G-PULTEC problems, please help!

[snipsnip]

Yeah, it can be either  2x15v or  2x12v wired back to front. Dont get one 15 and one 12 or it wont work properly.

 

[audiophreak]

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 .

 

[audiophreak]

.. 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

 

[pacemaker]

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

 

[audiophreak]

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

 

[benlindell]

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:

 

[audiophreak]

beautiful units benlindell , may I ask where you got the Toko's, I cant seem to locate them.

 

[benlindell]

Sorry, I mis-spoke, I used fastron inductors from mouser part number (22uh): 434-03-223J

 

[gyraf]

..you want mH, not uH...

 

[audiophreak]

Thank you both, I will try those.   

 

[JoleFIN]

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.

 

[gyraf]

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.

 

[snipsnip]

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?

 

[briomusic]

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.

 

[gyraf]

I wouldn't recommend making dual units - too many people has had trouble getting them hum-free...

Jakob E.

 

[snipsnip]

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

 

[briomusic]

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?

 

[telefunk]

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

 

[snipsnip]

I would just use a 2k pot, or 2k5 is probably better.

 

[telefunk]

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...