: Re: G-PULTEC problems, please help!
Post by: spase on September 20, 2011, 03:32:55 PM
where i can find that edcor adapter pcbs for this project?

I have 8 as I'm using the Lundahls now instead of the XS1100. But I'm from Germany so if you are not from Europe this wouldn't make much sense.

Im from Macedonia.In Europe :)
Title: Re: G-PULTEC problems, please help!
Post by: Celf on September 21, 2011, 02:16:43 PM
I have two questions

1: The heater doesn't seem to be elevated. Odd?

2: Can I get a 185vac (40mA) & 6.3vac transformer to work? For example, lowering the b+ RC resistor from 3k3 to 1k, and a voltage doubler for the 6.3vac before the LM317?
Title: Re: G-PULTEC problems, please help!
Post by: MicDaddy on September 21, 2011, 08:09:20 PM
Looking for a USA source for a suitable power on/off switch.   :'(

Majestic12 helped me with the Lorlin RMS1016 which Allied carries but has no stock.

Nothing suitable at radioshack  ::) or my local hardware  :P    any pointers would be appreciated.

Thanks!!   :D
Title: Re: G-PULTEC problems, please help!
Post by: sonicwarrior on September 22, 2011, 02:08:53 PM
@MicDaddy:
I have a similar problem and found this today:
http://www.groupdiy.com/index.php?topic=23458.msg279568#msg279568

I'll try the RMS1035 as Mouser has them in stock now (the linked thread is from 2007).
Title: Re: G-PULTEC problems, please help!
Post by: Celf on September 26, 2011, 06:04:39 AM
Anyone knows why the heater isn't elevated?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on September 26, 2011, 07:59:23 AM
The design does not elevate the heater - reason is to keep things simple.

You can easily try to lift the FF voltage if you like, but I haven't found it giving any significant benefit in real-life.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: schrobbelbop on October 18, 2011, 05:56:32 AM
Hi All!

Please help!!!

Im building a stereo pultec in a purusha case. But when i hook up 2 srpp board we have a hum! 50 hz and harmonics...
when i cut off 1 heater supply from 1 board it dissapears!
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on October 18, 2011, 07:15:37 AM
We do not recommend multiple G-Pultecs sharing the same case.

It's hard to tell what might be wrong without knowing details of your construction: Do you have individual supplies for the two amplifiers, or are you sharing one - and in that case, how? Is it a known-working solution, used by someone else also?

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: sonicwarrior on October 18, 2011, 01:19:31 PM
But when i hook up 2 srpp board we have a hum! 50 hz and harmonics...

Please search the thread. You are not the only one with this problem and several solutions have already been posted.
Title: Re: G-PULTEC problems, please help!
Post by: schrobbelbop on October 18, 2011, 01:33:35 PM
i've searched the forum, but what helped was playing around with grouding.

my sollution:  Connected the ground from each input together, and then to IEC ground, and give the toroid a turn and the schield around.
now it's just a slight 100 hz humm but almost not hearable with my monitors at unity gain.

people discharge the caps before you do anything... it hurts ALOT ;)
Title: Re: G-PULTEC problems, please help!
Post by: spase on November 06, 2011, 01:10:43 AM
can i use any of this power transformers here? - http://www.musikding.de/index.php/cat/c277_Toroidal-transfomer.html

Thank you
Title: Re: G-PULTEC problems, please help!
Post by: MicDaddy on November 18, 2011, 04:17:55 PM
Hello again,

back to the question of strapping 600 Ohm across the G-Pultec output....

I've found sometimes I want to put the G-Pultec in front of either 1176 (for whatever reason).  The 1176 has 600 Ohm front end and does not play nice with the G-Pultec terminated to the front end ie: hum poor tone/level etc...

If I am to strap 600 Ohms across the output, do I lose anything sonically when I use the G-Pultec on other devices that have or want to see a higher impedance load?

Should I just make up a cable/adapter to use when I want to put the G-Pultec in front of the 1176 instead of making a permanent mod with the resistor across the output?

I think I just answered my own question and will try to rig up a simple cable that will have the 600 Ohm resistor.  Is there a downside to doing it this way?

Thanks everyone for your always helpful support!!   8)
Title: Re: G-PULTEC problems, please help!
Post by: frazzman on December 12, 2011, 05:22:06 AM
Hey all  bout to build a couple of units of these, just wondering how essential the input tx is? Apart from it facilitating the balanced input are there any other benefits, does it impart any character? I thought given the input an output tx are the same that maybe I can do away with the input tx? Anyone compared, what's the verdict ?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on December 12, 2011, 07:41:02 AM
No real problem in building it without input transformer - most (though not all) of sonic signature is from output transformer.

But for balanced input operation, you'll need it.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: dan kelly on January 08, 2012, 11:43:15 AM
Hey everyone. I've been desperately trying to get this baby up and running on my own and have read these 14 pages over and over but finally must admit defeat. I'm really close so hopefully it's something minor.

Right, so far I have all the correct voltages, 6.3v at heater, 240ish v into tube also, 120v into output traffo, all good. The unit in bypass works fine, as clean as if it weren't in the signal chain. When bypass is switched off, this is what im getting:

Low Cut - OK
Low Frequency select - OK
Low Boost - Nothing (always seems bass heavy though, so maybe shorted to full setting somehow?)
High frequency select - Nothing
High Boost - Nothing
Bandwidth - Nothing
High Cut - OK
High Cut Frequency - Seems to make a difference between bottom 2 settings only.

So to summarise, I think my low frequency filter pcb is working correctly with the exception of the low boost seeming to be stuck on full setting. The unit is always bass heavy regardless of where any of the dials are.
My high frequency board appears to not be doing anything apart from the high cut and MAYBE the first 2 settings on the high cut frequency selection switch.

I can't for the life of me work out whats wrong with it. My PCB link wires are correct, I've tested the pots to ensure the resistance changes with operation and they do. I've been trying to trace the path of the audio to track down the fault but am getting nowhere. From what I gather, the audio enters the filter PCB's via the IN connection below the bypass switch, and returns via the OUT connection. Literally one path in and out, but i am confused as to how the signal gets past the first pot even! Obviously it does, but to try and understand the circuit more could someone please explain the following for me. The signal enters at IN, it then travels straight through the LF PCB to the HF PCB, without going to anything. It then goes into the high boost pot, on the left hand connection. Why does that pot then not affect the level going to everything else, and if that high boost pot was turned all the way clockwise, how does any signal pass at all?

Sorry for being a noob y'all. Great site btw.
Title: Re: G-PULTEC problems, please help!
Post by: alexc on January 17, 2012, 01:38:23 AM
So I just finished my first pair of g-pultec build in a 3RU.

I did them using Haufe (turns ratio 1:1) and Pikatron (turn ratio 2:1) traffos and I used a single PSU traffo with 250VAC (no CT) and 9VAC windings (no CT) and also I used input/output relay bypass modules at the XLRs.

So, each unit was fine and I tested all good individually.  :)

When I wired them both into the psu, the noise floor gets really bad.  :(

ie. 2x g-pultec blocks wired in parallel to psu hv and heater supplies

Checked the noise floor and it is shot to hell with both modules powered on together.

Further investigation revealed the problem to be noise on the heater grounds.

After trying a lot of things (basically re-inforcing the ground trace on each g-pultec with thick
grounding wire), I found the major fix :

     - connecting the "-ve" pin of the heater rectifier bridge of each channel direct to chassis star ground

Noise floor ended up at -83.5dBu RMS (averaged over 20-20KHz) improved from -60dBu before mods. Thats with eq engaged and flat (loop back of Motu interface gives -84.5dBu)

So now, I have dual g-pultec modules in a 3RU rack with a personal best noise floor.

Frequency response is flat as a pancake at  < +/- 1dBU at 20Hz and 20KHz
Curves are all as expected.
Overall gain (eq flat) of my implementation is around -3.6dBu with ECC88/6922

Sound is very pure - not at all 'tubey'. Going to sub the 6922 (which I don;t have many)
for russian 6n5p (which I have lots) a have a listen shortly.

Maybe a few more tweaks to come.   :D :D :D


Cheers
Title: Re: G-PULTEC problems, please help!
Post by: alexc on January 17, 2012, 02:08:11 AM
Hi Dan

About your problem - when you have switch positions which seem to not work, it's usually bad solders
or hairline fractures of the trace at the pad. These single sided pcbs are not the thickest traces
and the tracks can feel some stresses when you push the control pcb thru the holes of your front panel

(if they don't line up correctly and are at the right height off the pcb)

Check carefully the solders at the switches and pots as well as at the caps and then inductors.

Use the continuity test of your multimeter to make sure the connections make it from
on pad to the next.

Make sure your connections between the 2 halves of the control pcb are properly connected
and not intermittent or loose.

You can  narrow down the problem by identifying exactly which positions don't work
and correlating with the circuit diagram component.

I also once had an inductor open circuit which caused a couple of positions not to work.

By the way, how do you test? Some of the eqs can be subtle even at full boost/cut, depending on
the souce material.

Best way is to use a PC sound card with spectrum analyzer application which can do frequency sweeps.
That way you can exactly check each position and each cut/boost/Q knob.

A simple audio probe connected to pc powered speakers is also very helpful in tracking the audio path
(careful not to put it on high voltage traces though !!) so as to compare with schematic.

Cheers
Title: Re: G-PULTEC problems, please help!
Post by: JW on January 27, 2012, 03:37:04 PM
Hey guys,

Anybody have a recommendation for a GPultec output transformer that would be good for interfacing with 600ohm loads as well has higher impedance loads?

Is the Edcor XS1100 versatile in this regard? Seems like I read on some thread that there were issues when a 600 ohm load was connected to the GPultec out. The Edcor data says it's good for >600ohm loads, so . . . . .
Title: Re: G-PULTEC problems, please help!
Post by: alexc on January 27, 2012, 05:34:13 PM
I've used Carnhills as output transformers on Gyrafs srpp stages
as well as a number of other tube line amp stages.

I like them very much in tube outputs. The price is very reasonable from Colin at Audio Maintenance.
Similar to the Edcor XSM - maybe a little larger.

For 2:1 the VTB2291 ungapped is 2400/9600:150/600 so 2400:600 works.

They also work out well for 4:1 9600:600 applications

Apart from that, I've tried the Lundahl which is very transparent but very expensive,
the Edcor which works quite well and is cheap
as well as Haufe/Pikatron reused transformers - very transparent and can be cheap.

If I were going again, I'd pick some UTC. Sometimes you can find a suitable 1W max level 2:1
for a price at or below lundahls.

Title: Re: G-PULTEC problems, please help!
Post by: schrobbelbop on January 29, 2012, 09:28:38 AM
Still fighting with 100hz humming with my dual purusha eqp1a

seems to come off the 6.3 heater voltage. Can I use just the rectifiers from one pcb to feed the other with only DC?

any tips?

Title: Re: G-PULTEC problems, please help!
Post by: gyraf on January 29, 2012, 10:29:32 AM
Dual G-pultecs seems to be notoriously problematic regarding hum - we don't recommend doubling up like that.

Have you tried looking through previous posts here?

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: okgb on January 29, 2012, 10:44:08 AM
Grounding is an art in itself ,  if not star type than separate signal from psu grounds
but have the psu grounds meet at a chasis point near the power xfmr , especially any center taps ,
Study grounding , get tad to help you . good luck
Title: Re: G-PULTEC problems, please help!
Post by: schrobbelbop on January 29, 2012, 11:03:59 AM
yes, if spend my sunday reading over here offcourse ;)
but i don't know what i can try or not before i dammage it

i've spend hours with grounding, now only inputs go to pcb ground and iec to chasis.
that gives me almost no 50hz.

I've seen a picture somewhere from a dual unit witch shares 1 6.3v psu section for both the units.

i guess i can try that but use a bigger heatsink, cause it will double current demand on the lm317 reg..?

Title: Re: G-PULTEC problems, please help!
Post by: mitsos on January 29, 2012, 12:43:34 PM
Use LM350 instead of LM317, and higher current diodes instead of the tiny rectifier bridge (fast or schottkey are best). If you are rectifying 12VAC and then regulating down to 6.3V, you can modify the PSU and include a CRC filter prior to the regulator(instead of the single 4700uF cap).  No guarantees that this will solve your problem, but it did help me with some SB4000's (with stock PSUs they hummed, until I upped the rectifier and pre-reg caps, but this is brasil, our power sucks down here). 

2 ECC88's in series will use 730mA, a HUGE load for an LM317 which maxes at 1.5A (ideally with sufficient heatsinking) and 1A diodes. Give your heaters more breathing room.   That's also the case with the power trafo, make sure it's sufficiently spec'ed.

Hope that helps, if not, it'll only have cost you 5-10 euros.
Title: Re: G-PULTEC problems, please help!
Post by: schrobbelbop on January 29, 2012, 01:53:48 PM
Gonna try to feed both heaters with only one lm317 and larger heatsink attached to the case.
Tat also told me that this will be the cure when using 2 srpp boards.

keep u informed!

Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on January 29, 2012, 03:15:13 PM
Hi schrobbelbop,

       Not sure what else I can add to what Jakob, okgb and mitsos have already stated. I was able to build a Dual unit , ( see page 6 of this thread )   and had planed on splitting them up in to separate units if I ended up with a Hum/Buzz problem , but I lucked out and never did .

   I used a single PT that had  a single HT secondary  250v ct @ 130mA and a single 6.3v  heater secondary @2A  . 

    I split both secondaries from a terminal strip to each SRPP  PCB where I used a 33k 5w  dropping resister for the the HT so it sat at 245vDC  , and a TL1086 in place of the lm317 ( you'll have to check the specs , not sure you will be able to use this one )  the only reason I used it was the heater seconday was already 6.3vac - so rectified it's like  8.8vDC  - was not enough " differential"  to make the lm317 work  -  also  Kingston mentioned that just a dropping resistor could be used in this situation too.

  .. so anyway ,  If you look at the pics in the link in my post on page 6 ,  my XLR pin 1's are shild grounds from the SRPP PCB's  only. IEC and PT ground to Star ground stud only and thats it .

    I have another ground wire attached to Start ground ... I was going to connect to XLR pin 1's , however I've never hooked it up because so far I haven't had any grounding problems.


   I guess its just NewBee Luck ...  Hope I was able to help

Please let us know of your progress
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on January 29, 2012, 03:27:35 PM
So I just finished my first pair of g-pultec build in a 3RU.

I did them using Haufe (turns ratio 1:1) and Pikatron (turn ratio 2:1) traffos and I used a single PSU traffo with 250VAC (no CT) and 9VAC windings (no CT) and also I used input/output relay bypass modules at the XLRs.

So, each unit was fine and I tested all good individually.  :)

When I wired them both into the psu, the noise floor gets really bad.  :(

ie. 2x g-pultec blocks wired in parallel to psu hv and heater supplies

Checked the noise floor and it is shot to hell with both modules powered on together.

Further investigation revealed the problem to be noise on the heater grounds.

After trying a lot of things (basically re-inforcing the ground trace on each g-pultec with thick
grounding wire), I found the major fix :

     - connecting the "-ve" pin of the heater rectifier bridge of each channel direct to star ground.

Noise floor ended up at -83.5dBu RMS (averaged over 20-20KHz) improved from -60dBu before mods. Thats with eq engaged and flat (loop back of Motu interface gives -84.5dBu)

So now, I have dual g-pultec modules in a 3RU rack with a personal best noise floor.

Frequency response is flat as a pancake at  < +/- 1dBU at 20Hz and 20KHz
Curves are all as expected.
Overall gain (eq flat) of my implementation is around -3.6dBu with ECC88/6922

Sound is very pure - not at all 'tubey'. Going to sub the 6922 (which I don;t have many)
for russian 6n5p (which I have lots) a have a listen shortly.

Maybe a few more tweaks to come.   :D :D :D


Cheers

  ... just saw this post , BEAUTIFUL work alexc !!  nice piece of gear  8)
Title: Re: G-PULTEC problems, please help!
Post by: alexc on January 29, 2012, 04:08:30 PM
Thanks!

Here's a wiring pic
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on January 29, 2012, 05:40:38 PM
Hi alexc,
           
          Thanks for the pic .    It looks like you have a lot going on there as far as grounding goes.

  First off ... I am NO EXPERT -  so please take care with voltages and I hope the more experienced will chime in   ;D

  from the pic it looks like you have 7 ?  wires going to a " Star Ground "  bolt , then  another wire going to another ground bolt on the side panel by the PT ?  is this correct ?   if it is , that may be one problem - I would scrape the paint off from around the bolt that the 7 wires converge and that becomes the one and only ground point ( assuming I haven't missed anything )

 ... also , what are the white,red and black wires from the front panel going under the PCBs ? 

  ... another observation , you have 4 relays on the in /out puts for true bypass , and also a " power on " lamp  -  are you powering all of these from the 12v secondary ?  and if yes , what is the amp rating / output of the PT ?    two tube heaters, 4 relays , and indicator lamp may be too much of a load ... possibly

 
   ... ok , that's all I got , please be careful
     and I hope  it all works out for you , please post back with your progress
Title: Re: G-PULTEC problems, please help!
Post by: alexc on January 29, 2012, 06:03:48 PM
Been there, done that. Was careful. Have done this many times now.
And I measure the effect of each additional grounding activity as I go.

The case pieces don't make good contact, hence the ground wires connecting
the side back and bottom. Otherwise, a good deal more noise. Easier than removing
paint all over the place and also reduces connection resistance over paint removal.

Other wires are relay bypass switched power with bicolor leds, I run them at around 11VDC.

Nope - all the ratings are fine. Coils are 20mA or so each. Leds are about 5mA or so.
Thats around 50mA additional per channel. Which comes off pre heater regulator.

Along with around 400mA or so for a heater, thats around 450mA of transformer heater secondary. per channel with some  2W or so on each heatsink. Those heatsinks are good for 5W or so before getting too hot.

Traffo secondary is 9VAC (no CT) at 2.5A. Plenty there.
HV is 250VAC (no CT) at 100mA. Not even close there.

There is an additional 24VAC (no CT) which I don't use because I measured the noise
contribution of feeding the extras from one main PCB as around 1dBu worse.
Which is just fine.

What I've found is that every situation in different and there is a lot of experimentation
to get the best performance. As I said, the noise floor is now a couple of dB worse than
perfect right now! This puppy is in service - no more work required!

Cheers
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on January 29, 2012, 07:37:42 PM
This puppy is in service - no more work required!


Awesome ... I really am in love with how these things sound  :)      that PT seams a good sollution for the 230 mains situation too.   
                                             Congratulations !!!
Title: Re: G-PULTEC problems, please help!
Post by: schrobbelbop on January 30, 2012, 11:52:45 AM
Now running the dual pultec without any audible hum!

Feed both the 6.3v heaters with only one psu section.

I now bolted 2 heatsinks on 1 lm317, gets verry hot, but works fine. for sure i'm gonna ad a lager heatsink and attach it to the chasis.

left channel is just a tiny but hissing in the top end.. mayby a bad tube
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on January 30, 2012, 02:43:07 PM
Now running the dual pultec without any audible hum!

Feed both the 6.3v heaters with only one psu section.

I now bolted 2 heatsinks on 1 lm317, gets verry hot, but works fine. for sure i'm gonna ad a lager heatsink and attach it to the chasis.

left channel is just a tiny but hissing in the top end.. mayby a bad tube


  Good News !!!!   Congratulations !!!    ... how about some pix of the new baby   :)
Title: Re: G-PULTEC problems, please help!
Post by: schrobbelbop on January 31, 2012, 04:46:16 AM
(http://img209.imageshack.us/img209/4098/getattachmentvs.jpg) (http://imageshack.us/photo/my-images/209/getattachmentvs.jpg/)

Uploaded with ImageShack.us (http://imageshack.us)

(http://img819.imageshack.us/img819/155/fotofp.jpg) (http://imageshack.us/photo/my-images/819/fotofp.jpg/)

Uploaded with ImageShack.us (http://imageshack.us)

Up next, wiring the bypass pcb and get my HT voltage down it's now at 298... killing my tubes ;)
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on January 31, 2012, 09:36:37 AM
AAaahhhh  ....  Franks Enhanced Pultec filter boards with Gyraf SRPP tube stage .... EXCELLENT !!!!

    Looks great !!    Congratulations !!

  I may have some questions for you , as I am 80% done with a Dual unit of these myself   8)
Title: Re: G-PULTEC problems, please help!
Post by: mitsos on January 31, 2012, 07:40:16 PM
nice, good job. Glad it's as simple asthat. If the regulator heat bothers you you can also stick a series resistor to drop a few volts before the regulator, this way you can split the heat between the two.  I'd still swap the 317 regulator for an LM350, it's the same footprint, and is capable of higher current output at the same In->Out voltage difference, so it will be more stable over time.  Or just take it all out and go passive CRCRC!   8)
Title: Re: G-PULTEC problems, please help!
Post by: schrobbelbop on February 07, 2012, 06:20:26 AM
2 tubes suck out 0.73 amps, why change the 317 if it can handle 1.5 amps?
Title: Re: G-PULTEC problems, please help!
Post by: mitsos on February 07, 2012, 10:58:17 AM
2 ECC88's in series will use 730mA, a HUGE load for an LM317 which maxes at 1.5A (ideally with sufficient heatsinking) and 1A diodes. Give your heaters more breathing room.   That's also the case with the power trafo, make sure it's sufficiently spec'ed.
Note the word "ideally."  The datasheet specs are given for the metal can "K"package (TO-3), not the T (TO220) that we mostly use. TO220 is much worse in terms of heat dissipation and thus current limit, I don't know how much, because national doesn't specify.

Looking at it that way, the 1.5A limit doesn't seem a realistic limit, especially considering the heat produced at 730mA.
Title: Re: G-PULTEC problems, please help!
Post by: JW on February 08, 2012, 04:55:26 PM
Hey folks, I asked about output transformers earlier as far as upgrading from the Edcor I have in there. I'm thinking I will eventually change these pultecs to be closer to the original EQP-1A, so my question is, concerning a couple output options in the meantime. Trying to save myself some trouble in the future.

One is the 9600:600ohm Carnhill VTB2291 that AlexC mentioned earlier http://www.audiomaintenance.com/acatalog/Transformers_and_Inductors.html wired 2:1 or 4:1

The other is Sowter's Pultec output (9530) 7K2:600ohm  http://www.sowter.co.uk/specs/9530.htmbeing

If I got the more expensive Sowters, do you think they would work well after the SRPP stage for the time being? (it'll take me awhile to get around to building the original pultec amp/interstage section etc.)

The Carnhill's are cheaper but I don't know if I'd they'd be as good later if I built an amp modeled after the original EQP 1A, because they don't have the the feedback winding? 

Just thought I'd pick your brains . . .
Title: Re: G-PULTEC problems, please help!
Post by: alexc on February 08, 2012, 10:07:01 PM
SRPP in the gpultec circuit needs 2:1 otherwise you will have an output less than unity.
The SRPP make up amp is not really able to provide any more gain.

So, not recommended to have a higher ratio step down than that unless you want to use
another gain stage after the gpultec.

The original make up amp is very different to the gpultec so not really able to migrate from
one to the other. Basically it's a complete rebuild of the make up amp to get closer to the original.

Cheers
Title: Re: G-PULTEC problems, please help!
Post by: schrobbelbop on February 09, 2012, 01:52:36 PM


Up next, wiring the bypass pcb and get my HT voltage down it's now at 298... killing my tubes ;)

Finished! Bypass pcb is working, but had to add 3k3 resistors to my bypass led's because if i switched in bypass the relais didn't work when flipping de switch fast.. so led's are lighting a bit softer.... think there is not enough current.

HT is now 246v with 15K
heater voltage is 6.1v should be no problem i guess?

only thing left is the 6.3v diode rectifier is getting a bit hot... future will tell ;)
Title: Re: G-PULTEC problems, please help!
Post by: Songguy on February 09, 2012, 09:50:20 PM
I finished my g-pultec but have a problem. The HF controls are not working properly. LF works fine but the HF changes in frequency , boost and cut are barely noticeable.

My voltages are not right.

HT is 324V not 250
6.3V is 6.14V
The 220v coming off the transformer is 259V
The 9v from the transformer is 10.6V

Anyone think I only have a bad transformer? I'm using don-audio g-pultec transformer.

Title: Re: G-PULTEC problems, please help!
Post by: gyraf on February 11, 2012, 02:15:27 AM
Increase value of resistor between ht-capacitors until you have ca. 250V at tube anode.

This is rather important in order not to burn out tube early.

HF-boost not working can be either wrong or wrongly mounted parts (in particular the inductor), and/or too high a driving impedance (the pultec filter requires being driven from low-z source)

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: Songguy on February 11, 2012, 10:44:19 PM
Hi Jacob,
I still can't figure out what's wrong. Now no audio is passing at all. I checked all the caps, inductors and pots on the filter section and they all appear to be correct and in the correct places. There is continuity between all contacts.

One thing I noticed is that the LM317AT is really hot! if I touch the heatsink with a moist finger it actually makes a sizzle sound.

Do you think that larger resistor you mentioned before and a new LM317 will help the issue?

Chris
Title: Re: G-PULTEC problems, please help!
Post by: who on February 12, 2012, 05:08:21 AM
Hi Chris, just stumbling trough your thread.
How did you measure the voltage comming from the trafo? Before i send trafos i test it myself to prevent sending the wrong types (i have also a similar trafo in the program for mila projects with 250v) but 259v is too high for this trafo secondary and absolutely not normal... Do you have more detailed pics of the trafo and the connection?

Did you measure the DC voltage with the trafo connected and behind the bridge rectiviers or the disconnected with an measuring tool switched to AC? I ask cause the DC Voltage is >3XXvDC and
The other voltages seems to be ok, there must be a problem only with the hv path. Might be the resistor or the lm317 You might check it again. The LM317gets so hot cause the 259vdc. This is the absolute maximum better you put in a bogger resitor between the two big caps to get it down to min 250vdc (like Jakob sayd). Please disconnect the trafo and measure the AC voltages of the secondarys. its voltage should be 220vAC and not around 259vAC i will send you a second one of course then but honestly i can not beliefe that. I also contacted you via email. Let me know if you have any questions that i can try to help finding a solution.
Sincerely "who"
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on March 08, 2012, 09:21:50 AM
Hi All,
        A while back I successfully completed a Dual   G-Pultec with no Hum or Buzz issues with a Hammond PT that has 250vac secondary @140mA  and a 6.3vac secondary @2.0A     I wired the PT secondaries to a terminal strip and then split from there to the two separate PCBs.  The PT housing and IEC Earth connector both secured to a Star Ground Chassis point, but no circuit to Earth / Star ground point.

      I haven't had a problem yet , but this has always bothered me - so what I have done is strip all the PSU components from  one PCB and ran jumpers to get from PCB power inlets to proper traces  , Then on the other PCB ,  lowered the big dropping resistor and ran jumper wires to the other PCB from HT , Heater and Ground, Tapping off the ground wire that goes from one PCB to the other, and connecting it to the Star Ground point. So the circuit is now Star/Earth grounded , and i think by virtue of the XLR cable Shield from XLR connector to PCB - the incoming signal / piece of kit and outgoing signal/ piece of kit are now earth / Star grounded - so no additional wire from XLR input to Star Ground is needed ... right ??   

     I use the 1086 regulator for the heaters and its rated for 1.5a  , so it never gets too hot  -  on the HT side I have 250vac regulated to about 350 , with a 12k5  /  7w dropping resistor the HT goes up to about 310vdc from first fire up for a few seconds , then settles around 220vdc - heaters are at 6.2vdc 

  It all works and sound nice - but wanted to post what I've done ,  and see if anyone has any comments / suggestions  / recommendations 

  Thanks to All 
Title: Re: G-PULTEC problems, please help!
Post by: JW on March 11, 2012, 04:46:45 PM
Hey guys,
I have a couple Cinemag CMOQ-2S transformers that I had forgotten about. Can these be used as 2:1 output transformers?

It's a four winding transformer.

Cinemag doc says it can be driven by source impedance of up to 600ohm. Is that a problem?
What if I wire the primaries in series and just use one pair of the secondaries? That would make a 2:1 output, but would it be too much of a load for the SRPP stage?

http://www.cinemag.biz/output/CMOQ-2.pdf

If that doesn't work, I can pull a couple OEP262A2E's out of my dual G1176 inputs, as I almost always like the IC input better (I have a switch in there)

 Anyway, in regards to wiring a OEP 262A2E as a 2:1 step down can someone confirm that my wiring is correct?

This per Mnats' page, in regards to the G1176. http://mnats.net/1176_revision_j.html
But I think it's how you would wire the OEP for 2:1

The OEP has pins that look like this:

Pri      S1 S2 F1 F2

Gnd pin

Sec.   S1 S2 F1 F2



Pri:
Use F2 for +in, jumper F1 and S2, S1 is 0V from the board, and connected to ground pin

Sec:
F2 is + out, jumper F1 and S2, S1 is -out
Title: Re: G-PULTEC problems, please help!
Post by: nadje on March 19, 2012, 04:45:02 PM
Hey Guys,

I have finished building my dual pultec eq and am now in the stage of getting rid of hum and unwanted artifacts. One thing that occurs is that when audio goes thru my unit and i actually touch the unit you can hear this fairly good through my headphones. So like if i tap on the front panel. Also i hear i high pitched sound now and than that are the tubes? I think i've made a grounding mistake of some sort. Has anybody had experience with this phenomenon?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on March 21, 2012, 09:19:19 AM
Microphonics would probably be a bad tube.

Make sure not to run the tube at more than 250V for longer times, wears out tube quickly.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: MicDaddy on March 21, 2012, 06:50:44 PM
I've got a 'brrrrring' resonance in mine, thought it was the tube.. removed the tube and it's still there.  It's very glittery and high in frequency and has a short decay.

I first noticed it while using the unit.  I never do any switching while the unit is 'recording' or 'printing' so it hasn't bothered me and I had chalked it up to possibly being an old microphonic tube.  I was installing a new fender lamp and some knobs and noticed the sound still happens even with the unit unplugged (while clacking my new fancy yellow chicken knobs). 

Could it be the Lundahls or the IO inductor??  I've tried tapping the chassis and various components to recreate the sound, but only when clacking switches does it happen.  The Alphas on the front panel don't throw as hard and are not as loud, but with the Lorlin power and Bass Freq switches it's obvious.


EDIT:  It is the chassis.  I'm finishing Gpultec #2 and while assembling the chassis I've been reminded of the all too familiar brrrrrriiiiiiing.  Not sure how I'll dampen it but will try some things.  Doesn't affect the function of the eq but something I will try to remedy.

Title: Re: G-PULTEC problems, please help!
Post by: rooster21 on April 17, 2012, 02:51:19 PM
I have a question about the low frequency band. I've plotted some curves and I'm not sure if I'm getting the correct result. When I change frequencies (at maximum boost) what changes is the slope of the shelf instead of the frequency, the peak always remains at ~35hz, is this normal? I'm building 2 and I have the same result with both.
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on April 18, 2012, 08:36:40 AM
A shelving filter's cutoff frequency is most often defined at the spot where you have ½ the maximum lift/cut (in dB's) - so at the 9dB point if it's a 18dB boost like the one shown in the plot.

I read something like 300, 200, 150, 100, 80 and 50Hz from the plot - decent enough...

The peak around 35 is because of the built-in (tube/transformer) low-cut somewhere around 25Hz

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: rooster21 on April 18, 2012, 07:30:37 PM
Thank you once again Gyraf for clearing that up and putting my G-Pultecs one step further!

Giancarlo
Title: Re: G-PULTEC problems, please help!
Post by: Assistant on April 28, 2012, 04:17:54 PM
just finished my first pair of g-pultec eqs!  :D
what can i say? they sound amazing, can´t wait to use em in the next mixdown!

no smoke,no hum and this was my first tube project....more to come for sure ;)
before that i built 2 gssl, 2 studer mastering eqs, 1 ssl9k pre, 1 green mic pre and i´m currently finishing my stereo calrec eq.
have to post some pics sometime....
next up: 1176 rev d, porter net eq, 2 more gssl and i still have the forssell opto boards laying around here.

thanks to everybody in this help thread, i read almost everything here and it helped a lot.
also thanks to gyraf for this project in the first place, gustav for the pcbs, dan from collective for the cases, don audio for the inductors and lundahls.

best
nils
Title: Re: G-PULTEC problems, please help!
Post by: Assistant on April 28, 2012, 04:22:40 PM
inside pic:
Title: Re: G-PULTEC problems, please help!
Post by: synnys on May 03, 2012, 05:08:51 PM
Today i finished my second stereo pultec and unlike the first one, which was just perfect (really ;), this one isn't.

It's got a hum/buzz around -54dB, a very clean one... 50Hz 100hz ect the usual harmonics.

i tried:

- moving the PSU around (i got the one from don audio, so only 1 toroid)
- turning the PSU, even moved it out of the case
- i connected only the grounds of the optional unbalanced input at the PCB to the IEC connector (i use 4 LL5402, so the unbalanced hole was free to connect a ground)
- i connected only the input grounds to the IEC
- i disconnected the output grounds

but it all makes no difference, not even the tiniest bit... hum stays steady at -54dB

So what did i do different from the 1st build.

- I used balanced jack out instead of XLR because it's more practical for my setup (which wouldn't really have to make a difference i suppose?)
- I just saw that i used ECC82 instead of ECC88 in this build by accident, ordered the wrong ones unfortunately (right ones on the way! ;)
- turned the PCB's 180 degrees (which i kind of tested turning, but didn't seem to make a difference)

I know it's not recommended building a stereo in one case cause it's kinda cramped, but hey, the first one was perfect :D

Any recommendations on what to check next?

Title: Re: G-PULTEC problems, please help!
Post by: okgb on May 03, 2012, 11:14:54 PM
Look at ANY differences in grounding , is the jack grounded at the chasis , how is the psu
and signal grounded , if you have the first one still , directly compare the two for differences

Seeing the below post  , you don't have the first unit to simply swap the tube  ?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on May 04, 2012, 02:42:53 AM
Quote
- I just saw that i used ECC82 instead of ECC88 in this build by accident, ordered the wrong ones unfortunately (right ones on the way! ;)

These are not interchangable. Use ECC88 and try again.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: synnys on May 04, 2012, 02:48:36 AM
unfortunanely i'll have to wait for the postman to bring me some ecc88's, but could that be why i have a hum? cause of a different tube?
Title: Re: G-PULTEC problems, please help!
Post by: synnys on May 04, 2012, 08:32:31 AM
tubes were right after all! i used the russian 6h1n-eb

and my hum is gone now i changed some wiring on the psu.

noisefloor is now below -90dB  8)
Title: Re: G-PULTEC problems, please help!
Post by: synnys on May 04, 2012, 01:44:45 PM
my build:

(http://www.synnys.com/diy/2a.JPG)
Title: Re: G-PULTEC problems, please help!
Post by: Aleguitarpro on May 29, 2012, 08:31:41 PM
Hi. I've finished my G-pultec.
I haven't a real problem, but I've found that the unit has a lot of gain.

I haven't the same amount of gain of the original input, when I switch the BYPASS off: to have a right amount of signal,
I've to feed the G-pultec with a very low signal from my DAW.

It's normal?
Because I can't use in my G-pultec a normal signal from my DAW, without lowering consistently it directly from my DAW.

It's possible to put a general gain make up to the circuit?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on May 30, 2012, 05:56:56 AM
Gain should be more or less unity (1x) with unit bypassed. If it's not, there is a chance you've done something wrong on the filter board.

The filter board attenuates some 18dB when bypassed or set to neutral - and the amplifier stage just makes a steady 18dB gain (give or take tube parameter tolerances)

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: Aleguitarpro on May 30, 2012, 09:06:25 AM
Gain should be more or less unity (1x) with unit bypassed. If it's not, there is a chance you've done something wrong on the filter board.

The filter board attenuates some 18dB when bypassed or set to neutral - and the amplifier stage just makes a steady 18dB gain (give or take tube parameter tolerances)

Jakob E.

Today I've tested my unit: it boosts 12 db, bypassed and with the filter on (neutral settings).
In the filter board what could boost? You told me that I've made a mistake... maybe in any resistor value?
In the filter PCB I've the correct values in the 4 resistors (75R, 1k, 10k, 1M)...
The condensers values are right, too.
Any idea?

I forget to write that I've used OEP A262A2E transformer instead of LL5402.
I wire it in this way:

LL pin 5 - OEP pin 1               LL pin 10 - OEP pin 5
LL pin 4 - OEP pin 3               LL pin 9 - OEP pin 7
LL pin 3 - OEP pin 9                           
LL pin 2 - OEP pin 2               LL pin 7 - OEP pin 6
LL pin 1 - OEP pin 4               LL pin 6 - OEP pin 8

As attachment a photo of my build.

Datasheet of the trafo here:

OEP: http://www.canford.co.uk/ProductResources/ig/2739.pdf


Thanks for help!
A.
Title: Re: G-PULTEC problems, please help!
Post by: Aleguitarpro on May 31, 2012, 06:56:23 AM
SOLVED.

I made a mistake wiring the OEP transformer (exchange primaries and secondaries: the OEP must be wired in a opposite way to the LL... of course... I discovered it in the datasheet in OEP website, that is better than the one I used before: http://www.oep.co.uk/pdf/A262A2E.pdf )
An advice for anyone want to use this transformer: the best thing is to wire directly from their pins, glueing them on the PCB, without any adaptor or pcb.
The pinout to the LL not allow an easy disposition of the trace of the pcb for the OEP: I made an adaptor with a protoboard, but now I rewire them directly from the pins of the trafos.
It's easier and faster.
Sounds great with no noise.

Thanks.
Title: Re: G-PULTEC problems, please help!
Post by: rooster21 on June 15, 2012, 09:22:31 PM
Finished up my pair, here they are!
Title: Re: G-PULTEC problems, please help!
Post by: Aleguitarpro on June 19, 2012, 07:01:59 AM
I've received a PM about the wirings of the OEP a262a2e in GPULTEC instead using a LL5402.
I prefer to share here the wirings for these transformer to help who want to use them in GPULTEC project.

As I told in my previous posts, in a first moment I made ad adaptor in a proto board.
Then, I've rewired them directly from the transformer's pins into the pcb.
I've fixed them turned over with biadhesive tape in the pcb and soldered directly the wire from the pins of the trafos.
I think that it's the better thing to control the wirings and maybe in a future change the OEP with the LL or other trafos.
A thing to remember is that OEP is reversed respect to LL5402, so the primaries of the LL become the secondaries in OEP and vice versa.

Hope this could help!

Ale
Title: Re: G-PULTEC problems, please help!
Post by: juanjovincenzo on June 20, 2012, 07:53:40 PM
Hi guys.
A questions.....On an EQ type pultec is possible to use one ECC82 SRPP stage with a combination of a PEQ1 filter passive stage with a MEQ5 filter stage???.  Like Gyraf said about MEQ5 :  "Combine this with the Pultec PEQ1A, and you have just about everything you need EQ-wise."


If is possible  ...... what is the better way to combine both type of filters ......in series o parallel?

Sorry if the question is stupid. :-X

regards
Juanjo..
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on June 21, 2012, 05:51:55 AM
You would need a gain stage for each filter - they both attenuate the signal quite a lot.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: juanjovincenzo on June 21, 2012, 01:05:37 PM
Thanks Jacobs.

You would need a gain stage for each filter - they both attenuate the signal quite a lot.
Jakob E.

So I need to use two stage for each filter, but if I put both EQs inside a box, the correct way to link these are connecting the output  of PEQ1 to input of MEQ?
Regards
Title: Re: G-PULTEC problems, please help!
Post by: RYM on August 03, 2012, 04:02:49 AM
Hi,

i build 4 units of the G-pultec 2 with Edcor and two with Lundahl! The units with the eddies works great, but the other two units with the LL´s are have less gain (-8db or more) and are sounding a little bit thin. The Tube Voltages are 6.3V and 375V could it be that the 375V create the problem?

Best

Stefan
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on August 03, 2012, 04:30:34 AM
Yes - you absolutely NEED to keep the operating high-voltage (when tubes fully heated) below 250V by increasing the series resistor. Otherwise you'll probably kill the tubes too soon - they are only designed for 120V max (we split ht voltage between the two triode systems by running srpp).

Gain should be more or less unity with Lundall's - I haven't tried the Edcor equivalents (are you sure they are the same ratios?)

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: RYM on August 03, 2012, 04:40:07 AM
Hi Jakob,

thx for reply i will try! The Edco´s are the equivalent!! I will give a try and let you know !!

best

Stefan
Title: Re: G-PULTEC problems, please help!
Post by: RYM on August 21, 2012, 05:13:17 AM
Hi Jakob,

i fixed the voltages but there´s still the same problem .... i also changed the filter board from the working unit but nothing happend ....
any idea ?

best

Stefan
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on August 22, 2012, 02:04:16 AM
swap amplifiers between the working and non-working units to find if problem is in amp or filter? Then recheck wireing and component values (such as tube types and resistor values)?
Title: Re: G-PULTEC problems, please help!
Post by: RYM on August 27, 2012, 03:15:30 AM
Hi Jakob,

i changed the filter boards and now it works fine! now i tried to figure out whats wrong on the not working filter board:

and one thing is at the hi boost the signal lost a lot of gain. If  I put out the poti and short all 3 pins I have Unity gain. I´ve changed the poti but there is still the problem .....

Thx

Stefan
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on August 30, 2012, 01:59:48 AM
Stefan,

check and re-check. compare with schematic.
from description, it's hard to tell where fault could be.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: frazzman on August 30, 2012, 10:06:13 AM
Sorry if this is an obvious question but are Greencap Metalised Polyestor capacitors ok to use in the filter section, rather than the usual WIMA poly film caps? These are the caps i'm talking about: http://www.jaycar.com.au/productView.asp?ID=RG5222
The reason being is that i'm having an issue finding the wider 15mm lead spacing caps without a large minimum order quantity. The Greencap cap's I can get individually but they are different to the small WIMAs i've been using so I just want to know if the Greencaps are OK to use also
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on August 31, 2012, 12:26:10 AM
No problem in using different brand polyester caps.

But it's also easy enough to solder extension-leads to whatever caps you have at hand.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: spase on October 04, 2012, 11:39:23 AM
where did you find those 2k2 lin pots in europe?
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on October 04, 2012, 12:18:12 PM


I got them here 

http://www.audiomaintenance.com/acatalog/potentiometers_carbon_20mm_diameter_single_gang.html
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on October 05, 2012, 10:46:46 AM
2K or 2K5 will do fine as well - should be easy to find..

e.g.: http://www.musikding.de/Passive-parts/Potentiometers/Alpha-Pots-16mm/Mono/Alpha-Potentiometer-16mm-2-5k-lin::2886.html

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: jordan s on October 26, 2012, 05:09:58 AM
Greetings esteemed DIY'ers. I got this bad boy nearly all wired up and ready to go but the transformer wiring has me stumped at the moment. I'm using two Antek AN-0212 http://www.antekinc.com/pdf/AN-0212.pdf (http://www.antekinc.com/pdf/AN-0212.pdf). I'm getting a 6.7V heater which makes me think that the first transformer is wired properly but my HT readings are a bit funky (11V) so I could really use some help with configuring the reverse transformer.
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on October 26, 2012, 08:28:11 AM
The Antek AN-0212 is a 115v-primary-only transformer - you'll need a 230V type (at least for trafo2)
Title: Re: G-PULTEC problems, please help!
Post by: jordan s on October 26, 2012, 02:45:36 PM
Hm, I read this and thought it would work, "They are specially designed to work on all standard 115V or 230V at 50Hz or 60Hz."
I also thought I read of others on this board using Antek transformers for their G-pultecs.
Title: Re: G-PULTEC problems, please help!
Post by: jordan s on November 02, 2012, 06:51:51 PM
I want to note that I did successfully complete the build with the mentioned Antek transformers. I tested the reversed 115 sides of the second transformer with a light bulb and then put them in series to get 230V. I had to increase the value of the 2W resistor to 13K, now I've got around 235V for HT. Sounds great!
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on November 05, 2012, 04:19:16 AM
 :)
Title: Re: G-PULTEC problems, please help!
Post by: jordan s on November 08, 2012, 03:32:32 PM
Here's some shots of my build:
(https://sphotos-b.xx.fbcdn.net/hphotos-snc7/396682_402084369859977_1197887816_n.jpg)
(https://sphotos-b.xx.fbcdn.net/hphotos-ash3/536380_402084329859981_146472668_n.jpg)
(https://sphotos-a.xx.fbcdn.net/hphotos-ash3/530848_402084403193307_1457070474_n.jpg)
Title: Re: G-PULTEC problems, please help!
Post by: Tommy Radonicus on November 19, 2012, 07:09:23 AM
Nice Work .. Have you Fired it up yet and if so how is it sounding ??
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on November 25, 2012, 10:39:20 AM
nice Build jordan s   :)
Title: Re: G-PULTEC problems, please help!
Post by: sonicwarrior on November 25, 2012, 05:33:02 PM
I have a weird problem with my MEQ PCBs: The 680N (Wima MKS-4 or MKS-2) won't fit:

(http://www.sdiy.de/680N-too-big.jpg)

Does anyone know a narrower 680N preferably available @Mouser? (I only found even bigger 680N capacitors there if the data-sheets don't lie but maybe I'm not able to read them)
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on November 25, 2012, 05:38:01 PM
could you solder in on the other side ??
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on November 26, 2012, 04:28:34 AM
..or extend the pins with wires?
Title: Re: G-PULTEC problems, please help!
Post by: sonicwarrior on November 26, 2012, 01:57:08 PM
Thanks for the ideas. I'll try soldering it on the solder side first.  :)
Title: Re: G-PULTEC problems, please help!
Post by: miklos on December 12, 2012, 05:53:56 PM
Hi,

I'm just find this site today and i'm very exciting about what is possible. I just see all this community full of capacity and knowledge doing nice pro-gear by their hands and i really want to try to take this train, and the Eq seems "quite" easy.
Well I say "quite", cause looking at this board, it seems that it's not that easy, and that's frighten me a little. My last electronic lesson was 20 years ago, and yes, i know and do XLR from time to time and like to do that but i'm not sure i can really read and understand the electronic diagram for the G-Pultec.

So, i spend the day to find out some things over the internet but there are a lot of questions that i can't find easily ; maybe it's part of the beauty of making his own gear like that ?
Here are a few questions :

Is there a simple step by step somewhere where i can find :
- what is the best way to begin with (is that english ??) ?
- what are the good and improves components needed to go ? (http://www.don-audio.com ??)
- Where to find a nice PCB ? (https://pcbgrinder.com/index.php?route=product/product&path=59_70&product_id=61 ?)
- Where to find a nice case ? and how to print over metal as i see in this topic ?

Well, a lot of questions, and sorry if this very newbie questions, i didn't have time to search in all the forum but it seems to have a lot of informations, but maybe a little help would be very appreciate.
Thanks a lot
Title: Re: G-PULTEC problems, please help!
Post by: imloggedin on December 13, 2012, 12:01:23 PM
Here's some shots of my build:
(https://sphotos-b.xx.fbcdn.net/hphotos-snc7/396682_402084369859977_1197887816_n.jpg)
(https://sphotos-b.xx.fbcdn.net/hphotos-ash3/536380_402084329859981_146472668_n.jpg)
(https://sphotos-a.xx.fbcdn.net/hphotos-ash3/530848_402084403193307_1457070474_n.jpg)

Very nice. Where did you get the front panel and knobs?
Title: Re: G-PULTEC problems, please help!
Post by: synnys on December 14, 2012, 02:50:06 PM
Finished my build, very happy with the result, one problem though: The boost (hi) on the left channel doesn't do anything, on whatever frequency, it doesn't do anything.
What would be the first place to look? faulty pot meter? or something else?

Also my noise floor is around -82dB at 50Hz and -84dB at 100Hz. I find this very acceptable, but was just wondering what the noise floor of your pultecs are?

here are some pics of my build.

update: i checked all pot meter values against the right channel, both are the same. problem is somewehre in the filter board cause the left filter board on the right channel gives me the same error.

(http://i.imgur.com/eTCbX.jpg)
(http://i.imgur.com/wbAMo.jpg)
Title: Re: G-PULTEC problems, please help!
Post by: synnys on December 15, 2012, 07:53:37 AM
I'm aware of the thread in the pultec meta thread, which describes JW's exact same problem, only he had his amp/filter board wired incorrect and mine is absolutely wired correctly.

I'm replacing all the inductors now to see if that changes anything.

Edit: all inductors replaced, no difference.

stiil no hi boost. (q and freq also don't work for that matter)

Title: Re: G-PULTEC problems, please help!
Post by: miklos on December 15, 2012, 10:18:46 AM
Hi,

I've read all the topic and a few others and i thin i will try to build two units. But before trying to do it i want to clarify a few things that aren't still very clear.
On the power supply board, there are 2 units marked B350C1500 (350V/1.5A) and a 4700/25, are there trafo also ?

As seen on message 151, using the Edcor audio trafo could mean to have a specific PSB ?
And last one ; is anyone know a good electronic audio supplier here in France ?

thanks and excuse for my english
Title: Re: G-PULTEC problems, please help!
Post by: synnys on December 15, 2012, 11:07:25 AM
Hi,

I've read all the topic and a few others and i thin i will try to build two units. But before trying to do it i want to clarify a few things that aren't still very clear.
On the power supply board, there are 2 units marked B350C1500 (350V/1.5A) and a 4700/25, are there trafo also ?

As seen on message 151, using the Edcor audio trafo could mean to have a specific PSB ?
And last one ; is anyone know a good electronic audio supplier here in France ?

thanks and excuse for my english

B350C1500 is just a bridge rectifier (two diodes ) (this (http://www.musikding.de/Active-parts/Transistors/Rectifier/B500C1500RD-round-bridge::1383.html) one is fine)
4700/25 = 4u7 poly capacitor 250v (very large capacitor)  try this (http://www.musikding.de/Passive-parts/Capacitors/Film-Capacitors/MKP-axial/MKP-4-7uF-400V-axial::1993.html) one

try musikding.de for a supplier, they send through the whole of europe and they're cheap, fast and reliable.
Title: Re: G-PULTEC problems, please help!
Post by: miklos on December 15, 2012, 11:24:46 AM
B350C1500 is just a bridge rectifier (two diodes ) (this (http://www.musikding.de/Active-parts/Transistors/Rectifier/B500C1500RD-round-bridge::1383.html) one is fine)
4700/25 = 4u7 poly capacitor 250v (very large capacitor)  try this (http://www.musikding.de/Passive-parts/Capacitors/Film-Capacitors/MKP-axial/MKP-4-7uF-400V-axial::1993.html) one

try musikding.de for a supplier, they send through the whole of europe and they're cheap, fast and reliable.

Thanks a lot !
musikding seems to have a lot of things !
Title: Re: G-PULTEC problems, please help!
Post by: synnys on December 15, 2012, 11:38:56 AM
Ok so i replaced all pots, all inductors, all capacitors, all wiring between the filterboards and the wires between filter and amp board.

And stillll no freaking hi boost... someone care to shine a light on this, i don't understand where the problem could be left... i feel like i rebuilt the entire thing for nothing.
Title: Re: G-PULTEC problems, please help!
Post by: mitsos on December 15, 2012, 05:18:50 PM
If it's only the high boost that doesn't work (but the rest of the controls work perfectly???)  that points to a problem between the wiper of your hiboost pot, the inductor(s), the hiboost caps and the BW pot.  These are all in series, if there is a break somewhere in this series circuit, there is no high boost.  Could be a bad component (but looks like you replaced everything?), miswired pot, broken wire, bad solder joint somewhere, anything.   You could try injecting a (music not tone) signal to the input, turn the high boost halfway up and probe along the above-mentioned parts until you find where the signal stops.

Take a look at the schematic, a simplified way to look at it is as if the "hi boosted" signal travels from the wiper of the high boost pot through the LC circuit, through the Bandwidth pot back to the rest of the circuit.   

good luck
Title: Re: G-PULTEC problems, please help!
Post by: synnys on December 17, 2012, 07:57:19 AM
When i measure the hi boost pot (10k) i get only 0.88k ohm when it's connected to the circuit. When disconnected i get a perfect 10k, so the pot is working proper.

When i measure the same at my working channel, i get about 3.88k ohm connected and 10k disconnected.

So what can cause this drop in resistance? All resistors on the filterboard are correct.

Also, i changed the hi boost pot to a 50k, and the resulted in a volume drop, so the signal does pass that pot. I also switched the Q pot from the working channel, didnt matter.

correct me if i'm , looking at the schematic, the signal goes thru the hiboost to the high freq switch, then to hi Q and then via bypass to the amp.
And since the pots are working and i replaced ALL caps and inductors, can i conclude the problem lies within my rotary switch? seems like the only component that could break the signal path... (nope that wasn't it either...)
Title: Re: G-PULTEC problems, please help!
Post by: Harpo on December 17, 2012, 11:37:25 AM
4700/25 = 4u7 poly capacitor 250v (very large capacitor)  try this (http://www.musikding.de/Passive-parts/Capacitors/Film-Capacitors/MKP-axial/MKP-4-7uF-400V-axial::1993.html) one
or better not.  ??? (you'd need 1000 of these 4u7 caps in parallel to get to 4700uF)
Heater supply calls for a 4700uF cap with a 25V min.voltage rating.
This will not be a poly cap, but an electrolytic capacitor.

Title: Re: G-PULTEC problems, please help!
Post by: synnys on December 17, 2012, 12:09:05 PM
4700/25 = 4u7 poly capacitor 250v (very large capacitor)  try this (http://www.musikding.de/Passive-parts/Capacitors/Film-Capacitors/MKP-axial/MKP-4-7uF-400V-axial::1993.html) one
or better not.  ??? (you'd need 1000 of these 4u7 caps in parallel to get to 4700uF)
Heater supply calls for a 4700uF cap with a 25V min.voltage rating.
This will not be a poly cap, but an electrolytic capacitor.

huh what are you on about?

the schematic clearly states a 4u7 250V polycap.

Title: Re: G-PULTEC problems, please help!
Post by: synnys on December 17, 2012, 12:12:30 PM
oh wait, we're not talking bout the same cap :D

sorry your right, i thought he meant the other one  :-[
Title: Re: G-PULTEC problems, please help!
Post by: miklos on December 17, 2012, 12:57:59 PM
I was talking about the other one labeled : 4700/25 with a "+".

Is that really the same as 4u7 250 ?
Title: Re: G-PULTEC problems, please help!
Post by: synnys on December 17, 2012, 01:02:17 PM
no, what harpo said is right. its a 4700uf 25v electrolytic cap
Title: Re: G-PULTEC problems, please help!
Post by: synnys on December 17, 2012, 02:08:13 PM
If it's only the high boost that doesn't work (but the rest of the controls work perfectly???)  that points to a problem between the wiper of your hiboost pot, the inductor(s), the hiboost caps and the BW pot.  These are all in series, if there is a break somewhere in this series circuit, there is no high boost.  Could be a bad component (but looks like you replaced everything?), miswired pot, broken wire, bad solder joint somewhere, anything.   You could try injecting a (music not tone) signal to the input, turn the high boost halfway up and probe along the above-mentioned parts until you find where the signal stops.

Take a look at the schematic, a simplified way to look at it is as if the "hi boosted" signal travels from the wiper of the high boost pot through the LC circuit, through the Bandwidth pot back to the rest of the circuit.   

good luck

Ok so i just did the following:

i duct taped the tip of the jack coming from my sound card out to a wire and soldered that to the IN on the filter pcb.

(i duct taped the sleeves of two jack cables together with some wire)

and now i'm touching all solder points on the filter pcb with the tip of the jack going into my soundcard. so i can hear the music playing thru the cable.

guess what? the signal NEVER stops. i can hear music on EVERY solder point on the filter pcb.
not every point has the same volume ofcourse, and some points (at the caps) sound EQ'ed. which makes sense.

But it seems the signal path is not broken, how come the high boost doesnt work then?
Title: Re: G-PULTEC problems, please help!
Post by: Harpo on December 17, 2012, 03:08:35 PM
...and mine is absolutely wired correctly.
Maybe assume it is not.
I'd double check the bypass wire connections (sw2A from schematic = sw1B from pcb silkscreen) that might cause your low ohm reading.
Title: Re: G-PULTEC problems, please help!
Post by: synnys on December 17, 2012, 03:11:37 PM
bypass switch is good, it works so it must be good,

hi cut and lo boots/cut work fine. just the HFboost that keeps bugging me.
Title: Re: G-PULTEC problems, please help!
Post by: synnys on December 19, 2012, 09:13:23 AM
Problem solved!

I found out while remeasuring everything, that the 1M resistor above the bypass switch was giving me 1M at both positions of the bypass switch while that should have been bypassed.

So it was a bad connection in the bypass switch after all, but i didn't think of that before because the lo freq circuit was bypassed all right by that same switch!

:D!

Title: Re: G-PULTEC problems, please help!
Post by: rooster21 on January 09, 2013, 10:50:22 PM
I've got a question for those using the #47 fender lamp.

I have some 60hz hum being introduced when my lamp is connected, a noise reading of [email protected] vs [email protected] with no lamp. I'm getting power from the 6.3v point on the PCB and dropping it with a 42ohm 2watt resistor.

Is anyone else getting similar values? Any other suggestions on how to power the lamp?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on January 15, 2013, 01:45:38 AM
Take AC lamp power directly from one of the the 12V secondaries, with a suitable dropping resistor. That way you don't mess with the regulated DC heater voltages. Just keep the lamp leads twisted, and some distance away from the filter board.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: rainton on February 09, 2013, 02:54:49 PM
hello everybody,

I also have two GPultecs here. But they are still from the time when I was not DIYing so a friend built them for me some years back.

Now I moved and so did the entire studio and it seems the pultecs didn't like moving too much:

They both work but with one of them when I switch the LoBoost to 100Hz the signal gets pretty loud and some frequency seems to be boosted -
but it's rather in the midrange - definitely way above 100Hz!

The other Pultec does the same thing when boosting at 16khz -> signal level raises and the boost is also somewhere in the midrange - definitely way below 16khz...

I just opened them up and was suspecting the caps at the respective frequency  selection points but a) this merely estimated and b) I don't know which cap is for which frequency...

some help would be highly appreciated
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on February 11, 2013, 04:26:47 AM
..check integrity and soldering of the capacitor that gets switched into circuit at the failing frequencies..

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: rainton on February 24, 2013, 03:57:43 PM
Thanks Jakob,
I unsoldered all the components in question and checked them with the DMM - they seem to be ok.
After soldering them back to the pcb both units seem to work again :)
Title: Re: G-PULTEC problems, please help!
Post by: muffy1975 on March 06, 2013, 04:47:53 AM
An output transformer question.

While yo can sub the correct Lundahl for and OEP, can i sub/swap in a Carnhill VTB1148 output transformer. Would this work?

The specs are

Turns Ratio; N1:N2 = 1+1:1.7+1.7 DC Coil Resistances: P1:P2:S1:S2 = 6:6:20:20 (Ohms)


I thought this might be of better quality than an OEP and half the price of the Lundahl.


Thanks for any light/help

Kind regards

Michael de A
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on March 06, 2013, 09:50:00 AM
Depends entirely on it's inductances - impossible to tell from those specs.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: ibanman555 on March 16, 2013, 10:59:30 PM
Hi Everyone!

This is my first post and I apologize if this has been answered elsewhere (many posts to weed thru!), but some of you may already know the answer...

I am planning on piecing together the G9 Mic Pre, G1176 and the G-Pultec to make a pseudo record channel for my home studio. I'll make them all separately of course, but I'm looking for one thing.  The G-Pultec DIY page doesn't include a list of components like the others, it just helps when ordering all the appropriate parts needed for the build, and also you all may have substituted better parts for the build.

Does anyone have a good current components list for the G-Pultec? I would greatly appreciate it and looking forward to this build, you may see more of me in the future! Thanks in advance!
Title: Re: G-PULTEC problems, please help!
Post by: synnys on March 17, 2013, 02:24:08 AM
8   2x6 lorlin
4   10k lin
2   1k lin
2   100k log
2   2k2 lin
2   22mH
2   47mH
4   100mH
2   18n
2   12n
2   6n8
2   3n3
6   33n
4   47n
2   68n
4   100n
2   150n
6   220n
2   330n
2   22n
2   15n
2   10n
2   470n
2   680n
2   1u
2   2u2
4   10k
4   1k
2   75r
4   470r
2   1k8
2   2k2
2   470k
2   3k3 2W
2   LM317
4   220u 350v
2   4u7 250v
2   470u 16v
2   4700 25v
2   10u 25v
2   heatsink
8   3pin connector
4   LL5402
2   ecc88 / 6dj8
2   fuse 4at
4   bridge rectifier 350 1.5a


This is a list i made for a stereo pultec.

But all the components are on the silkscrene of the PCB
Title: Re: G-PULTEC problems, please help!
Post by: ibanman555 on March 17, 2013, 04:11:43 PM
Many thanks for the list... helps make sure I don't overlook anything. But I suppose I should just take my time with this as well.
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on March 21, 2013, 03:07:02 AM
Quote
4   10k lin

Circuit works best with one log(lf boost) and one lin(hf-boost).

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: mrdarwin on April 24, 2013, 08:02:45 AM
Hi everybody!
I just finished my first Gpultec with OEP A262A2e output transformers and unbalanced inputs, and it sounds great.
The output level is less 2,7dB than input level... Is it normal? because OEP instead Lundahl?
I'm confused with wiring transformers:
output: OEP 1:2 ,secondary and primary in series and the primary goes to output balanced, so the transformer works for 2:1, is it correct?
Do I have to wire the OEP in the same way like the lundahl(2:1 oep, 1:0.5 lundahl)? inverse?

If I want use balanced input, do I have to wire the OEP in the same way like the lundahl?

thanx!
Title: Re: G-PULTEC problems, please help!
Post by: frazzman on May 10, 2013, 03:43:55 AM
Quick question - i've built a few of these with unbalanced input (so no input trafo).

Given that Pin1+3 are tied together for unbalanced input, should I still connect pin 1 on input XLR to star ground?

At the moment I have the star ground connected to filter PCB gnd and output pin1 terminal gnd, but I have not connected star gnd to XLR input pin1. Should I???

Everything seems to work fine but I am trying to minimise noise

Thanks
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on May 11, 2013, 01:54:27 AM
No simple answer. Try to see what works best in your case.

As always, interfacing to an unbalanced input depends on whether the previous stage is electronically or transformer balanced.

But you should connect xlrpin1 to ground in any case.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: frazzman on May 11, 2013, 02:25:41 AM
No simple answer. Try to see what works best in your case.

As always, interfacing to an unbalanced input depends on whether the previous stage is electronically or transformer balanced.

But you should connect xlrpin1 to ground in any case.

Jakob E.

thanks Jacob, I ended up connecting both xlrs and filter gnd to star gnd and that seems to have given me the best rresult. zero noise in bypass and low boost, interestingly the first freq in the high boost is the most noisy but the rest of the high freq positions get quieter,  particular 6.8k which is just as quiet as bypass. I think others have also noted this finding
Title: Re: G-PULTEC problems, please help!
Post by: frazzman on May 13, 2013, 07:37:23 AM
Just thought I'd share a lesson learnt today when troubleshooting one of my very noisy gpultecs. I had two built identically, both sounded great but one had a horrid hum/buzz even in bypass or with power off I'd still get noise on my meters. So after many hours of troubleshooting and checking grounds etc. The lesson learnt (and this could apply to any build is, if you're using a 'flat packed' style enclosure - make sure when you assemble it that all sides, front, back, top and bottom all have continuity with each other! You should be able to measure ohms from your earth connection to every single chassis screw hole!! After filing off all the powdercoat around each screw hole, I could then measure continuity between earth and every piece of the enclosure, and funnily enough the unit is dead quiet now. Zero noise in bypass. Seems pretty obvious in the end but an easy oversight when you know you've tightened every screw as tight as you can...but it still was not enough in this situation.  Ymmv
Title: Re: G-PULTEC problems, please help!
Post by: frazzman on May 23, 2013, 07:21:55 PM
Hrmmm... I'm still having issues with noise on one of my builds. I managed to minimise it a lot by ensuring proper grounding and continuity between all pieces of the chassis. I'm still finding that I have a slight buzz on the high boost, its more apparent at 2.1khz and gets progressively quieter at each step up. My ground is now spot on so I am wondering if maybe cheap inductors are to blame? When I disconnect the filter PCB theres no noise so I know that it has something to do with something on the filter PCB.... are average inductors a vulnerability when it comes to noise in the high boost? I have no noise at all in the low boost or in bypass. Thanks!
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on May 24, 2013, 02:23:50 AM
You have magnetic interference from power transformer to the HF boost inductor.

Options:

- Rotate and/or move power transformer until noise goes away
- Move inductor away from power transformer (on extension cabling)
- Magnetically shield inductor (e.g. in an OEP can)
- Magnetically shield power transformer - box it in some soft iron or mount a shield between transformer and inductor

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: AntoineQ on May 26, 2013, 05:38:50 AM
Hi everyone,

I've noticed a difference between GPultec schematics and PCB layout. In schemo, pin 7 of the input transformer goes to filter section and pin 10 to ground, while pin 7 goes to ground and pin 10 to filter in PCB.
Doesnt it give a phase inverted signal to the filter?

Antoine.
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on May 26, 2013, 01:55:19 PM
yes, and then the amplifier reverses again. The pcb layout is tested and found good - if you have polarity problems, you just swap pin2+3 at output XLR...

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: atticmike on June 05, 2013, 02:48:20 PM
I don't get it why nobody experiences the same hpf as I do. Does it have to do with the aurora's impedance?
Title: Re: G-PULTEC problems, please help!
Post by: imloggedin on June 10, 2013, 11:38:31 AM
What power transformer have people been using?
Title: Re: G-PULTEC problems, please help!
Post by: atticmike on June 10, 2013, 12:01:11 PM
What power transformer have people been using?

Found out that it's rather a build issue, I've opened up a separate thread for that, any input's hugely appreciated.

http://www.groupdiy.com/index.php?topic=52634.0
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on June 11, 2013, 04:17:43 AM
Naa, that is for input transformer, not power transformer...

As for power transformers, generic 12V or 15V 30VA toroid transformers are known to work.

Look earlier in this thread for multiple options.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: atticmike on June 11, 2013, 12:29:48 PM
@Jakob

Do you refuse to answer because I've opened up a separate thread for my issue?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on June 12, 2013, 04:15:08 AM
Hi Mike,

Certainly not -  I simply don't know (or have opinion about) the LL88 ASC transformer...

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: atticmike on June 12, 2013, 10:17:58 AM
Hi Mike,

Certainly not -  I simply don't know (or have opinion about) the LL88 ASC transformer...

Jakob E.

The issue is not about the LL88 transformer. It's about a malfunction of the powerboard and I don't know where it's coming from / how to fix it.

Could you please check the topic out?
Title: Re: G-PULTEC problems, please help!
Post by: frazzman on June 24, 2013, 10:19:44 AM
Troubleshooting a build for my friend.... we have an issue somewhere on the amplifier pcb. I've tried his filter pcbs and xlr wiring looms on one of my builds and they work fine.

As for the issue here - not getting any output really, well infact with headphones turned up to max I can hear a very very quiet signal, barely registering on the meters. All components appear correct, as are orientations. Tube emits a healthy glow

Were using a don audio toroid,  as I have done in the past so no room for trafo wiring errors.
No input tx

Tried swapping tubes, no luck...

A bit stumped on where to go next, my experience in the past with these is that they are a pretty straightforward build.. any ideas or suggestions ? Thanks in advance
Title: Re: G-PULTEC problems, please help!
Post by: frazzman on June 24, 2013, 08:54:49 PM
Some further testing shows that voltage across 3k3 resistor is too low at around 100v. Working unit shows around 250v. What I can't work out is why it's so low. Component wise there isn't much different between my working build and my buddies non working build. The only component difference i could observe was different bridge rectifiers and he's used higher voltage caps - I.e. 35v when unit calls for 16v , but surely that wouldn't make a difference ?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on June 25, 2013, 02:08:56 AM
If you have a drop of 100V over a 3K3 resistor, you're drawing some 30mA - which is more than you should. I think the normal range is somewhere around 5mA.

Check that you have some 1.5-2.5V at the lowest cathode, and some 100-120V at the upper cathode.

Swap tube for a known-working one?

(35V capacitors are recommended for heater supply - 16V is on the low side)

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: frazzman on June 25, 2013, 03:00:24 AM
If you have a drop of 100V over a 3K3 resistor, you're drawing some 30mA - which is more than you should. I think the normal range is somewhere around 5mA.

Check that you have some 1.5-2.5V at the lowest cathode, and some 100-120V at the upper cathode.

Swap tube for a known-working one?

(35V capacitors are recommended for heater supply - 16V is on the low side)

Jakob E.

Hi Jakob,

Thanks for the reply. I've swapped the tube from my working build into the non working one but it doesn't help the situation.

For the polarised caps, this build has:
470uF/50V
10uF/35V
4.7uF/250V
4700uF/25V

..Which all looks good to me?

I'm just going through making measurements and comparing to the working unit.

Am I supposed to be measuring relative to gnd?

For example - when I measure either side of the 3k3 resistor + gnd I get 50.4VAC which is way too low.

Should I go through and measure voltage at each of the tube socket pins relative to ground and compare to working unit?

Measurements on the screw terminals indicate the right voltage coming in from the toroid PS secondaries - we have 262V across the 2x HV terminals and 10.4V across the other (i'm using Don's toroid).

I can see that obviously I am loosing some voltage along the way but I can't work out why...

The wiring is all solid, i've checked for shorts and there are no other differences to the working build so I suspect a bad component somewhere...
Title: Re: G-PULTEC problems, please help!
Post by: frazzman on June 25, 2013, 09:15:23 AM
On second check... scratch what I said in my previous post about the measurements being off between the working and non working units.

I stupidly forgot that I didn't have the PCB linked to ground so my measurements referenced to chassis ground where off when making comparisons between the two units.

Once I had the non working build pcb tied to gnd (as per the working unit) - I was able to replicate pretty much the exact same voltages between each unit (referenced to ground on both the working and non working units).

The voltages are more or less the same on each of the tube socket pins and across 3k3 resistor.

So that leads me to think that voltages are not the source of my low/virtually non existent makeup gain. With head phones on full blast, I can hear the EQ working correctly. What could be resulting in my lack of gain issue?

Bear in mind that I swap to the working unit with the exact some configuration, everything works beautifully (so this rules out a audio interface/levels i/o issue).

It's safe to say this ones got me beat tonight but I'm really eager to resolve it

Thanks again
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on June 26, 2013, 04:07:08 AM
If you have approximate correct voltages, the amplifier is working.

Check that you have signal coming in on the first grid of the tube.

Check connection from amplifier output (cathode of upper tube half), through 4u7 output capacitor, and through transformer primary (continuity check the trafo)

Check continuity on your output - you should have some 15 Ohms between XLR(m)pins 2+3 - this is your transformer secondary.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: firfe on June 26, 2013, 03:00:51 PM
I finished my g-pultec but have a problem. The HF controls are not working properly. LF works fine but the HF changes in frequency , boost and cut are barely noticeable.

My voltages are not right.

HT is 324V not 250
6.3V is 6.14V
The 220v coming off the transformer is 259V
The 9v from the transformer is 10.6V

Anyone think I only have a bad transformer? I'm using don-audio g-pultec transformer.

hi
i've the same problem with the don audio trafo.
i've change the 3K3 with a 18K10w and it's looks ok ...
but i've a buzz ....
maybe try with another trafo.
what was the issu ?

thank you in advance and sorry for my english
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on June 26, 2013, 11:56:52 PM
Pultec depends on low drive impedance - i.e. the preceding stage must be able to drive it. Many consumer hifi thingys will not, and symptom is lower hf boost available. This can also come from wrong input transformer, if it has too high DC resistance.

As for hum/buzz, see earlier solutions

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: who on July 11, 2013, 08:30:41 AM
Hi there,
i also follow the thread and several people wonder about the voltage differences with the g-pultec trafo. The reason is the Uo voltage (without load) which is 248V on this 220v/0,1A model. If there are differences 253V/259V/... this can be caused by tolerances by the measuring tool or over-/undervolted mains in the European power system. The 220V are the value which can be recieved by loading the trafo with 0,1A. Loading it with less than 0,1A means the value will be a little bit more than 220V. Stressing it with more than 0,1A will kill the trafo. It will get hot, melt and short. This model is to be used in stereo and mono builds but for mono builds you have to switch the 3k3 resistor. 18k 10w like firfe mentioned is a good value to get it down to the 250v tube voltage. I also thought about making a trafo for mono builds but switching the resistor just does the job.

- Don -
Title: Re: G-PULTEC problems, please help!
Post by: Patch on July 12, 2013, 01:18:07 PM
Hey Guys, i hope somone can help me because i am rather confused.......

For measuring the voltages of the GPultec, i have found info but it assumes that the person knows a bit about electronics which i only know a limited amount. I am a good builder and have built a Neve 1290 clone and the GSSL with SC mods so i am capable.

But where do i pull the ground from on the board to measure the AC voltages?

"Who" (the guy's name) has stated here:

If the trafo is ok you can measure the high voltage most easy at the 3k3 2W resistor legs. The first leg should have around 350v rectivied and the second leg 250v.
The second point to measure is the outer leg on the 10u 25v cap or the outer leg of the 470R resistor between the cap and fuse holder.
You should get out 6,3v there. The minus pole of the measuring tool goes to ground. 


But "Frazzman" comments confuse me:

On second check... scratch what I said in my previous post about the measurements being off between the working and non working units.

I stupidly forgot that I didn't have the PCB linked to ground so my measurements referenced to chassis ground where off when making comparisons between the two units.

Once I had the non working build pcb tied to gnd (as per the working unit) - I was able to replicate pretty much the exact same voltages between each unit (referenced to ground on both the working and non working units).


Frazzman was getting about 50V from the 3k3 Resistor legs, which is close to what i'm getting (with going to chassis/Mains ground) , i get 59/60V from that (CHECK THE LINK IN THE PIC BELOW), but i don't get what he means by tieing the PCB to ground? Is he talking just about measuring from PCB ground and not AC/chassis ground? Or is there somthing i'm missing?

https://docs.google.com/file/d/0BzCEO-3AWPiebGpZWHE1bkNtMGs/edit?usp=sharing (https://docs.google.com/file/d/0BzCEO-3AWPiebGpZWHE1bkNtMGs/edit?usp=sharing)

Could someone clearly tell me exactly which points on the board i need to measure including both taps of the multimeter, i.e wher to take ground from......

Thank you so much for your help

Title: Re: G-PULTEC problems, please help!
Post by: Patch on July 12, 2013, 03:07:13 PM
Ok, i'm guessing you do measure from Mains ground, but when i do i seem to get 60-70V literally all over the board and even from the 2ndtransformer's primaries and secondaries, so i'm pretty confused. If i measure the Mains live pin i get bang on 240V so me multimeter is ok.

Confusingly i measured straight after the toroid transformer and im getting a rating of 70 volts (wich obviously seems wrong), i measure it up to the top leg of the PCB fuse and its still 70ish, then after the the signal goes through the fuse i measure the other end of the fuse pin and it reads about 60, i then get that through the whole board pretty much ( i havent measured all points) even at the 2nd TRX pri's & 2nds and even from the xlr pins and filter board...  (all of these with one of the multimeter poles attached to MAINS GRND)

Foolishly i'm not a bread board guy, i build all of my projects direct into the chassis..... so i'm gonna pull the toroids out and see whats up there ( i know i know should have done it to start, but i was hopefull id nailed rhe config...guess not!).....

For the transformers ive got a torodial Amveco 62062-p2s02 : http://www.digikey.co.uk/product-search/en?x=0&y=0&lang=en&site=uk&KeyWords=62062-p2s02

and a Triad fs12-1000 http://www.digikey.co.uk/product-detail/en/FS12-1000/237-1046-ND/242491

The Amveco documentation says: For 230V operation, connect primaries in series by connecting black and red
lead wires together and apply 230V across yellow and violet leads wires. So i did just that and soldered the Yellow lead to Mains Neutral, then soldered the Red lead to Mains Live.        I assume this is correct.  I then wired the secondaries in Parallel by putting blue and red togther and then brown and green together. I know nothing about voltage law/theory , i did this because i saw a comment in another post saying to do it and also all pics i can find with this TRX have this config.......

But why am i getting 70v from the secondaries???? is it becuse it wired to the circuit? I'm about to pull them so i guess i'll find out.

##correction#  ok it cannot be right to measure voltages from MAINS GRND.... as even when i pull the torriod i get the same 70V.....Please can somone tell me how to measure voltages on this board i'm stuck.... many thanks
Title: Re: G-PULTEC problems, please help!
Post by: Harpo on July 12, 2013, 06:07:50 PM
Ok, i'm guessing you do measure from Mains ground,
Whatever your idea of Mains ground might be, you might mean safety ground that is always connected to your case ground by a solid connection with a green/yellow wire, capable of standing current flowing at fault condition.
Quote
If i measure the Mains live pin i get bang on 240V so me multimeter is ok.
Know what you measure and between which potentials. For measuring mains voltage, set your multimeter for reading AC voltage at a range setting higher than expected, just in case your meter is not auto sensing. From your previous post you seem to be located in europe (please update your profile with your location data. Not only mains voltages differ when asking at an intercontinental forum), so set it to greater than 230VAC. You measure between mains life and neutral (not safety ground).
Quote
Confusingly i measured straight after the toroid transformer
from whatever POV after might be, you measure AC voltage across the 1st. transformer secondary connections. This has no reference to mains neutral or safety ground. With your unloaded Amveco 115+115:12V transformer and your higher 240VAC mains you will get a slightly greater than 12VAC, maybe 15VAC secondary readout.
Quote
The Amveco documentation says: For 230V operation, connect primaries in series by connecting black and red
lead wires together and apply 230V across yellow and violet leads wires.
correct, assuming you insulated this series connection so it never could touch your case ground or other parts causing a short.
Quote
So i did just that and soldered the Yellow lead to Mains Neutral, then soldered the Red lead to Mains Live.   I assume this is correct.
NO! Your description is missing the mains fuse and the mains power switch between the IEC mains socket and the 1st. transformer.
Quote
I then wired the secondaries in Parallel by putting blue and red togther and then brown and green together.
Must still be the Amveco transformer you're talking about. If so, this will be correct.
This transformers secondary AC voltage connects thru the fuse on pcb and splits to your 2nd. backwards connected Triad transformer (with both secondary and primary windings connected in series for a 12.6:230V stepup config) for your HT part of circuit and to the heater supply rectifier.
Your quote from member Who refers to a different single transformer.
The reference to 'ground' is the DC reference voltage on pcb. Easiest spot to touch up your black wire multimeter probe might be one of the center pins at the 3-pin molex-connectors [Bal.output], [Bal.input] or [ToFilterPcb]. After your AC voltages from the transformers have passed the rectifiers, set your meter for reading DC voltage when measuring your supply rails (with your red wire probe) in respect to prementioned reference voltage (with your black wire probe).
Title: Re: G-PULTEC problems, please help!
Post by: Patch on July 12, 2013, 09:12:23 PM
Thank you Harpo for taking the time to answer. Your answer has made things a lot clearer now. Yes i had forgotten to put my location and did it literally minutes before your post.

But unfortunately it seems my Stereo G Pultec is not working after first build, shame i was hoping it might. I guess everyone does!

I tested it and the board does not pass audio, at least the right channel doesnt. i havent tested the Left yet but it also has bad voltage readings like the right so i doubt it will.

The Amveco toroid is outputing 15V from the secondaries so thats fine ( i measured this in AC mode i assume thats right. And i've definitely hooked up the right configuration with no shorts as far as i can see.  But all other readings are off, and i set the meter to DC. They seem really really low, and on both boards. Any Ideas why? or trouble shooting procedures? Any help would be much appreciated.

Using your advice Harpo, i connected the black multimeter probe to the GND of the filter connector pins on the PCB. And these readings were made (multimeter reading to the right of each pic is the corresponding reading) :

(http://i282.photobucket.com/albums/kk280/iamproof/reading1-1.jpg) (http://s282.photobucket.com/user/iamproof/media/reading1-1.jpg.html)(http://i282.photobucket.com/albums/kk280/iamproof/reading2-1.jpg) (http://s282.photobucket.com/user/iamproof/media/reading2-1.jpg.html)(http://i282.photobucket.com/albums/kk280/iamproof/reading4-1.jpg) (http://s282.photobucket.com/user/iamproof/media/reading4-1.jpg.html)(http://i282.photobucket.com/albums/kk280/iamproof/reading5-1.jpg) (http://s282.photobucket.com/user/iamproof/media/reading5-1.jpg.html)(http://i282.photobucket.com/albums/kk280/iamproof/reading3-1.jpg) (http://s282.photobucket.com/user/iamproof/media/reading3-1.jpg.html)(http://i282.photobucket.com/albums/kk280/iamproof/reading6-1.jpg) (http://s282.photobucket.com/user/iamproof/media/reading6-1.jpg.html)


So they seem totaly off!! :(
Title: Re: G-PULTEC problems, please help!
Post by: Patch on July 12, 2013, 09:53:38 PM
To be clear im using 4 seperate transformers for the stereo build

(http://i282.photobucket.com/albums/kk280/iamproof/IMG_1008.jpg) (http://s282.photobucket.com/user/iamproof/media/IMG_1008.jpg.html)
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on July 13, 2013, 02:34:42 AM
where do you put the negative pin from your multimeter?
Title: Re: G-PULTEC problems, please help!
Post by: Patch on July 13, 2013, 08:08:30 AM
Hi, i'm connecting the negative (black) to the center pin of the filter connector point on the main PCB. I have tried other points of the ground too like centre pin of the xlr and one of the legs of a resistor by the fuse, but i get the same results, hardly any voltage picked up.

The baords i had soldered about 2.5 years ago and were left around for ages before i recently started up again. I'm wondering if they were touched by people in my flat, maybe got knocked a little.   Maybe the regulators went, or the rectifiers..... would that be a sign of low voltage....

But it strange both left and right board are showing such low values.
Title: Re: G-PULTEC problems, please help!
Post by: Harpo on July 13, 2013, 08:12:37 AM
..But all other readings are off, and i set the meter to DC. They seem really really low, and on both boards. Any Ideas why?
..i connected the black multimeter probe to the GND of the filter connector pins on the PCB. And these readings were made (multimeter reading to the right of each pic is the corresponding reading) :
None of your measurement settings are as from my previous blabla..
Pic 1-4: expected DC voltage in respect to reference voltage about 250V. Your meter setting is for max.20VDC.
Pic 5: expected AC voltage in respect to the other transformer winding side ~15V. Your meter setting is for max.20VDC.
Pic 6: expected DC voltage in respect to reference voltage about 4.78V. Your meter setting is for max.200mVDC.
The polarization of the 10uF cap right side next to the voltage regulator is not visible. Make sure, caps +side connects to the vregs center pin/caps -side connect to the copper flooded reference voltage area. If you got this backwards, expect this cap to be faulty.
Maybe optical artifact, but your transformer secondary fuses on pcb (these are not the mains fuse) don't seem to make contact to both sides of the fuseholder.

Make sure, your meters battery is fresh.
Your black wire probes touchup point for reference voltage isn't visible, but might not make a proper conduction. Maybe solder a piece of wire to the pcb traceside to the copper flodded area (the negative pin side of the big 220uF/350V caps seems a comfortable spot to solder on) and take this wire end for your DC reference voltage.
Title: Re: G-PULTEC problems, please help!
Post by: Patch on July 13, 2013, 04:00:17 PM
None of your measurement settings are as from my previous blabla..
Pic 1-4: expected DC voltage in respect to reference voltage about 250V. Your meter setting is for max.20VDC.

I set it to .20vdc because it was the only denominator that i could get a reading on, if i go above i get a zero reading

Pic 5: expected AC voltage in respect to the other transformer winding side ~15V. Your meter setting is for max.20VDC.

Ah of course, its obvious now you tell me, i need to pop it on the board again to retest

Pic 6: expected DC voltage in respect to reference voltage about 4.78V. Your meter setting is for max.200mVDC.

again if i push up the meter settings the reading goes to zero

The polarization of the 10uF cap right side next to the voltage regulator is not visible. Make sure, caps +side connects to the vregs center pin/caps -side connect to the copper flooded reference voltage area. If you got this backwards, expect this cap to be faulty.

hmm checked this and they are in the right polarization

Maybe optical artifact, but your transformer secondary fuses on pcb (these are not the mains fuse) don't seem to make contact to both sides of the fuseholder.

Yeh it looks like it but i had to shorten one end of the fuse holder to free the trx connection on the pcb. But there is definitely contact.

Make sure, your meters battery is fresh.
Your black wire probes touchup point for reference voltage isn't visible, but might not make a proper conduction. Maybe solder a piece of wire to the pcb traceside to the copper flodded area (the negative pin side of the big 220uF/350V caps seems a comfortable spot to solder on) and take this wire end for your DC reference voltage.


i havent put a fresh battery but i will, but the meter does tell me when it is running low. Thats a good idea for the DC ref, but did check that i was getting connection to the pin by checking the 'connection beep setting' on the multi meter and connecting the red pole to the ground on the filter board and it was defo well connected. But your wire idea seems more reliable so i'll try it when i get this on the bench.

Just for peace of mind here is how i've wired the TRX. i must admit i wasn't hugely confident that it was correct but from tried to figure it from this thread and googleing,  is this the correct method?

Really appreciate the help, thank you[/size]

Title: Re: G-PULTEC problems, please help!
Post by: Harpo on July 13, 2013, 04:56:16 PM
Just for peace of mind here is how i've wired the TRX. i must admit i wasn't hugely confident that it was correct but from tried to figure it from this thread and googleing,  is this the correct method?
No. The Triad (Trafo 2 from schematic) has to be connected backwards to operate the step up ratio.
Transformers series connected primary windings are between 1/4 and series connected secondary windings are between 5/8.
The 5/8 Triad secondary winding ends connect to the 1st.transformers secondary windings with the fuse on pcb in between.
The 1/4 Triad primary winding ends connect to the '220V Trafo 2' connections on pcb.
Your wiering is 1st.transformer stepped down to about 12VAC and this 12VAC stepped down by the 18.3:1 ratio again, giving about 0.65VAC.
Title: Re: G-PULTEC problems, please help!
Post by: Patch on July 13, 2013, 05:06:45 PM
Just for peace of mind here is how i've wired the TRX. i must admit i wasn't hugely confident that it was correct but from tried to figure it from this thread and googleing,  is this the correct method?
No. The Triad (Trafo 2 from schematic) has to be connected backwards to operate the step up ratio.
Transformers series connected primary windings are between 1/4 and series connected secondary windings are between 5/8.
The 5/8 Triad secondary winding ends connect to the 1st.transformers secondary windings with the fuse on pcb in between.
The 1/4 Triad primary winding ends connect to the '220V Trafo 2' connections on pcb.
Your wiering is 1st.transformer stepped down to about 12VAC and this 12VAC stepped down by the 18.3:1 ratio again, giving about 0.65VAC.

Harpo you are the man!!!!!!!! clearly the problem! I'll get this on the bench right now and change it.... i'll post the findings
Title: Re: G-PULTEC problems, please help!
Post by: Patch on July 13, 2013, 05:55:43 PM
ahh shucks i got excited too quickly.... stupidly i drew the wiring on the pic the wrong way round. I did actually have it wired the correct way to start with.  Woops that was a bit stoopid on my part.  So the problem still remains :(.... but it made so much sense with your calculation...agh shucks

My bad, so this is the way i have it wired.
(http://i282.photobucket.com/albums/kk280/iamproof/wiringtrxs222.jpg) (http://s282.photobucket.com/user/iamproof/media/wiringtrxs222.jpg.html)

Title: Re: G-PULTEC problems, please help!
Post by: Patch on July 13, 2013, 08:06:13 PM
I now lifted the board and soldered a wire to the ground to do testing with.

I only get 2V from the 250V rail  , then i turned power off, turned back on then i only get 0.08v..... I get absolutely no voltage from  the 6.3v rail. I'm testing all this in DC.

I then switch the meter to measure AC and place the probes here as shown in the pic, but i dont get any reading above zero. Shouldn't i be getting 15Vac from here? Are the toroids still measurable when soldered to the PCB?:


(http://i282.photobucket.com/albums/kk280/iamproof/board-1.jpg) (http://s282.photobucket.com/user/iamproof/media/board-1.jpg.html)
Title: Re: G-PULTEC problems, please help!
Post by: Harpo on July 13, 2013, 09:23:06 PM
I now lifted the board and soldered a wire to the ground to do testing with.
Be careful at the HT rail spots. When this rail works it will bite you loooong after you powerd off! Discharge the 220uF/350V caps thru a bleeder resistor.
Quote
I then switch the meter to measure AC and place the probes here as shown in the pic, but i dont get any reading above zero. Shouldn't i be getting 15Vac from here? Are the toroids still measurable when soldered to the PCB?
Sure. Begin from start. Have the tube fitted in its socket. Measure AC mains voltage arriving at your IEC inlet. Nada? replace blown mains fuse.
Confirm this AC voltage arriving across your 1st.transformer primary windings. Nada? flip the units power switch to ON.
Confirm the 1st.transformer secondary winding arriving with maybe 13VAC at your red/black circled markings (you now have a load connected, so voltage will be lower than your previous 15VAC no load voltage measurement).
Measure DC voltage (about 13VAC*SQRT(2)-2*0.7V=17V raw DC) between the rightmost (in) pin at the voltage regulator and your traceside reference voltage wire. Nada? replace broken rectifier.
Measure DC voltage (about 1,25*(1+1800/470)=6.04V) between the center (out) pin at the voltage regulator and your traceside reference voltage wire. Nada? replace broken LM317 voltage regulator or remove the following short that forces this vreg to shut down.
Heater supply now should be working.

Confirm the 1st.transformer secondary winding arriving with maybe 13VAC at your backwards connected 2nd.transformer secondary windings. Nada? replace broken fuse on pcb.
Confirm 2nd.transformer primary winding arriving with maybe 235VAC back to pcb.
Measure DC voltage (about 235VAC*SQRT(2)-2*0.7V=330V raw DC) between the side next to the rectifier of the 3K3/2W voltage dropping resistor and your traceside reference voltage wire. Nada? replace broken rectifier.
Title: Re: G-PULTEC problems, please help!
Post by: Patch on July 14, 2013, 04:01:41 PM
Harpo, sorry ive been a bit of a noob and seen i did a silly thing but your help has been very educational and the circuit is much clearer now and procedures too, so cheers for that :)
 
Ok ive been over it some more and i realized i had done a very stupid thing. On much closer inspection to the fuses on the board i saw that they actualy had burnt out, because to my utter stupidity i had started building these over 2 years ago and had left the boards around until now, but i initialy had put a 400ma fuse on the board....dohh!

So i've replaced them with 2 amp 250V Fuses (closest i have lieing around) and bingo! The valves light up!  On my Right board i get great readings, pretty much 6.3V at the heater and pretty bang on 250v at the HT.  AND IT SOUNDS FREAKING AMAZING!!!!!!!!!  the low end is out of this world!!! big props to you mr.Jacob! amazing unit.

BUT......

Only issue with the right channel is that the 'High cut frequency' selector switch doesnt affect anything when i turn it, it sounds dead...

The left channel is more drastic, it doesn't pass audio and it's very noisy. Readings are off too, i'm getting about 4'ish Volts from the heater and lower voltage on the HT, around the 200v mark.  I will follow the procedure from your inital comment Harpo and see if i can figure out the deal....

But could you tell me a little more detail about how to bleed the big cap with the resistor as now that the board is live i dont fancy giving myself a 300v shock :o
Title: Re: G-PULTEC problems, please help!
Post by: Patch on July 14, 2013, 04:31:00 PM
Ok i was being a lazy noob,..  i found a good page that explains how to disscharge caps in valve circuits, might help for other noobs out there wondering the same thing:

http://ampmaker.com/discharging-capacitors-946-0.html (http://ampmaker.com/discharging-capacitors-946-0.html)

Title: Re: G-PULTEC problems, please help!
Post by: Harpo on July 14, 2013, 07:02:38 PM
..i'm getting about 4'ish Volts from the heater..
double check resistor values 470R and 1K8 at the voltage regulator. Might as well be a bad LM317. Make sure the heatsink ist attached in a way that generated heat can be transfered (without overtightening the fixing bolt). Check for noisy output again after you fixed the heater supply.

Quote
..i found a good page that explains how to disscharge caps in valve circuits..
essentialy says it all, but with emphasis on 'temporary' bleed resistor. You do the math -consulting ohms law- for required resistor rating with given 250VDC and 10K bleed resistor when the unit is still powered or you simply forgot to remove this bleeder after working on this unit and power on again. A permanent bleeder (maybe 100K/2W) adds 2.5mA to the HT load current and takes a little longer to discharge but might be a safer bet. 
Title: Re: G-PULTEC problems, please help!
Post by: Patch on July 14, 2013, 09:03:55 PM
WEll turns out everything that was wrong with this build was just avoidable mistakes.

My first issue with the power was just because i had put the wrong fuse on the circuit.  The second issue with the Left channel board was a stupid one again. I flipped the board up and re took voltage readings, and they came out fine, just 0.1 volts difference compared to the second (working) board. so i was about to re-solder the Lundahl transformer, thinking it may have a cold solder joint, when i realosed that i'd actually never even soldered the 220n caps in the audio path. I'd clipped them ready for soldering but hadnt actually soldered them, a good lesson is to recheck the board if you've left it lieing on the bench for 2 years!

So after soldering them down everything works great!! Im astonished at how good this unit sounds, all that i love about tube circuits that big ass bottom end and just that analogue 'je ne c'est quoi' / mojo......WOW!!!!!!!!!! How did i ever live without a unit like this. So chuffed.

Only little thing is the Hi cut frequency selector, i dont hear it making any difference, same for both boards, is this normal? is it doing somthing so suttle im not yet hearing it? i havent done any test tone readings yet.

Again thank you so much  Harpo! :-) i need to look into ohm law a bit more me thinks......  And of course Gyraf!

on a side note closest i had for the bleeding cap was a 3k3 2watt, but it worked fine, made me feel soooo much more confident working on the board after seeing the 125volts leak out of the caps that they were storing......im tempted to do a G9 now hihi
Title: Re: G-PULTEC problems, please help!
Post by: ding on August 10, 2013, 12:49:31 AM
So I have been trying to understand how to wire up the power with what I got. I could have made it easy on myself by getting the Don-Audio toroid but I bought some parts from a forum member and it came with the FS12-1000 transfo and the Amveco 62062 toroid. This is my first big build so I am trying to wrap my head around the wiring as simple as it may be. I have very little experience aside from a few guitar pedals so I drew this diagram in photoshop to see if I could understand it better. Does this diagram look right? How and where am I supposed to wire the LED? Thanks in advanced for your help.

Alain

EDIT: removed incorrect diagram to avoid it coming up in google searches, will post correct info up ahead. Reply #432.
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on August 10, 2013, 04:37:04 AM
looks almost right at a glance - but:

- You'll want second transformer 115V windings in series (giving 230V), not in parallel as shown (which will give 115V AC)
- You'll want to use both second transformer low-voltage windings - put those in parallel.

- you'll need to connect BOTH red and yellow to power-switch NO - otherwise you'll have one primary winding constantly powered

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: ding on August 10, 2013, 08:05:44 AM
Jakob,

First off I want to thank you for what you do. This is very new to me so I appreciate your help. I forgot to mention that I am in the US. I imagine you are talking about the FS12-1000 and not the toroid when you refer to it needing to be in series. Is that right? I understand what you mean about the power, it was a bit late last night. :-[
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on August 10, 2013, 11:11:16 AM
Yup, by "the second transformer" I mean the non-toroid.

It's clear from the drawing that you plan to run off 115V mains. You still need to step up to 230VAC at the second transformer.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: ding on August 10, 2013, 08:40:15 PM
Thanks so much Jakob. :) I think I got it. Is this right? The second transformers secondaries are 6.3v in parallel @ 2A.

EDIT: removed incorrect diagram to avoid it coming up in google searches, will post correct info up ahead. Reply #432.
Title: Re: G-PULTEC problems, please help!
Post by: Harpo on August 12, 2013, 09:55:59 AM
The second transformers secondaries are 6.3v in parallel @ 2A.
Connect both primary and secondary windings in series, IE 12.6V:230V
or both primary and secondary windings in parallel, IE 6.3V:115V.
Connected as drawn will give doubled stepup ratio (and blow up some parts that are not rated for this overvoltage).

Quote
As far as I have researched I need an ON-ON DPDT rotary switch. I am guessing 2 pole. Does anyone have any leads on where I can get one of these?
A common avail. Lorlin type 2x6 rotary switch, switches endstop washer limited to pos.2, will do the trick for cheap.
Please update your profile with your location data.
Title: Re: G-PULTEC problems, please help!
Post by: ding on August 12, 2013, 03:08:02 PM
Hello Harpo and thanks for your help. So I obviously misunderstood Jakob's quote below?

- You'll want second transformer 115V windings in series (giving 230V), not in parallel as shown (which will give 115V AC)
- You'll want to use both second transformer low-voltage windings - put those in parallel.

Jakob E.

So I will put the second transformer in series both on mains and secondary. It will give me a 12.6V @ 1A. I will then have to use a resistor to lower the voltage on that so I can power the on lamp. I have seen people pull the current from the tube PCB labeled 6.3v but I would rather not mess with that. Also thanks for the quick reply about the rotary switch. I was searching for something so specific not realizing I could use something right in front of me. I think I deleted that post about 5 minutes after I wrote it so you were paying attention.  :) Again thanks so much. I imagine this will be the beginning of an addiction.  ;D
Title: Re: G-PULTEC problems, please help!
Post by: ding on August 12, 2013, 07:29:03 PM
Just to double check. First transformer in parallel and second one in series like below. I used a 50 ohm resistor for the lamp.

EDIT: removed incorrect diagram to avoid it coming up in google searches, will post correct info up ahead. Reply #432.
Title: Re: G-PULTEC problems, please help!
Post by: Harpo on August 12, 2013, 07:51:41 PM
So I obviously misunderstood Jakob's quote below?
- You'll want second transformer 115V windings in series (giving 230V), not in parallel as shown (which will give 115V AC)
- You'll want to use both second transformer low-voltage windings - put those in parallel.
Jakob E.
Seems so. Up to your latest post, saying its a dual 6.3V secondaries, Jakob most likely was assuming, you use a dual 12VAC secondary windings for your 2nd. transformer as shown on pcb connections and schematic.

Quote
So I will put the second transformer in series both on mains and secondary. It will give me a 12.6V @ 1A.
...but this transformer is connected backwards. The 12.6V @ 1A is rated load current for the usual step down ratio. With this now backwards 12.6/230 or 1:18.25 step up ratio, avail.AC current goes down by the same ratio, IE 1A/18.25=54.8mA AC current. This AC voltage get fullwave rectified at cost of form factor 1.8, leaving 30mA avail.DC current for your HT rail.
Quote
I will then have to use a resistor to lower the voltage on that so I can power the on lamp.
If it is a lamp (from a previous post it might be a LED?), a 12V incandescent lamp can connect to the 1st.transformers secondary AC connections without series resistor. Lower voltage lamps or wanted lesser brightness will need a voltage dropping resistor.
Quote
I have seen people pull the current from the tube PCB labeled 6.3v
..probably connecting to a LED with needed current limiting resistor.
Title: Re: G-PULTEC problems, please help!
Post by: Harpo on August 12, 2013, 08:03:22 PM
I used a 50 ohm resistor for the lamp.
Maybe, but missing info.
Incandescent lamp @ ? V and ? W.
The 50R series resistor rated for ? W.
Title: Re: G-PULTEC problems, please help!
Post by: ding on August 12, 2013, 10:19:01 PM
Quote
this transformer is connected backwards. The 12.6V @ 1A is rated load current for the usual step down ratio. With this now backwards 12.6/230 or 1:18.25 step up ratio, avail.AV current goes down by the same ratio, IE 1A/18.25=54.8mA AC current. This AC voltage get fullwave rectified at cost of form factor 1.8, leaving 30mA avail.DC current for your HT rail.
Thanks. When I read that and look at this... http://gyraf.dk/gy_pd/pultec/gy_pd_sch.gif (http://gyraf.dk/gy_pd/pultec/gy_pd_sch.gif) ...it makes sense. I'm taking this very slow and learning. BTW I was planning on using a fender 6.3v 150ma bulb but I imagine that a 12v bulb would be easier. I just did not want the light to be as bright as the eye of Sauron.  :) But reconsidering I think easier is better. I will look into a 12v bulb. Thanks.
Title: Re: G-PULTEC problems, please help!
Post by: ding on August 18, 2013, 12:27:30 AM
I have been having trouble finding the 12n and 18n WIMA or Orange Drop caps for the filter section. Right now I am using Sprague Goodman caps but they look weird in there with the ODs and WIMAs. So I got to wonder does anyone have a source for 12n and 18n ODs or WIMAs? Is there a recommended replacement brand for these? Does it even matter for this build as long as they are polyester or polypropylene?

Thanks
Title: Re: G-PULTEC problems, please help!
Post by: audiophreak on August 18, 2013, 01:40:57 AM
Hi,
      for the 12n I used WIMA 10n - 10%  and sorted out for highest value ( 11n I think , WIMA has tight tolerance )  , for the 18n I used a 15n and  pigy backed a 3n to the solder pads under the PCB.
Title: Re: G-PULTEC problems, please help!
Post by: ding on September 10, 2013, 08:23:17 AM
First of thanks to all that lent me a hand. I tried out my GPultec for the first time last night and it sounds very, very nice!!!! I have noticed that some of my diagrams of incorrect wiring were coming up in google searches for GPultec. In light of this I have removed them from my posts. I don't want people to be wiring their equipment wrong because of an image on google image search. I will update my diagram shortly but for now I just want to reference Patch's image which is the CORRECT way to do it. The only difference is that I wired my primaries on the toroid in parallel for the US.

Thanks all

BTW I got a 120v jewel light and just wired it up in series parallel with the lorlin on switch. It is bright as all hell but works like a charm.
Title: Re: G-PULTEC problems, please help!
Post by: Harpo on September 10, 2013, 09:43:50 AM
BTW I got a 120v jewel light and just wired it up in series with the lorlin on switch. It is bright as all hell but works like a charm.
..assuming in series might be a typo. If this lightbulb fails one day, this series connection will act like a 2nd mains switch that can only be switched to On again by exchanging the lightbulb. Hook it up in parallel to your mains transformer primary winding and a voltage dropping resistor in between (ask ohms law for resistance and wattage) will decrease the lightbulbs brightness to taste.
Title: Re: G-PULTEC problems, please help!
Post by: ding on September 10, 2013, 06:07:33 PM
Yes, you are right on that actually it is in parallel. I just had a brain fart while typing. I will try the resistor but I am just tickled that I have no trouble-shooting in my future so I had not thought that far ahead yet. Thank you, you and Jakob are a great help and an invaluable resource.
Title: Re: G-PULTEC problems, please help!
Post by: APL on September 13, 2013, 11:53:44 AM
Hi,
I am a Newbie . I have just received the excellent PCBs from PCB Grinder and want to get started, however I have been reading the various messages to see what the potential problems are. I can see human error and poor workmanship account for most problems (I’m capable of both of these) however there also seems to be some issues and improvements to the original design over last 10 years. I thought it would be better to ask questions before picking up the soldering iron.

I consider my electronics knowledge and skills are average, certainly less than many contributors here. I have made kits before but they were simply putting the supplied parts together following instructions, this project is more difficult. Hopefully more experienced people can tell me what is right or wrong.  Comments from experienced builders would be useful for me but also for others to produce a working Pultec with minimum problems.

Firstly I wanted to ask about Power supply. I should point out I am talking about a standard 1 channel Pultech as per Jacobs design.

1.Transformers
 1.1      The original schematic shows 2 x 240:12V transformers. Jacob has said that this was because it was difficult to obtain a suitable single transformer with correct secondary voltages when he designed the G Pultec. The 2 transformers would be less expensive than Dan Audio type but take up more space.
Question 1   Are there any advantages/disadvantages having the original 2 transformers over the one (Don Audio type)? I am particularly thinking of noise issues which seem to common problem.

The original schematic shows 12V secondary’s, however Don Audio type are 9V
Question 2. If I decided to use 2 transformers could I use 240:9v 30 VA. or are 12V secondary’s essential to the 2 transformer design?

2. PSU board
Reading comments there seems to be a lot of recommendations to change and experiment with resistors and other components to get correct tube voltages. I really want to avoid this. I am ok soldering once, but unsoldering and resoldering will probably lead to problems, therefore I would like to achieve correct values first time if possible. So assuming I have chosen the Don Audio transformer:

2.1 Bridge Rectifier – I see in Reply #168 (June 2011) somebody recommends moving the 220v rectifier off the PSU board to the back of the case to reduce chance of AC noise.
Question 3 -  is this a good modification? If so what type and value rectifier should be used?

2.2   Resistor 3K3  should be replaced with 18K 10Watt resistor when using Don Audio Transformer (Reply #400 July 2013)
Question 4 – Why is such a large power value required compared to original 2 W?

2.3 Power regulator – If using Don Audio type transformer with  LM317? 
Question5  what difference (if any )does it make having input of 9v instead of the design voltage of 12v? Is the LM317 still the best option?

2.4   Resistors (heater circuit) – Linked to question 2.3 above, with 9v supply what values should the original 470R and 1K8 resistors be changed to?

2.5 trimmer (heater circuit) – again related to above, someone suggested replacing 1K8 resistor with 2.5k-5k trimmer to get 6.3 V on heater. Is this a good recommendation?

 Any comments would be appreciated. I have similar questions about the rest of the build (sorry) but they can wait for another day.

Aidan
Title: Re: G-PULTEC problems, please help!
Post by: ding on September 15, 2013, 11:13:08 PM
I can't comment on all the technical stuff you wrote about because I don't really know and I am new to this like you but I can tell you about my experience building one. This is my first project besides a few guitar pedals. I used all wima and orange drop for the EQ section. I also used 2 transformers, the amveco and the triad. I followed the BOM exactly, no experimenting. The PCB and the transformers are as far apart as they can be. My box sounds excellent. Absolutely no noise and no trouble-shooting. It all just worked. I threw it up on waves q-clone and all the frequencies are pretty on and it sounds analog sweet. If you don't want to mess around I suggest you just follow the BOM exactly, take your time and you will get a nice sounding box. Good luck.
Title: Re: G-PULTEC problems, please help!
Post by: Harpo on September 16, 2013, 06:21:47 AM
1.1      The original schematic shows 2 x 240:12V transformers.
It doesn't. It shows two 220:12 VAC transformers.
Your 240:12 is a 20:1 step down ratio, the 220:12 is a 18.3:1 step down ratio.

Quote
Question 2. If I decided to use 2 transformers could I use 240:9v 30 VA. or are 12V secondary’s essential to the 2 transformer design?
Only if both transformers are 240:9. A 240:9 is a 26.7:1 step down ratio. When you connect this 2nd.transformer backwards to your 1st.transformers 9VAC secondary winding, you'll get 240VAC back on paper. If the 1st.transformer still is a 240:12 and you connect the 2nd. 240:9 transformer backwards expect about 12VAC*26.7=320VAC at your 2nd.transformer primary winding. This 320VAC gets fullwave rectified to about 320*SQRT(2)=452V raw DC voltage and your diodes and caps have to be rated for at least this voltage. As AC mains voltage isn't a constant, these numbers might vary by +/-10%. If you have 10% high mains, expect the HT raw DC voltage to increase to even more insane 498VDC when you want about 250VDC for your HT rail. The voltage dropping 3K3/2W from schematic will start to drop the HT voltage only after HT current is flowing. This will not be initially, as it takes a little time before the tube heaters are operating.

Quote
2.3 Power regulator – If using Don Audio type transformer with  LM317? 
Question5  what difference (if any )does it make having input of 9v instead of the design voltage of 12v?  Is the LM317 still the best option?
Less wasted heat. 9VAC*SQRT(2)=12.7V raw DC; 12VAC*SQRT(2)=17V raw DC. The differential to 6.3VDC times current demand is transfered to heat, so the 9VAC secondary requires lesser heatsinking. The LM317 is common avail., cheap and gets the job done.

Quote
2.4 Resistors (heater circuit) – Linked to question 2.3 above, with 9v supply what values should the original 470R and 1K8 resistors be changed to?
Nothing to change. The ratio of these resistors set the heater supply voltage to 1.25*(1+1800/470)+0.00005*1800=6.13VDC with perfect parts and typical parameters, but all parts come with tolerances, so they most likely will not be perfect.

Quote
2.5 trimmer (heater circuit) – again related to above, someone suggested replacing 1K8 resistor with 2.5k-5k trimmer to get 6.3 V on heater. Is this a good recommendation?
If it helps better sleep... just pretrim to 1K8 and dial in the final voltage to please your eye. The tube probably won't care.
Title: Re: G-PULTEC problems, please help!
Post by: APL on September 16, 2013, 12:04:22 PM
Thanks for replies regarding power supply questions, very helpful.

There has been a lot of discussion regarding grounding. I notice in photos some finished  Pultechs some have very little grounding wiring  while others look like a plate of green and yellow spaggetti. Is there a definititive method of grounding a single channel Pultec if so can you give me  reply number and date reference.

Thanks 
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on September 17, 2013, 02:53:37 AM
General grounding:

- Power input gnd to chassis gnd.
- Wire XLR's pin1's together.
- Wire from xlrF(input)pin1 to input gnd on PCB.
- Also wire from this point xlrF(input)pin1 to chassis gnd.

Done

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: APL on September 22, 2013, 04:12:56 AM
Thanks for the info Jacob that sounds simple.

I have just found the "Pultech Meta" page which lists the other Pultec threads. Very useful for new starters saves asking same questions.
Title: Re: G-PULTEC problems, please help!
Post by: APL on October 01, 2013, 03:17:04 PM
Sorry If this question has been answered before but I cannot find any information.

On the schematic (Rev 3) there is a 10k resistor conected between XLR ground and 2 resistors (1K & 10k) next to switch 3a/b.There is no place on the  PCBGrinder PCB's for this resistor. I have asked Gustav and he confirms there is a discrepancy. He agrees the 10k resistor is present on Rev3 schematic  but his board is Revision 4.

a) is this 10k resistor needed, if so where would the best place to add it?
b) Is there a Rev 4 schematic? The rev 3 schematic is used on the Gyraf and PCBgrinder websites.

Thanks
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on October 02, 2013, 03:14:28 AM
This 10K is there to simulate the load of the omitted interstage transformer. I don't think it's needed.

Try building without, and see for yourself (remember to reoprt back here) if problematic, you can always solder it to underside of pcb.

There is no new schematic (sch and pcb revision numbers dosn't follow each other)

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: APL on October 02, 2013, 11:37:22 AM
Thanks for the reply Jacob.

I assume it must not be critical or somebody  would have reported by now. I will let you know if there is a problem but it wont be anytime soon - Im slow.
Title: Re: G-PULTEC problems, please help!
Post by: drivebystudios on October 08, 2013, 07:44:12 PM
Hi there,

I've just finished a BOM for the gPultec. I've seperated it out to make life easy for anyone that wants to substitute Caps, Pots etc.
I'm pretty sure its correct, but if anyone spots anything thats incorrect, messeage me and I'll update it!

Cheers

GPULTEC - Bournes Pots   
http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=2cc0c52744

GPULTEC - Other bits   
http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=69335a7714

GPULTEC - Panasonic Capacitators   
http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=334ceea274

GPULTEC - Pots & Switches   
http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=4dea3c693a

GPULTEC - Power PCB   
http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=b8e7d2b0da

GPULTEC - Resistors   
http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=bfd9240598
Title: Re: G-PULTEC problems, please help!
Post by: APL on October 13, 2013, 11:22:35 AM
I was just looking at your BOM.

Are you sure about the Lorlin CK2375 switches? the description is 4pole 2/3 position. You need 2 pole 6 position. I went for Lorlin CK1060 from Farnell. I think they are shorting type which apparently have longer life than non shorting.

I have just ordered my components from Farnell and Banzai music if thats any help.

 
Title: Re: G-PULTEC problems, please help!
Post by: fatheaddrummer on November 07, 2013, 01:55:52 PM
Hey DrivebyStudios,

Thank you so much for your BOM, this is really cool!! ;-) But I think so too about the switches. It have to be 2x6....

Does anyone have experience with the LL5402 as Input transformer? The Gyraf schematic is suggesting this trafo, but i read that it takes away some low end and a LL1540 would work better. Unfortunately i can't remember where I read it...Any experiences with that?

Best,
Christian
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on November 08, 2013, 07:35:02 AM
Quote
..but i read that it takes away some low end and a LL1540 would work better. Unfortunately i can't remember where I read it...

The G-pultec circuit works quite well as-is, and the 1540 is NOT usable here because of it's high copper resistance.

You'll only start loosing low end if you drive the eq from a high output resistance - but then you wouldn't be able to drive the eq-stage anyway.

If you find the source of this rumor, let me know

Jakob E.

Title: Re: G-PULTEC problems, please help!
Post by: fatheaddrummer on November 09, 2013, 08:43:51 AM
Ok, now this is clear!
Thank you so much!!

Best,
Christian
Title: Re: G-PULTEC problems, please help!
Post by: dmnieto on November 10, 2013, 11:54:29 AM
Hi everybody,

I posted a similar question on the rev f, 1176 thread (with mnats board). I am planning to build a g-pultec, but I would like to know if I need to make some changes in my 1176, let me explain.

My intention is to allow signal chain in which the output of the 1176 can drive the g-pultec without bass rolloff. The 1176 has a quite beefy line amp, but i am wondering if i need to do impedance matching as well.

I have currently wired the output so I have a 1:3.16 winding in the EA11148, which is what is needed for the nominal 600 Ohm output.
Now, would it be better to change the wiring so i have a 1:1 winding and a nominal 60 Ohm output?

thanks
Title: Re: G-PULTEC problems, please help!
Post by: drivebystudios on November 10, 2013, 07:07:03 PM
Sorry... i didn't finish the switches and pots BOM properly...if someone could give me the right mouser part numbers I'll update the BOM!

PS: PCB Grinder is now selling a kit with the lundahls... the package is extremely good value, well worth the price considering time and shipping!!!

 ;)
Title: Re: G-PULTEC problems, please help!
Post by: dmnieto on November 13, 2013, 07:24:43 PM
So... should I wire for 60 Ohm output or 600 Ohm? Or it should not matter?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on November 14, 2013, 04:15:58 AM
So... should I wire for 60 Ohm output or 600 Ohm? Or it should not matter?

Does not compute - can you rephrase your question?

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: dmnieto on November 14, 2013, 12:11:53 PM
Does not compute - can you rephrase your question?

Jakob E.

Sorry, I asked my question before... I have built a 1176 clone, and I was wondering if I had wired the output transformer for a 600 Ohm output impedance. It is also possible to change the wiring to have a 60 Ohm output impedance.

So my question was, if I wanted to be able to drive the input of g-pultec with the 1176 without inducing a low frequency roll-off, should I rewire the output of the 1176 to 60Ohm, or it does not matter?

Title: Re: G-PULTEC problems, please help!
Post by: gyraf on November 15, 2013, 05:35:27 AM
Should not matter - 1176 output impedance is very low.
Title: Re: G-PULTEC problems, please help!
Post by: APL on November 15, 2013, 10:46:02 AM
Driveby: Look at Mouser 10SM160 I think its the  most suitable

Ive just finished PSB board. I got 6.11V heater which is OK, but  I got 272V with 3k3 resistor. Ive never seen any equation posted  to calculate correct Resistance value ( I assume it is a function of tube parameters and input voltage -voltage divider? ) so I started to add series resitors to reduce voltage.It was only when I had a mountain of 4 resistors and I was still too high that I noticed there was a linear relationship between the resistor value and voltage. I may have just discovered ohms law but if its a breakthrough I dedicate my Nobel Physics prize to Jacob. :)  I drew a graph Volts againt resistor value  for my results a perfect straight line  I then read off resitance at 220V giving 17K. The closest resistor I had was 15k which give 234V on tube.

If you dont know any better. like me, it may be worth going straight from the 3k3 to 15k,if thats still too high draw graph. This worked for me but if this is rubbish I hope somebody will correct me.
Title: Re: G-PULTEC problems, please help!
Post by: dmnieto on November 15, 2013, 01:00:20 PM
Should not matter - 1176 output impedance is very low.

Thanks Jakob, I guessed so much but I wanted to be sure.

I really appreciate the work you have done on your DIY projects, they are really a wonderful learning experience
Title: Re: G-PULTEC problems, please help!
Post by: fatheaddrummer on November 17, 2013, 07:40:57 AM
Hey, I have a (maybe silly) question ;-)

In the Gyraf schematic I can find 2 Tubes (I think it's a cathode follower setup?), but in the PCB Layout I am just able to find 1 Tube!? So I am I blind or do I miss some information?

Thank you!!

Best,
Christian
Title: Re: G-PULTEC problems, please help!
Post by: okgb on November 17, 2013, 09:45:04 AM
12AX/t/u/  tube type's have two sections , Is that what you are seeing ?
Title: Re: G-PULTEC problems, please help!
Post by: fatheaddrummer on November 18, 2013, 04:59:48 AM
I'm sorry i don't know 12AX/t/u/ tubes, but I'm talking about ECC88 Tubes. In the schematic there are two of them, but the PCB layout just has space for one...

Schematic: http://gyraf.dk/gy_pd/pultec/gy_pd_sch.gif
PCB Layout: http://gyraf.dk/gy_pd/pultec/gy_pd.pdf

Thank you!

Best,
Christian
Title: Re: G-PULTEC problems, please help!
Post by: Harpo on November 18, 2013, 05:17:02 AM
..I'm talking about ECC88 Tubes. In the schematic there are two of them, but the PCB layout just has space for one...
Did you try to Google for 'ECC88 datasheet' ?  ;)
Title: Re: G-PULTEC problems, please help!
Post by: fatheaddrummer on November 18, 2013, 05:46:46 AM
Haha ;-) Ok, got it!

Thank you! ;-)

Best,
Christian
Title: Re: G-PULTEC problems, please help!
Post by: ding on December 23, 2013, 02:09:05 PM
I hand wound and inductor for my first one but for my second one I decided to try out an inductor that David from Cinemag agreed to make for me for a very reasonable price. David is an awesome dude! He might put it up on the Cinemag website. Anyways, I was trying to figure the best way to drill up and attach this little guy and I did not know whether to post in the Lab or here but here seemed to be the most obvious place. I decided on 3 options but I can't figure out the best recourse or if there is a better option 4.

Option 1 - Drill all the holes for the pins on the PCB. Attach the inductor on the "pads side" with the pins facing the components. Use a circuit pen to draw some pads to attach the 4 mounting pins to the PCB. I don't know if the pen is necessary or if I can just hold the inductor mounting pins with solder. Solder wires from the pins to the correct pads on the PCB. Lead wires will be short but thats a lot of drilling and I dont have a press.

Option 2 - Drill a single hole on the PCB. Attach the inductor on the "pads side" with a single nylon screw by the center with the pins facing away from the front panel. Solder wires from the pins to the correct pads on the PCB. Lead wires will be a little longer but only 1 hole to drill.

Ooption 3 - Use a breadboard to attach the inductor to. Mount the breadboard on the bottom of the chassis. Solder wires from the pins to the correct pads on the PCB. Lead wires will be a lot longer but the PCB will remained untouched and in case of drill accident unharmed.

Any thought on the best option? Here is option 1.
Title: Re: G-PULTEC problems, please help!
Post by: ding on December 23, 2013, 02:09:54 PM
Here is option 2. Option 3 is obvious. I will drill on the green marks.
Title: Re: G-PULTEC problems, please help!
Post by: APL on December 24, 2013, 04:47:03 AM
Don't know if its best option as I have'nt tested it, but I'm going for option 3.

I have built a separate plug in  board as I am initally trying cheaper inductors with the intention of replacing in future with more expensive Sowter on another plug in board.

I did wonder about problems with longer cables,might use screened cables. One advantage  you could possibly move inductors away from interference. I was thinking of mounting them in a OEP mu metal transformer case.
Title: Re: G-PULTEC problems, please help!
Post by: dipfrik on January 01, 2014, 01:02:47 PM
Finished two of them over holidays. What a nice sounding and easy build! ;)
Need to A-B-C'ing them against the "B" a Drip V2 and the "C" a Recproaudio Kit (PTP pain  8))

Cheers, Sven
Title: Re: G-PULTEC problems, please help!
Post by: sedit1 on January 02, 2014, 02:09:30 AM
Finished two of them over holidays. What a nice sounding and easy build! ;)
Need to A-B-C'ing them against the "B" a Drip V2 and the "C" a Recproaudio Kit (PTP pain  8))

Cheers, Sven

Nice build, please report back when you have done the A-B-C ;)
Title: Re: G-PULTEC problems, please help!
Post by: berkleystudios on January 02, 2014, 02:19:48 AM
Finished two of them over holidays. What a nice sounding and easy build! ;)
Need to A-B-C'ing them against the "B" a Drip V2 and the "C" a Recproaudio Kit (PTP pain  8))

Cheers, Sven

where did you get those cases? look great with your knobs
Title: Re: G-PULTEC problems, please help!
Post by: berkleystudios on January 02, 2014, 02:25:18 AM
never mind found them :)
Title: Re: G-PULTEC problems, please help!
Post by: berkleystudios on January 05, 2014, 02:05:28 AM
okay I have a pair on the way (should be here within the week hopefully) and I have several BA283 cards sitting around doing nothing. So I wanted to implement them into my G Pultec if that was possible.

attached is just a modified schematic and block diagram. would this be where I would need to attach it to replace the SRPP stage? and would I need to modify the power supply because I would be replacing the tube stage?


( if I should have started a new thread for this, my apologies. Just let me know and Ill remove this post)

Thanks guys!
Title: Re: G-PULTEC problems, please help!
Post by: berkleystudios on January 06, 2014, 08:53:26 AM
proposed schematic with modded power supply
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on January 06, 2014, 10:56:20 AM
What gain do you have in BA283?

for 30VAC transformer, your storage electrolytic will need to be 50V (or at least over 42.5V)
Title: Re: G-PULTEC problems, please help!
Post by: berkleystudios on January 06, 2014, 11:30:54 AM
What gain do you have in BA283?

for 30VAC transformer, your storage electrolytic will need to be 50V (or at least over 42.5V)

should be about 34db of gain. I havent finished the cards yet so i cant say for certain.


good to note. can you tell me why? (curious because I was told just any voltage rating about the V i was working in.)

Title: Re: G-PULTEC problems, please help!
Post by: Harpo on January 06, 2014, 11:51:29 PM
proposed schematic with modded power supply
You don't want to connect the rectifier the way shown (shorting out the transformer).
The (too high) 30V transformer secondary is AC voltage that gets rectified to 30V*SQRT(2), ignoring the voltage drop in the rectifier giving out a 42.43VDC pk. AC mains voltage isn't a constant and might vary by +/-10% depending on location or time of day and the transformer secondary side will follow with same variation%. The 30VAC is the transformers secondary voltage at rated load and will be higher unloaded (lookup the regulation % at your transformers datasheet, maybe 15%). If AC mains is high and no load connected, this 42.43VDC pk might rise up to 42.43*1.1*1.15=53.67VDC pk and the cap between rectifier and voltage regulator has to be rated for at least this voltage. For a regulated 24VDC out, a 24VAC transformer secondary will leave enough headroom above the voltage regulators dropout voltage in a 10% low mains scenario, only requires 50V rated caps and keeps it way cooler as the differential voltage between input and output of your voltage regulator times current drawn is transfered to heat. Depending on gain/level and connected load impedance of the following piece of gear, a single BA283 may consume up to 150mA of DC power. Your PSU uses a full wave bridge rectifier (form factor K=1.8 ), so the transformer will need at least a VA rating of ((24V*0.15A DC consumption)+1.82W vreg.dissipation+~2W rectifier dissipation)*form factor 1.8=12.8VA. Good luck.
Title: Re: G-PULTEC problems, please help!
Post by: berkleystudios on January 07, 2014, 05:17:48 AM
proposed schematic with modded power supply
You don't want to connect the rectifier the way shown (shorting out the transformer).
The (too high) 30V transformer secondary is AC voltage that gets rectified to 30V*SQRT(2), ignoring the voltage drop in the rectifier giving out a 42.43VDC pk. AC mains voltage isn't a constant and might vary by +/-10% depending on location or time of day and the transformer secondary side will follow with same variation%. The 30VAC is the transformers secondary voltage at rated load and will be higher unloaded (lookup the regulation % at your transformers datasheet, maybe 15%). If AC mains is high and no load connected, this 42.43VDC pk might rise up to 42.43*1.1*1.15=53.67VDC pk and the cap between rectifier and voltage regulator has to be rated for at least this voltage. For a regulated 24VDC out, a 24VAC transformer secondary will leave enough headroom above the voltage regulators dropout voltage in a 10% low mains scenario, only requires 50V rated caps and keeps it way cooler as the differential voltage between input and output of your voltage regulator times current drawn is transfered to heat. Depending on gain/level and connected load impedance of the following piece of gear, a single BA283 may consume up to 150mA of DC power. Your PSU uses a full wave bridge rectifier (form factor K=1.8 ), so the transformer will need at least a VA rating of ((24V*0.15A DC consumption)+1.82W vreg.dissipation+~2W rectifier dissipation)*form factor 1.8=12.8VA. Good luck.

Thanks Harpo! that is quite a bit of info but I understand most of it! can you go over what the form factor is? that is new to me.
Title: Re: G-PULTEC problems, please help!
Post by: Harpo on January 07, 2014, 06:18:59 AM
Describes the efficiency of AC current/DC current ratio of the type of rectification used (full wave bridge, full wave bridge with center tap, full wave with center tap, full wave center tap with choke, halfwave, ...) as a result of the different current waveforms.
some simple explanation at http://www.amveco.com/Technical_Notes_3.htm (http://www.amveco.com/Technical_Notes_3.htm)
a little more in depth at http://www.visionics.a.se/html/curriculum/Experiments/FW%20Rectifier/Full%20Wave%20Rectifier1.html (http://www.visionics.a.se/html/curriculum/Experiments/FW%20Rectifier/Full%20Wave%20Rectifier1.html)
Title: Re: G-PULTEC problems, please help!
Post by: berkleystudios on January 07, 2014, 07:08:39 AM
Describes the efficiency of AC current/DC current ratio of the type of rectification used (full wave bridge, full wave bridge with center tap, full wave with center tap, full wave center tap with choke, halfwave, ...) as a result of the different current waveforms.
some simple explanation at http://www.amveco.com/Technical_Notes_3.htm (http://www.amveco.com/Technical_Notes_3.htm)
a little more in depth at http://www.visionics.a.se/html/curriculum/Experiments/FW%20Rectifier/Full%20Wave%20Rectifier1.html (http://www.visionics.a.se/html/curriculum/Experiments/FW%20Rectifier/Full%20Wave%20Rectifier1.html)

Thanks!
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on January 08, 2014, 12:56:50 AM
Pultec circuit needs some 20-23dB gain IIRC
Title: Re: G-PULTEC problems, please help!
Post by: gimlay on January 08, 2014, 12:31:23 PM
Hey diyers

I have a question about the lorlin switches. Im having a hard time getting mine into the board. Would it be ok if i opened up the holes on the board a little with a tiny file or screwdriver? Im worried obout breaking off on off the pins on the switch. I dont want to try and just jam that thing in there. I bought my boards from pcb grinder they seem pretty heavy duty but all the tracces are inside so its hard to know what the best approach is.

Thanks

Gabe
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on January 09, 2014, 03:40:38 AM
Hi Gabe,

No problem in widening the holes a bit to better fit switches.

The only place you need to worry about this, is when you work on double-sided, through-plated pcb's - where there may be needed through-plating inside the pcb holes.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: ding on February 15, 2014, 09:57:18 PM
This is what I ended up doing.
Title: Re: G-PULTEC problems, please help!
Post by: spudstyle on February 19, 2014, 04:54:20 AM
Hello guys,

I plan to make 2 G-Pultec units. I will buy PCB at PCB Grinder but I need some details about capacitors:

- What's lead spacing for 3n3, 6n8 etc ? And for the 330n, 470n, 4u7 etc ? Is it 7.5mm and 10mm ?
- Wich kind of caps I need ? Wima MKS2 ? MKS4 ? What is the best ?
- What is the voltage for small caps (3n3 to 100n) ? 63v ? And 250v the others ?

Last question: Where I can find 3n3, 6n8 and 12nf caps in Europe ? Can't find @ Farnell or RS !

Thanks for your help :)
Title: Re: G-PULTEC problems, please help!
Post by: ding on February 19, 2014, 08:36:59 AM
Hello guys,

I plan to make 2 G-Pultec units. I will buy PCB at PCB Grinder but I need some details about capacitors:

- What's lead spacing for 3n3, 6n8 etc ? And for the 330n, 470n, 4u7 etc ? Is it 7.5mm and 10mm ?
- Wich kind of caps I need ? Wima MKS2 ? MKS4 ? What is the best ?
- What is the voltage for small caps (3n3 to 100n) ? 63v ? And 250v the others ?

Last question: Where I can find 3n3, 6n8 and 12nf caps in Europe ? Can't find @ Farnell or RS !

Thanks for your help :)

The lead spacing is in Don Audio's excel file. What WIMA sounds best is a never ending debate. Filter caps can be 63v and up. good luck.
Title: Re: G-PULTEC problems, please help!
Post by: spudstyle on February 19, 2014, 09:59:53 AM
Ok thank you ding.

Anyone know where I can find the 3n3, 6n8 and 12nf in France or Europe ? Thanks

EDIT: is it better to use Styroflex ? I've found the 3n3, 6n8, 12 and 18 in France ! And it's better to use resistors like Vishay CMF55 series ?
Title: Re: G-PULTEC problems, please help!
Post by: dipfrik on February 19, 2014, 07:20:09 PM
Mouser ;)

 3n3  = 80-PHE450MK4330JR17T
 6n8 = 505-FKS36800/100/10P
 12nf = 5989-250V.012-F

Cheers, Sven
Title: Re: G-PULTEC problems, please help!
Post by: ding on February 20, 2014, 09:41:39 AM
Ok thank you ding.

Anyone know where I can find the 3n3, 6n8 and 12nf in France or Europe ? Thanks

EDIT: is it better to use Styroflex ? I've found the 3n3, 6n8, 12 and 18 in France ! And it's better to use resistors like Vishay CMF55 series ?

Give them a try. I personally like wima on the low and orange drop on the high but it is DIY so give it a go.
Title: Re: G-PULTEC problems, please help!
Post by: spudstyle on February 21, 2014, 03:38:18 AM
Ok, so if I want something sweet on the high, wich is better ? Wima, Orange drop or Styroflex ? I can't try every caps, not enough money :(

EDIT: do you think Cinemag CML-150T is better sounding than Toko inductors ? I just need to change some caps but it's not a problem.
Title: Re: G-PULTEC problems, please help!
Post by: ding on February 21, 2014, 09:46:33 AM
Ok, so if I want something sweet on the high, wich is better ? Wima, Orange drop or Styroflex ? I can't try every caps, not enough money :(

EDIT: do you think Cinemag CML-150T is better sounding than Toko inductors ? I just need to change some caps but it's not a problem.

What sounds better depends on individual taste. I cannot/will not go into that. You will just need to experiment and find what you like. that is the best part of DIY, else just buy a used pultec from evilbay and call it a day. As far as inductors go there is something to be said about a multi-tap inductor with the proper ferrite. My taste right at this moment is that I like WIMA on the lows, orange drop on the highs, and custom inductor (hand wound or other wise) but that is what sounds good to my ears right now. Winding your own multi-tap is easy if you have a meter that measures in mH. I have built one with toko, one with hand wound, and one with cinemag and I do prefer the hand-wound/cinemag but that could just be mystical self mental masturbation than anything else. I thought toko sounded pretty good too. If you are going the cinemag route you need to call Cinemag and ask them to wind you a G-Pultec inductor 22,69,169,269. All in all, if you just use Wima and toko and everything thats in the BOM you will have a nice sounding piece of equipment that you will enjoy for many years. Don't get caught up too much into what caps are good. those are things that are not important. Use Polystyrene, polypropylene or polyester for the filter and audio portions of the main board and you will get a good sound.   ;D
Title: Re: G-PULTEC problems, please help!
Post by: APL on February 23, 2014, 10:31:40 AM
I also used mixture of WIMA and orange tops. I bought from Banzai Music in Berlin who had a good range.

However I found it difficult getting all WIMAs with correct lead spacing to fit  board. The WIMA leads are also very short and you cannot always bend them to fit. Also the larger value WIMAs I bought were too wide to fit in the space.

I also need to paralell some orange tops to get correct values

The ideal WIMAs and orange tops may be out there but I didnt find them.
Title: Re: G-PULTEC problems, please help!
Post by: spudstyle on February 23, 2014, 03:13:47 PM
Thanks for your answers guys. I found all I need except the 2u2 in 7.5mm. My BOM is ok :)

Do you know if the original frequencies knobs exist in chinese model ? I found the original but it's $10 for a knob ! I found all other knobs, volume, off/on and the chickenhead (Tube-tech style no dakaware).
Title: Re: G-PULTEC problems, please help!
Post by: ding on February 23, 2014, 08:41:14 PM
no problem  ;) I love old knobs so mine are all dakaware. on my last one I spent $120 just on knobs.  :o enjoy your new toy.
Title: Re: G-PULTEC problems, please help!
Post by: spudstyle on February 26, 2014, 04:53:06 AM
I got a new question :)

I want to change some frequencies on the lows. I've seen that we have 20-25-30-40-60 and 100 Hz but I don't want the 20 & 25 Hz, I want to make something like 30-40-60-80-100 and 120 Hz. How can I calculate the frequencies on this filter ? I understand how to calculate the Hi filter (LC) but not the Lo :/
Sorry, I'm not electronician ^^
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on February 26, 2014, 05:13:59 AM
The frequencies (on all but HI-Boost) are proportional to the capacitors, as they are first order RC filters. Larger capacitors, lower frequencies. Try out some, and see what you like.

Not much to be gained IMO by changing frequencies, that's not where the magic works...

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: djob on March 05, 2014, 06:37:02 AM
hi all!
money saving question...
here it's 230v mains power, and i happen to have a 230v:6.3v valve transformer for the heater, so can i skip buying the stacked transformers and just run straight from the mains power acording to rest of the gpultec psu schematic.

cheers :)
Title: Re: G-PULTEC problems, please help!
Post by: Harpo on March 05, 2014, 08:46:01 AM
money saving question...
here it's 230v mains power, and i happen to have a 230v:6.3v valve transformer for the heater, so can i skip buying the stacked transformers and just run straight from the mains power acording to rest of the gpultec psu schematic.
Brilliant approach against overpopulation. :o
Just don't run straight from mains power.
Title: Re: G-PULTEC problems, please help!
Post by: spudstyle on March 05, 2014, 09:07:00 AM
The frequencies (on all but HI-Boost) are proportional to the capacitors, as they are first order RC filters. Larger capacitors, lower frequencies. Try out some, and see what you like.

Not much to be gained IMO by changing frequencies, that's not where the magic works...

Jakob E.

Ok but don't understand how to calculate the low filter. What caps values I need if I want 20-30-40-60-80-100 Hz in the flow filter ? Thanks
Title: Re: G-PULTEC problems, please help!
Post by: ding on March 05, 2014, 10:53:59 AM
The frequencies (on all but HI-Boost) are proportional to the capacitors, as they are first order RC filters. Larger capacitors, lower frequencies. Try out some, and see what you like.

Not much to be gained IMO by changing frequencies, that's not where the magic works...

Jakob E.

Ok but don't understand how to calculate the low filter. What caps values I need if I want 20-30-40-60-80-100 Hz in the flow filter ? Thanks

https://www.google.com/#q=RC+filters+calculator (https://www.google.com/#q=RC+filters+calculator)  :P
Title: Re: G-PULTEC problems, please help!
Post by: spudstyle on March 06, 2014, 02:20:08 AM
The frequencies (on all but HI-Boost) are proportional to the capacitors, as they are first order RC filters. Larger capacitors, lower frequencies. Try out some, and see what you like.

Not much to be gained IMO by changing frequencies, that's not where the magic works...

Jakob E.

Ok but don't understand how to calculate the low filter. What caps values I need if I want 20-30-40-60-80-100 Hz in the flow filter ? Thanks

https://www.google.com/#q=RC+filters+calculator (https://www.google.com/#q=RC+filters+calculator)  :P

I know google and I got a calculator but I don't understand the filter in the schematic. I'm not electronician. Where is the filter ? This is the filter between 10k resistor and "2u2-1u-680n-etc" ? Please explain me, I don't ask you to do the job, I just want to understand :)
if you think otherwise, it's because my english sucks lol
Title: Re: G-PULTEC problems, please help!
Post by: who on March 07, 2014, 11:17:11 AM
inductors and the caps make the filter.

Don
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on March 08, 2014, 02:06:41 AM
..but the inductors are only involved in the high-boost section.

spudstyle - it is all in the schematic. If the schematic does not make sense to you, try the mentioned empiric approach:

Quote
Larger capacitors, lower frequencies. Try out some, and see what you like.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: djob on March 20, 2014, 06:25:51 AM
money saving question...
here it's 230v mains power, and i happen to have a 230v:6.3v valve transformer for the heater, so can i skip buying the stacked transformers and just run straight from the mains power acording to rest of the gpultec psu schematic.
Brilliant approach against overpopulation. :o
Just don't run straight from mains power.

Thanks much Harpo,
I've now got my hands on a lovely transformer that powered four valves in a big old radio. Puts out 354v x2 (708v), 6.9v, and 5.5v. Heard up to 6.9v is ok on 'the valve wizard' but no center tap on the 6.9v so I'm thinking to create an artificial centre tap with resistors. However seems 354v much too high, any idea on the best work around for that? Cheers everyone!
Title: Re: G-PULTEC problems, please help!
Post by: Harpo on March 20, 2014, 08:09:59 AM
I've now got my hands on a lovely transformer that powered four valves in a big old radio. Puts out 354v x2 (708v), 6.9v, and 5.5v. Heard up to 6.9v is ok on 'the valve wizard' but no center tap on the 6.9v so I'm thinking to create an artificial centre tap with resistors. However seems 354v much too high, any idea on the best work around for that? Cheers everyone!
Transformer is AC voltage, so 354VAC get rectified to 500V raw DC (or from your 'x2 (708v)' number to even more insane 1001V raw DC. As AC mains voltage isn't a constant and might vary by +/-10%, giving 550VDC (or 1100VDC), your caps need a higher than this number voltage rating. The higher rated caps and resistor(s) for the needed voltage drop probably will cost you more than using the correct transformer. Selling the then not more needed radiator for room heating might further compensate. ::)
Title: Re: G-PULTEC problems, please help!
Post by: frazzman on March 20, 2014, 08:51:02 AM
This sounds like a recipe for lost limbs or worse... I suggest buying a custom wound gpultec trafo from donaudio, purpose built for this application with all the windings you need...
Title: Re: G-PULTEC problems, please help!
Post by: Gustav on March 23, 2014, 10:39:47 AM
Just put the final screw in a two channel version using a lovely case from our own Frank Röllen.

Its duplicated from Jakob's layout, and it does things to the sounds going into my ears that put a smile on my face - or maybe thats the other way around. Sunstroke set in hours ago.

Gustav
Title: Re: G-PULTEC problems, please help!
Post by: Audioman on April 20, 2014, 05:44:58 PM
Finally today i finish my two unit !! Sound fantastic !!
Thanks to Jakob for the fantastic layout and all the guys of this fantastic Forum !!
Title: Re: G-PULTEC problems, please help!
Post by: Audioman on April 20, 2014, 05:46:26 PM
Picture Two !!
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on April 21, 2014, 04:12:26 AM
Very nice and clean build! Well done!

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: veve on April 26, 2014, 10:24:05 AM
How does they sounds?
Is it the PCB Grinder kit?

Title: Re: G-PULTEC problems, please help!
Post by: Gustav on April 27, 2014, 09:45:51 AM
How does they sounds?
Is it the PCB Grinder kit?

Thats Jakob's original PeQ layout.

Gustav
Title: Re: G-PULTEC problems, please help!
Post by: veve on April 27, 2014, 04:02:09 PM
Oh Gustav I just realized that you're the man behind Pcb Grinder  ;D.

I've send email to you about the little mistakes on your CTQ page.  :D
Title: Re: G-PULTEC problems, please help!
Post by: 4earstudios on May 01, 2014, 03:11:03 PM
Hi there

I did much searching but i dont really find an answer to this

I am building a Dual Pultec Enhanced Version. Im in the process of wiring the Led and the bypassboards from silent:arts. My problem as- i am an noob to this - is that i dont know/where exactly these are connected. i ve read i can take the current for the  power led from the heater 6,3v. But how to connect the bypass boards and the led on these, there is nothing writen on them (HWBP36) ( +,-, leds? )

Has anybody used this boards too?

Thx Daniel

Title: Re: G-PULTEC problems, please help!
Post by: gyraf on May 02, 2014, 07:09:55 AM
I don't think the bypass board is compatible here, we don't have standard opamp voltages available...

You can wire a LED from the 6.3V - use a 220 Ohms to 470 Ohms in series to control LED current.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: 4earstudios on May 03, 2014, 01:02:40 PM
Hi Jakob
Thx for your insight, i´ll let the bypassboard bypassed ;D

Bye Daniel
Title: Re: G-PULTEC problems, please help!
Post by: Harpo on May 03, 2014, 01:45:28 PM
Im in the process of wiring the Led and the bypassboards from silent:arts. My problem as- i am an noob to this - is that i dont know/where exactly these are connected. i ve read i can take the current for the  power led from the heater 6,3v. But how to connect the bypass boards and the led on these, there is nothing writen on them (HWBP36) ( +,-, leds? )
Just use the type of relais that matches the HWBP36 pcb footprint and your available supply voltage (for instance Omron G5V-2-H1 DC6).
For about 10mA wanted LED forward current in order to not exceed parts limits and LED used as a status display (not building a headlight here) maybe use a (6.3V-1.9V)/0.01A=440 ohm series resistor in between 6.3V supply voltage, LED and 0V. The 1.9V example value will differ depending on colour and type of LED used. Just look up the parts datasheet of your LED and look up the forward voltage Vf parameter.
Title: Re: G-PULTEC problems, please help!
Post by: APL on May 07, 2014, 12:39:07 PM
I have recently finished and  tested my G pultec. The low boost and cut appear to be working and so is bypass. The Q, high boost and high cut do not seem to be doing anything.

I see others have reported similar problems. I have checked following.

High boost - I have checked continiuity to pot, caps and through switch all appears ok. I get a range of resistances between switch and common (blue ) of sowter inductor eg at 2.3 khz setting resistance is 33.5ohm at 18.7 kHz= 8.5 ohm. At other settings in between, resistance is within this resistance band. So High boost inductor seems to be ok or at least doing something. The capacitor values are also correct.

Q pot- Checking again I suspect I may have problem with pot or more  like joints at pot or molex connecter to PCB. I will stip everything down and sort this.

High Cut - This all appears to ok.

a) I can see that problem with Q pot could affect high boost but would it affect high cut? If not any suggestions?

b) Somebody else  had these symtoms and eventually appears to have concluded he had the in and out mixed up between passive board and the power supply/amp. I have connected out to out and in to in. I assume that is correct?

c) I previously mentioned about the mystery 10k resistor shown attached to the junction of 10k and 1k resistors on low freq circuit, but missing on actual circuit board. Jacob thought it was probably redundant, however I would to add it in case it is relevent to my problems. Can I solder this directly across OUTPUT and GND connection below Bypass switch or is there a better location?

I would be grateful for any suggestions.

 

Title: Re: G-PULTEC problems, please help!
Post by: APL on May 10, 2014, 11:31:44 AM
Ignore last post. I resoldered Q pot and a few other connections and it all works fantastic no noise. I did not need to add the 10k resistor.

It sounds good with one OEP output transformer. I just need to replace with the 2 llundahl transformers I just bought in Black market so should sound even better.

Thanks to everybody who helped especially Jacob for help and the design.
Title: Re: G-PULTEC problems, please help!
Post by: veve on May 12, 2014, 04:45:04 PM
I just realised that there is some differences between the frequencies of the original eq and the Gyraf eq. I bought the original case from Collective Cases so, is it possible to get the original frequencies? :(
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on May 13, 2014, 01:01:50 AM
Have you read this thread and the Pultec META?

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: veve on May 13, 2014, 03:25:31 AM
Not the whole tread  :-[

I think now I have to... :-\

Please don't blame me :'(

Anyway, is it difficult to modify to have the original frequencies? If it's then I will buy a front panel with de Gyraf frequencies..
Title: Re: G-PULTEC problems, please help!
Post by: ding on May 13, 2014, 02:03:18 PM
Dan is a pretty cool guy. I'm sure if you email him and send back the front panel he would be able to help you out here. Not trying to put words in Dan's mouth here so check with him first. I have bought lots of cases and panels from him and have nothing but great things to say about him. :)
Title: Re: G-PULTEC problems, please help!
Post by: veve on May 14, 2014, 09:40:57 AM
Ok thank's..

I will built my Pultec first and see if it works... Then after I will advise with the front panel  ;D
Title: Re: G-PULTEC problems, please help!
Post by: frazzman on May 25, 2014, 08:19:38 AM
Hi all,
I've had one of my pultecs sitting on the shelf a while, I always thought it sounded "good" but never "great". Today I put it under the microscope and noticed in RMAA that there was a wide +3db sub bass boost ~25hz going on both with all knobs zero'd AND in bypass.
Any ideas where to look, possible wrong component ? Aside from this all else is well, no noise and all freq positions work fine... Appreciate any insight
Title: Re: G-PULTEC problems, please help!
Post by: frazzman on May 25, 2014, 09:18:35 PM
Hi all,
I've had one of my pultecs sitting on the shelf a while, I always thought it sounded "good" but never "great". Today I put it under the microscope and noticed in RMAA that there was a wide +3db sub bass boost ~25hz going on both with all knobs zero'd AND in bypass.
Any ideas where to look, possible wrong component ? Aside from this all else is well, no noise and all freq positions work fine... Appreciate any insight

Looks like I'm not the only one who has observed this frequency response:

https://groupdiy.com/index.php?topic=21818.0

That user reports simular behavior.

Is this boost 'normal'?

If so, why? And how could it be changed? I think that boost produces a kind of 'wooly' sound...?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on May 27, 2014, 06:32:23 AM
Resonance between output capacitor, transformer primary, and whatever load you give it?

Try with a larger output capacitor and see if that helps - e.g. a 10uF

"wooly" is not in that area, at least in my nomenclature

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: mhartung on May 27, 2014, 02:45:28 PM
Hello everyone!
I have a Gyraf pultec I built a few years ago, that recently started to show some problems.

Symptoms: Low freq cut pot does nothing (Low freq boost works normal), AND the HF "bandwidth" pot reduces HF when turned clockwise. When the HF bandwidth pot is full CCW, there is HF gain at the correct freq. It looks like from the schematic that these could be relate to the same fault, but since I'm not smart enough to know, that's why I'm here.

Anyone care to bite on what the fault might be??

Thanks in advance!
Cheers
mike

Title: Re: G-PULTEC problems, please help!
Post by: gyraf on May 28, 2014, 05:19:29 AM
Nothing in there that wears out - try replacing the pots in question..

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: mhartung on May 28, 2014, 09:38:04 AM
Thanks Jacob!
I'll try that.
m
Title: Re: G-PULTEC problems, please help!
Post by: jwhmca on May 28, 2014, 09:21:15 PM
Shoot me if this is a simple search solution!

My own PCB etch of  this thing... didn't print it from gyraf layout, just made my own, so who knows...

With the EQ "IN" and all the controls down... I'm getting about 1db signal loss? This is normal?

Title: Re: G-PULTEC problems, please help!
Post by: gyraf on May 29, 2014, 01:28:23 AM
With the EQ "IN" and all the controls down... I'm getting about 1db signal loss? This is normal?

A matter of component tolerance - specially the exact value of the 10K hi-boost pot, which forms upper part of the overall-attenuator of the filter in bypass

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: goatsounds on June 06, 2014, 03:21:05 PM
I made a stereo version of the PCBgrinder pultec, and it sounds great! But I've noticed that the left channel is about 0,5 or 1 dB lower than the right channel, and when I boost the highs all the way the differance is a little annoying. How can i compencate for that?

Allso i see that the plate voltage on the left is 240V, and the right is 245V.
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on June 10, 2014, 04:43:39 AM
Raw gain in a ECC88 varies a couple of dB. Try swapping/replacing tube?
Title: Re: G-PULTEC problems, please help!
Post by: naths101 on June 11, 2014, 06:42:27 AM
Hi guys,
I'm getting conflicting information everywhere I look... For the power switch, is it SPST, SPDT or DPDT??
Cheers!!
Title: Re: G-PULTEC problems, please help!
Post by: Majestic12 on June 16, 2014, 07:50:14 AM
Hi guys,
I'm getting conflicting information everywhere I look... For the power switch, is it SPST, SPDT or DPDT??
Cheers!!

You can use either SPST, SPDT, DPST or DPDT. But DPST would be best.
Title: Re: G-PULTEC problems, please help!
Post by: naths101 on June 16, 2014, 08:42:19 AM
You can use either SPST, SPDT, DPST or DPDT. But DPST would be best.

thanks mate!
Title: Re: G-PULTEC problems, please help!
Post by: emanuele.stragliotto on July 10, 2014, 05:08:23 AM
Hi everyone! I just finished soldering and mounting pcbs and other parts for this project...But get into these problems...
On first test the eq seems working but at really low volume...had mounted both input and output lundhals...Had also a lot
of noise... I am a beginner so I tried to disconnect the filters board to try to figure out where the problem might be...but the
background noise still remains...Thanks for any help!!!
Emanuele
Title: Re: G-PULTEC problems, please help!
Post by: weiss on July 13, 2014, 01:30:07 PM
hey guys. i wanted to know, how i need to wire a 4 pole pot (e.g. something like this: http://de.mouser.com/Search/ProductDetail.aspx?R=CK2375virtualkey12200000virtualkey10WA177) to swith the pultec on and off?

this is how my frontpanel looks
Title: Re: G-PULTEC problems, please help!
Post by: Harpo on July 13, 2014, 02:24:57 PM
hey guys. i wanted to know, how i need to wire a 4 pole pot (e.g. something like this: http://de.mouser.com/Search/ProductDetail.aspx?R=CK2375virtualkey12200000virtualkey10WA177) to swith the pultec on and off?

this is how my frontpanel looks

Something like this (https://www.buerklin.com/datenblaetter/G077060_TD.pdf?ch=50160) switch with 45° indexing for switching mains voltage (whatever your mains voltage might be).
(not a pot and you don't need 4 switch poles. Your link shows a Lorlin type rotary switch with 30° indexing, capable of switching 150mA and 6.35mm (not 6mm) spindle diameter)
Please update your profile with your location data.
Title: Re: G-PULTEC problems, please help!
Post by: weiss on July 13, 2014, 08:02:20 PM
Something like this (https://www.buerklin.com/datenblaetter/G077060_TD.pdf?ch=50160) switch with 45° indexing for switching mains voltage (whatever your mains voltage might be).
(not a pot and you don't need 4 switch poles. Your link shows a Lorlin type rotary switch with 30° indexing, capable of switching 150mA and 6.35mm (not 6mm) spindle diameter)
Please update your profile with your location data.
okay so i need to buy a new one ;)
thanks

weiss
Title: Re: G-PULTEC problems, please help!
Post by: APL on July 15, 2014, 12:32:43 PM
Emanuele,
I dont think anybody answerered your question about noise. Try looking back through posts here. Im no expert but possible problems may be
1 faulty tube
2 the power transformer interfering with inductors. Solution move transformer or shield inductors
3 Grounding is a common reason.See post #439 17 Sept 2013 for correct method

Hope you find the cause of problem .
PS Remember to Check and recheck you solder joints and continuity
Title: Re: G-PULTEC problems, please help!
Post by: pieca on August 25, 2014, 10:56:18 AM
Hi everyone,

I'm currently building a stereo gyraf Pultec based on PcbGrinder's CTQ PCB.
There is no fuse on this pcb, and I need to put a fuse in front of my transformer (from don audio)
What is the correct fuse value for 2 boards?

Thanks for your help
Title: Re: G-PULTEC problems, please help!
Post by: weiss on August 25, 2014, 11:10:47 AM
Hi everyone,

I'm currently building a stereo gyraf Pultec based on PcbGrinder's CTQ PCB.
There is no fuse on this pcb, and I need to put a fuse in front of my transformer (from don audio)
What is the correct fuse value for 2 boards?

Thanks for your help

I'm using a 315mA in my ctq.. the voltage the fuse covers has to be higher than your local mains supply
Title: Re: G-PULTEC problems, please help!
Post by: pieca on September 03, 2014, 05:28:58 PM
Hi,

I want to connect a 6,5v jewel light to the 5V output of my toroid transformer (Don-audio).
Do I need to put any resistor or not?

Thanks for your help
Title: Re: G-PULTEC problems, please help!
Post by: weiss on September 04, 2014, 04:45:18 AM
I want to connect a 6,5v jewel light to the 5V output of my toroid transformer (Don-audio).
Do I need to put any resistor or not?

What Lamp? Could be that it won't be as bright as usual.
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on September 04, 2014, 10:45:12 AM
5V to a 6.3V lamp won't be a problem at all.

If it's not actually a lamp, but a LED, you still need a 100R series resistance

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: pieca on September 04, 2014, 12:18:38 PM
thanks!

It's a real lamp so no resistor !
Title: Re: G-PULTEC problems, please help!
Post by: pieca on September 11, 2014, 05:28:16 AM
Almost done !

Just have to solder audio in/out, and turn the switch ON…

(http://www.pierre-caillet.fr/EQP1.JPG)
Title: Re: G-PULTEC problems, please help!
Post by: weiss on September 11, 2014, 05:48:55 AM
wow this looks great, pieca! you must have paid much for these rca knobs though...
Title: Re: G-PULTEC problems, please help!
Post by: pieca on September 11, 2014, 06:10:13 AM
you must have paid much for these rca knobs though...

no, only 12$ for 6 knobs including shipping from china  ;)
MP for seller name

Frontplate made by Frank
Pcb by pcb grinder (CTQ)

Title: Re: G-PULTEC problems, please help!
Post by: pieca on September 11, 2014, 06:41:33 PM
so after first start-up : no smoke  ;D

6,04 V on the heating circuit
I have 245 V AC on the output of my transformer but 273 V DC at the valve with a 10K resistor (4w)

I'm a noob with the ohm law…
I've a 15k and a 22k resistors (both 4w), which is the better replacement one in order to get a proper voltage at the valve?

Thanks for your help
Title: Re: G-PULTEC problems, please help!
Post by: Gustav on September 12, 2014, 03:03:11 AM
so after first start-up : no smoke  ;D

6,04 V on the heating circuit
I have 245 V AC on the output of my transformer but 273 V DC at the valve with a 10K resistor (4w)

I'm a noob with the ohm law…
I've a 15k and a 22k resistors (both 4w), which is the better replacement one in order to get a proper voltage at the valve?

Thanks for your help

If you measure VDC before the drop resistor, you can check exactly how much VDC you are dropping with your installed 10K resistor.

I will assume its 340VDC before the drop, and you measured 273VCD after, so the drop = 67V.


Ohms law: Voltage(V) = current(I) x resistance(R).


Calculating I

We know the voltage, V (67) and the resistance, R (10K), so we can fill in  ohms law to find the unknown I.

67(V) = I x 10000(R) or 67(V)/10000(R) = I

I = 0,0067 ampere (6,7ma)

Calculating V

For a target value of 250V, you will want a voltage drop from 340 to 250 = 90V.

Calculating R

Now that we know I and V, we can find R

90(V) = 0,0067(I) x R or 0,0067(I)/90(V) = R

R = 13433.


I have tried and had no luck getting close to the expected value calculating it like this, but I am not sure if its because of current draw changes, bad math skills (I hope someone will correct me if thats the case) or something third. I would just install the 15K resistor and see what values I get.

If you try to calculate it, remember to measure VDC before the drop resistor to insert the correct value instead of the 340V

Gustav
Title: Re: G-PULTEC problems, please help!
Post by: pieca on September 12, 2014, 03:36:05 AM
Thanks Gustav for theses explanations !

So, before the dropping resistor, I have 328V DC

I've switched my dropping resistor for a 22K (metal oxyde 5W) and  now I have 230 V DC for the tube : it seems good !

BUT : my dropping resistor is relatively HOT is 5W sufficient ?

Thanks for your help
Title: Re: G-PULTEC problems, please help!
Post by: Gustav on September 12, 2014, 03:55:10 AM
Thanks Gustav for theses explanations !

So, before the dropping resistor, I have 328V DC

I've switched my dropping resistor for a 22K 5W and  now I have 230 V DC for the tube : it seems good !

BUT : my dropping resistor is relatively HOT is 5W sufficient ?

Thanks for your help

Finding V  - >328 - 230 = 98V

Finding I -> 98(V)/22000(R) = 0,0045(I)

Power = I^2 x R = ?

I dont know if theres a shorter method, but if you plug in the numbers, you should see that 5W is sufficient.

Gustav
Title: Re: G-PULTEC problems, please help!
Post by: pieca on September 12, 2014, 04:21:56 AM
thanks again Gustav !

Next step : Audio Test  :)
Title: Re: G-PULTEC problems, please help!
Post by: pieca on September 12, 2014, 07:11:38 AM
so, audio test report…

Not so good…

Low cut and boost : ok
High Cut : Ok

But High Boost and HF Q doesn't work at all on both channels >:(

I'm using a don audio inductor, I don't think there is a cabling problem, and I don't know were to search…
I've also tried in bypass (as in older posts with high problems…)

The level is quite different between bypass and all pots to zero

Any idea?
Title: Re: G-PULTEC problems, please help!
Post by: pieca on September 12, 2014, 07:51:32 AM
solved!!!

Found on the Gpultec meta tread something about the same issue : filter board and amp board wired backward…

I'm using CTQ pcb. There is a star on the amp PCB and another one on the filter pcb. I've used this star as a mark, but it is not

This thing is huge, and sound really great !!!!!
Flat when pots are zeroed (except a half DB more at 20hz when engaged), but really nothing

Not a single hum or noise issue, I'm happy

Thanks again to Gyraf, gustav, and every one on this forum   :D
Title: Re: G-PULTEC problems, please help!
Post by: APL on September 12, 2014, 08:06:11 AM
Have you actually got it working or did you just find a post explaining a similar problem?

As I had a similar problem and it wasnt the solution.
Title: Re: G-PULTEC problems, please help!
Post by: pieca on September 12, 2014, 08:08:07 AM
Have you actually got it working or did you just find a post explaining a similar problem?.

Yes, inverting cabling between amp board and filter board solved my issue
Title: Re: G-PULTEC problems, please help!
Post by: APL on September 12, 2014, 08:24:00 AM
good pleased its working. I had similar problems (post 514) and it turned out to be Q pot connections although I had been very confident the connections were good.

Regarding that resistor I couldnt calculate it either. But when first voltage was too high I changed to higher value resistance and got a lower voltage, I plotted values of voltage against resistance and I got a straight line. I read off the required resistor value at the required operating voltage extrapalate if necessary.  well this worked for me

Where did you get those Chinese knobs I couldnt find them when I searched?
Title: Re: G-PULTEC problems, please help!
Post by: pieca on September 12, 2014, 08:36:13 AM
Where did you get those Chinese knobs I couldnt find them when I searched?

've founded them on Ebay, but the seller doesn't seems to sell them anymore…
Title: Re: G-PULTEC problems, please help!
Post by: veve on September 16, 2014, 02:07:39 PM
Very nice unit Pieca! Congratulation :D

I have a similar problem. I've mesured 12vdc on the heater and 340vdc  without a tube in the socket.. In my first test, the tube died few minutes after I turn the power on so I'm afraid to put another tube to take measurment... The first tube was a free tube so it's not a tragedy  ;D but my others tubes are expensive so I don't want to take some risk ;D

Do you measured with a tube in?

It's my first tube diy so I'm a newbie  ;D
Title: Re: G-PULTEC problems, please help!
Post by: Gustav on September 16, 2014, 02:22:58 PM
Very nice unit Pieca! Congratulation :D

I have a similar problem. I've mesured 12vdc on the heater and 340vdc  without a tube in the socket.. In my first test, the tube died few minutes after I turn the power on so I'm afraid to put another tube to take measurment... The first tube was a free tube so it's not a tragedy  ;D but my others tubes are expensive so I don't want to take some risk ;D

Do you measured with a tube in?

It's my first tube diy so I'm a newbie  ;D

first of all - remember, the voltages you are working with are dangerous.

In order for the tube to work, even if its placed in the circuit, it needs its heater voltage, which is regulated to about 6,3V through your LM317 regulator.  If the regulator gets too hot, it will shut down, so you might see the following behavior.

- Tube glows,
- High voltage is dropped over drop resistor.
- Tube stops glowing.
- Voltage is equal on both sides of the drop resistor (since theres no load (tube not working) on the supply, the resistor will not drop the voltage)

Let the regulator cool and try again. There is probably nothing wrong with your tube, and you can probably get it to glow again.

If you are feeding the circuit 12V, I doubt you can cool your LM317 without using the case as a heat sink. To do this, you need to isolate it electronically from the case.

For my first PeQ, I spent a few days before I realized that my LM317 was shutting down, and I was really confused about the behavior over the drop resistor, so you are not alone, if this turns out to be your problem.

If its not, I would still make sure the LM317 is sufficiently cooled before trying with a new tube.

Gustav
Title: Re: G-PULTEC problems, please help!
Post by: veve on September 16, 2014, 03:34:04 PM
Thanks for the answer Gustav..

My regulator is not hot that's what I don't understand.. Maybe I have to change it to see whats appen and also check  the board to see if I didn't made a mistake but I'm pretty shure that's not the case..

I think I have to resolve the heater problem first to avoid problems with the tube.
Title: Re: G-PULTEC problems, please help!
Post by: Gustav on September 16, 2014, 04:39:27 PM


My regulator is not hot that's what I don't understand..

Even with a tube installed? Your measurement of 12VDC indicates that the regulator is not seeing a load  either. You would either get approximately 6,3V with a regulator working on a load, or nothing with the regulator shutting down.

I dont know if theres a way to fake a load over the tube socket to make sure theres no risk of ruining any more tubes if that is what happened.  Someone might be able to help with that.

Gustav
Title: Re: G-PULTEC problems, please help!
Post by: veve on September 17, 2014, 01:40:44 AM
Maybe I CAN put a resistor in the socket to simulate the heater and see if I get 6,3v. What is the average current in the heater?
Title: Re: G-PULTEC problems, please help!
Post by: Gustav on September 17, 2014, 08:56:06 AM
Maybe I CAN put a resistor in the socket to simulate the heater and see if I get 6,3v. What is the average current in the heater?

Did you at least try the tube you declared dead?

Gustav
Title: Re: G-PULTEC problems, please help!
Post by: pieca on September 17, 2014, 09:26:39 AM
Hi all !

After more testing, I've found that there is about 1Db of gain between left and right channel in my build…
My tubes are paired, so I don't suspect them

But I found this :
measure your 10KA high boost pot end-to-end resistances, and add a trimmer (say, 1-2k) to the one that has lesser value. This is probably the lesser of two evils, as pots will be slightly uneven (then again, they are most of the time anyway).

measuring my High boost pot end to end gives me :
9K on the hotter channel
10K7 on the other

So if I put a 2K trimmer in series on my 9K pot ( to get 10K7 total), I should get the same amount of gain on both channels.
Is it correct ?

Is it a preferred place to put the trimmer (Input or output) ?

Thanks again for your help
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on September 17, 2014, 09:51:14 AM
Put the trimmer at the input end.

Or better yet, find two hi-boost pots that are approximately the same, then trim.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: veve on September 17, 2014, 10:54:07 AM
The glass is broken so I don't think the tube works again.
I've tried with a new tube and with only the heater tension connected. I've measured 1,27V but the LM317 was'nt too hot.
Title: Re: G-PULTEC problems, please help!
Post by: pieca on September 17, 2014, 12:27:36 PM
Ok, I've put a trimer

Result : perfect balance between channels +- 0,2 DB from 20hz to 20 kHz ;D

Only 1db High boost difference at full boost… not a big deal

Will try with matched pots when possible

Thanks Gyraf, your project is TERRIFIC !!!!!!!!!!!!!!!!!!!!!!!!!!
Title: Re: G-PULTEC problems, please help!
Post by: MountCyanide on September 19, 2014, 12:30:15 PM
This was my first tube project and I'm happy to report that it went pretty darn smooth.
I broke out the acid and got to etching.

(http://mountcyanide.com/G_PULTEC_and%20_MTC_SS_Pultec/G_Pultec_PCB_popped)

I used the Don Audio toroid (and inductor) and I got stuck for a moment when the high voltages were too-- well, high. The 18k /10-watt resistor fix that I found earlier in this thread worked a charm at knocking the juice right down to where it needed to be. I used the Collective Case and this piece sounds grand. I busted my tube virginity and I kept calm by keeping an eye on the permanently hooked up multimeter that made sure the bleeder resistors were doing their jobs. I'm certainly digging this piece.

(http://mountcyanide.com/G_PULTEC_and%20_MTC_SS_Pultec/G_Pultec_MTC.JPG)

But---- being a fiend of transistor sound --- and a fiend of learning this stuff--- I just had to make a solid state version.  I did a bunch of searches and fact-schematic-gathering and decided on the pretty well worn path of the 2520. I just etched and built a bunch of 312's from scratch so the API circuit was very familiar to me. I did a sort of fusion of the Gyraf input (with lundahl 5402) and the 325 circuit in Photoshop.  And, of course, used the Gyraf Filter PCB.

(http://mountcyanide.com/G_PULTEC_and%20_MTC_SS_Pultec/MTC_SS_Pultec_CMOQ2S)
( Yes, that's a Mnats/Hairball DIY-990 in there. I hadn't prepared the gar2520 yet at this point. It sounded very good in there. But that's not the kind of good I was going for with this.)

I routed and manipulated everything for a nice tight and custom layout that could use 5mm terminals. Initially wiring up a Cinemag CMOQ2S as one often does with 2520 amps I recalled an old Scully 280 that I've had for decades just stashed away in a closet that was ripe with transformers. There's a 600:600 Freed tranny (32035) that seemed would be appropriate so I wired it up and sure enough--- I dug it. I find it more subdued than the CMOQ.  A bit mellow and dare I say vintage. Well, certainly. It's pretty damn old. And lovely sounding. A nice pairing for the aggressive gar2520. (Not that gar's is more aggressive than any 2520, I mean 2520's being  aggressive in general.)

(http://mountcyanide.com/G_PULTEC_and%20_MTC_SS_Pultec/MTC_SS_Pultec.JPG)

Opted for Fastron Inductors. Because if I was going solid state and aggressive I might as well try these little sub-dollar suckers. I dig em. Temporary unengraved front panel. Oddly in Neve Grey-Blue.

(http://mountcyanide.com/G_PULTEC_and%20_MTC_SS_Pultec/MTC_SS_Pultec_Front1)

Gotta say -- besides all of this learning for me- this is so damn gratifying!  But the best part is : IT WORKS. I'm stoked. I pulled. it. off.  Woo.  Additionally, I'd be more than happy to share the etch file. Just say the word. Thanks GroupDIY. Having a blast.
Title: Re: G-PULTEC problems, please help!
Post by: Gustav on September 19, 2014, 01:28:05 PM
This was my first tube project and I'm happy to report that it went pretty darn smooth.
I broke out the acid and got to etching.

(http://mountcyanide.com/G_PULTEC_and%20_MTC_SS_Pultec/G_Pultec_PCB_popped)

I used the Don Audio toroid (and inductor) and I got stuck for a moment when the high voltages were too-- well, high. The 18k /10-watt resistor fix that I found earlier in this thread worked a charm at knocking the juice right down to where it needed to be. I used the Collective Case and this piece sounds grand. I busted my tube virginity and I kept calm by keeping an eye on the permanently hooked up multimeter that made sure the bleeder resistors were doing their jobs. I'm certainly digging this piece.

(http://mountcyanide.com/G_PULTEC_and%20_MTC_SS_Pultec/G_Pultec_MTC.JPG)

But---- being a fiend of transistor sound --- and a fiend of learning this stuff--- I just had to make a solid state version.  I did a bunch of searches and fact-schematic-gathering and decided on the pretty well worn path of the 2520. I just etched and built a bunch of 312's from scratch so the API circuit was very familiar to me. I did a sort of fusion of the Gyraf input (with lundahl 5402) and the 325 circuit in Photoshop.  And, of course, used the Gyraf Filter PCB.

(http://mountcyanide.com/G_PULTEC_and%20_MTC_SS_Pultec/MTC_SS_Pultec_CMOQ2S)
( Yes, that's a Mnats/Hairball DIY-990 in there. I hadn't prepared the gar2520 yet at this point. It sounded very good in there. But that's not the kind of good I was going for with this.)

I routed and manipulated everything for a nice tight and custom layout that could use 5mm terminals. Initially wiring up a Cinemag CMOQ2S as one often does with 2520 amps I recalled an old Scully 280 that I've had for decades just stashed away in a closet that was ripe with transformers. There's a 600:600 Freed tranny (32035) that seemed would be appropriate so I wired it up and sure enough--- I dug it. I find it more subdued than the CMOQ.  A bit mellow and dare I say vintage. Well, certainly. It's pretty damn old. And lovely sounding. A nice pairing for the aggressive gar2520. (Not that gar's is more aggressive than any 2520, I mean 2520's being  aggressive in general.)

(http://mountcyanide.com/G_PULTEC_and%20_MTC_SS_Pultec/MTC_SS_Pultec.JPG)

Opted for Fastron Inductors. Because if I was going solid state and aggressive I might as well try these little sub-dollar suckers. I dig em. Temporary unengraved front panel. Oddly in Neve Grey-Blue.

(http://mountcyanide.com/G_PULTEC_and%20_MTC_SS_Pultec/MTC_SS_Pultec_Front1)

Gotta say -- besides all of this learning for me- this is so damn gratifying!  But the best part is : IT WORKS. I'm stoked. I pulled. it. off.  Woo.  Additionally, I'd be more than happy to share the etch file. Just say the word. Thanks GroupDIY. Having a blast.

Self etching  ;D

Gustav
Title: Re: G-PULTEC problems, please help!
Post by: Rocinante on September 20, 2014, 11:41:32 PM
Gustav,
That's awesome man.  Seriously. Here I am reading and rereading this thread, silently trying to troubleshoot my own Pultec in the hope that I find someone who has had similar issues and there you go and present some bad ass modification indicative of the gdiy spirit and with genuine modesty show us all what else can be done (which along with other talented gdiy members also portrays your understanding of the design).
My hat goes off to you there sir. I'm sure it sounds magnificent.
Title: Re: G-PULTEC problems, please help!
Post by: Gustav on September 23, 2014, 01:43:47 AM
Gustav,
That's awesome man.  Seriously. Here I am reading and rereading this thread, silently trying to troubleshoot my own Pultec in the hope that I find someone who has had similar issues and there you go and present some bad ass modification indicative of the gdiy spirit and with genuine modesty show us all what else can be done (which along with other talented gdiy members also portrays your understanding of the design).
My hat goes off to you there sir. I'm sure it sounds magnificent.

Hi Rocinante.

I quoted the full post and commented, which must have made it appear like my post, but I can't take credit for the self etch gain stage swap. :)
 
But since were on the subject, I did remove the  gain stage for a project myself.

(https://pcbgrinder.com/download/Random/TDG.jpg)

(https://pcbgrinder.com/download/Random/TDB.jpg)

Even did a quick lay out in Eagle for a two channel version.

https://pcbgrinder.com/download/Random/BTUBEDRIVER.pdf

You can use the existing board for a channel, though.

Gustav
 
Title: Re: G-PULTEC problems, please help!
Post by: MountCyanide on September 24, 2014, 06:31:45 PM
Yeah, that was me.
Perhaps I seem overstoked but I started all of this diy in January of this year.
Each consequent fix of this audio electro-addiction requires a higher dose.
Plus, copying circuits and mashing them up and tweaking em seems to makes for really good learning.
Title: Re: G-PULTEC problems, please help!
Post by: Rocinante on September 25, 2014, 10:18:00 AM
Lol. Oops. I guess its an optical illusion or finally paying off the brain alterations/ damage I did in my youth.
Amazing stuff then Mount cyanide. I havent gotten to self etching yet but im positive I see at least a 312 in the future.
I am currently waiting for some 18k resistors to arrive as I am pretty sure thats what's the issue with my build.
I too used the Don Audio xfmr and am having some audio trouble; I can just barely hear it if I crank my monitor way up. I ran a scope across as well as a cap/guitar cord probe and I have signal and continuality through the whole filter section. It seems to stop just before the output xfmr. My readings on the srpp are like others pretty weird/off.  I'm guessing/ hoping this 18k swap (which I just ran out of that value of course dammit) will be the solution.   
Its a great build anyway and I certainly learned a lot referring to this thread.
Title: Re: G-PULTEC problems, please help!
Post by: MountCyanide on September 26, 2014, 06:17:20 AM
Thanks dude.
Make sure it's a high watt 18k.
I used a 10.
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on September 26, 2014, 06:48:43 AM
I don't think you need that high-powered a dropping resistor for high voltage:

The ECC88 SRPP stage draws only ca. 5mA, which equates to 1W per 200V dropped across it (UxI=P: 200Vx0.005A=1W).

Remember that it's often easier to just add another resistor in series than to find the exact value you're after.

And then two ½W resistors can dissipate the whole 1W, providing they share load equally.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: MountCyanide on September 26, 2014, 06:52:42 AM
Oh ok. I was following previous advice --and further promoting (slight) misinformation haa.
Title: Re: G-PULTEC problems, please help!
Post by: djfatum on September 28, 2014, 06:29:16 AM
what power transformer should be for G-Pultec ???

Andrzej
Title: Re: G-PULTEC problems, please help!
Post by: Gustav on September 29, 2014, 12:20:52 PM
what power transformer should be for G-Pultec ???

Andrzej

9V or 12V and 220V secondaries - or use Jakobs solution with two trafos attached.

I am not sure why it says 15VAC for the first trafo, I would use two 12VAC transformers, but I am sure Jakob will explain the reasoning behind it.

Gustav
Title: Re: G-PULTEC problems, please help!
Post by: djfatum on September 29, 2014, 03:51:19 PM
I wonder about the power of a single transformer 50VA
second  220 v  & 9v  whether it is a good solution for stereo ??

https://pcbgrinder.com/index.php?route=product/product&path=60&product_id=122

Andrzej
Title: Re: G-PULTEC problems, please help!
Post by: weiss on September 29, 2014, 05:17:23 PM
I wonder about the power of a single transformer 50VA
second  220 v  & 9v  whether it is a good solution for stereo ??

https://pcbgrinder.com/index.php?route=product/product&path=60&product_id=122

Andrzej

you need these specs: Primary: 2 x 115v (230v) / Secondarys: 220V 0,1A / 9V 2,5A / 5V 0,5A

e.g.: http://www.don-audio.com/g-pultec-power-trafo-sec-220v-9v-5V
Title: Re: G-PULTEC problems, please help!
Post by: Mraihala on October 16, 2014, 07:55:52 PM
Hello!

Is it possible to use Lundahl LL1540 in this?

Best,

Mikko
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on October 17, 2014, 03:06:43 AM
Is it possible to use Lundahl LL1540 in this?

Not really - it has way too high copper resistance for low-impedance stuff like this.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: MicDaddy on January 02, 2015, 05:00:07 PM
What is the expected (any?) insertion loss with the eq in "bypass"?  I thought it had enough gain to be minimal but am now experiences some lower level going through one gpultec.
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on January 04, 2015, 10:40:25 AM
Depends on actual tube gain.

We are using the raw gain of the tube, no feedback.

 I've seen figures from -3 to +2dB

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: elziel on January 14, 2015, 03:45:20 PM
Hi everyone !

I've just finished my g pultec and it's so fantastic sounding unit. This topic was very helpfull in my build, but there is one problem that i have occured in my build  that wont let me sleep... is it normal that all freqency selector switches are popping when switched?
Title: Re: G-PULTEC problems, please help!
Post by: weiss on January 14, 2015, 04:57:51 PM
Hi everyone !

I've just finished my g pultec and it's so fantastic sounding unit. This topic was very helpfull in my build, but there is one problem that i have occured in my build  that wont let me sleep... is it normal that all freqency selector switches are popping when switched?

is it a loud pop or a click? You could check the direction of all the electrolytic caps.
Title: Re: G-PULTEC problems, please help!
Post by: kante1603 on January 14, 2015, 05:04:33 PM
Hi everyone !

I've just finished my g pultec and it's so fantastic sounding unit. This topic was very helpfull in my build, but there is one problem that i have occured in my build  that wont let me sleep... is it normal that all freqency selector switches are popping when switched?
MBB or BBM switches?


Best,


Udo.
Title: Re: G-PULTEC problems, please help!
Post by: elziel on January 14, 2015, 06:12:21 PM
Hi everyone !

I've just finished my g pultec and it's so fantastic sounding unit. This topic was very helpfull in my build, but there is one problem that i have occured in my build  that wont let me sleep... is it normal that all freqency selector switches are popping when switched?
MBB or BBM switches?



Best,


Udo.

BBM i think.
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on January 15, 2015, 08:23:30 AM
then yes, normal
Title: Re: G-PULTEC problems, please help!
Post by: SKJGProject on January 21, 2015, 12:48:27 PM
i have bought a unit several years ago from a quite experienced builder from here...unit was damaged during shipping (transformers were to heavy to survive the rude handling from the dhl guys) but fortunately only mechanical mounting got loose.

due to the veroboard build and my lack of experience i can't use this unit until now  because i get a quite high level hum/buzz in one of the two channels.

this is a pic of the inside, maybe someone can figure out some problems with untwisted wires that should be twistes or trafo placement etc...otherwise i have to sell this unit to someone who might be able to fix it!

Title: Re: G-PULTEC problems, please help!
Post by: gyraf on January 22, 2015, 05:18:27 AM
Loosen toroid power transformer bolt slightly, and turn the transformer while listening for the spot where hum is lowest.

Probably when the wire breakout point of the transformer is pointing furthest away from your input transformers (as it's here the most stray field exits the toroid).

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: MicDaddy on February 03, 2015, 11:19:50 PM
Using one of my G-Pultecs, all but one of the low frequency positions work.

When switched to this problematic position the overall output level becomes HUGE and there is no low end "filtering" happening.  Is it possible that there is no attenuation happening and at the same time being amplified by the makeup?

Have yet to open it up.  It was working just fine for years. 

Guesses?  Failing switch, open/shorted cap?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on February 04, 2015, 01:31:16 AM
One capacitor not connected through switch to circuit.
Title: Re: G-PULTEC problems, please help!
Post by: MicDaddy on February 04, 2015, 11:46:06 AM
Thank you Jakob, I'll post back what I find. 

I've never heard a real Pultec, but as far as equalizers go I enjoy these units very very much.
Title: Re: G-PULTEC problems, please help!
Post by: Shiftworker on February 07, 2015, 07:16:35 AM
I have 2 GPultecs built by someone in November. He got 99% correct ( ithink) but got very lazy with the soldering, heatsink etc.
I ironed out the basic problems by finding the bad joints and a much bigger heatsink. Now [Allen Heath 62 --> Patchbay --> L / R pultecs --> Patchbay --> interface...]. One minute the signal is happy and level, then one ch will dip with bass roll-off. I wait a bit and it sorts itself out. 
It is shorting somewhere, but I aint no engineer and don't have no more time to deal with it. 3 months is my limit.

Buider rang loads of times but with lame answers.

If anyone is in London and could help, obviously with bench time ££

Title: Re: G-PULTEC problems, please help!
Post by: gyraf on February 08, 2015, 09:54:23 AM
double-check heater voltage!
Title: Re: G-PULTEC problems, please help!
Post by: darkus on February 18, 2015, 02:23:11 PM
Hi! Just wired up the first of my two g-pultecs and im getting very little gain out of this. It seems to work as it should otherwise, and it sounds good. Its just that i have about 65dB gain loss! The unit is dead quiet too, no hiss or hum, i just need to use a preamp to add gain after the eq. Bypass mode has the same, little amount of gain. The in-going signal was a -8dB RMS mastered track peaking at -6 so there was definately enough gain going in.

Im using Edcor WSM transformers, 600:600 for input and 15k:600 for output. Im thinking if i just wired them wrong? Both are wired like this:

LL5402             Edcor

 2                                1
 5                                4
 7                                5
10                              8

Ive connected LL5402 pad 3 to the shell of edcor trafo.

Ive measured voltage before output cap and it shows me 122V dc so it should be good right?
Title: Re: G-PULTEC problems, please help!
Post by: Deepdark on February 18, 2015, 02:50:17 PM
too low inductance at the transformer?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on February 19, 2015, 05:31:16 AM
65dB gain loss is wrong.

1) Using the filter alone, no amplification, should give you approximately 20-25dB loss when set to neutral - check this first. If loss is different, check for wrong order-of-magnitude resistors, pots - and for shorts. The whole filter can be checked with unit powered off completely.

2) The amplifier board should give you some 20-25dB of gain from input to xlr's. Check this. If wrong, look at cabling, pcb integrity, and connection (through a capacitor) to the grid of lower tube half.

Substitution of transformers is not always a great idea: we use 5402 as 1:1 for the output - your 4:1 will give you 12dB less than what we set out for.

+122V at output coupling capacitor shows that tube driver stage is setting right, and can be expected to be alright if it checks out in point 2).

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: darkus on February 20, 2015, 04:30:20 AM
Tried to rewire trafos. Also tried multiple different combinations. Im close to giving up. Tbh i dont have time to figure sh*t out with these edcors. Ill eliminate them and use LL5402 only for output with unbalanced input.

Am i losing gain again if i build this with LL5402 output and unbalanced input?



Title: Re: G-PULTEC problems, please help!
Post by: gyraf on February 20, 2015, 07:31:25 AM
Am i losing gain again if i build this with LL5402 output and unbalanced input?

That should be unity within the raw-gain-tolerances of the tube used, so within 3dB or so

But I think the problem is more than this.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: darkus on February 21, 2015, 04:39:13 PM
Ok so my friend came over to troubleshoot these and after hours of testing the trafos alone and in circuit we found the problem.
I had misplaced a 2.2ohm resistor over the output pins 2&3 when there should be 2.2kOhm....LOL.

So much trouble for such a stupid mistake. They work perfectly now and sound stellar.

Pics:
https://db.tt/1a0o6Cco
https://db.tt/LSQYy8gl
https://db.tt/EA2V7rD4
https://db.tt/V96SO1XF

Don Audio custom power transformer, PCB Grinder inductors, filter caps are Don Audios Cap kit (selected wimas,styroflex,polys)
Edcor trafos (600:600 and 15k:600) and DIY-Racked case.

Even tho i had to wire everything (because of the 3U case) i think this is one of my cleanest builds so far.
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on February 22, 2015, 09:29:36 AM
wrong order-of-magnitude resistors
;)
Title: Re: G-PULTEC problems, please help!
Post by: MicDaddy on February 24, 2015, 05:45:59 PM
Hmm, 25Hz attenuate working, boost is full bandwidth... off come the knobs  ::)

Update:  all caps measure good from pad side except 1uF measured nada...reflow & presto  8)

sidenote knobs didn't need to come off.  Hooray!

Looking back on the schematic, it is clear now.  Still learning
Title: Re: G-PULTEC problems, please help!
Post by: Gustav on March 05, 2015, 02:15:53 AM
Matched for stereo.

All controls detented.

Quite happy about the result, I have to say.

Gustav
Title: Re: G-PULTEC problems, please help!
Post by: mickdundee63 on March 19, 2015, 09:31:25 AM
I have just finished my build and it sounds as it should except for high boost and high Q. I've been through the thread and have confirmed that my in/outs to the amp are correct and my switch is working correctly. I've confirmed the correct wiring and correct operation of the high boost pot and the Q pot.

The thing is I'm actually getting some effect from the high boost but it's very subtle. So it seems like audio IS passing through the high boost section of the circuit but not functioning properly.

Could this be an inductor problem? i.e. the switch is engaging the caps in the high boost section but the inductor isn't functioning properly?
Title: Re: G-PULTEC problems, please help!
Post by: mickdundee63 on March 20, 2015, 06:12:14 AM
Solved it - had a 2k pot in the high boost section
Title: Re: G-PULTEC problems, please help!
Post by: spase on March 30, 2015, 08:25:55 PM
anyone have the edcor xs 1100 wiring diagram for this pultec eq?
Title: Re: G-PULTEC problems, please help!
Post by: mrkrawn on April 03, 2015, 11:00:17 AM
Hi guys.
I just finish a stereo g pultec.
I started by check 6.3v and 250v rail.

Its ok for 6.3v but i read 290v between  the 3k3 2w big resistor and 220uf cap.

So i try to replace the 3k3 by a 20k 10w and i read 275v.
I use Power Transformer - Pri.: 2x115v- Sec.: 220v, 9v and 5v from Don Audio

should i put a 40k to get my 250v ?
Thanks


Title: Re: G-PULTEC problems, please help!
Post by: mrkrawn on April 03, 2015, 12:07:42 PM
i just try a 40k i read 300v between A1 and 220uf 350v cap.
Something goes wrong??
Title: Re: G-PULTEC problems, please help!
Post by: Gustav on April 03, 2015, 01:42:05 PM
i just try a 40k i read 300v between A1 and 220uf 350v cap.
Something goes wrong??

What is A1?

You should measure the voltage after the drop resistor. It should remain relatively unchanged before the resistor.

If you suddenly dont see a drop, you should check if your LM317 overheated and shut down (No regulation means no heater voltage, which will result in a zero current draw on tubes, which means no drop over the high voltage drop resistor).

You haven't stated your location, so we dont know what mains you have.

Gustav
Title: Re: G-PULTEC problems, please help!
Post by: mrkrawn on April 03, 2015, 01:59:42 PM
thanks gustav
A1 is pin 4 of tube socket ecc88.
I'm in 220v country.
I did my first test with no tube and no front panel
i just check voltage before put the ecc88
the 6.3v is ok my lm317 is not hot.
Is it normal with no tube to get 300v between  250v point pcb and 220uf350v negative leg?
Thanks
Title: Re: G-PULTEC problems, please help!
Post by: kante1603 on April 03, 2015, 02:06:07 PM

I hope we're talking of the same built here,I refer to Gustav's stereo kit now.The psu must have a load,so I started with the tubes inserted and a higher value drop resistor.
The tweaked it down.


Best,


Udo.
Title: Re: G-PULTEC problems, please help!
Post by: mrkrawn on April 03, 2015, 02:40:18 PM
i have build 2 pcb from gyraf pultec rev4 not stereo version
Title: Re: G-PULTEC problems, please help!
Post by: Gustav on April 04, 2015, 01:25:18 AM

Is it normal with no tube to get 300v between  250v point pcb and 220uf350v negative leg?


220VAC x square root of two (or about 1,4) will land you at about 310VDC, so thats nothing out of the ordinary.

Again, you will not see a drop with no tubes installed, simply because there is no current draw. (V = R x I, and with no tube installed, I = 0)

Gustav
Title: Re: G-PULTEC problems, please help!
Post by: mrkrawn on April 04, 2015, 07:30:45 AM
Thanks gustav

 i will try to take mesurement with the ecc88 put in the socket with a 20k 10w to start.
I read in this topic a guy  put a 18k another guy a 33k5.
So Whats the best for G pultec 250V 240V 225V ?
i think i will  test one channel with LM350 or LM338 to be sure.
I don't want to broke my 2 matched ecc88 which cost me a lot .

Thanks for your help guys
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on April 04, 2015, 08:44:21 AM
Best is probably some 210-225V with unit heated up.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: mrkrawn on April 04, 2015, 08:57:20 AM
Thanks a lot Jakob
Title: Re: G-PULTEC problems, please help!
Post by: mrkrawn on April 04, 2015, 09:41:42 AM
I just do my test:

With a 40k i've got 170V
With a 20k i stopped  at 250v but it increasing.

I will try to buy a 30k or 33k5
The 6.3v Work perfect :)

That 's not my day! >:(
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on April 04, 2015, 12:54:18 PM
...just use some low-power resistors in parallel - e.g. 100K or 220K.

In general, there's rarely any need for more than 2W resistor total - we're only drawing some 5-6mA.

(to calculate dissipated power in W, multiply voltage drop in V x 0.005A )

Aim at ca. ½W per 100V drop in voltage across resistor.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: mrkrawn on April 05, 2015, 10:27:30 AM
Hi

New try today with a 23k5 and LM350
Result 213V and 6.00V. :)

I will try to get a real 6.3V But everything seems good now.
Thank to all
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on April 06, 2015, 12:59:30 AM
6.0V is plenty fine for heating.

Read tube data sheets, says +/-10%, you do the math...

Jakob E.

Title: Re: G-PULTEC problems, please help!
Post by: mrkrawn on April 06, 2015, 09:06:02 AM
Hi

I did my first listening test today with different transformers from OEP(Not the best, but good for test)
A262A7E ratio: 1+1:1+1
a262a2e ratio: 1+1:2+2

My 1st try with
Input with 2:2      A262a2e
output  with 2:1 A262A7E

2nd try With Input A262A7E 1:1
output  With Input A262A7E  2:1

I'm loosing 3 DB compare to the signal coming.
It's a little bad
I've read Pultec is really low impedance
So should i  decrease the impedance of my transformers?
Oep A262A7E is 600ohm
Maybe a 150ohm will be better?
Another idea i had is increase voltage of tube to 220V i'm at 217V but i'm not sure.

Otherwise my EQ sound very good.
Free Hum Free noise.
I try to ear any noise or hum but No.
What a f**kin warm low and tasty high. :)


Title: Re: G-PULTEC problems, please help!
Post by: mrkrawn on April 07, 2015, 05:43:21 PM
Hi
I have a question about these 2 resistors.
Are they here especially for Lundahl Transformers?
I forget to put them.

Thanks
Title: Re: G-PULTEC problems, please help!
Post by: snaper on April 18, 2015, 03:00:02 PM
Just finished it today, thank you for this Gyraf!
Everything is fine, sounds awesome...arghm...except the high cut rotary switch.
It seems it doesnt do anything.
What should I check?
Title: Re: G-PULTEC problems, please help!
Post by: Gustav on April 19, 2015, 02:52:49 AM
Just finished it today, thank you for this Gyraf!
Everything is fine, sounds awesome...arghm...except the high cut rotary switch.
It seems it doesnt do anything.
What should I check?

Do you mean the pot for amount of gain or the switch for selecting the frequency? (I am guessing the pot)

The problem will be isolated to the connections to, around and from the control on this.

Gustav
Title: Re: G-PULTEC problems, please help!
Post by: spase on April 19, 2015, 10:59:22 PM
anyone can tell me how to wire the edcor sx1100 on input...
i tryed to go unbalanced everything its fine,but want to have a balanced connection and dont know how to wire the input tranie.
Title: Re: G-PULTEC problems, please help!
Post by: snaper on April 20, 2015, 04:58:37 AM
Just finished it today, thank you for this Gyraf!
Everything is fine, sounds awesome...arghm...except the high cut rotary switch.
It seems it doesnt do anything.
What should I check?

Do you mean the pot for amount of gain or the switch for selecting the frequency? (I am guessing the pot)

The problem will be isolated to the connections to, around and from the control on this.

Gustav
Actually I was talking about the High Cut switch, not the Freq selectro switch for the High.
Its working, but only if I turn on the High Attenuate pot.
Its OK for me in this way. (If its not correct :D)
Title: Re: G-PULTEC problems, please help!
Post by: mrkrawn on April 20, 2015, 07:19:20 AM
anyone can tell me how to wire the edcor sx1100 on input...
i tryed to go unbalanced everything its fine,but want to have a balanced connection and dont know how to wire the input tranie.

Maybe this can help you spase.
Title: Re: G-PULTEC problems, please help!
Post by: spase on April 20, 2015, 07:49:56 PM
i tryed with this pcb, everything its working unbalanced , thats only with the output transformer, but when i add input nothing happens i dont have any signal.I think  its the problem with the wiring on  that input transformers becouse unbalanced everything its working.
Title: Re: G-PULTEC problems, please help!
Post by: mrkrawn on April 21, 2015, 08:25:18 AM
edcor xs1100
signal come to
pin2 +/pin1 -

signal to xlr out
pin7 + /pin8 -

If you do that you must  hear the signal.
Title: Re: G-PULTEC problems, please help!
Post by: spase on May 02, 2015, 02:48:46 PM
i connected everything , when i try to connect from my main output from the soundcard i have great signal, but when i try from my other outputs i have very low level signal.Anyone know something about this?

p.s everything its working on the filter board.
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on May 04, 2015, 03:18:38 AM
If unbalanced source, make sure to de-balance (xlr pins 1+3 shorted)

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: Audioman on May 12, 2015, 03:02:26 AM
Hi Guys,
I have a problem with one of my two G-Pultec,
I used JJ E88CC gold pin tubes but one of the two tubes after a few hours of activity is dead
if apply 0 dbu to the input the output read -35 dbu ...
in the other unit instead if apply 0 dbu on the input i read -5,41 dbu at the output , is it all normal ?

P.S. where i can download the high resolution schematics ?
Title: Re: G-PULTEC problems, please help!
Post by: frazzman on May 15, 2015, 01:33:14 AM
Hi all,

Does anyone know if a 4db drop in level is "normal" when the EQ is engaged (even in bypass, but same with circuit "in" but no boost or attenuation).

No input transformer and EDCOR Xs1100 on the output.

Everything else seems to function ok but HT voltage is way too high at 324V. Need to replace 3K3 resistor with 18K perhaps?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on May 21, 2015, 04:16:15 AM
Fabio (Audioman) and frazzman,

We've been through this a couple of times before:

Gain through the GPultec depends on two things:

1 - The actual raw gain of the tube used - this varies some +/- 2½dB on NOS tubes, probably more on new-production ones. You could use Russian 6N23P for slightly more gain in average (if you can find those).

2 - The ratio of the values of hi-boost potentiometer (10KA) and the hi-cut potentiometer (1KA) - this is where we do the actual -20dB no-eq-attenuation (Schematic - http://www.gyraf.dk/gy_pd/pultec/gy_pd_sch.gif )

For adjusting to unity gain, you could probably put a 1K Ohm trimmer potentiometer at the TOP (clockwise end) of the hi-cut pot and adjust for unity at no-hicut-setting. Only side-effect of this will be slightly less available maximum-hi-cut at pot extreme setting.

If you do this, let us know how/if it works - would be nice to have in this thread
EDIT: Confirmed working -
Just letting you know the 1k trimmer at the Hi cut CW position does indeed work and allow for trimming to unity gain. I now have no level difference with pultex engaged.

Please also note that this circuit was made for LL5402's in and out - other brands of transformers or no-input-transformer may very well give varying results.

Jakob E.

ps: I've had quite a few JJ tubes fail me after short time. Maybe it's poor production standards, maybe they are specified slightly different than real E88CC's, and don't like us going to extremes of cathode/heater potential differences. I use Philips 6922, and like them a lot.

DO NOT run this circuit above +250V HT - the tubes don't like this. Raise series resistor value until you have some 200-250V HT under load (tube heated, ca. 30sec.). A standard 0.6W type resistor will nearly always do fine - you do the math of power dissipated at given resistor and given voltage drop....
Title: Re: G-PULTEC problems, please help!
Post by: Audioman on May 21, 2015, 07:04:20 PM
@ Gyraf i had mount the trimmer as you suggest but doesn't work , i measured a gain loss of 3 dbu .
i have also tested the amplifier section with a physical bypass in/out , and the amplifier gains 18 dbu in full bandwith
i also verify the 10k resistor on the control pcb and all is correct.
now with the tube very hot and the signal generato at 0 dbu in bypass mode i have a loss of 2,3 dbu
let me know how can i do to solve the problem
Thank you in advance
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on May 21, 2015, 11:33:59 PM
how much gain variation do you get with a 1K trimmer?
Title: Re: G-PULTEC problems, please help!
Post by: frazzman on May 25, 2015, 02:32:07 AM
Fabio (Audioman) and frazzman,

We've been through this a couple of times before:

Gain through the GPultec depends on two things:

1 - The actual raw gain of the tube used - this varies some +/- 2½dB on NOS tubes, probably more on new-production ones. You could use Russian 6N23P for slightly more gain in average (if you can find those).

2 - The ratio of the values of hi-boost potentiometer (10KA) and the hi-cut potentiometer (1KA) - this is where we do the actual -20dB no-eq-attenuation (Schematic - http://www.gyraf.dk/gy_pd/pultec/gy_pd_sch.gif )

For adjusting to unity gain, you could probably put a 1K Ohm trimmer potentiometer at the TOP (clockwise end) of the hi-cut pot and adjust for unity at no-hicut-setting. Only side-effect of this will be slightly less available maximum-hi-cut at pot extreme setting.

If you do this, let us know how/if it works - would be nice to have in this thread

Please also note that this circuit was made for LL5402's in and out - other brands of transformers or no-input-transformer may very well give varying results.

Jakob E.

ps: I've had quite a few JJ tubes fail me after short time. Maybe it's poor production standards, maybe they are specified slightly different than real E88CC's, and don't like us going to extremes of cathode/heater potential differences. I use Philips 6922, and like them a lot.

DO NOT run this circuit above +250V HT - the tubes don't like this. Raise series resistor value until you have some 200-250V HT under load (tube heated, ca. 30sec.). A standard 0.6W type resistor will nearly always do fine - you do the math of power dissipated at given resistor and given voltage drop....

Thanks Gyraf for your reply!

I dropped my 3k3 resistor to 22k and now have a healthy HT voltage within the acceptable range.

I still have a about a 6-7db volume drop when the unit is inserted (in bypass and with circuit in).

I always used the lundhals in the past but thought Id give an edcor xs1100 a shot as don-audio had an adaptor board that made it easy. As you said, you didn't design it for this transformer so it probably has something to do with that.  Never had an issue when I built with the lundhals in the past.

Anyone had any experience with the edcors on these builds?

I was wondering if the 10k and 2k2 resistors strapped across the input and output connectors should be omitted when not using lundhals?

Cheers
Title: Re: G-PULTEC problems, please help!
Post by: Audioman on May 31, 2015, 02:45:53 PM
@ Gyraf  sorry for the delay in responding you , it's been a busy period .
The gain variation with the 1k trimmer is 48 dbu
let me know
Thanks

how much gain variation do you get with a 1K trimmer?
Title: Re: G-PULTEC problems, please help!
Post by: Rocinante on May 31, 2015, 04:25:53 PM
Fabio (Audioman) and frazzman,

Thanks Gyraf for your reply!

I dropped my 3k3 resistor to 22k and now have a healthy HT voltage within the acceptable range.

I still have a about a 6-7db volume drop when the unit is inserted (in bypass and with circuit in).

I always used the lundhals in the past but thought Id give an edcor xs1100 a shot as don-audio had an adaptor board that made it easy. As you said, you didn't design it for this transformer so it probably has something to do with that.  Never had an issue when I built with the lundhals in the past.

Anyone had any experience with the edcors on these builds?

I was wondering if the 10k and 2k2 resistors strapped across the input and output connectors should be omitted when not using lundhals?

Cheers

Hey having some difficulties with the Edcors as well did you figure out the problem?
Thanks
Title: Re: G-PULTEC problems, please help!
Post by: frazzman on June 01, 2015, 08:06:28 PM
Fabio (Audioman) and frazzman,

Thanks Gyraf for your reply!

I dropped my 3k3 resistor to 22k and now have a healthy HT voltage within the acceptable range.

I still have a about a 6-7db volume drop when the unit is inserted (in bypass and with circuit in).

I always used the lundhals in the past but thought Id give an edcor xs1100 a shot as don-audio had an adaptor board that made it easy. As you said, you didn't design it for this transformer so it probably has something to do with that.  Never had an issue when I built with the lundhals in the past.

Anyone had any experience with the edcors on these builds?

I was wondering if the 10k and 2k2 resistors strapped across the input and output connectors should be omitted when not using lundhals?

Cheers

Hey having some difficulties with the Edcors as well did you figure out the problem?
Thanks

Hi there,

Nope, just ordered lundhals instead. I've built about 5 units in the past with lundhals and had no issue at all. That was the knot variable that changed in this instance.

Cheers
Title: Re: G-PULTEC problems, please help!
Post by: Rocinante on June 02, 2015, 12:17:15 AM
Bummer. Yeah in the other G-pultec I built I used Lundahls as well. Thanks for replying. I'll keep searching till i give in I guess.
Title: Re: G-PULTEC problems, please help!
Post by: frazzman on June 02, 2015, 01:17:29 AM
Bummer. Yeah in the other G-pultec I built I used Lundahls as well. Thanks for replying. I'll keep searching till i give in I guess.

Do you have a loss of volume, like I do, when the circuit is engaged?

I have this, even in bypass. Apart from that, everything works and sounds nice as it should.

I'm wondering if the 10k and 2k2 resistors strapped across the input/output should be omitted when not using Lundhals?

I haven't tried that yet, but maybe an idea.
Title: Re: G-PULTEC problems, please help!
Post by: Rocinante on June 02, 2015, 02:51:40 AM
I can follow the circuit with a tracer and everything is perfect up until the edcor.  There the volume drops tremendously.  Ive seen people with the edcors but I believe its been with Purusha's adapters.  I'm actually looking for his to compare the pin outs to the Don audio one's.  Cant seem to find any pics yet though.  Via a suggestion I read on here I'm gonna desolder both the transformers and the resistors and then put everything back one at a time while running a sine wave.
Title: Re: G-PULTEC problems, please help!
Post by: frazzman on June 02, 2015, 05:48:35 AM
I can follow the circuit with a tracer and everything is perfect up until the edcor.  There the volume drops tremendously.  Ive seen people with the edcors but I believe its been with Purusha's adapters.  I'm actually looking for his to compare the pin outs to the Don audio one's.  Cant seem to find any pics yet though.  Via a suggestion I read on here I'm gonna desolder both the transformers and the resistors and then put everything back one at a time while running a sine wave.

An update for you....

I removed the 2k2 resistor from across the output tx.... seems to have fixed the problem.

I now only have around a 3dB difference when the circuit is in.

It sounds pretty good. I'm not sure if removing that resistor is 'normal' practice when using the EDCOR XS1100 as a substitute. I'm just doing some comparisons now with another unit that has Lhundal's. So far all the boost and cuts work as expected, i'm just interested to see if the frequency response is hindered by the omission.

So far so good.

Try it and tell me what you think.
Title: Re: G-PULTEC problems, please help!
Post by: Rocinante on June 02, 2015, 12:21:13 PM
I can follow the circuit with a tracer and everything is perfect up until the edcor.  There the volume drops tremendously.  Ive seen people with the edcors but I believe its been with Purusha's adapters.  I'm actually looking for his to compare the pin outs to the Don audio one's.  Cant seem to find any pics yet though.  Via a suggestion I read on here I'm gonna desolder both the transformers and the resistors and then put everything back one at a time while running a sine wave.

An update for you....

I removed the 2k2 resistor from across the output tx.... seems to have fixed the problem.

I now only have around a 3dB difference when the circuit is in.

It sounds pretty good. I'm not sure if removing that resistor is 'normal' practice when using the EDCOR XS1100 as a substitute. I'm just doing some comparisons now with another unit that has Lhundal's. So far all the boost and cuts work as expected, i'm just interested to see if the frequency response is hindered by the omission.

So far so good.

Try it and tell me what you think.
This is good news. Thanks I will
Title: Re: G-PULTEC problems, please help!
Post by: weiss on June 24, 2015, 01:18:39 PM
i want to build a stereo unit but both channels should be affected exactly the same. how could one use a single set of controls (frequency, attenuation, boost etc.) for the two channels?
is there anything important? dual gang pots should work, right? what about the switches?

thanks for your answer

weiss
Title: Re: G-PULTEC problems, please help!
Post by: Gustav on June 24, 2015, 01:27:30 PM
i want to build a stereo unit but both channels should be affected exactly the same. how could one use a single set of controls (frequency, attenuation, boost etc.) for the two channels?
is there anything important? dual gang pots should work, right? what about the switches?

thanks for your answer

weiss

Same thing. Should work with double double stacked switches. (4 x6?)

Or, you could do two separate channels on the board I made.

Gustav
Title: Re: G-PULTEC problems, please help!
Post by: weiss on June 24, 2015, 01:45:32 PM
hey gustav, thanks. what do you mean by "do two separate channels on the board"? I will try that, but it must work, right?
It is just a matter of saving space on the front panel, so i don't need duplicated controls for each channel ;)
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on June 25, 2015, 03:54:29 AM
Notice that dual-gang potentiometers rarely track better than 10%, so don't expect good stereo tracking unless you are heavily selecting all components.

This is the primary reason why so few companies make stereo eq's.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: weiss on June 25, 2015, 06:53:21 AM
Notice that dual-gang potentiometers rarely track better than 10%, so don't expect good stereo tracking unless you are heavily selecting all components.

This is the primary reason why so few companies make stereo eq's.

Jakob E.

Ah okay, now i get the problem. Maybe you can tell me how these guys achieved to do it in stereo?
Title: Re: G-PULTEC problems, please help!
Post by: Harpo on June 25, 2015, 08:02:45 AM
... unless you are heavily selecting all components.
Ah okay, now i get the problem. Maybe you can tell me how these guys achieved to do it in stereo?
Maybe ask Steffen ?... (http://www.steffenmuellermastering.com/contact/)
Title: Re: G-PULTEC problems, please help!
Post by: fatheaddrummer on August 10, 2015, 01:36:05 PM
Hi everybody,

I just finished my G Pultec with the PCB from Gustav, Lundahl Transformers, ECC88....
Everything works fine, but i have a very little hum. A little less when in bypass mode, a little more, when it's turned on. Compared to a normal signal it is really really quiet. I only can hear the hum when i turn on my speakers to nearly maximum - so it's actually not a big deal, but I think it is not neccesary?!

I connected the main PCB to ground.

Is there anything else i should connect to ground? What are the stars on the Filter PCBs for?

In addition i realised that the wire of my power LED is causing a lot more hum. It nearly dissapears when i movr the wire outside the case....should i use a shielded wire and connect one end of the shield to ground?

Is it possible that i mounted the main PCB too close to the Power Trafo?

Any ideas?

Thank you very much!!

Best,
Christian
Title: Re: G-PULTEC problems, please help!
Post by: Gustav on August 11, 2015, 12:58:49 AM
don't expect good stereo tracking unless you are heavily selecting all components.



Ah okay, now i get the problem. Maybe you can tell me how these guys achieved to do it in stereo?

Didnt he just do that!?

Gustav
Title: Re: G-PULTEC problems, please help!
Post by: frazzman on August 11, 2015, 06:04:29 PM
Fabio (Audioman) and frazzman,

We've been through this a couple of times before:

Gain through the GPultec depends on two things:

1 - The actual raw gain of the tube used - this varies some +/- 2½dB on NOS tubes, probably more on new-production ones. You could use Russian 6N23P for slightly more gain in average (if you can find those).

2 - The ratio of the values of hi-boost potentiometer (10KA) and the hi-cut potentiometer (1KA) - this is where we do the actual -20dB no-eq-attenuation (Schematic - http://www.gyraf.dk/gy_pd/pultec/gy_pd_sch.gif )

For adjusting to unity gain, you could probably put a 1K Ohm trimmer potentiometer at the TOP (clockwise end) of the hi-cut pot and adjust for unity at no-hicut-setting. Only side-effect of this will be slightly less available maximum-hi-cut at pot extreme setting.

If you do this, let us know how/if it works - would be nice to have in this thread

Please also note that this circuit was made for LL5402's in and out - other brands of transformers or no-input-transformer may very well give varying results.

Jakob E.

ps: I've had quite a few JJ tubes fail me after short time. Maybe it's poor production standards, maybe they are specified slightly different than real E88CC's, and don't like us going to extremes of cathode/heater potential differences. I use Philips 6922, and like them a lot.

DO NOT run this circuit above +250V HT - the tubes don't like this. Raise series resistor value until you have some 200-250V HT under load (tube heated, ca. 30sec.). A standard 0.6W type resistor will nearly always do fine - you do the math of power dissipated at given resistor and given voltage drop....

Hi Jakob,

Just letting you know the 1k trimmer at the Hi cut CW position does indeed work and allow for trimming to unity gain. I now have no level difference with pultex engaged.

Good solution!

Thank you
Title: Re: G-PULTEC problems, please help!
Post by: Patch on September 22, 2015, 08:20:31 AM
Notice that dual-gang potentiometers rarely track better than 10%, so don't expect good stereo tracking unless you are heavily selecting all components.

This is the primary reason why so few companies make stereo eq's.

Jakob E.

When you say 'heavily selecting components' is there anything else to take into account other than using identical components bought in the same batch used across both boards, matched inductors, matched valves?

I plan on attempting a 1U version stereo G Pultec and am looking for ganged pots (haven't managed to source all yet) and double deck rotary switches (oof expensive!) and would obviously like a near perfect stereo tracking.

"rarely track better than 10%"............. oooh nooo that doesn't sounds great. Really that bad? I really can't fit 2x every pot/switch on a 1U stereo....  Would the stepped switches with resistors instead of pots be more precise? I'd rather have pots than steps but if needs must....

Any tips on on getting good tracking for dual gang would be mucho appreciated.
Title: Re: G-PULTEC problems, please help!
Post by: Patch on September 22, 2015, 08:23:57 AM
Also forgot to ask, I can only find a  2k ohm dual gang pot rather than a 2k2....is 2k ohm ok to use, will it affect the High Q in a bad way?

http://www.digikey.co.uk/product-search/en?pv1092=2&pv1=380&pv1849=3&FV=fff40004%2Cfff80540&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25  (http://www.digikey.co.uk/product-search/en?pv1092=2&pv1=380&pv1849=3&FV=fff40004%2Cfff80540&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25)
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on September 23, 2015, 01:18:58 AM
2K is fine
Title: Re: G-PULTEC problems, please help!
Post by: qwerty8787 on October 10, 2015, 11:04:33 AM
Hi everyone!

Got a PQD-2 on the bench, almost finished.
I am experiencing volume loss when circuit is engaged, about -1.5 dB, and an overall loss of about -3dB/-4dB (depending on channel, because of tube mismatch I guess).

I tried to put the 1K trimmer above the "cut high" rotary switch and managed to get 0dB overall loss when unit is bypassed. But I still have about the same loss between bypassed and active.

What am I missing?

Thanks to everyone in advance  :D

Title: Re: G-PULTEC problems, please help!
Post by: gyraf on October 12, 2015, 10:08:18 AM
Quote
managed to get 0dB overall loss when unit is bypassed. But I still have about the same loss between bypassed and active.

Question not entirely clear?

If you're having overall gain loss with the unit in your chain, bypassed or not, it's dependent on actual tube gain. We don't use gain regulated by feedback, so you depend on raw gain being about right.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: qwerty8787 on October 13, 2015, 08:18:33 AM
Hy Jakob!

I wrote my question badly. I'll try to explain again my issue:

Before 1k-trim mod:

Ch1 Bypassed: ≈ -3.dB (got there with the trimmer)
Ch2 Bypassed: ≈ -4 dBdB (same as Ch1)

Ch1 Engaged: about -1.5dB LESS THAN when bypassed
Ch2 Engaged: about -1.5dB LESS THAN when bypassed

After 1k-trim mod:

Ch1 Bypassed: 0 dB (got there with the trimmer)
Ch2 Bypassed: 0 dB (same as Ch1, trimmed manually)

Ch1 Engaged: -1.30 dB
Ch2 Engaged: -1.35dB

So my point is: I managed to get perfectly matched channels when in bypass, but still experiencing some loss when active (actually this loss is pretty close between channels).

I'm quite sure tubes are not matched, cause I'm using random old vintage tubes I found in a drawer. But even if I throw in 2x ECC88 bought from Banzai as matched, the result is the same.

My guess is that this trim mod enables to compensate for tube gain mismatch but not for "eq" loss...or at least this is what I get seeing that mismatch is pretty close between channels after mod.


Title: Re: G-PULTEC problems, please help!
Post by: miszt on February 22, 2016, 03:27:52 PM
Just finished my stereo g-pultec/pqd2, sounds awsome, rich, smooth and well just awsome :D

I seem to have a imbalance somewhere though, i'm loosing a few db on one channel (left), the loss is still there in bypass mode

Some things i noticed

The right channel tube glows far more brightly than the left (they are brand new, new production electro-harmonix), coincidence that this channel is also louder? (dont know much about tubes or how the glow reflects its function) - i've read that tubes need to "burn in", but i presume that wouldnt be the cause of that kind of imbalance....could the tubes just be mismatched? (they were sold as a matched pair)

The only 2 components which are not matched less than 1% are the big 4.7k caps near the transformers (they are about 4% out from each other)... would these caps be responsible for (~4.5-6db loss, haven't measured exactly, just running noise and saws thru atm)

Anything else i should check?

Cant work out if this is the same issue as discussed above, using a trimmer to match channels? The problem form me is overall level difference rather than on specific freq bands (which all seem to be matched relative to the overall difference (so far))
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on February 23, 2016, 02:18:08 AM
miszt - we've discussed this several times before in this thread.

Most part of raw-gain-mismatch comes from tube's gains that vary due to production tolerances (try swapping them)

Most part of bypass/in gain mismatch comes from mismatched ratio ResistanceLowCutPot/ResistanceHiBoostPot

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: miszt on February 23, 2016, 06:01:31 AM
miszt - we've discussed this several times before in this thread.

Most part of raw-gain-mismatch comes from tube's gains that vary due to production tolerances (try swapping them)

Most part of bypass/in gain mismatch comes from mismatched ratio ResistanceLowCutPot/ResistanceHiBoostPot

Jakob E.


Thanks for clarifying a bit; i did read that, but its confused me, because my pots/switches are matched within 0.1% (switched using pcbgrinder switch calculator lists) - the cut and boost all appear to work on every step, so no loose/bad connections afaik

so can i ignore the switches and just focus on tube matching?

Or is the bypass loss only going to be down to the lowcut/highcut switches being somehow mismatched?


Update: i've gone over all the resistors, no mismatch/accidently placed one, i did also use meter to check (i know not very accurate in circuit, but it didnt give me anything to be concerned about) - unfortunetly my filter board is hard wired onto the gain board, so i cant accurately check the resistance of the full signal path of each channel either....waiting for caps to discharge then i'll give it a go tho...

But i'm guessing i just need better matched tubes (although confirmation would be good...

(everything on the filter board does what it should, all changes at each freq seem to be correct relative to the difference in total gain on each channel)


The only other pair of tubes i have are a pair which were sold as matched NOS Siemens, but arrived clearly not even the same brand; will give them a try later tho

Well at least i can use this in m/s mode in the meantime :)

update 2 - seems i have a dodgy tube in the "NOS" set, gain keeps dropping and climbing *sigh* ...but the EH work well in M/S mode with makeup for the lower gain tube

Can anyone recommend a UK supplier of properly matched tubes for this? Bought a few sets already but reall  cant afford to keep buying pairs and cross my fingers, would rather pay a little extra and know they will be equal gain straight off (i'm sure this must be possible? I cant believe manley for eg supply replacement tubes that are mismatched)
Title: Re: G-PULTEC problems, please help!
Post by: miszt on March 01, 2016, 08:28:35 AM
I asked the supplier I purchased the EH 6922 how close they could match the tubes; explaining that my two they had supplied are giving me upto 6db difference between left/right, i got this reply:

Quote
We match the 6922 on average within 1mA on the Anode and no more than 2mA.  This is normally an accepted good match.
 You can request a specific specification on ordering and we would take this into consideration before dispatching.

no idea what that means or how that relates to the balance of left/right?

can anyone shed any light? or better yet recommend a shop that sells them specifically matched for stereo operation - if 6db difference is "acceptable", then I guess we all have different definitions of acceptable
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on March 02, 2016, 03:02:48 AM
I think we mentioned earlier in this thread that socalled "matching" of small-signal tubes is not worth the paper the figures are written on.

Matching is for power tubes, ensuring approximately the same current vs. grid voltage.

For GPultec you'll want tubes matched for raw gain "Amplification factor" or µ

If you really need matching, the best way is to buy a handful and use the best-matching ones

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: miszt on March 02, 2016, 01:07:46 PM
I think we mentioned earlier in this thread that socalled "matching" of small-signal tubes is not worth the paper the figures are written on.

Matching is for power tubes, ensuring approximately the same current vs. grid voltage.

For GPultec you'll want tubes matched for raw gain "Amplification factor" or µ

If you really need matching, the best way is to buy a handful and use the best-matching ones

Jakob E.

thanks for the info!

i didn't spot that particular post, read thru the whole thread and ran 100's of internet searches on the subject too lol

ah well, i'll stick with make up gain in my DAW for now, noise floor is low enough that it doesn't matter too much the way I'm using the EQ; amazed how quiet this thing actually is tbh, very happy :D



one last question:  I have a pair of NOS siemens, and I thought that one of them was faulty, the gain on that channel varied wildly and erratically - since I took them out and put in some EH's, I also spotted that one of my inductor connections had come loose (just one! somehow lol), so i fixed it and just carried on

now I've put the NOS tubes back in, I was going to make a note of which one had the varying gain and return them to the shop; but after ~45minutes so far, there has been no variance at all? ...could that dodgy inductor connection have been the cause of the tube gain randomly changing? (it was varying by quite a bit, ~20db up and down randomly (without touching any of the controls - i didn't note whether it was just while in bypass or not))


update: well over an hour playing with the EQ, and both NOS tubes are behaving themselves..so i guess it must have been the dodgy inductor connection?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on March 03, 2016, 05:48:30 AM
yup, intermittent inductor can easily mess up gain.

Other than that, it could be slightly dirty tube pins - common on NOS like the ones I use - that cleans up when inserted/extracted a couple of times..

Happy EQ'ing!

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: Vac11 on March 21, 2016, 09:18:39 AM
Hi Jakob,

I have one question ... Is it necessary for the capacitor on the output value 4u7F? IS it sufficient even less value? For example 0,47uF? (for build with Lundal ll5402)

I want to use at this point a better paper in oil capacitor from Jensen, and 4u7F value is a bit bigger (about 10x5 cm) and more expensive ...

Thanks for the clarification

M.

EDIT:

I found answer from august 2004:
http://groupdiy.com/index.php?topic=1649.0

"Yes, there is a 4.7uF/250V polyester cap driving the output transformer. The output is somewhat low impedance, so with a lower value capacitor you'll loose low-end......

Jakob E."
Title: Re: G-PULTEC problems, please help!
Post by: darkus on July 01, 2016, 03:23:20 AM
Hi all.

So ive used my G-Pultecs for a while and i have a list of problems i need to sort out.

Low boost kicks in almost full with a very slight pot turn, like 1-2 on the frontpanel scale. The low end at 2 sounds like its  at 6 and after mid way rotation the low end boost pot has no function.  >:( High boost however works like complete opposite, it sounds like nothing is happening before mid way, its all in the 5-10 of the frontpanel scale.  :o Both attenuators are soft across the whole turn which is imo how they are supposed to be so i think they are ok.

Both units have very low output, i lose about -10dB in gain. Im using edcor WSM 15k:600 for both trannies, should i try Lundahls instead? Could they fix the boost issues as well?

Also something is going on with the panel light indicator in both units. Ive used Don Audio trafo https://www.don-audio.com/g-pultec-power-trafo-sec-220v-9v-5V and i have a BA9S lamp in the 5v wires withouth a resistor. The lights worked for first few days, then they didnt light up anymore for few weeks, and now it comes and goes. Sometimes when i turn the units on they might light up for few mins and or then they dont.  ???

If anyone could help me fix some of these issues id be so happy.  :-* :-* :-*
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on July 01, 2016, 06:47:15 AM
1) check response curves of your pots. Linear/Log in the right places?
2) I don't know the edcors, but the price difference alone points towards them not being anything like the LL5402
3) I'm guessing at a loose bulb in the indicator. Screw it back in?

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: jonasmaks on July 30, 2016, 04:27:46 PM
Hello,
I've measured G-Pultec Hi Boost frequency curves and found out that they are quite inconsistent quality wise - from Q=3 at 2.1kHz to Q=2 at 11kHz. I'm using stand alone Murata inductors for my build (R1900 series, as closest substitution to Toko which are practicaly impossible to find). Has anyone measured G-Pultec based on Toko or multitaped inductor frequency responses to compare (some links I found on forum are gone)? Could it be cure for such behaviour - adding some resistor in series with the inductor to compensate  higer Q? But graphs show that biggest difference of Q apears on same inductor (say on 11 and 16 kHz). Any thoughts (and measurement graphs :) ) would be appreciated!
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on July 31, 2016, 02:06:11 AM
This is exactly what the math would predict, and how we would expect it to behave.

Does the unit somehow Sound wrong?

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: jonasmaks on July 31, 2016, 06:13:42 AM
Hi Jakob,
Yes, we are powerless against math :). I just thought the lower the C, the bigger is Q (http://www.radio-electronics.com/info/formulae/q-quality-factor/rlc-q-factor.php).
Here is nothing wrong with the sound - unit works great (kudos to you!) and compares perfectly with commercial Warm Audio model EQP-WA. Just sharing my own experience and trying to gather more knowledge about the use of different inductors.

Jonas M.
Title: Re: G-PULTEC problems, please help!
Post by: febo2609 on October 11, 2016, 02:53:56 PM
If someone used a coil for G-Pultec eq1 from  Don Audio store.
What are the experiences with them.
Is Sowtek coils better than Don audio coil.
Best regards
Title: Re: G-PULTEC problems, please help!
Post by: Audioman on October 11, 2016, 06:28:16 PM
yours is a question or a statement?

If someone used a coil for G-Pultec eq1 from  Don Audio store.
What are the experiences with them.
Is Sowtek coils better than Don audio coil.
Best regards
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on October 12, 2016, 04:07:17 AM
There's not a whole lot of difference between these inductors, even if manufacturers would like you to believe there is.

You may even roll your own, and it will probably be as good as any.

No Angel dust in there.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: snaper on November 06, 2016, 12:42:28 PM
I've finished my GPultec last year and I love it!
But. I really could use it after my mixer as a master eq ;)
So, I've decided to give a stereo upgrade to my actual unit.
I've found the recommended dual switches , but, csant find a 4pdt switch for bypass.
So my idead is that bypass the onboard bypass, and use a relay bypass board from diy-tubes.
(I'm using an opamp gain stage, so no tubes involved, I can totally avoid the circuit)

Using the relay bypass sounds more ok to then having a dummy switch.

Could you help me out on where to place jumpers in the board to avoid the switch?
Title: Re: G-PULTEC problems, please help!
Post by: snaper on November 29, 2016, 04:48:09 AM
Has anybody a drawing about the original Pultec knobs?
Ordered them from Don-Audio, still "under delivery", and I have to cut the shaft of pots / switches...
Title: Re: G-PULTEC problems, please help!
Post by: PitchFork38 on December 12, 2016, 10:33:06 AM
Hi
Maybe it's a stupid question but If I use a mic preamp with balanced output (like the G9) before my G-pultec.
Do I need to use the optional balanced or unbalanced Input in the Pultec ?
I don't really understand the function of this optional input.
It I use the unbalanced, input transformer is useless ?
Thank's
Title: Re: G-PULTEC problems, please help!
Post by: Audioman on January 18, 2017, 06:44:42 AM
@frazzman can you post a picture of the installed trimmer on the pcb ?
Just to see how to install correctly the trimmer
Thank you in advance !!


Hi Jakob,

Just letting you know the 1k trimmer at the Hi cut CW position does indeed work and allow for trimming to unity gain. I now have no level difference with pultex engaged.

Good solution!

Thank you
Title: Re: G-PULTEC problems, please help!
Post by: petermontg on January 27, 2017, 10:47:18 AM
Curious if someone could help me shed some light.

I am reading 247 and 5.9 which are within tolerance. Before the 4.7uf I am reading a 68v. Should I have something else here?

I am passing no audio at all. Both trafos are lundahl running balanced line.

Any ideads

Edit: okay I see it should be closer to 125v

All voltages check have reading of 122v on the output.

The SRPP is driving a loss of about -80db unit is hiss and and hum free. If I tap the tube I can here it.

I read earlier in the thread it could be inductance issues. 

Could someone shed some light for me?
Title: Re: G-PULTEC problems, please help!
Post by: petermontg on January 29, 2017, 10:21:22 AM
Turns out I had a 470R across the 470k on input, would explain the loss.

Silly mistake.
Title: Re: G-PULTEC problems, please help!
Post by: PitchFork38 on February 26, 2017, 02:59:07 PM
Hi !

I purchased a G-Pultec Mono Power Transformer from Don audio

https://www.don-audio.com/g-pultec-mono-power-trafo-sec-220v-9v-5V

The 3 secondaries should be :

220v    0,05A      (red)           "HT"
 9v         1A            (green)       "Heater"
5V         0,5A        (blue)          "LED"

On my transformer it's :

245V           (red)
6V                  (green)
11.3V           (blue)

It's a problem because my heater voltage is too low (4V) and HT is 345V.
If I switch the green and blue secondary on the PCB, it's closer to the "real" value of the secondaries and I get a correct value for the heater voltage (6V).
But it's not the same current (green 1A and  blue 0.5A), is it a problem ?

Pierre
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on February 27, 2017, 02:32:31 AM
Hi Pierre,

It's probably better to ask don-audio about this - it is not the standard way of building this power supply..

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: kurganyuriy1987 on May 27, 2017, 09:14:48 AM
Hi everyone!
Can i get somewhere gerber files for  g pultec pcb's?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on June 03, 2017, 02:43:46 AM
No. There are pdf drawings available for self-etching.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: petermontg on June 26, 2017, 05:11:01 PM
Finally got around to getting mine finished and in the desk.

Those amps are spectacular. Beaut of  a low end and the detail in the stereo image is fantastic.

Thanks so much for the project Jakob . Great EQ.

Best
Peter
Title: Re: G-PULTEC problems, please help!
Post by: sr1200 on July 18, 2017, 08:58:56 PM
Weird problem today with mine (thats been working fine for years).  The inductors responsible for the 2.1 to 6.8k boost seemed to stop working. the 12 and 18k work fine.  I opened the unit looked around, checked solder points, everything is good.  I plugged it back in, problem is still there.  I tapped one of the "107C" inductors with the rubber on the back of the screw driver i had in my hand and it started working...  switched to lower freq. and its not working... tapped the little inductor and the lower freq starts working now too....  do inductors go bad like that?  (again, no cold solders).
Title: Re: G-PULTEC problems, please help!
Post by: Gustav on July 19, 2017, 07:05:14 AM
  I tapped one of the "107C" inductors

Dont know whats up with the inductor, but with that marking, I want to ask if you are sure you have the right value in there?

Gustav
Title: Re: G-PULTEC problems, please help!
Post by: sr1200 on July 19, 2017, 07:38:02 PM
As far as Im aware i have the right ones in there.  When I do a sweep to show the freq. they line up pretty well with the advertised value on the front panel.
Title: Re: G-PULTEC problems, please help!
Post by: petermontg on July 20, 2017, 11:41:06 AM
It could be  a cold solder elsewhere apart from the filter board.

When problem solving mine.... I had a cold solder in my amp on the right side. When chasing it a tap on the inductor on the left side would knock it out. worth checking you input amps
Title: Re: G-PULTEC problems, please help!
Post by: sr1200 on July 20, 2017, 08:21:35 PM
@petermontg - good call indeed, thats exactly what it was. (not the same spot but a completely unrelated spot)  had to find it with a magnifying glass though!  Cheers!
Title: Re: G-PULTEC problems, please help!
Post by: petermontg on July 21, 2017, 03:28:07 PM
@petermontg - good call indeed, thats exactly what it was. (not the same spot but a completely unrelated spot)  had to find it with a magnifying glass though!  Cheers!

Glad to help. My heart was close to breaking before I find mine. I wouldn't wish a cold solder on anyone.
Title: Re: G-PULTEC problems, please help!
Post by: petermontg on September 09, 2017, 04:27:44 PM
Just a thought.
Has anybody successfully added a bypass switch for the HI freq selections on the boost while still maintaining the boost section?

Id like to able to drive the inductor a little but without adding any freq selections,

Best
Peter

 
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on September 10, 2017, 02:31:28 AM
Does not work that way: without the capacitor, the high- boost would be a mis-aligned low-boost starting at a very high frequency.

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: petermontg on September 17, 2017, 08:16:38 AM
Does not work that way: without the capacitor, the high- boost would be a mis-aligned low-boost starting at a very high frequency.

Jakob E.

Thanks Jakob. I had forgotten that part.
Title: Re: G-PULTEC problems, please help!
Post by: weiss on September 24, 2017, 01:56:27 PM
I bought 2 power trafos for a stereo g pultec project years ago with following specs from micandmod (https://micandmod.com/hardware-parts/223-power-transformer-pultec-eqp-1a-gyraf.html):

Voltages, primary: 0-115V, 0-115V
Voltages, secondary: 0-9V/1A, 0-220V/50mA, 0-11V/500mA

can these be used to power 2 pcb's? i am worried about the 11V compared to the 5V secondaries offered with this one:
 https://www.don-audio.com/g-pultec-power-trafo-sec-220v-9v-5V
Title: Re: G-PULTEC problems, please help!
Post by: petermontg on September 24, 2017, 03:53:40 PM
I bought 2 power trafos for a stereo g pultec project years ago with following specs from micandmod (https://micandmod.com/hardware-parts/223-power-transformer-pultec-eqp-1a-gyraf.html):

Voltages, primary: 0-115V, 0-115V
Voltages, secondary: 0-9V/1A, 0-220V/50mA, 0-11V/500mA

can these be used to power 2 pcb's? i am worried about the 11V compared to the 5V secondaries offered with this one:
 https://www.don-audio.com/g-pultec-power-trafo-sec-220v-9v-5V

 I used the G9 one from Don Audio without any issues in  stereo version.
Don't cheap out on the shielding....... Save yourself a headache,
Title: Re: G-PULTEC problems, please help!
Post by: petermontg on September 27, 2017, 04:02:49 PM
So, I did a little mod on mine today.

A little switch to bypass the whole mid boost section connecting back to the 0mh pin which leads back to the lowend boost and high freq cut.

Unit sound so much better when using the lowend only, really opens it up and you can have lowend boost for days.
Going to put it under scope tomorrow see how its reacting.

Switch connecting is
Pin 1 (bottom) - 0mh
Pin 2 (middle) - output from SRPP
Pin 3 (top) - to filter input.

Ground stayed the same connect straight to filter.

Have fun, if anyone try's it.

Best
Peter
Title: Re: G-PULTEC problems, please help!
Post by: darkus on October 12, 2017, 02:57:32 AM
Hi all!

Im still having issues with my build. The output is really low and thin, I can hear the filters are working its just that the signal sounds very broken, thin and low gain.

Ive checked my xlr wiring and terminating resistors are correct. Im using wired Alpha switches and LL5402 in/out. Don Audio PT.
I read that I should recalculate the big watt resistor value for the don audio PT, currently I have one thats suggested in the bom. Is there a chance my tube is broken? I havent actually measured what voltage the PT is giving to the tube.

(https://dl.dropboxusercontent.com/s/dtgmceiu3fi0ax3/IMG_20170619_133112_fotor.jpg?dl=0)
Title: Re: G-PULTEC problems, please help!
Post by: petermontg on October 13, 2017, 08:11:37 AM
What toroidal are you using? Check your voltage after the 3K3/2W. I doubt your tube is broken. There are 3 voltage to power the SRPP. 
Title: Re: G-PULTEC problems, please help!
Post by: weiss on March 28, 2018, 02:39:15 PM
Hey guys, I'm having problems figuring out how to wire the RM-8 inductor by don audio..
https://www.don-audio.com/G-Pultec-Inductor-RM8-22mH69mH169mH269mH (https://www.don-audio.com/G-Pultec-Inductor-RM8-22mH69mH169mH269mH)

the connections on the pcb are 2 per inductor but the rm8 combines all 4 together with one output for each value.
so which pin should be used for the second connection of each value?

(https://www.don-audio.com/bilder/produkte/gross/Inductor-312mh-155mh-78mh-39mh-26mh_2_b2.jpg)

I hope you get what I mean..

thanks
Ansgar
Title: Re: G-PULTEC problems, please help!
Post by: Gustav on March 29, 2018, 04:31:17 AM
Hey guys, I'm having problems figuring out how to wire the RM-8 inductor by don audio..
https://www.don-audio.com/G-Pultec-Inductor-RM8-22mH69mH169mH269mH (https://www.don-audio.com/G-Pultec-Inductor-RM8-22mH69mH169mH269mH)

the connections on the pcb are 2 per inductor but the rm8 combines all 4 together with one output for each value.
so which pin should be used for the second connection of each value?

I hope you get what I mean..

thanks
Ansgar

The pic you attached

You see how one step on the switch connects to the end of two inductors at a time?

You are just tapping into windings on a single inductor and setting them up to switch in series instead of using single inductors.

Gustav

Title: Re: G-PULTEC problems, please help!
Post by: weiss on March 29, 2018, 06:43:08 AM
The pic you attached

You see how one step on the switch connects to the end of two inductors at a time?

You are just tapping into windings on a single inductor and setting them up to switch in series instead of using single inductors.

Gustav

ahhh now i get it.. thanks Gustav!
Ansgar
Title: Re: G-PULTEC problems, please help!
Post by: jon83 on May 30, 2018, 03:14:11 PM
Hi all,

Can someone tell me what the resistor values on the Don Audio filter board are? On the original they're marked as 1k, 1k, 10k, and 75r, is that right? If so, what do they correspond to, R1, R2 etc. Cant seem to find this anywhere online.

Title: Re: G-PULTEC problems, please help!
Post by: weiss on June 27, 2018, 07:51:02 AM
Hey guys.
I experienced some weird behaviour with my new g pultec. Everything works except in one position (60Hz) of the low frequency rotary switch (2x6) it is louder than the other selectable frequencies (20-100Hz). I checked the wiring for mistakes but i couldn't find an explanation for this behaviour. any ideas? is the switch broken?? it also makes "sound" during switching, whereas the other switches just mute during switching...

thanks,
Ansgar
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on June 27, 2018, 08:36:01 AM
Louder as in: if you test it at 60Hz signal - or louder like in "all frequencies are boosted"?

First is a property of eq's :-) - last points to a defective capacitor or connection..

Jakob E.

Title: Re: G-PULTEC problems, please help!
Post by: weiss on June 27, 2018, 12:26:36 PM
Louder as in: if you test it at 60Hz signal - or louder like in "all frequencies are boosted"?

First is a property of eq's :-) - last points to a defective capacitor or connection..

Jakob E.

second one!
let me try to explain: in the low boost section i can select (rotary)

20Hz, 30Hz, 50Hz, 60Hz, 80Hz, 100Hz

When i switch to 60Hz the whole signal gets boosted like 5 db's or so. A single frequency is not the problem but the overall loudness difference. but only on this switch position, all the other positions i can select in the low section work like expected. I resoldered the whole switch connections so that leaves a dead cap?
Title: Re: G-PULTEC problems, please help!
Post by: weiss on June 29, 2018, 06:33:18 AM
which capacitor would be most likely responsible for this? anyone?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on June 30, 2018, 01:48:43 AM
..the one associated with the problematic step on the switch...
Title: Re: G-PULTEC problems, please help!
Post by: weiss on July 10, 2018, 03:27:05 PM
..the one associated with the problematic step on the switch...

sorry for being so dumb. I found the problem. It was indeed a bad connection.
Thanks Jakob!
Title: Re: G-PULTEC problems, please help!
Post by: andow on October 10, 2018, 06:29:27 PM
Can somebody tell me if a Haufe RK310/2 would be suitable as input transformer?
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on October 13, 2018, 03:04:08 PM
Impossible to tell. Try and report back?

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: weiss on January 22, 2019, 05:12:31 AM
just built another stereo pultec! the device is alive and working but:

the hi boost freq setting at 3k gives me 1k, 1k equals to 2k and 2k gives me 3k in the analyzer. so the frequencies are actually switched around..
I double checked the values and they match the schematic, any ideas how i could find the error ?
which one is the cap that needs to be switched  ???
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on January 22, 2019, 06:38:00 AM
The capacitors in series with the inductor and Q-pot controls the frequencies of high-boost

Smaller capacitor => higher frequency

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: weiss on January 24, 2019, 01:53:10 AM
The capacitors in series with the inductor and Q-pot controls the frequencies of high-boost

Smaller capacitor => higher frequency

Jakob E.

thanks, you solved it!
it was indeed too small ::) ::)
Title: Re: G-PULTEC problems, please help!
Post by: weiss on February 05, 2019, 05:28:49 AM
If i want to transform potentiometers of a dual mono pultec into stepped switches, is it as easy as using the 1x12 lorlins, adding resistors to it (like in the pqd2) and connect it?

i found these pcb's: http://diy-tubes.com/index.php?route=product/product&path=59&product_id=167

might that work?

thanks
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on February 06, 2019, 05:55:13 AM
I don't see why not? But you don't actually need pcb's for that, do you?

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: weiss on February 06, 2019, 06:13:39 AM
I don't see why not? But you don't actually need pcb's for that, do you?

Jakob E.

thanks, yes not really  ::)
Title: Re: G-PULTEC problems, please help!
Post by: petermontg on February 06, 2019, 11:07:38 AM
Is it possible to control the iput in the amp.

And if so where about would i

Best
Peter
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on February 08, 2019, 01:00:32 AM
say again?
Title: Re: G-PULTEC problems, please help!
Post by: weiss on February 08, 2019, 05:12:20 AM
Is it possible to control the iput in the amp.

And if so where about would i

Best
Peter

you want to control intput or output gain?
Title: Re: G-PULTEC problems, please help!
Post by: Mike Havok on March 23, 2019, 09:43:26 PM
Hi all,

Can someone tell me what the resistor values on the Don Audio filter board are? On the original they're marked as 1k, 1k, 10k, and 75r, is that right? If so, what do they correspond to, R1, R2 etc. Cant seem to find this anywhere online.

Probably a bit late but for anyone else needing them they are:

R1 = 75R
R2 = blank
R3 = 10K
R4 = 10K
Title: Re: G-PULTEC problems, please help!
Post by: petermontg on April 17, 2019, 02:41:57 PM
you want to control intput or output gain?

What I am trying to do is just to control the input into the SRPP.

Any Ideas wold be great.

Best
Peter
Title: Re: G-PULTEC problems, please help!
Post by: weiss on April 17, 2019, 04:15:41 PM
What I am trying to do is just to control the input into the SRPP.

Any Ideas wold be great.

Best
Peter

You could replace the 10k resistor in front of the SRPP (between filter pcb in and ground next to 220n coupling cap to ground) with a potentiometer to attenuate the signal.
Title: Re: G-PULTEC problems, please help!
Post by: petermontg on April 19, 2019, 08:37:19 AM
Thanks I'll give it a go over the weekend.

Best
Peter
Title: Re: G-PULTEC problems, please help!
Post by: weiss on May 23, 2019, 07:17:52 PM
Hey guys,

i built a pultec with stereo potentiometers and dual gang switches from a kit i bought off a member here. But the high section (boost & attenuation) doesn't do anything on both channels..
Low section works as expected. i checked the wiring and couldn't find any loose connections.
Could you give me a hint where to look ?
Otherwise this eq is working fine.

thanks
Ansgar
Title: Re: G-PULTEC problems, please help!
Post by: gyraf on May 24, 2019, 06:28:27 AM
High boost and high cut are two entirely different functions, so it's probably more that one error. Maybe switch miswireing?

Jakob E.
Title: Re: G-PULTEC problems, please help!
Post by: weiss on May 24, 2019, 07:03:54 AM
High boost and high cut are two entirely different functions, so it's probably more that one error. Maybe switch miswireing?

Jakob E.

Oh okay! alright, i'll check.

thanks for the persistent help  :)
Title: Re: G-PULTEC problems, please help!
Post by: weiss on May 24, 2019, 01:01:21 PM
High boost and high cut are two entirely different functions, so it's probably more that one error. Maybe switch miswireing?

Jakob E.

Now i completely rewired the 3 switches, replaced the 4 filter boards but nothing changed  :-[
I am not using lorlin switches mounted on the pcb but these front panel mounted dual gang switches:
(https://cdn-reichelt.de/bilder/web/xxl_ws/C200/RS2212.png)

I put the marked with 1 as the first position of each switch, that should be correct - or not?
Does the  high freq selection switch need connection from the poles to the pcb? It seems they are only connected to each other.
Title: Re: G-PULTEC problems, please help!
Post by: weiss on May 25, 2019, 09:55:01 AM
i am absolutely confused where this might come from. i used two completely different filter boards and wired all switches from the beginning but still the high section doesn't do anything...   :-[
Is there someone who might have experienced the same?
I am clueless  :-\
Title: Re: G-PULTEC problems, please help!
Post by: weiss on May 25, 2019, 10:41:47 AM
not sure if this helps..

(https://i.ibb.co/zh9RqJN/61-E6-EEAA-4-A72-41-ED-B0-C3-DA9-F4-B924-F02.jpg) (https://ibb.co/zh9RqJN) (https://i.ibb.co/tmRxQYL/D7352944-9175-4-F86-AA02-8-E840-A20-DF58.jpg) (https://ibb.co/tmRxQYL)
Title: Re: G-PULTEC problems, please help!
Post by: Harpo on May 26, 2019, 03:51:23 AM
Ansgar, is this a dual 2x6 rotary switch for sure (4 pole connections) ?
As you didn't fit all wire connections where the joins were made on pcb, you did all (5 per side, 10 for stereo) corresponding joins at the switches poles and throws directly ?
Title: Re: G-PULTEC problems, please help!
Post by: weiss on May 26, 2019, 05:43:49 AM
Ansgar, is this a dual 2x6 rotary switch for sure (4 pole connections) ?
As you didn't fit all wire connections where the joins were made on pcb, you did all (5 per side, 10 for stereo) corresponding joins at the switches poles and throws directly ?

hey, yes it has 2 poles per channel so 4 in total and 6 positions.
I made all the connections which are needed on the pcb. when no lead was going from the switch on the pcb then i didn't wire it. hope this makes sense..

Like said there is no problem at all with the low section, this is what makes me wonder :-/
Title: Re: G-PULTEC problems, please help!
Post by: Harpo on May 26, 2019, 09:51:17 AM
For Hi-boost frequency selection, deck 1, pole A and throw 1...6, pole B and throw 7...12. Deck 2 hooked up the same.
You joined throw 1 with 2, 4 with 5, 8 with 9 and 11 with 12 and you joined pole A with pole B ?
(hookup of low section and Hi-cut is different from Hi-boost)
Title: Re: G-PULTEC problems, please help!
Post by: weiss on May 26, 2019, 10:29:14 AM
For Hi-boost frequency selection, deck 1, pole A and throw 1...6, pole B and throw 7...12. Deck 2 hooked up the same.
You joined throw 1 with 2, 4 with 5, 8 with 9 and 11 with 12 and you joined pole A with pole B ?
(hookup of low section and Hi-cut is different from Hi-boost)

yep, exactly what i did
Title: Re: G-PULTEC problems, please help!
Post by: Harpo on May 26, 2019, 12:45:34 PM
...but the pcb layout is differing from schematic and has the throw connections just the other way round, IE you'd have to join 2 with 3, 5 with 6, 7 with 8 and 10 with 11, else you'd be partly shorting out an inductor winding section. As this mixup in your case only would give a different frequency response, the error must be in a different spot. Something like a broken pcb trace, a broken, wrong connected or wrong value Hi-boost Q pot, ...
good luck
Title: Re: G-PULTEC problems, please help!
Post by: weiss on May 26, 2019, 02:48:55 PM
hm i would be happy if i got a changing frequency response at all. i already replaced the q pot and high boost and cut potentiometers. no change.
Title: Re: G-PULTEC problems, please help!
Post by: weiss on May 29, 2019, 12:32:12 PM
found the problem after reading this post......


Problem solved!

I found out while remeasuring everything, that the 1M resistor above the bypass switch was giving me 1M at both positions of the bypass switch while that should have been bypassed.

So it was a bad connection in the bypass switch after all, but i didn't think of that before because the lo freq circuit was bypassed all right by that same switch!

:D!


i somehow... didn't wire the bypass switch  ::)