GroupDIY

Project Specific Discussions => Dynamic Processors => Topic started by: abechap024 on May 21, 2012, 07:41:47 PM

Title: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: abechap024 on May 21, 2012, 07:41:47 PM
Hello,

Thanks everyone! Time for another group buy of Rev 2 PRR-176 Vari-mu compressor Stereo PCB boards!!
Here is the white market thread:

http://www.groupdiy.com/index.php?topic=51031.msg647827#msg647827

Thanks!

Here are the Docs

www.acsoundstudio.com/public_html/prr_176/rev_2/BOM_POWER_REV2.pdf (http://acsoundstudio.com/prr_176/rev_2/BOM_POWER_REV2.pdf)
www.acsoundstudio.com/public_html/prr_176/rev_2/BOM_REV2.pdf (http://acsoundstudio.com/prr_176/rev_2/BOM_REV2.pdf)
www.acsoundstudio.com/prr_176/rev_2/REV2_PRR_176_WIRING_GUIDE.png (http://www.acsoundstudio.com/prr_176/rev_2/REV2_PRR_176_WIRING_GUIDE.png)

Wiring guide uploaded :)
Thanks!


White Market Thread:  http://www.groupdiy.com/index.php?topic=51031.msg647827#msg647827
Title: Re: PRR-176 Vari-Mu Rev 2
Post by: mitsos on May 22, 2012, 10:30:54 AM
nice! do you have a list of revisions?
Title: Re: PRR-176 Vari-Mu Rev 2
Post by: abechap024 on May 22, 2012, 12:23:28 PM
Good idea! I'll get them together along with a picture of the rev 2 board :)
Title: Re: PRR-176 Vari-Mu Rev 2
Post by: Hank Dussen on May 23, 2012, 03:28:35 PM
How about some extra PSU PCB's for us version 1 builders?  ;D
Title: Re: PRR-176 Vari-Mu Rev 2
Post by: ArnauTS on May 24, 2012, 07:04:16 AM
Money sent ;D
Title: Re: PRR-176 Vari-Mu Rev 2
Post by: roy on May 25, 2012, 03:28:13 AM
money sent
Title: Re: PRR-176 Vari-Mu Rev 2
Post by: ilfungo on May 26, 2012, 09:21:07 AM
Payment sent for 2 x PRR 176 Rev 2

It's possible to add extra PSU board for rev 1?


Thanks!!!
Title: Re: PRR-176 Vari-Mu Rev 2
Post by: jandoste on May 26, 2012, 11:00:04 AM
Payment sent for 2 x PRR 176 Rev 2

It's possible to add extra PSU board for rev 1?


Thanks!!!

+1
Title: Re: PRR-176 Vari-Mu Rev 2
Post by: minor_glitch on June 03, 2012, 08:55:57 PM
I'd definitely like a psu board for my rev1 if you plan to sell any individually.
Title: Re: PRR-176 Vari-Mu Rev 2
Post by: abechap024 on June 04, 2012, 10:44:10 AM
I'd definitely like a psu board for my rev1 if you plan to sell any individually.

Good Idea, I'm most likely going to also offer these separately, will post when I have a price.
Title: Re: PRR-176 Vari-Mu Rev 2
Post by: JayDubrek on June 05, 2012, 09:45:12 AM
+1 in the PSU board Abe!
Jay
Title: Re: PRR-176 Vari-Mu Rev 2
Post by: petrol vendor on June 06, 2012, 11:51:41 AM
hello, sorry i don´t see what this projekt is... what parts are needed, etc....
Do you have a link about this projekt?
Title: Re: PRR-176 Vari-Mu Rev 2
Post by: petrol vendor on June 06, 2012, 11:52:55 AM
ok, sorry, i was blind. no link needed... Thanks for doing this!!!!
Title: Re: PRR-176 Vari-Mu Rev 2
Post by: abechap024 on June 19, 2012, 10:45:55 AM
Hi Ya'll,
Thanks for the orders. Sent the order to the Fab House yesterday, so should get them in a couple weeks! I ordered extra so people can still order if they choose!
Thanks!

Abe


Errata for Rev 2:

Power resistors to 10 ohms
Fixed Smaller Edcor footprint
Fixed INA input ground on pin 1
Attack/Release cap now on board for both channels
Fixed B voltage power (more caps)
Made both channels more alike for ease of stuffing
A dedicated switch for bypass
Changed 50k resistors to 56k
Fixed various Cap footprints
Made a consistent 100nf or 0.1uf
Made power supply off board
Made same TX options for input for interstage
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/1712*
Post by: astroschnautzer on July 25, 2012, 03:40:00 PM
Q: what does the comments behind resistors and caps mean;  "res400" ,"CAP300RP" etc...., is it size?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/1712*
Post by: abechap024 on July 26, 2012, 12:07:31 AM
Q: what does the comments behind resistors and caps mean;  "res400" ,"CAP300RP" etc...., is it size?
yep thats the size in mils. which i think is 1 mil = to 1/1000 inch
Best,
Abe
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/1712*
Post by: astroschnautzer on July 26, 2012, 02:29:44 AM
Thanks.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/1712*
Post by: Edward on July 27, 2012, 06:33:22 AM
Any recomendations on what  trimmers ( VR 10, 12, 7, 8 ) to use for the power PCB? And is 1N4764A-TAP ( Mouser part # 78-1N4764A-TAP ) a good choice for D14?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/1712*
Post by: abechap024 on July 28, 2012, 05:17:36 PM
Any recomendations on what  trimmers ( VR 10, 12, 7, 8 ) to use for the power PCB? And is 1N4764A-TAP ( Mouser part # 78-1N4764A-TAP ) a good choice for D14?

Yep that looks fine for d14. for trimmers look on eBay...they seem the be the least expensive: example

http://www.ebay.com/itm/10pcs-5K-Trimmer-Trim-Pot-Variable-Resistor-3296-/310353115764?pt=LH_DefaultDomain_0&hash=item48427cba74#ht_2788wt_1270

Best,
Abe
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/1712*
Post by: herrmann on July 29, 2012, 06:11:15 AM
LM337 is missing in the bom.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/1712*
Post by: ilfungo on July 30, 2012, 07:07:59 AM
thanks Abe
The PCBs arrived today!!!
Sorry for a stupid  question:
is possible to add something like  Drip time constant PCB on this project?
Thanks
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/1712*
Post by: abechap024 on July 30, 2012, 08:29:30 AM
thanks Abe
The PCBs arrived today!!!
Sorry for a stupid  question:
is possible to add something like  Drip time constant PCB on this project?
Thanks

Great! Glad you got them. Time constant, like an "auto-release" found on the SSL? It would surely be possible, I think just adding a resistor network along with the caps would work. I'd have to double check the SSL schematic to be sure....

Yea, you could make it on a switch, and switch out the release pot, or somehow incorporate it. Then build up something like on the GSSL just scaling down the capacitance/resistance values to 1uf (or 2uf) or whatever you want! there are no rules.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/1712*
Post by: ilfungo on July 31, 2012, 07:59:30 AM
Sorry any news about new wiring guide?
Thanks


someone can tell me how to do input (Log 10k) and Out (100k Log) stepped with Lorlin switch?
Thanks
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on July 31, 2012, 11:33:04 AM
Sorry any news about new wiring guide?
Thanks
www.acsoundstudio.com/prr_176/rev_2/REV2_PRR_176_WIRING_GUIDE.png

Quote
someone can tell me how to do input (Log 10k) and Out (100k Log) stepped with Lorlin switch?
Thanks

http://www.quadesl.com/attenuator.html

hope this helps!
Best,
Abe
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on July 31, 2012, 02:09:32 PM
Thanks Abe!!!

I do not understand "Total attenuation db"? :o
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on July 31, 2012, 03:05:35 PM
Thanks Abe!!!

I do not understand "Total attenuation db"? :o

Ok, thats a good question, because if using a lorin you only have 12 steps, so you want to maximize usable steps. I would say for a compressor -40dB max attenuation might be a good starting point. But it depends. you might want to wire up a potentiometer first and see what range on the potentiometer you use the most then measure the resistance and us that to make your lorin switches.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on August 01, 2012, 08:51:10 AM
Thanks Abe I make some experiments...

For GSSL Time Constant can i use this?

Should I change something or I can copy it?
thanks
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on August 01, 2012, 10:17:29 AM
Thanks Abe I make some experiments...

For GSSL Time Constant can i use this?

Should I change something or I can copy it?
thanks

Well looking at it I would say give it a shot. Just copy the 750k/91k & 0.47uF/6.8uF and switch it into the circuit, though I don't expect it to react exactly the same, you'll probably need some tweeking with values and you'll have to modify/change the existing PCB. I find the comp to be pretty musical as is, and never felt the need for an "auto" release, but who knows, you don't miss what you've never tried!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on August 01, 2012, 09:49:07 PM
sorry ... , something is missing in the second channel?
 ???

 :)
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: herrmann on August 02, 2012, 01:45:34 AM
I think it's the same wiring as the L channel.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: baadc0de on August 02, 2012, 05:11:41 AM
Received! Nice boards, love the smilies

EDIT: also, isn't this board of the variety where if you link it, only the left controls are "in"?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on August 02, 2012, 10:29:35 AM
sorry ... , something is missing in the second channel?
 ???

 :)

Haha! Sorry 'bout that. I'll update the picture. Thanks for pointing it out!


Received! Nice boards, love the smilies

EDIT: also, isn't this board of the variety where if you link it, only the left controls are "in"?

Thanks! And yes, when stereo link only the Left controls work, makes it a lot easier to setup stereo cohesiveness, instead of trying to match attack/release  controls.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on August 03, 2012, 02:51:00 PM
I just finished the rev 2!
I have a strange problem on the first channel:
when I go up with the output pot (full CW) increases the compression ....
even with no input signal, the meter starts to score more and more compression ...
I checked all connections and they seem ok.
What can be?
Has anyone finished the REV 2?
thanks
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on August 04, 2012, 03:11:51 PM
Problem solved ( bad trimmer)...
with Lundahl 1540 (as interstage)
optional resistor value?
thanks
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on August 06, 2012, 08:49:08 AM
Hello ABE I got a strange problem:
the first channel
pot output from half to three quarters, and distorted sound strange, if I decrease or increase, the problem goes away .....
rechecked all components
replaced the doa
replaced all ICs
but nothing changes ..
What can be?
Thanks
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on August 06, 2012, 11:16:04 AM
the first channel
pot output from half to three quarters, and distorted sound strange, if I decrease or increase, the problem goes away .....
So just he first channel? have you check the pot? Does it happen when stereo linked/not? compression not? bypassed etc...?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on August 06, 2012, 12:01:46 PM
Yes just the first channel
I changed the pot but nothing has changed.
always the case (compression in or out)
in mono and in stereo,
The only thing I've noticed that if I exclude physically
U1 or U2 the problem goes away ...
 :o
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on August 06, 2012, 01:17:47 PM
This is a sample of the noise output pot.
starting from zero up to the maximum...


http://www.sendspace.com/file/xyn9u6
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on August 06, 2012, 03:08:56 PM
Yes just the first channel
I changed the pot but nothing has changed.
always the case (compression in or out)
in mono and in stereo,
The only thing I've noticed that if I exclude physically
U1 or U2 the problem goes away ...
 :o

So if you take out the ne5534 or the tl072 from the sidechain it doesn't make that noise? That is strange, quick fix is you could strap a 10pf to 100pf capacitor across your output pot, that would probably help. when did you start noticing this? have you cleaned your board of flux?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on August 06, 2012, 03:09:56 PM
have you tried trimming the threshold gain down on that channel?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on August 07, 2012, 07:52:39 AM
hello Abe
thanks for the help!
I tried everything
with a capacitor of 100pF partially solve ....
just do not understand what could be the problem.
There is a procedure for calibration?
I want to be sure it is not a calibration problem
(all components used are perfectly matched :o)
Thanks
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on August 09, 2012, 10:56:40 AM
Thanks for this wonderful project!
I think I've solved all the problems ...
I have just one doubt:

I used as a Lundahl 1540 interstage
What is the value optional resistor for this transformer?
THANKS!!!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on August 09, 2012, 06:42:38 PM

I used as a Lundahl 1540 interstage
What is the value optional resistor for this transformer?
THANKS!!!

Pretty sure you want 100k on the interstage primary, and then on the secondary you can leave open if it sounds good or try 10k-1k
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on August 09, 2012, 08:35:33 PM
R36 100k?
R 168 open 1-10k ?
thanks
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on August 10, 2012, 11:09:57 AM
R36 100k?
R 168 open 1-10k ?
thanks

Yes. Also you are working on a rev 1, right? in order to keep things as organized as possible you should direct any further questions to the rev 1 thread. Sorry for any confusion!
Best,
Abe
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on August 10, 2012, 01:14:39 PM
Thanks Abe
no i'm working on rev 2!!!
I've used all the rev 1 components and transformer for rev 2.....

Sorry for a stupid question but, because the resistor value (R36 and R168) are perfectly reversed compared to those used with Edcor?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on August 10, 2012, 02:32:42 PM
Thanks Abe
no i'm working on rev 2!!!
I've used all the rev 1 components and transformer for rev 2.....

Sorry for a stupid question but, because the resistor value (R36 and R168) are perfectly reversed compared to those used with Edcor?

oh! Okay, my mistake, I figured because on rev1 they are silked "opt" and on rev 2 they are silked "1k" and "100k" respectively.  And your right r36 should be 1K. So just stick to the silk, thats why its there! ;)
Best,
Abe
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on August 16, 2012, 07:33:25 AM
hello
I need a little help:
I still have problems with the meter,
marks perfectly half of the true compression.
I read on a post that changing some resistor values ​​in the circuit you can use a VU meter.
Can you tell me what resistance?

HP filter I used 1uf + .1 uf

I would like to move more of the cut on the side-chain (180-200Hz)
What is the value of capacitor should I use?
Thanks
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: herrmann on August 17, 2012, 08:53:19 AM
Hey guys,
Just finished my unit !
(http://herrmann.records.free.fr/diy/prr176-1.JPG)

I love Jeff's knobs  :)
(http://herrmann.records.free.fr/diy/prr176-2.JPG)

"Kingston" input mod, edcor 4:1 interstage, and 2523 output. Well, all is working good, and sound very good, except a nasty 50Hz noise coming around the edcor. Ordered a pair of 1540, hope this will solve the problem.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on August 17, 2012, 09:12:29 AM
Great Job herrmann!!!!
With lundhal 1540 I've solved all my noise problems....
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on August 17, 2012, 09:46:01 AM
Looks Great! Congrats!

So how are you debalancing the inputs? is it going into the Discrete opamp and then into the input pot and the the TX?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: herrmann on August 19, 2012, 07:02:17 AM
Exactly.
I don't know how to setup correctly the threshold trim, for what I understood, it's just a matter of personal taste ?
And I just discover that my tubes are microphonic (ebay sylvania 6bc8), should I be worried about that, or is this kind of tube prone to be microphonic ?
Thanks
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on August 20, 2012, 07:40:09 AM
Exactly.
I don't know how to setup correctly the threshold trim, for what I understood, it's just a matter of personal taste ?
And I just discover that my tubes are microphonic (ebay sylvania 6bc8), should I be worried about that, or is this kind of tube prone to be microphonic ?
Thanks

Yes, I don't have an exact value to set the threshold at, but how the calibration procedure would go is (after you've done your THUMP removal) you would set for X dB of output from you signal generator, set the input both to MAX (that way you can take the input potentiometer  tolerance out of the equation) and attack all the way fast and release also all to the fast. Then you adjust your threshold down till you get 1dB gain reduction.

Yes some (most) of the tubes I've used seem to have a little bit of microphonics. Haven't noticed it adversely affecting performance too much, though haven't strictly tested for it.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: kilmister on August 20, 2012, 03:19:50 PM

I have also question about threshold.
If I've undertund schematic right 1k trimmer is gain adjust for sidechain circuit? I thought if there's any advantage to put pot on the frontpanel to have user adjustable thershold? Opinions?

Cheers,
Paavo
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Kingston on August 20, 2012, 07:00:43 PM

I have also question about threshold.
If I've undertund schematic right 1k trimmer is gain adjust for sidechain circuit? I thought if there's any advantage to put pot on the frontpanel to have user adjustable thershold? Opinions?

Cheers,
Paavo

It's a set and forget. What kind of levels you are pushing into the tube stage, and how much compression you expect out of that. It's not threshold at all, but headroom. Think about it like you would with a 1176. I personally set it quite loud, so that very low input level is "some compression" and very high input level is a "fist in you face aih!".
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: herrmann on August 24, 2012, 05:34:17 AM
Received and soldered my interstage lundahl. Noise almost away, I still have a residual AC noise, I suspect the Hammond transformer I use for 100V (http://www.hammondmfg.com/229.htm (http://www.hammondmfg.com/229.htm))
I will try to move it and see.
Also, when I made the thump adjustment, I discover that one of my tube gets funky/distort really bad. Time to buy another tubes, will try RCA.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: WNStudios on August 28, 2012, 02:47:03 PM
(https://fbcdn-sphotos-g-a.akamaihd.net/hphotos-ak-snc6/s720x720/221858_10151215513959880_1036184568_n.jpg)

Mine is on the way, should be mostly populated by the end of the week. Still a long way to go though.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: jandoste on August 31, 2012, 04:53:39 PM
Hey Abe,
I almost finished and everything seem ok expect R116 and R115  smoke :o... I checked all wire connexion and they look ok! Do you have any idea?
I use 990C and edcors....
Thanks
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on August 31, 2012, 10:04:29 PM
Hey Abe,
I almost finished and everything seem ok expect R116 and R115  smoke :o... I checked all wire connexion and they look ok! Do you have any idea?
I use 990C and edcors....
Thanks

Yes, you probably have a short on the right channel.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: kilmister on September 02, 2012, 06:08:12 PM
It's a set and forget.

Roger that!

Another opinion plz.
What you guys think about stepped in and output attenuators with 2dB steps from -40dB to 0dB? I have a feeling the range would be fine...?

-Paavo

Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on September 02, 2012, 08:48:59 PM
I was thinking the same thing ....
but I can not do this....?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Kingston on September 03, 2012, 05:11:38 AM
Another opinion plz.
What you guys think about stepped in and output attenuators with 2dB steps from -40dB to 0dB? I have a feeling the range would be fine...?

even -30dB to 0dB is enough. In fact I did exactly that. You know, bebek and their cheap 24-step elmas...
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: kilmister on September 03, 2012, 07:04:01 AM
Thanks Kingston!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: jandoste on September 03, 2012, 05:53:32 PM
Thanks Abe,

yes, it was a short on the right channel ??? ::) Now it works but I have some NOISE and don't know where it comes :-[ :-[ ?

any idea?

Thanks

(http://i1236.photobucket.com/albums/ff442/jandoste/x.jpg)

Hey Abe,
I almost finished and everything seem ok expect R116 and R115  smoke :o... I checked all wire connexion and they look ok! Do you have any idea?
I use 990C and edcors....
Thanks

Yes, you probably have a short on the right channel.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: kilmister on September 03, 2012, 11:04:04 PM
A sneak peak of my project...
Initial testing going on. Sound passes through no noticeable hums or buzzes.
Still have to do stepped attenuators, some DOAs and nice front panel instead this wooden one.

(http://www.5by5.fi/diy/prr176/tn_prr176_initial_test.jpg) (http://www.5by5.fi/diy/prr176/prr176_initial_test.jpg)

Sound good this far, thanks Abe!

-Paavo
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on September 04, 2012, 10:45:26 AM
Thanks Abe,

yes, it was a short on the right channel ??? ::) Now it works but I have some NOISE and don't know where it comes :-[ :-[ ?

any idea?

Thank

Good! Me thinks you have a grounding issue somewhere, Your in Rev 2 right? With the off board power supply? Unless you did something wrong it is more than likely ground loop, or something.

Do you have an oscilloscope? Check the power supply. Also measure the Smoothed DC before the regulators make sure you have AT LEAST a couple of volts headroom if not more (example 21V DC before regulator being rectified down to 18V) If you don't have headroom than the regulators can't regulate properly = noise. Just trim the regulators down if you need more headroom in the power supply. (which inversely effects audio headroom, but usually not a problem)

I'm sure I mentioned this before, but just to make sure, Ground all your XLR jacks directly to chassis then connect chassis and audio ground only at one point. Some people uses a low ohm resistor (10r) in parallel with a low ESR capacitor (poly 0.1uf) to connect the two grounds. I haven't found that necessary, but to each their own.

Also, I forget if you have a scope available to you or not, but It might help you isolate the power rail that has hum. If that is the case, or if its coming from the transformer (probably not if your using a torriod, unless it is getting hot) or ground loop.

Remember it IS something, always. Sometimes I think its voodoo or majic or Wht the hck. But its always something. Sorry hard to troubleshoot over the net.

PS Builds looking really cool guys!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: detonator on September 05, 2012, 10:35:35 AM
Perhaps a noobish question, but I don't care. I was wondering if it possible to create a switch between at output stage? This is ment to switch between the chip or the transformer.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on September 06, 2012, 01:37:07 AM
Perhaps a noobish question, but I don't care. I was wondering if it possible to create a switch between at output stage? This is ment to switch between the chip or the transformer.

Yes. One easy way would be to wire up both and then using a DPDT switch (or even better a relay) just switch between the 2 output (pin 2 and 3 in the xlr)
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: detonator on September 06, 2012, 02:11:57 AM
Thanks abe
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: labak on September 11, 2012, 08:52:42 AM
Hi All!

Sorry for this question but What are the real specs of the Power Xformers?
I wanna built an external Power supply for, and I would like to try to avoid 2 Xformers! Is there somebody who find the Power Xformer one piece?

Thanks for this project!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: kilmister on September 15, 2012, 05:56:34 PM
Power transformer was discussed in Rev1 thread:
http://www.groupdiy.com/index.php?topic=44586.msg583319#msg583319

Be sure you read all posts - especially Kingston's
 
-Paavo
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: mrcase on September 18, 2012, 11:41:50 AM
Hey all!

Which powertransformers would you suggest for 230V Europe build?
how would I connect the two transformers?

cheers
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Hank Dussen on September 18, 2012, 12:34:36 PM
If anyone is interested, I have a custom made 230V transformer from the group buy, for sale.
I didn't use it, because it doesn't fit in a 1U case.

Pieter
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Holger on September 18, 2012, 02:46:44 PM
Hi, I'll take the transformer
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: detonator on September 18, 2012, 04:48:57 PM
I'm interested when it's leftovet
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: herrmann on October 08, 2012, 05:46:24 AM
I just noticed that my unit is actually out of phase. On both channels. I checked the 2623 output wiring, and it's good : input orange, Hi output black with green and brown connected. Has anyone this issue too ?

Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: astroschnautzer on October 09, 2012, 12:13:09 PM
Could someone suggest an output transformer, I am looking to be using this for mastering purposes + tracking, it can be a expensive one (lundahl)...
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on October 10, 2012, 11:51:34 AM
I just noticed that my unit is actually out of phase. On both channels. I checked the 2623 output wiring, and it's good : input orange, Hi output black with green and brown connected. Has anyone this issue too ?

I'll run some tests and confirm. Easy solution would be to switch pins 2/3. You can do this because using an output transformer and/or the drv134 or that chips are fully differential, it will work even into unbalanced equipment

Could someone suggest an output transformer, I am looking to be using this for mastering purposes + tracking, it can be a expensive one (lundahl)...

for output? just a 1:1 will work, there are literally thousands of possible options. Try a Jensen output transformer if you are in the states, or if lundahls are easier to get, I've heard very good things about them too. With 1:1s the difference of transformers can get harder to hear, (if they are decent quality to begin with) But if you are going for clean, try the jensen or lundahls. Sorry I don't have model numbers, as that takes the fun out of it for you.  ;) :D :D
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: astroschnautzer on October 10, 2012, 02:32:23 PM

Could someone suggest an output transformer, I am looking to be using this for mastering purposes + tracking, it can be a expensive one (lundahl)...

for output? just a 1:1 will work, there are literally thousands of possible options. Try a Jensen output transformer if you are in the states, or if lundahls are easier to get, I've heard very good things about them too. With 1:1s the difference of transformers can get harder to hear, (if they are decent quality to begin with) But if you are going for clean, try the jensen or lundahls. Sorry I don't have model numbers, as that takes the fun out of it for you.  ;) :D :D
Thanks, I got right there already, I'm just totally new to all this transformer stuff and am struggling with all kinds of info, like is 2:1+1 same as 1:1 and is balanced and unbalanced drive just the same as do I want to use a balanced or unbalanced output? And are you telling me that there probably won't be a audible difference if output transformers are used? How about the interstage transformers, how crusial are those transformers for the sound, saw some builds with lundahl input and some others (edcor?) in the interstage so was wondering that is the input that is the inportant bit?... Sorry for so many questions, totally new to all this stuff...
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on October 10, 2012, 03:27:30 PM

Could someone suggest an output transformer, I am looking to be using this for mastering purposes + tracking, it can be a expensive one (lundahl)...

for output? just a 1:1 will work, there are literally thousands of possible options. Try a Jensen output transformer if you are in the states, or if lundahls are easier to get, I've heard very good things about them too. With 1:1s the difference of transformers can get harder to hear, (if they are decent quality to begin with) But if you are going for clean, try the jensen or lundahls. Sorry I don't have model numbers, as that takes the fun out of it for you.  ;) :D :D
Thanks, I got right there already, I'm just totally new to all this transformer stuff and am struggling with all kinds of info, like is 2:1+1 same as 1:1 and is balanced and unbalanced drive just the same as do I want to use a balanced or unbalanced output? And are you telling me that there probably won't be a audible difference if output transformers are used? How about the interstage transformers, how crusial are those transformers for the sound, saw some builds with lundahl input and some others (edcor?) in the interstage so was wondering that is the input that is the inportant bit?... Sorry for so many questions, totally new to all this stuff...

Hello,
Yes I totally understand, transformers are seemingly very confusing, with so many different options and the indepth math behind it all. I feel fairly comfortable with my view of transformers now, it could definitely be improved up, but I feel like its enough of a working knowledge...

Basically there are a couple things to worry about when selecting a transformer:

What level is it designed for?
You want to consider this because transformers have an optimum range of were they sound the best, hit them too soft and they don't sound as clean, hit them too hard and they start to saturate and distort. Usually the transformer designer worrys about this stuff, you don't have to worry about it. Unless you start using Mic transformers as line, etc etc etc switching them backwards etc etc etc.

What impedance are they designed for?
Thinking about transformers more of MIRRORS is an easier way that I find my brain can digest better. It reflects impedances to the circuit that has the output (sending the signal) and to the circuit input (receiving the signal) You want to match impedances for optimum transfer and frequency response. That is were the "600ohm" and "10kohm" transformers come from. Like speakers, the lower the ohm the more difficult it is for the output circuitry to drive the transformer. Yes transformers are a load, and you need adequate power to drive them. Also ratios are a part of this. Say you want to use a 1:2 output transformer for the output, cause you want a little more color...well your going to have to consider that whatever load you put on the output is going to look harder to drive (lower impedance) to the output because the transformer is 1:2. But also you will have an increase of gain on the output. On the other hand if you wanted to use a 2:1 output transformer for the output for more color, you would lose gain (not a problem here because the 176 has a bunch) but whatever load you drive will be easier for the output circuitry because it "looks" like a higher impedance to the circuitry thanks to that reflection of the transformer. Remember Higher impedances are easier to drive.

a 1+1:2 transformer is that same as a 1:1 they are just telling you that there are 2 completely independent windings on the primary. They could either be wired in series (in phase) to make it just like a 1:1 or in parallel to give it better bass response (more inductance) and a 1:2 ratio.

There are not free lunches in transformers, no free gain, as you can see you need the proper circuitry to be able to drive the various loads...

To answer your question a lundahl 1+1:2 would work fine just make sure you wire it correctly. If your going for transparency just wire the 2 primary windings in series to make it 1:1 (or 2:2, which is the same thing)
 
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Edward on October 10, 2012, 04:01:07 PM
I'm slowly gathering parts to start building this very interesting project. Thanks to all who made that possible. This is my most complex build so far and I'm learning alot of new stuff along the way as well, which is nice.

I have a question. Does anyone who have finished this build posted any sound samples of it we can listen to? I know every build is unique, but it would be nice to listen to some sound samples while learning about the G9 power transformer trick etc  ;D



Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on October 10, 2012, 04:20:42 PM
I'm slowly gathering parts to start building this very interesting project. Thanks to all who made that possible. This is my most complex build so far and I'm learning alot of new stuff along the way as well, which is nice.

I have a question. Does anyone who have finished this build posted any sound samples of it we can listen to? I know every build is unique, but it would be nice to listen to some sound samples while learning about the G9 power transformer trick etc  ;D

I'd also be interested in hearing peoples units with other options... I'll run some through when I get a chance.

I'm finishing a build for a friend and once its done I'm going to run some sound samples through it. It has edcors in it now but am going to put cinemags in it. Figured it will be interesting to compare the different transformers in the same exact build.


I used a PRR-176 with DRV/INA input and Edcor interstage on the most recent band to track vox and guitar through, and got to say it did its job very nice...when I listen to the beatles, It reminds me of the PRR-176 a little bit, same type of sound (probably cause the early beatles albums were slathered in Vari-mu!)

I could upload those but there would be nothing to compare them to.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: astroschnautzer on October 11, 2012, 03:55:00 AM

Could someone suggest an output transformer, I am looking to be using this for mastering purposes + tracking, it can be a expensive one (lundahl)...

for output? just a 1:1 will work, there are literally thousands of possible options. Try a Jensen output transformer if you are in the states, or if lundahls are easier to get, I've heard very good things about them too. With 1:1s the difference of transformers can get harder to hear, (if they are decent quality to begin with) But if you are going for clean, try the jensen or lundahls. Sorry I don't have model numbers, as that takes the fun out of it for you.  ;) :D :D
Thanks, I got right there already, I'm just totally new to all this transformer stuff and am struggling with all kinds of info, like is 2:1+1 same as 1:1 and is balanced and unbalanced drive just the same as do I want to use a balanced or unbalanced output? And are you telling me that there probably won't be a audible difference if output transformers are used? How about the interstage transformers, how crusial are those transformers for the sound, saw some builds with lundahl input and some others (edcor?) in the interstage so was wondering that is the input that is the inportant bit?... Sorry for so many questions, totally new to all this stuff...

Hello,
Yes I totally understand, transformers are seemingly very confusing, with so many different options and the indepth math behind it all. I feel fairly comfortable with my view of transformers now, it could definitely be improved up, but I feel like its enough of a working knowledge...

Basically there are a couple things to worry about when selecting a transformer:

What level is it designed for?
You want to consider this because transformers have an optimum range of were they sound the best, hit them too soft and they don't sound as clean, hit them too hard and they start to saturate and distort. Usually the transformer designer worrys about this stuff, you don't have to worry about it. Unless you start using Mic transformers as line, etc etc etc switching them backwards etc etc etc.

What impedance are they designed for?
Thinking about transformers more of MIRRORS is an easier way that I find my brain can digest better. It reflects impedances to the circuit that has the output (sending the signal) and to the circuit input (receiving the signal) You want to match impedances for optimum transfer and frequency response. That is were the "600ohm" and "10kohm" transformers come from. Like speakers, the lower the ohm the more difficult it is for the output circuitry to drive the transformer. Yes transformers are a load, and you need adequate power to drive them. Also ratios are a part of this. Say you want to use a 1:2 output transformer for the output, cause you want a little more color...well your going to have to consider that whatever load you put on the output is going to look harder to drive (lower impedance) to the output because the transformer is 1:2. But also you will have an increase of gain on the output. On the other hand if you wanted to use a 2:1 output transformer for the output for more color, you would lose gain (not a problem here because the 176 has a bunch) but whatever load you drive will be easier for the output circuitry because it "looks" like a higher impedance to the circuitry thanks to that reflection of the transformer. Remember Higher impedances are easier to drive.

a 1+1:2 transformer is that same as a 1:1 they are just telling you that there are 2 completely independent windings on the primary. They could either be wired in series (in phase) to make it just like a 1:1 or in parallel to give it better bass response (more inductance) and a 1:2 ratio.

There are not free lunches in transformers, no free gain, as you can see you need the proper circuitry to be able to drive the various loads...

To answer your question a lundahl 1+1:2 would work fine just make sure you wire it correctly. If your going for transparency just wire the 2 primary windings in series to make it 1:1 (or 2:2, which is the same thing)
Thks for the detailed answer, so that means if I bough a 1+1:1+1 I could choose if I wire it 1:2, 1:1 or 2:1? Also still wondering about the interstage, how important that stage is for the sound?... And should I get a "balanced drive" version if I want a balanced XLR output?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: herrmann on October 11, 2012, 09:25:16 AM
Quote
Does anyone who have finished this build posted any sound samples of it we can listen to?
I will.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on October 11, 2012, 10:25:20 AM
Thks for the detailed answer, so that means if I bough a 1+1:1+1 I could choose if I wire it 1:2, 1:1 or 2:1?

Yes.

Quote
Also still wondering about the interstage, how important that stage is for the sound?...
Fairly important. I would get good ones.

Quote
And should I get a "balanced drive" version if I want a balanced XLR output?

I don't know what that means. Is it a type of transformer? If so any transformer is "balanced drive" and will drive a balanced XLR
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: astroschnautzer on October 11, 2012, 12:40:49 PM


Quote
And should I get a "balanced drive" version if I want a balanced XLR output?

I don't know what that means. Is it a type of transformer? If so any transformer is "balanced drive" and will drive a balanced XLR
Lundahl has this labelled as"drive type" on their website, many different types : http://www.lundahl.se/sidor/line_out.html    EDIT: Think I got some info : http://www.lundahl.se/pdf/ovrigt/feedbck.pdf ...This indicates (looking at the scematics) that I would need a unbalanced drive if input to transformer is taken from the "optional tranformer out" output which ha two pins... Am I correct?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Kingston on October 11, 2012, 02:53:05 PM
Lundahl LL1540 for input and interstage is what I used. These stages (both stage require high impedance input) are most crucial if you want to invest in quality. PRR176 is surprisingly well fit for mastering if you don't skimp on the transformers and match the tubes.

Output transformer is far less picky. Any line level 600:600ohm transformer will do and they will all be very high spec and sound great. For example classic api EA 2503, Edcor wsm 600:600, Lundahl LL5402.  Lundahl might actually be a waste of money in this stage. Don't shy away from Edcor wsm 600:600 just because it's cheap. In my opinion it's their greatest product and easily the best price/performance ratio of any modern line level transformer.

While many opamps will sound great in this unit, check out PPA APP992 in the white market.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: astroschnautzer on October 11, 2012, 03:36:28 PM
Lundahl LL1540 for input and interstage is what I used. These stages (both stage require high impedance input) are most crucial if you want to invest in quality. PRR176 is surprisingly well fit for mastering if you don't skimp on the transformers and match the tubes.

Output transformer is far less picky. Any line level 600:600ohm transformer will do and they will all be very high spec and sound great. For example classic api EA 2503, Edcor wsm 600:600, Lundahl LL5402.  Lundahl might actually be a waste of money in this stage. Don't shy away from Edcor wsm 600:600 just because it's cheap. In my opinion it's their greatest product and easily the best price/performance ratio of any modern line level transformer.

While many opamps will sound great in this unit, check out PPA APP992 in the white market.
Thanks, this helps alot, and saves some money. Thanks for the opamp suggestion too, I had also planned to buy these because I read your opamp shootout here at the forum ( If these where them)...
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Kingston on October 11, 2012, 04:00:06 PM
]Thanks, this helps alot, and saves some money. Thanks for the opamp suggestion too, I had also planned to buy these because I read your opamp shootout here at the forum ( If these where them)...

These are the same ones. But since that shoot out I actually did a major project where I found out that in optimal environments (very difficult to create) there should not be significant audible differences between opamps (there are very little measurable differences, how could you then hear anything). In that shoot out tested APP992 in places where PSU and decoupling was sub-optimal, and this is where it sounded incredibly good. Kind of a safe choice. Perhaps it has better PSRR than many others, the test was shamefully unscientific. Don't draw too many conclusions from it.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: herrmann on October 15, 2012, 06:13:49 AM
Here is some samples of mine. It's a basic addictive drums loop. Att/Rel 0=full CCW, 10=full CW. Time 1 is 1uF tant, 2 is 2uF tant, 3 is 1uF electrolytic and 4 is 1uF PIO.
Gar2520, LME, RCA tube, and 2623 output transformer.
http://herrmann.records.free.fr/PRR176/ (http://herrmann.records.free.fr/PRR176/)
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Edward on October 15, 2012, 03:29:39 PM
Sounds really good herrmann, thank you for sharing!  :D
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Hank Dussen on October 16, 2012, 05:59:06 AM
Here is some samples of mine. It's a basic addictive drums loop. Att/Rel 0=full CCW, 10=full CW. Time 1 is 1uF tant, 2 is 2uF tant, 3 is 1uF electrolytic and 4 is 1uF PIO.
Gar2520, LME, RCA tube, and 2623 output transformer.
http://herrmann.records.free.fr/PRR176/ (http://herrmann.records.free.fr/PRR176/)


Thanks Herrmann! I definitely prefer the 1uF time constant caps...
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Edward on October 21, 2012, 11:58:49 AM
Question:

I have one dual primary 115/230V toroidal transformer 50va 0-25v 0-25v and one mini open toroid 7.0va 12v+12v both from Rapid Electronics. I connected the primaries on the first transformer in series and feed it ~230VAC and the secondary side is also connected in series to get a center tap and 25VAC on each end. My first problem is that i measure ~29VAC between CT and each end and ~59VAC across both ends. Is my transformer not working correctly or is there something i'm missing?

However i went ahead an connected the second transformer to the first one, secondary side first and in series as well. On the primary side of the second transformer i get 115VAC, which i guess is ok?

Can some one confirm if this is ok?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on October 21, 2012, 12:18:37 PM
Hi guys!
I am very happy with this compressor!!!
I would like to make a  mastering version,
but
can anyone help me to calculate the steps for switch version?
In-out - attack - release.
thanks
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on October 22, 2012, 09:53:10 AM
Question:

I have one dual primary 115/230V toroidal transformer 50va 0-25v 0-25v and one mini open toroid 7.0va 12v+12v both from Rapid Electronics. I connected the primaries on the first transformer in series and feed it ~230VAC and the secondary side is also connected in series to get a center tap and 25VAC on each end. My first problem is that i measure ~29VAC between CT and each end and ~59VAC across both ends. Is my transformer not working correctly or is there something i'm missing?

However i went ahead an connected the second transformer to the first one, secondary side first and in series as well. On the primary side of the second transformer i get 115VAC, which i guess is ok?

Can some one confirm if this is ok?

Thats fine, they are going to give you a little extra which is what you usually want.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Edward on October 22, 2012, 11:07:14 AM
Question:

I have one dual primary 115/230V toroidal transformer 50va 0-25v 0-25v and one mini open toroid 7.0va 12v+12v both from Rapid Electronics. I connected the primaries on the first transformer in series and feed it ~230VAC and the secondary side is also connected in series to get a center tap and 25VAC on each end. My first problem is that i measure ~29VAC between CT and each end and ~59VAC across both ends. Is my transformer not working correctly or is there something i'm missing?

However i went ahead an connected the second transformer to the first one, secondary side first and in series as well. On the primary side of the second transformer i get 115VAC, which i guess is ok?

Can some one confirm if this is ok?

Thats fine, they are going to give you a little extra which is what you usually want.

Thanks!

I have now learned that unloaded a transformer will give more voltage than when its drawing its rated current.

Do you think the smaller transformer will be fine with the higher load? Maby i should have gotten a 0v-18v, 0v-18v instead of the 0v-25v, 0v-25v...

...could a resistor be added to lower the voltage to <24VAC to the second transformer?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on October 23, 2012, 05:35:43 AM
Question:

I have one dual primary 115/230V toroidal transformer 50va 0-25v 0-25v and one mini open toroid 7.0va 12v+12v both from Rapid Electronics. I connected the primaries on the first transformer in series and feed it ~230VAC and the secondary side is also connected in series to get a center tap and 25VAC on each end. My first problem is that i measure ~29VAC between CT and each end and ~59VAC across both ends. Is my transformer not working correctly or is there something i'm missing?

However i went ahead an connected the second transformer to the first one, secondary side first and in series as well. On the primary side of the second transformer i get 115VAC, which i guess is ok?

Can some one confirm if this is ok?

Thats fine, they are going to give you a little extra which is what you usually want.

Thanks!

I have now learned that unloaded a transformer will give more voltage than when its drawing its rated current.

Do you think the smaller transformer will be fine with the higher load? Maby i should have gotten a 0v-18v, 0v-18v instead of the 0v-25v, 0v-25v...

...could a resistor be added to lower the voltage to <24VAC to the second transformer?

No, you should be fine. A resistor is only going to add more heat. You might want to heatsink the heater regulator to the chassis though (using proper insulation of course!) But you will probably be fine.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Edward on October 23, 2012, 07:26:06 AM
Would Mouser part: 532-4880M work as an insulator here? Sorry for all my questions, but i just want to make sure the PSU part is at least a little safe before i proceed :)

Thanks for your help so far Abe!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: astroschnautzer on October 24, 2012, 11:54:56 AM
Caold anybody give a hint on good quality meters that fits the 1u case from collectivecases..? hopefully from europe or ebay...
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on October 24, 2012, 02:57:14 PM
Caold anybody give a hint on good quality meters that fits the 1u case from collectivecases..? hopefully from europe or ebay...


http://www.ebay.com/itm/Panel-VU-Meter-TN-73-0dB-1-288V-76x59mm-LED-lamp-NISSEI-/130384936913?pt=LH_DefaultDomain_0&hash=item1e5b8c3fd1


you have to take off the front cover and cut the bottom off of it for it to fit. Not that hard, just don't huff the fumes!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: astroschnautzer on October 25, 2012, 01:56:27 AM
Caold anybody give a hint on good quality meters that fits the 1u case from collectivecases..? hopefully from europe or ebay...


http://www.ebay.com/itm/Panel-VU-Meter-TN-73-0dB-1-288V-76x59mm-LED-lamp-NISSEI-/130384936913?pt=LH_DefaultDomain_0&hash=item1e5b8c3fd1


you have to take off the front cover and cut the bottom off of it for it to fit. Not that hard, just don't huff the fumes!
thanks, not really sure I understand exactly what to do but I trust I will get it when I see them in front of me...

+ one more question, about caps, Is a good practice to elna/mundorf caps on audio path and for example panasonic fc for the rest, or should the PSU caps be high quality or how do you peeps do with your capacitors?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: astroschnautzer on October 31, 2012, 04:22:43 AM
Caold anybody give a hint on good quality meters that fits the 1u case from collectivecases..? hopefully from europe or ebay...


http://www.ebay.com/itm/Panel-VU-Meter-TN-73-0dB-1-288V-76x59mm-LED-lamp-NISSEI-/130384936913?pt=LH_DefaultDomain_0&hash=item1e5b8c3fd1


you have to take off the front cover and cut the bottom off of it for it to fit. Not that hard, just don't huff the fumes!
I'm not really sure how to cut the bottom off of these and still keep the meter mechanism working since the mechanism is in the part that is supposed to be cutted off, can you ellaborate a little on this one? + I think you have given a bad hint on meters, havent got the case yet but these look alot bigger than would fit that case (looking at the pictures...)


EDIT: Yep, definitely not the right meters.... looks like these would go in a 1176 case....
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on October 31, 2012, 12:14:53 PM
Sorry, my mistake,hard to tell from those pictures. I would just get them from hairball unless you have a local nessei dealer.
best,
abe
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: astroschnautzer on October 31, 2012, 01:34:13 PM
Sorry, my mistake,hard to tell from those pictures. I would just get them from hairball unless you have a local nessei dealer.
best,
abe
Ok, too bad, maybe I find a project these fit into.... :-[
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: usekgb on November 02, 2012, 11:15:02 PM
I finally got around to begin this build today.  I installed all of the parts that I had on hand, and order most of the rest of them.  I'm so excited to get this going!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Edward on November 03, 2012, 03:49:14 AM
I finally got some time to finish the PSU part, so last night i powered it up with a VARIAC.

I increased the input some 20% at a time and did some measuring and at first everything looked fine except that Heater - was not showing up.

At 60% i noticed a familiar smell and R32 (or was it R16), the 120 Ohm resistor was starting to glow up... I decided to quit because i was not in the mood to make lighting effects.

So my questions are: What exactly are VR7, 8, 10 and 12 doing? And does anyone have a hint on how to trouble shoot the Heater - line?

I would be really thankful for any help on this.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: usekgb on November 03, 2012, 12:39:06 PM
Heater - should be at 0V, as it is tied to the power transformer's center tap.  All of those trimmer resistors in the power supply are setting the voltages that you will need on the main pcb.  Set your volt meter for Scott, and measure the voltages compared to ground.  Adjust the trimmers until you get the voltages that you need.  Also, the BOM calls for three LM317's, but the silk screen on the power supply calls for two LM317's and one LM337.  The LM337 is required for the -18V rail.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Edward on November 03, 2012, 01:25:28 PM
I see, thank you very much for clearing that up for me. I noticed it said LM337 on the PCB but I doublechecked the BOM and went with LM317. Guess that explains the glowing resistor.

I was expecting +6.3 and -6.3 for the heater +/- but I don't know where I got that from.

Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on November 03, 2012, 01:51:03 PM
Ah! Let me correct the BOM. Sorry bout that gents.

And like you found out, heater needs to have 12.6v difference between them
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: usekgb on November 04, 2012, 01:25:50 AM
No problem.  Easy typo to make.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Edward on November 05, 2012, 04:53:38 PM
Replaced one LM317T for a LM337T and one burned 120Ohm resistor and now it's working like it should. A reminder for me to keep checking the schematic whenever in doubt. I blame no one but myself for that.

However, I have one more stupid question regarding this PSU. Hopefully I can soon move forward and do the fun part, i do hate building PSUs...

On the Plate V+ line i measure 120VDC with ~115VAC on the input side. Expecting ~100VDC i now wonder what kind of problem I have here?

Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Rellister on November 05, 2012, 05:19:35 PM
Hi Edward,
Are you building this in a 1U chassis? If so, were you able to fit two toroids for euro power in there with the pcb?
Just wondering how to solve this case-wise.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Edward on November 05, 2012, 05:35:53 PM
Hi Edward,
Are you building this in a 1U chassis? If so, were you able to fit two toroids for euro power in there with the pcb?
Just wondering how to solve this case-wise.

Yes, my plan is to fit it into a 1U case, but I don't have a case yet so I can't tell you how. It's been done before thou, just scroll through the Rev 1 build thread. I can post pictures when I'm done but i think it's gonna take a while.



Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Kingston on November 05, 2012, 06:48:41 PM
Hi Edward,
Are you building this in a 1U chassis? If so, were you able to fit two toroids for euro power in there with the pcb?
Just wondering how to solve this case-wise.

Needs a deep case. I used 280mm, but consider this a bare minimum. There will be problems with heat especially if high rail voltages and DOA's are used. 1U needs a vented cover and a spare 1U (or at least half U) area in a rack for reliability.

If I had to choose now I would do 2U instead and would recommend it to others as well.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on November 07, 2012, 03:09:32 PM
Hi
I've tried to make a stepped version of input but now the compression kick in very early...
what is the problem?
Thanks
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on November 07, 2012, 03:37:50 PM
Hi
I've tried to make a stepped version of input but now the compression kick in very early...
what is the problem?
Thanks

Well maybe 30db pad isn't enough? Or it is enough, but you have to possibly hit it softer if you don't want it to compress. Also try raising the threshold so you have more breathing room.

You can configure it however you like!

Me, I like to be able to compress things to the extreme. Though, maybe not the best thing all the time I'm beginning to find. Things to consider is the higher the threshold, the potential for better noise floor, but too high and you might get some weird distortion on fast peaks  that overload the circuitry because you have to gain it so got to get the desired compression. Probably easier for me to lay down hard rules, but were is the fun in that?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: earl on November 08, 2012, 09:57:24 AM
This is interesting the unit comes on: tubes glow can hear the output pot working: unit is showing gain (not passing
 input signal though) BUT after about a minute the tubes shut off and big noise.  Ideas? anyone? Thanks
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Holger on November 08, 2012, 11:33:51 AM
I assume that you have two problems. Check the heater regulator. Is it possible that the regulator gets too warm and is collapsing after a minute? If so, exchange it, maybe mount it off board on a heat sink. After that problem is solved, you should check where you can trace an audio signal in the signal path.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: earl on November 08, 2012, 02:07:09 PM
Thought stuff was getting warm there.  I will try that out thanks Holger.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Axelerator on November 09, 2012, 06:38:21 AM
..hm..also interested in a hybrid comp like this.. ;)
is there a pcb left ?

axel
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: diylan on November 10, 2012, 01:15:50 PM
I'm a little fuzzy on which Hairball meters are the best fit for the Collective Cases case. Abe, you mentioned one model, but it looks a lot more like another. For clarification, are you guys using the:

8027-B 1mA

or

8027-WF 1mA
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: astroschnautzer on November 12, 2012, 10:02:37 AM
I'm a little fuzzy on which Hairball meters are the best fit for the Collective Cases case. Abe, you mentioned one model, but it looks a lot more like another. For clarification, are you guys using the:

8027-B 1mA

or

8027-WF 1mA
the 8027-WF 1mA needs some melting of the glass, and additionally some melting of the meter enclosure, its not beatiful but it keeps inside the box (so you don't see it) and you have to be careful not to melt too much so that the meter mechanism is affected..... with the 8027-B 1mA you might not have to do  melting. (?)...
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: dandeurloo on November 12, 2012, 12:11:09 PM
Abe has a Mod for the meter to work.  We decided on that meter and its placement for the look of it in the panel and function.  Its a pretty easy little mod.  I think Abe explained it in a post some place. 
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Edward on November 12, 2012, 03:29:53 PM
On the Plate V+ line i measure 120VDC with ~115VAC on the input side. Expecting ~100VDC i now wonder what kind of problem I have here?

I found a site about zener diodes as voltage regulators and it had a calculator for finding out the power rating of the zener diode. I entered 100V as Vout, 115V as Vsource and 50mA for Imax. The result is 5W. Could it be D14 which in my case is 100V/1W that is failing? Even if Vsource is dropped to 100V the result is still 5W for the zener.
Sorry for my noob questions...
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on November 13, 2012, 03:24:12 AM
On the Plate V+ line i measure 120VDC with ~115VAC on the input side. Expecting ~100VDC i now wonder what kind of problem I have here?

I found a site about zener diodes as voltage regulators and it had a calculator for finding out the power rating of the zener diode. I entered 100V as Vout, 115V as Vsource and 50mA for Imax. The result is 5W. Could it be D14 which in my case is 100V/1W that is failing? Even if Vsource is dropped to 100V the result is still 5W for the zener.
Sorry for my noob questions...

Your forgetting to put the 3k in series before the voltage drop in that calculation i believe. You also have to have the power supply loaded for it to read 100v  :)
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Edward on November 13, 2012, 04:03:51 AM
On the Plate V+ line i measure 120VDC with ~115VAC on the input side. Expecting ~100VDC i now wonder what kind of problem I have here?

I found a site about zener diodes as voltage regulators and it had a calculator for finding out the power rating of the zener diode. I entered 100V as Vout, 115V as Vsource and 50mA for Imax. The result is 5W. Could it be D14 which in my case is 100V/1W that is failing? Even if Vsource is dropped to 100V the result is still 5W for the zener.
Sorry for my noob questions...

Your forgetting to put the 3k in series before the voltage drop in that calculation i believe. You also have to have the power supply loaded for it to read 100v  :)

Thanks Abe. It's the same answer to all my questions, loaded the measurmets will be correct.

Kinda like saying during soundcheck that it will sound better when the crowd shows up. :) Got it.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: astroschnautzer on November 13, 2012, 10:35:42 AM
Abe has a Mod for the meter to work.  We decided on that meter and its placement for the look of it in the panel and function.  Its a pretty easy little mod.  I think Abe explained it in a post some place.
Yep, but it needed some additional cutting (melting) atleast for the box I have, it has a bent front edge so its abit higher there, maybe earlier boxes didn't have a bent front edge (?)
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ethervalve on November 21, 2012, 12:41:51 PM
Hi astroschnautzer,
I ordered one of the Collective Cases enclosures too (still in transit).
Do you mean the top panel of the enclosure has a 'lip' that curves down and meets the front panel?
If so, I wonder if it would be easier just to grind that part down with a dremel or file? I've had to do that a bunch with 'Circuit Test' brand enclosures (which seem to be the cheapest option here in Canada).
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on November 21, 2012, 12:54:48 PM
Hi astroschnautzer,
I ordered one of the Collective Cases enclosures too (still in transit).
Do you mean the top panel of the enclosure has a 'lip' that curves down and meets the front panel?
If so, I wonder if it would be easier just to grind that part down with a dremel or file? I've had to do that a bunch with 'Circuit Test' brand enclosures (which seem to be the cheapest option here in Canada).

no, well actually you could gind and gain about 1/16" but you would still need to cut off some of the meter.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ethervalve on November 21, 2012, 01:40:34 PM
Cool--sounds like it's no biggie.
Thanks for the details.
Hey, if you ever have the chance to create that calibration doc you mentioned earlier, it would be much appreciated! (The threshold adjustment is really the main thing I'm confused about).
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: astroschnautzer on November 21, 2012, 01:53:56 PM
It might just be that if you gain the 1/16 you wouldnt have to cut the body of the meter just the front cover part wich is easier, have to be careful with the body part that you don't destroy the whole meter....
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: tommypiper on November 22, 2012, 01:58:05 AM
Sorry any news about new wiring guide?
Thanks

www.acsoundstudio.com/prr_176/rev_2/REV2_PRR_176_WIRING_GUIDE.png


Just curious, what apps are you guys using to create these colorful wiring guides?  Some of them have cabling drawn out in curves  and elipses very nicely.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on November 23, 2012, 12:55:08 PM
Cool--sounds like it's no biggie.
Thanks for the details.
Hey, if you ever have the chance to create that calibration doc you mentioned earlier, it would be much appreciated! (The threshold adjustment is really the main thing I'm confused about).

Its really not that big of a deal. I mentioned how to do it in an eairlier thread (check the rev 1) The 2 trimmers closest to the base of the 6bc8 tube adjust thump, the one near the tip of the tube adjusts the meter (adjust till meter reads "0")

The threshold is just were you want your compressor to start compressing. Make it some arbitrary value, -10db or +4db, depends on how much you want the unit ot be able to compress. Something that I personally can't answer for you.
Some people want to be able to have a huge range of compression and therefor would set the threshold lower, others want to just barely grab 5-10db, those people would logically probably set the threshold higher. If your looking for a "do this" answer, I'm deliberately not giving you one, your going to have to sit down and experiment and hear for yourself :) :) :) There is no big secret.
Ps really dig your studio/band. very cool 60s vibe.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on November 23, 2012, 12:56:29 PM
Sorry any news about new wiring guide?
Thanks

www.acsoundstudio.com/prr_176/rev_2/REV2_PRR_176_WIRING_GUIDE.png


Just curious, what apps are you guys using to create these colorful wiring guides?  Some of them have cabling drawn out in curves  and elipses very nicely.

I just used Photoshop, the really talented people here that turn everything into amazing artwork i bet use adobe illustrator. I've tried to get my brain around the curve tools and just can't do it yet!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ethervalve on November 24, 2012, 02:23:08 PM

Its really not that big of a deal. I mentioned how to do it in an eairlier thread (check the rev 1) The 2 trimmers closest to the base of the 6bc8 tube adjust thump, the one near the tip of the tube adjusts the meter (adjust till meter reads "0")

The threshold is just were you want your compressor to start compressing. Make it some arbitrary value, -10db or +4db, depends on how much you want the unit ot be able to compress. Something that I personally can't answer for you.
Some people want to be able to have a huge range of compression and therefor would set the threshold lower, others want to just barely grab 5-10db, those people would logically probably set the threshold higher. If your looking for a "do this" answer, I'm deliberately not giving you one, your going to have to sit down and experiment and hear for yourself :) :) :) There is no big secret.
Ps really dig your studio/band. very cool 60s vibe.
Hey thanks Abe, that actually clears matters up for me. I hadn't had any luck finding a service manual for any vari-mu comp; I'm glad to hear it's a 'to taste' sort of adjustment (as opposed to, say, the q bias step in the 1176 or some of the adjustments for a gain brain). My console's inserts are -10dBu so I'll try splitting the difference between that and +4dBu line level for the onset of gain reduction.
BTW great job getting this project happening and making it so flexible in terms of configuration (i'm going for chip I/O). I'd always thought a vari-mu comp would be out of reach money-wise.
(and thanks for the kind words RE band/studio).
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: prh on November 24, 2012, 05:42:32 PM
Could the threshold trimmer be replaced by a front panel pot?  Any disadvantages to this?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on November 24, 2012, 06:01:16 PM
Could the threshold trimmer be replaced by a front panel pot?  Any disadvantages to this?

Good point. I was thinking the same thing. You could do it and even have it replace the input pot, or not. Would probably make it more flexible in some instances.
Title: Input transformers
Post by: prh on November 26, 2012, 02:32:46 AM
I have some Carnhill VTB9046 line input transformers.  Could these be used either input or inter-stage with the Vari-mu?

Data from the AML Carnhill guide:

Series 1°     Parallel 1°     Series 2°     Parallel 2°     Gain  dB
10k ohm                           2k4 ohm                            -6
10k ohm                                               600 ohm       -13
                   2k4 ohm        2k4 ohm                            0
                   2k4 ohm                            600 ohm        -6

Thoughts?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Holger on November 26, 2012, 05:04:18 PM
Snapshot:

(http://audiofor.tv/diy/ProjectFotoFolder/176/1.jpg)
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ethervalve on November 27, 2012, 12:43:56 PM
 :o nice! If you don't mind divulging your shop secrets, how did you label the illuminated switches?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Holger on November 28, 2012, 03:20:15 AM
No secrets here, I used transparent foil for overhead projectors.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Edward on November 29, 2012, 06:17:02 AM
Do I ground the PSU pcb from pin 4, which is the CT? Is that the only connection to ground needed from the pcbs?

Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on November 29, 2012, 08:34:48 AM
with vu meter I can not get a correct reading of the compression
this might work?
Thanks


http://www.ebay.it/itm/PM-2-1MA-MOVING-COIL-METER-1MA-/130753131630?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item1e717e746e
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: earl on November 30, 2012, 03:07:19 PM
@ Edward : Abe says ground from one of the smoothing caps down the line from ct. :)
EDIT: Thinking that was the rev 1 version where i read that. 
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Dr_J on December 01, 2012, 11:25:09 AM
Hi Ifungo,

yes 1mA meter would do the job.
But what's the problem with your VU meters? They have to work to, have they!?
Maybe you just need to make a new scale for them!?
Check out my post in the REV 1 thread.

ROCK-ON!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on December 01, 2012, 01:41:55 PM
Thanks Dr_J
I don't know how to make a new scale for VU Meter....
Can you help me with some info?
Thanks!!!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on December 01, 2012, 01:54:26 PM
Do I ground the PSU pcb from pin 4, which is the CT? Is that the only connection to ground needed from the pcbs?

What do you mean exactly? You don't need to add anything. The only connection you will need to "ground" (connecting the audio ground to chassis ground) will be at one of the input XLRs (you have all the pin 1s of all your xlrs connected directly to chassis at the xr right? ) and you only connect any of the XLR pin 1s at ONE and only one xlr to the respective pin 1 on the pcb.
Hope that helps :)


Abe
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Edward on December 01, 2012, 04:08:17 PM
Do I ground the PSU pcb from pin 4, which is the CT? Is that the only connection to ground needed from the pcbs?

What do you mean exactly? You don't need to add anything. The only connection you will need to "ground" (connecting the audio ground to chassis ground) will be at one of the input XLRs (you have all the pin 1s of all your xlrs connected directly to chassis at the xr right? ) and you only connect any of the XLR pin 1s at ONE and only one xlr to the respective pin 1 on the pcb.
Hope that helps :)


Abe

I was reading the rev 1 thread and somebody was writing about that... From now on I will try to stick to the plan and stop trying to figure out stuff by my own as it usually turns out horribly wrong. Thanks again.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: earl on December 02, 2012, 04:23:35 PM
Hey Abe 1 channel of sonic bliss complete... squishy aggression.  Sounds of glory.  Thanks for making this truly unique project available.  Using lundahl's and 2520's.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on December 03, 2012, 01:29:02 PM
Do I ground the PSU pcb from pin 4, which is the CT? Is that the only connection to ground needed from the pcbs?

What do you mean exactly? You don't need to add anything. The only connection you will need to "ground" (connecting the audio ground to chassis ground) will be at one of the input XLRs (you have all the pin 1s of all your xlrs connected directly to chassis at the xr right? ) and you only connect any of the XLR pin 1s at ONE and only one xlr to the respective pin 1 on the pcb.
Hope that helps :)


Abe

I was reading the rev 1 thread and somebody was writing about that... From now on I will try to stick to the plan and stop trying to figure out stuff by my own as it usually turns out horribly wrong. Thanks again.

Hi Edward,
Sorry I know its pretty confusing!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on December 03, 2012, 01:31:04 PM
Hey Abe 1 channel of sonic bliss complete... squishy aggression.  Sounds of glory.  Thanks for making this truly unique project available.  Using lundahl's and 2520's.

Thanks for the kind words :) Much thanks goes to PRR though, hes the mastermind behind the original idea. I must agree, these units do sound nice!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: sedit1 on December 04, 2012, 02:25:14 PM
Hi!

I'm having a problem with my power transformer(s) 230v

I have 2x25vac and 2x15vac toroids.

I've connected one 24vac secondary to 15vac secondaries witch are connected in series and I get 260vac am I doing something completely wrong here?

Thanks!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on December 04, 2012, 08:24:59 PM
Hi!

I'm having a problem with my power transformer(s) 230v

I have 2x25vac and 2x15vac toroids.

I've connected one 24vac secondary to 15vac secondaries witch are connected in series and I get 260vac am I doing something completely wrong here?

Thanks!

Do you have the 15V transformer the one that is connected to the mains? Also maybe measure each transformer to be sure of the voltage they are putting out.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: sedit1 on December 05, 2012, 12:37:10 AM
Hi!

I'm having a problem with my power transformer(s) 230v

I have 2x25vac and 2x15vac toroids.

I've connected one 24vac secondary to 15vac secondaries witch are connected in series and I get 260vac am I doing something completely wrong here?

Thanks!

Do you have the 15V transformer the one that is connected to the mains? Also maybe measure each transformer to be sure of the voltage they are putting out.

Thanks Abe,

The 2x24v is connected to mains. Transformers measure 2x24->28vac 2x15->18vac. I've connected them like in the g9 picture http://i73.photobucket.com/albums/i222/skylargray/G9/G9Toroidconnections.jpg

I think that might be the problem? Because I was just testing this with tx's what I have at home already but they are just single primary straight to 230v. So I think I need the 15vac to be dual primary and also connect the "new secondary" in series?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on December 05, 2012, 12:22:36 PM
Well if you have the 24V connected to mains, and then connect that to the 15V transformer your going to get more that 230V on the output. Which for the G9 is fine, but this project you only want 120V or so.

When you apply 15V to the secondary side of the 15V transformer  you will get the spec'ed 230V on the primaries. What happens when you increase the voltage on the secondaries? The voltage will raise faster on the primaries. So if you apply 24Vs to the 15v transformer its no big surprise you are getting more than 230v right?

(I know the whole "secondary" and "primary" is a little confusing because we are flipping the transformer around and essentially using the primary and the secondary etc etc, don't get confused its all the same to the power transformer!)

So then applying the same logic to the 24V transformer. When you apply roughly 24V on the secondarys of the transformer you get roughly 230V on the output, right? Since we want a little more than half that voltage, we'll apply a little more than half that on the secondaries. Wait, you still have that 15V transformer right? That will be perfect.

Make sense?

230::15::24::150ish

BE SAFE!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: sedit1 on December 05, 2012, 12:51:10 PM
Well if you have the 24V connected to mains, and then connect that to the 15V transformer your going to get more that 230V on the output. Which for the G9 is fine, but this project you only want 120V or so.

When you apply 15V to the secondary side of the 15V transformer  you will get the spec'ed 230V on the primaries. What happens when you increase the voltage on the secondaries? The voltage will raise faster on the primaries. So if you apply 24Vs to the 15v transformer its no big surprise you are getting more than 230v right?

(I know the whole "secondary" and "primary" is a little confusing because we are flipping the transformer around and essentially using the primary and the secondary etc etc, don't get confused its all the same to the power transformer!)

So then applying the same logic to the 24V transformer. When you apply roughly 24V on the secondarys of the transformer you get roughly 230V on the output, right? Since we want a little more than half that voltage, we'll apply a little more than half that on the secondaries. Wait, you still have that 15V transformer right? That will be perfect.

Make sense?

230::15::24::150ish

BE SAFE!

Thanks Abe this makes perfect sense!

This was just testing the technique. My main Idea was that I would order 1x18v and 1x12v dual primary toroids -> 230::18vac::12vac secondaries in series::172.5vac (new secondary in series)
Then I would still have the other 18v winding for my 18vac input.

Does this make any sence or would it be just easiest to buy 230->115vac toroid and also use 2x18vac for 18v?

Thanks!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on December 05, 2012, 04:36:43 PM

Does this make any sence or would it be just easiest to buy 230->115vac toroid and also use 2x18vac for 18v?

Thanks!

You could use both ways. Though getting a separate (or a transformer with the correct taps) for 115V would be best.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ethervalve on December 08, 2012, 04:31:43 PM
Hi all,
Just got mine together and turned it on, psu voltages are ok but I need to do a bit of troubleshooting.
I'm a little confused by one thing in the schematic (incidentally, is the Rev1 schematic still OK to follow for Rev2 boards?):
when using the IC input option (which I'm doing), do I just jumper the OPT_1 and OPT_2 pads? Or do any of the transformer pads require bridging?
Thanks in advance
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on December 09, 2012, 03:30:26 AM
Hi all,
Just got mine together and turned it on, psu voltages are ok but I need to do a bit of troubleshooting.
I'm a little confused by one thing in the schematic (incidentally, is the Rev1 schematic still OK to follow for Rev2 boards?):
when using the IC input option (which I'm doing), do I just jumper the OPT_1 and OPT_2 pads? Or do any of the transformer pads require bridging?
Thanks in advance

You still need the interstage transformer, or the 2 interstage transformers per channel. 4 total for the board. then you bridge both "in-ops" if your using the chip input as apposed to a t-pad attenuator. And yes rev 1 schematic is still good.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ethervalve on December 09, 2012, 11:10:39 AM
ha, I'm a buffoon. Thanks Abe. The one channel I have enough transformers for sounds great! (Seems to make cymbals sound a little nicer than are in reality; also really get's that 'September Gurls' comp'd guitar sound nicely).

edit:
I love this thing enough that I'm mulling the idea of building a second one next year. Have any of the earlier builders noticed if the threshold calibration remains stable over time? I ask this because I'm thinking it would be cool to have a 2 or 3-way switch with different calibrated threshold settings. In my case I'd be using it 75% of the time as a console insert (nominal -10dBu) and the remaining quarter of the time connected to +4dBu 2-track outs.
Also, have any of you who used the hairball/nissei meters tried replacing the scale? I'm OK with it as is, but it would be interesting to know if scale modding worked out for anyone.
Title: Tube Newb
Post by: prh on December 13, 2012, 07:16:58 PM
I'm gradually acquiring parts for the Vari-mu, for use with the AC Sound pcb set.

This will be my first construction involving tubes, and I note that a 6bc8 is specified for this project.

Can I get some ideas of preferred tube brands and alternative types, which are suitable for the project, as well as reputable places to buy from?

Basically I have little idea what to look out for, so any help is appreciated.

Cheers,  Paul H
Title: Re: Tube Newb
Post by: abechap024 on December 15, 2012, 03:19:33 AM
I'm gradually acquiring parts for the Vari-mu, for use with the AC Sound pcb set.

This will be my first construction involving tubes, and I note that a 6bc8 is specified for this project.

Can I get some ideas of preferred tube brands and alternative types, which are suitable for the project, as well as reputable places to buy from?

Basically I have little idea what to look out for, so any help is appreciated.

Cheers,  Paul H

Ive used different kinds and honestly haven't really been able to tell a difference...not that i was specifically looking for one, but seems like any decent 6bc8 tube works fine here. other peoples experience might be different though.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on December 15, 2012, 08:40:27 PM
Heres some sound samples I put together, and thought I would share them. I'm using pretty much stock stuff....1uf Tant cap, ne5534 on input API type opamp 2520 on output. Cinemag input and PM1000 1:1 output for interstage:

https://docs.google.com/open?id=0BzDAglyU_ZBAbm5CV1pNVFo3SE0
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: kramerb1 on January 07, 2013, 06:15:40 PM
Almost done with this project but had a couple issues that I wanted to ask about. I'm using GAR1731 DOAs for input and output gain, and INA/DRV chips on ins and outs. All PS voltages read correct. On the output pins of the output 1731s, there is between 250 and 400 mV of DC offset (does this seems excessively high?). It seems like this DC is being passed to the DRV chip then essentially being doubled on the xlr. Should the output of the 1731 be cap coupled? I do have some 600/600 edcors that I could throw on the output instead, preceded by the bi-polar cap, but I'd like to get the chips working. Would it really be necessary to have a bi-polar cap in this situation if I'm only reading a positive offset voltage on the output of the 1731s?

Where should the max of the needle be when I calibrate the Hairball's 8027-WF 1mA meters? Where should I take the voltage from to power the leds in the meters? Should I run them in series (seems to make the most sense)? I don't want to draw any more current from the heater circuit as it already seems to be running the regulator pretty hot, unless perhaps I could take it pre-regulator. Do I have to throw a high wattage resistor in series to drop down the voltage? Any idea what those leds can take?

Thanks for this project Abe! PS, when are you going to get a board for that PI compressor  ;).

Brian

Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on January 07, 2013, 08:05:17 PM
Almost done with this project but had a couple issues that I wanted to ask about. I'm using GAR1731 DOAs for input and output gain, and INA/DRV chips on ins and outs. All PS voltages read correct. On the output pins of the output 1731s, there is between 250 and 400 mV of DC offset (does this seems excessively high?). It seems like this DC is being passed to the DRV chip then essentially being doubled on the xlr. Should the output of the 1731 be cap coupled? I do have some 600/600 edcors that I could throw on the output instead, preceded by the bi-polar cap, but I'd like to get the chips working. Would it really be necessary to have a bi-polar cap in this situation if I'm only reading a positive offset voltage on the output of the 1731s?

Hi! Yea the DRVs do seem to pass DC. They supposedly are supposed to negate it by having the caps near the output but I guess not. (from the data sheet) I would put a cap between the opamp and the DRV chip. Bi-polars are ALWAYS a fine choice when dealing with audio, or anything for that matter.

Quote
Where should the max of the needle be when I calibrate the Hairball's 8027-WF 1mA meters?
The higher the needle the more resolution it will show. Doesn't matter, wherever you want it.

Quote
Where should I take the voltage from to power the leds in the meters? Should I run them in series (seems to make the most sense)? I don't want to draw any more current from the heater circuit as it already seems to be running the regulator pretty hot, unless perhaps I could take it pre-regulator. Do I have to throw a high wattage resistor in series to drop down the voltage? Any idea what those leds can take?

Run them off the negative rail, run them in series and try a 1k to 10k (i forget exactly what I used last build) depending on how bright you want them. And because you are running them off the negative rail, jsut remember to wire it up correctly (positive to ground, neg to neg power)

Quote
Thanks for this project Abe! PS, when are you going to get a board for that PI compressor  ;).
Your welcome, home you get some good use out of it! Also I'm getting ready to do a kickstarter for the Pi.... :)




Brian


[/quote]


Also I've been doing some more testing and it seems without shielded transformers on the input and interstage, the transformers are very susceptible to hum pickup.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ethervalve on January 08, 2013, 11:56:51 AM
Hey I finished the second channel of mine--love it! Last session it handily beat both my rev a 1176, rev d 1176, and la2a clones in a blind test for a particular vocalist's track.
The stereo matching is working very well too (nearly identical GR up to 10dBs).

The only issue left to resolve is the side-chain high-pass: It doesn't seem to have an audible or measurable effect on gain reduction.
Any clues for troubleshooting?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on January 08, 2013, 01:24:51 PM
Hey I finished the second channel of mine--love it! Last session it handily beat both my rev a 1176, rev d 1176, and la2a clones in a blind test for a particular vocalist's track.
The stereo matching is working very well too (nearly identical GR up to 10dBs).

The only issue left to resolve is the side-chain high-pass: It doesn't seem to have an audible or measurable effect on gain reduction.
Any clues for troubleshooting?

Great news!! Yes for the HPF, you might want to put a smaller cap in there for a more audible HP. You could even do one super small so to give it a de-esser type control.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: gato on January 08, 2013, 08:03:39 PM
Both this and the clx 160vu are great projects. I especially like how many options can be played with on this board. Can't wait for that pi
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ethervalve on January 11, 2013, 12:39:31 PM


Great news!! Yes for the HPF, you might want to put a smaller cap in there for a more audible HP. You could even do one super small so to give it a de-esser type control.
Thanks Abe. Unfortunately, changing the cap out for a smaller value didn't change anything. I added sockets for trying different values and even with a .01uf in place, the HPF switch won't affect the level of compression for a 20hz tone. Perhaps I'm missing something obvious?
 
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on January 11, 2013, 04:44:39 PM


Great news!! Yes for the HPF, you might want to put a smaller cap in there for a more audible HP. You could even do one super small so to give it a de-esser type control.
Thanks Abe. Unfortunately, changing the cap out for a smaller value didn't change anything. I added sockets for trying different values and even with a .01uf in place, the HPF switch won't affect the level of compression for a 20hz tone. Perhaps I'm missing something obvious?

Doh! You know what, I think those caps are labeled backwards. Try putting the HPF in the one labeled 1uf. Thanks for catching that...
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: prh on January 11, 2013, 06:22:08 PM
Doh! You know what, I think those caps are labeled backwards. Try putting the HPF in the one labeled 1uf. Thanks for catching that...

Can you clarify this please?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ethervalve on January 11, 2013, 06:35:36 PM


Great news!! Yes for the HPF, you might want to put a smaller cap in there for a more audible HP. You could even do one super small so to give it a de-esser type control.
Thanks Abe. Unfortunately, changing the cap out for a smaller value didn't change anything. I added sockets for trying different values and even with a .01uf in place, the HPF switch won't affect the level of compression for a 20hz tone. Perhaps I'm missing something obvious?

Doh! You know what, I think those caps are labeled backwards. Try putting the HPF in the one labeled 1uf. Thanks for catching that...
Excellent! That's all it took. Works great.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ethervalve on January 11, 2013, 06:40:40 PM
Doh! You know what, I think those caps are labeled backwards. Try putting the HPF in the one labeled 1uf. Thanks for catching that...

Can you clarify this please?
Hi prh, he just means the caps labelled C1 and C35 on the PCB should change places in channel one; C38 and C36 should switch places for channel two.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: prh on January 11, 2013, 07:46:21 PM
Hi prh, he just means the caps labelled C1 and C35 on the PCB should change places in channel one; C38 and C36 should switch places for channel two.

Ah, thanks for that!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: DAN_000 on January 12, 2013, 12:20:14 AM
Hi,

Should I use R7-R8 and R87-R95 when in center tap mode ?  Im using 1540 on both input and interstage.

thanks
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: astroschnautzer on January 13, 2013, 09:16:49 AM
Hi,

Should I use R7-R8 and R87-R95 when in center tap mode ?  Im using 1540 on both input and interstage.

thanks
Would also like to know what the practical difference is between using center tap or resitors?....
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: baadc0de on January 19, 2013, 04:52:13 AM
Just did center-tap myself.
Here is a pic of my build:

(http://farm9.staticflickr.com/8219/8393743727_db911be335_z.jpg) (http://www.flickr.com/photos/[email protected]/8393743727/)

The PRR is obviously the one on top, Fester's TG on bottom. Copy RCA knobs, hairball meters. LL1540  as inputs and interstage, gar1730 on first DOA, gar2520 on output. Chip balanced output. Used the german groupbuy toroid.

Two more quirks to iron out, one channel compresses, the other one kind of expands.. the meter moves forward a tad when compressing. Must be a wiring fault or cold joint somewhere.

The other is that VU meter bulbs need some juice, so I'll probably just take the 20-0-20 out from the transformer. One of the "20" windings has 1A current available, the other 0.5A, so I'm thinking to rectify the 1A separately, smooth out using a 2200uF and that should be it. The bulbs are rated 12V 100mA. I've measured resistance on one and it's 12Ohms, so putting 24Ohms for two in parallel PSU designer says they would be getting 9.9VMRS.

Also, here is the usual sound sample:

https://dl.dropbox.com/u/12679166/prr176/jazzvoc_off.wav

https://dl.dropbox.com/u/12679166/prr176/jazzvoc_prr176.wav

Cheerio.

Hi,

Should I use R7-R8 and R87-R95 when in center tap mode ?  Im using 1540 on both input and interstage.

thanks
Would also like to know what the practical difference is between using center tap or resitors?....
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Dr_J on January 20, 2013, 01:51:37 PM
Hey baadc0de,

this is a cool frontpanel and cool knobs as well!!  :D
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: baadc0de on January 21, 2013, 01:31:53 AM
Hey baadc0de,

this is a cool frontpanel and cool knobs as well!!  :D

Thanks mate.. unfortunately, I'm still struggling to get the 1st channel to compress. I've checked the wiring, components.. slowly getting out of ideas. Getting my scope up, we'll see what's happening in there.

EDIT: seconds after the post, I found C33 to be in the other way around. Changed it, no luck, changed ICs, still no luck. The scope sees -1VDC at output of D1/D2. So I guess it should be the wiring..

PS: there is correct movement on the 1st channel's GR meter when they are in link mode. I can't verify audio since I only have two cables at home :)
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on January 21, 2013, 11:30:53 AM
Hey baadc0de,

this is a cool frontpanel and cool knobs as well!!  :D

Thanks mate.. unfortunately, I'm still struggling to get the 1st channel to compress. I've checked the wiring, components.. slowly getting out of ideas. Getting my scope up, we'll see what's happening in there.

EDIT: seconds after the post, I found C33 to be in the other way around. Changed it, no luck, changed ICs, still no luck. The scope sees -1VDC at output of D1/D2. So I guess it should be the wiring..

PS: there is correct movement on the 1st channel's GR meter when they are in link mode. I can't verify audio since I only have two cables at home :)

Build looks great! I had trouble with one of my builds doing exactly what you were saying and it turned out to be a bad bypass switch. So I would double check around the bypass wiring, and solder joints...the channel that isn't compressings' tl072 and sidechain area.
Good luck!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ethervalve on January 21, 2013, 12:26:03 PM
aside: hey Abe, are you planning on making another run of these boards? I'm hoping to build a second one in a 2RU chassis with switchable thresholds and few other bells and whistles.
Also: you wouldn't happen to know if a slight step-up, 1 + 1 : 2.28 transformer would be suitable for the inter-stage? The Lundahl LL1521B seems to come up for sale for decent prices used quite frequently. According to a doc on the Lundahl site: "The LL1521B is a high impedance line input transformer, very similar to the LL1540 but with a slight stepup."
Thanks!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: Dr_J on January 22, 2013, 03:41:09 PM
Hi baadc0de,

don't know if it may help, but I had this problems
http://www.groupdiy.com/index.php?topic=44586.740

Good luck!

ROCK-ON.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on January 22, 2013, 09:37:43 PM
aside: hey Abe, are you planning on making another run of these boards? I'm hoping to build a second one in a 2RU chassis with switchable thresholds and few other bells and whistles.
Also: you wouldn't happen to know if a slight step-up, 1 + 1 : 2.28 transformer would be suitable for the inter-stage? The Lundahl LL1521B seems to come up for sale for decent prices used quite frequently. According to a doc on the Lundahl site: "The LL1521B is a high impedance line input transformer, very similar to the LL1540 but with a slight stepup."
Thanks!

Yes, Im going to get another run together  soon! :) Also yes that should be fine. ANY transformer will work (within reason) the only things changing will be gain and frequency response, also interestingly enough i found attack and release times changed with different transformers?? (answer me that one somebody!)
Best,
Abe
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: labak on January 31, 2013, 03:40:29 AM
Hi all!

I'm currently looking for a group buy of some power Xformers for this project!

Before a big thanks to DR-J and Kingston who did and helped it before!

Price is 33€ (Netto) + Shipping for one piece. Shipping 2-3 weeks after Order.

Specs : 230V // 20VAC 0.5A (opamps), 20VAC 1A (opamps + heater), 120VDC 50mA (B+)!!!

Same as DR-J already did.

Let me know who is in?

Best.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ArnauTS on January 31, 2013, 08:06:17 AM
I'm in for one for power trafo.
Was hoping for a new group buy run  :D
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: labak on January 31, 2013, 12:37:37 PM
Only 2 we are? :(

I'll send the order on Monday!

Best.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: WNStudios on January 31, 2013, 06:04:11 PM
I'm in!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: labak on February 04, 2013, 11:43:07 AM
Hi ArnauTS and WNStudios!

Look at you PM Boxes, dudes.

Best.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: baadc0de on February 05, 2013, 02:11:04 AM
After putting the project on the backburner, coming back to it was easy;

faulty (intermittent) bypass switch, depending on horizontal-vertical operation. And a tiny weeny solder bridge with a via near R166 on the up (component) side of the PCB (missed that one since I was looking for bridges on the other side).

Thanks for the help, both problems were hinted at in this thread!

Cheers!

Hi baadc0de,

don't know if it may help, but I had this problems
http://www.groupdiy.com/index.php?topic=44586.740

Good luck!

ROCK-ON.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: prh on February 11, 2013, 10:01:13 PM
Is there a circuit description somewhere for this project?   I guess a "canonical" thread is what I am looking for.

Thanks.  Paul
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: astroschnautzer on February 14, 2013, 02:19:23 AM
http://www.acsoundstudio.com/diyhosting/PRR_176.jpg
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: supiarmando on February 19, 2013, 06:28:05 AM
here we go! since this morning the unit running (after struggling with the LM350 because of temerature issue)!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: prh on February 19, 2013, 05:32:13 PM
I am having trouble locating suitable tube sockets for the 6bc8 tubes.  I bought some 9 pin sockets from ebay, which are too large.  (I am a tube noob).

Can someone please post a link for the correct tube sockets? 

@Austroschnautzer:  thanks for the circuit.  I found an early article by PRR which provides the circuit description of the original circuit.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on February 19, 2013, 06:29:32 PM
I am having trouble locating suitable tube sockets for the 6bc8 tubes.  I bought some 9 pin sockets from ebay, which are too large.  (I am a tube noob).

Can someone please post a link for the correct tube sockets? 

@Austroschnautzer:  thanks for the circuit.  I found an early article by PRR which provides the circuit description of the original circuit.

Here:

http://www.ebay.com/itm/160580213397?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

and some nice holders so your tube don't fall out if your ship it or something:

http://www.ebay.com/itm/251037957427?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: prh on February 19, 2013, 08:09:20 PM
I am having trouble locating suitable tube sockets for the 6bc8 tubes.  I bought some 9 pin sockets from ebay, which are too large.  (I am a tube noob).

Can someone please post a link for the correct tube sockets? 

@Austroschnautzer:  thanks for the circuit.  I found an early article by PRR which provides the circuit description of the original circuit.

Here:

http://www.ebay.com/itm/160580213397?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

and some nice holders so your tube don't fall out if your ship it or something:

http://www.ebay.com/itm/251037957427?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
Many thanks!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: astroschnautzer on February 25, 2013, 03:34:06 AM
Question about fuse:  I  have 40VA transformer with three outputs, how to calculate fuse for this (I'm in eu, 230v mains).... I'm getting 0.17 amps with 40/230 mut that seems a bit small, can this be correct?


TS 40VA PRI: 230V SEC:
20V (1A)
20V (500mA)
120V (50mA)
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: astroschnautzer on March 06, 2013, 09:42:10 AM
Just got this working after some troubleshooting ( still though the other output transformer seems to be broken) , and it sounds awesome, best on vocals and acoustic instruments and plucky transients just as I was hoping to, its sounds like the 60's.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: baadc0de on March 06, 2013, 10:04:16 AM
http://www.youtube.com/watch?v=HjP2e-bq4Ao
Sorry for the plug :)

The PRR176 is sounding great, sitting on the guitar (two gefell m582 through silentarts jensamp). Lots of other awesome DIY gear can be seen in the video.

This PRR in question has LL1540, moamps's melcor DOAs and RCA 6BC8s.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on March 07, 2013, 01:58:32 AM
Sounds great! Great work. Also these do have that 60's mojo,  the best kind! :) Glad you got them going.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: WNStudios on March 31, 2013, 09:58:01 AM
My build is put on hold for a while, but i did manage to finish the front.

(https://fbcdn-sphotos-g-a.akamaihd.net/hphotos-ak-snc6/9999_10151608071764880_2077929158_n.jpg)
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on April 12, 2013, 06:31:13 AM
I would like to do another 176 with Carnhill output
which model should I use?
Thanks
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on April 13, 2013, 05:42:28 AM
???
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: baadc0de on April 17, 2013, 01:42:32 AM
http://www.audiomaintenance.com/acatalog/CA-18-VTB2281_extended_info.html

This one.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ilfungo on April 17, 2013, 07:51:45 AM
Thanks!!!
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: shot on April 29, 2013, 10:07:50 PM
Hey Abechap, I was just wondering...

When will you do another batch of PCBs for this compressor?
Anytime soon? 

;)
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ethervalve on May 08, 2013, 10:25:36 AM
Hi all,
I got a second pcb and I'm interested in trying to add switchable thresholds for this one.
Before I waste money on parts, could anyone advise me if either a 3PDT switching between two pre-set trimmers would make sense? Or prehaps even a 3 pole Lorlin rotary switch with three or four different trimmers? Would anyone know if shorting vs non-shorting would matter in this sort of application (eg is there a potential for monitor-destroying pops or other switching noises)?
Thanks in advance.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on May 08, 2013, 02:32:33 PM
Hi all,
I got a second pcb and I'm interested in trying to add switchable thresholds for this one.
Before I waste money on parts, could anyone advise me if either a 3PDT switching between two pre-set trimmers would make sense? Or prehaps even a 3 pole Lorlin rotary switch with three or four different trimmers? Would anyone know if shorting vs non-shorting would matter in this sort of application (eg is there a potential for monitor-destroying pops or other switching noises)?
Thanks in advance.

Cool idea...you could even just make it a pot and have a genuine threshold knob. If you do use a switch, and their are pops, it won't be a big deal, it will just peg the gain reduction circuit which will be the opposite of a pop to the outputs...Just mess with the gain resistors around the sidechain amp, or replace the trim pot with a pot/switch
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ethervalve on May 08, 2013, 03:57:05 PM
Hey thanks for the info Abe. hmmm if it were repeatable, pegging the gain reduction could even be a handy hack for starting a mix with the compressor slightly in recovery...

I might try the pot idea on one of the two units. I'd like to do the switches for one in order to have a more optimal fixed threshold for either line/tape return level or the much lower insert level on my mixer.


Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: geotone on May 10, 2013, 01:02:07 PM
Hi all,


I'm yet another newbie - just ordered all the parts for Gyraf's PQ1549 and looking forward to putting that together. And as my next project I'd like to take up this - gotta plan ahead! So Abe, add my name to the list of people hoping for another run of PCB's!


Thanks for all the work and shared information here, this is a goldmine.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: prh on May 13, 2013, 06:23:36 AM
Does anyone do a 2RU front panel or case for this project?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: labak on May 20, 2013, 01:41:32 AM
Hi All!

After a long night of reading previous posts on rev1 and rev2, testing, soldering, desoldering, replacing everything possible on the PSU board, I'm still at the same point :

==> +/- 18V are ok.
==> + 1.5V is ok.
==> HT is 140V unloaded, It seems to be too high, isn't it ?
==> Heaters power : NO SHOW  :o. In fact I have 1.32V output, loaded and unloaded. The Lm350 is cold as Ice.
I replaced all regulators 3 times, diodes the same and resistors too.

I saw that some the same kind of weird issue, but nobody explain what they did to sort it!

Any help is welcome.

Best.

Chris.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: labak on May 20, 2013, 01:51:26 AM
At the input of the Lm350 I have 30V!

Direct output of the Lm350 I have 8.43V and the trimmer can only decrease it, this voltage is the max I can have.
At heater 2 only 1 and something Volts.

Best.

Chris.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on May 20, 2013, 09:33:03 AM
Hi Chris,
Very interesting...your HV is OK because it needs to be loaded in order to have the correct voltage. Also I don't know whats going on with your Heaters, but your just going to have to work through it, the fact that the LM350 is cold is a big clue, it means for whatever reason it is not working, I would check voltages, your parts are probably OK the problem lies elsewhere on the power board. Its something simple, correct trim pot and resistor?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: labak on May 21, 2013, 10:54:32 AM
Hi Abe!

Thanks for the HELP!

I've found it! It was the Molex pin that does not contact the cable from deported LM350!

Sometimes it's right under your nose and you are blind!!!

Thanks again!

Best regards.

Chris.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ethervalve on May 23, 2013, 03:33:31 PM
Hi all,
I finally gathered all the parts for my second prr-176 (using a Rev 1 board) and before I start I was wondering if anyone had any opinion on the best use of the transformers I have on hand.
My already built rev2 currently has Edcor 10k:10k for input and interstage. I've since acquired four Lundahl LL1540s.
I was initially going to have one of them all-Edcor and the other all-Lundahl, but I just wanted to check if anyone has an opinion on where the higher quality Lundahls might be used to their best potential (input vs interstage).
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: baadc0de on May 23, 2013, 04:33:58 PM
Hi all,
I finally gathered all the parts for my second prr-176 (using a Rev 1 board) and before I start I was wondering if anyone had any opinion on the best use of the transformers I have on hand.
My already built rev2 currently has Edcor 10k:10k for input and interstage. I've since acquired four Lundahl LL1540s.
I was initially going to have one of them all-Edcor and the other all-Lundahl, but I just wanted to check if anyone has an opinion on where the higher quality Lundahls might be used to their best potential (input vs interstage).

Interstage. There have been reports of the compressor picking up more hum/noise there.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: labak on May 28, 2013, 08:52:27 AM
Hi All!

Almost finished mine, with a lot of options onto. ;)

Just one thing is going weird.

I've put Threshold on a switch (made with vischay/resistors). It's a nice option too, kind of compression switch.

On channel 2 when switch is fully CW, I have more compression, normal. On channel 1 it's totally over compressed and distorted (Nuke fonction).

I tried all: swapped the tubes, swapped all the IC's, swapped the switch socket. All is going well on Channel 2 but never on Channel 1.

Thing intersting is that I have almost 14VDC across the release tant cap on Channel 1 and Normal voltage across tant cap in Channel 2 when last position is engaged.

Any ideas, expsriences, help with this kind of problem.

Best regards.

Chris.

Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: labak on May 28, 2013, 08:59:42 AM
One more thing!

Do you know where could I find a Matched Pair of 6bc8?

I've tested a lot and actually I have a Zenith on one channel and a Sylvania on the other!

I have 1.5 db of gain reduction difference on high threshold settings. I cannot adjust it tightly because it's all detended and 1 set of switch for both Channels (Mastering Style).

Maybe if I put a trimmer before the threshold switch on both Channel, I could tight them?

Best regards.

Chris.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on May 29, 2013, 08:30:29 AM
Hi Chris,
Have you adjusted the threshold trimmer for both channels?

Also I'm sure you've taken note of this, but I'll say it anyway, how the 2 connectors are wired aren't the same for both channels due to the way the stereo link has to work. So I would assume your problem is how it is wired up, somewhere...
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ethervalve on May 29, 2013, 10:01:52 AM


Interstage. There have been reports of the compressor picking up more hum/noise there.
Hey thanks for the advice, I decided to go all-Lundahl for the rev 1. My rev 2 is very quiet with the Edcors.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on May 29, 2013, 11:19:24 AM


Interstage. There have been reports of the compressor picking up more hum/noise there.
Hey thanks for the advice, I decided to go all-Lundahl for the rev 1. My rev 2 is very quiet with the Edcors.

Really!?! I need to get my rev 2 working with edcors (I have a box of them) for some reason it wouldn't, and when I switched out the transformers with mu-metal covered ones, it was dead quiet.

Maybe cause I live in the city and there is tons of junk in the air??

IDK I'm going to build another one with edcors and see, I love the tone of the steel core edcors, nice and warm.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: labak on May 29, 2013, 11:32:39 AM
Hi Abe!

Thanks for the help, really appreciate it!

Before my stepped pot for Threshold I put now trimmers, like this I can adjust it perfectly!

No stereo link at all for it

Stereo pots, stepped, but no link! I connect direct S and C point together on channel 2.

One more thing.

I'm using the same meter as in my Gssl, 1mA one! No move at all, really small move in fact almot 1db when full compression. And when unit is fired up, the meter goes for full reduction even with no signal in!

Best regards.

Chris.

Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on May 29, 2013, 12:28:33 PM
Hi Abe!

Thanks for the help, really appreciate it!

Before my stepped pot for Threshold I put now trimmers, like this I can adjust it perfectly!

No stereo link at all for it

Stereo pots, stepped, but no link! I connect direct S and C point together on channel 2.

One more thing.

I'm using the same meter as in my Gssl, 1mA one! No move at all, really small move in fact almot 1db when full compression. And when unit is fired up, the meter goes for full reduction even with no signal in!

Best regards.

Chris.

Great!

And just to verify bout the meters...you know they respond like the 1176 meters right? basically they are full deflection with no gain reduction.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: labak on May 29, 2013, 12:41:37 PM
Quote
Great!

And just to verify bout the meters...you know they respond like the 1176 meters right? basically they are full deflection with no gain reduction.

I've seen that and think that!

But finally 1ma meter is not made for it? Moves are too small with, aren't they?

Anyway, I will update to something else.

I'm thinking about doing a kind of tube and harmonic box! What do you think if we had a switch to cut the tube HT, and run audio thru tubes?

Thanks for all.

Best regards.

Chris.

Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on May 29, 2013, 01:08:50 PM
Quote
Great!

And just to verify bout the meters...you know they respond like the 1176 meters right? basically they are full deflection with no gain reduction.

I've seen that and think that!

But finally 1ma meter is not made for it? Moves are too small with, aren't they?

Anyway, I will update to something else.

I'm thinking about doing a kind of tube and harmonic box! What do you think if we had a switch to cut the tube HT, and run audio thru tubes?

Thanks for all.

Best regards.

Chris.

1ma should be fine...but vu seem to work ok too..just changes your scale.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: labak on May 29, 2013, 08:25:14 PM
True! 1mA is ok!

My meters do not have enough internal resistances!

Just put a trimmer in between + and - and it rocks.

All the options and settings are rocking. Thanks for all Abe!

Best regards.

Chris.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ethervalve on May 30, 2013, 09:07:21 AM


Interstage. There have been reports of the compressor picking up more hum/noise there.
Hey thanks for the advice, I decided to go all-Lundahl for the rev 1. My rev 2 is very quiet with the Edcors.

Really!?! I need to get my rev 2 working with edcors (I have a box of them) for some reason it wouldn't, and when I switched out the transformers with mu-metal covered ones, it was dead quiet.

Maybe cause I live in the city and there is tons of junk in the air??

IDK I'm going to build another one with edcors and see, I love the tone of the steel core edcors, nice and warm.

Hey Abe, I haven't done measurements but under use I've never noticed objectionable noise or hum. Subjectively, it's quieter than my LA2A clones and about on par with RevD 1176 clones. I do mainly record to tape with no noise reduction tho, so I'm seldom listening for post-nuclear-holocaust-esque digital silence. I'll do some measurements after I finish the 2nd one (tonight hopefully!)
I also would really like to know the attack and release specs. For measuring release, would an above-threshold tone followed by a below-threshold tone be the way to go?
One last thing, I found a couple THAT1646 chips in my junk drawer. Has anyone tried these chips out in place of DRV134s?
PS I just noticed Mouser stocks a switched 100k liner pot should anyone wish to do a build with bypass on the attack pot (like the original 176): http://www.mouser.com/ProductDetail/Alpha-Taiwan/RV170SF-10-15R1-B100K/
   
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: dogma on May 30, 2013, 09:28:27 AM
Hey Abe - when are you going to do another run of kits?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: RYM on June 04, 2013, 08:23:27 AM
Hi,

have a problem with the psu .... i only get +6.3V but -0. I don´t find the fault ... any ideas?

thx
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on June 04, 2013, 01:24:25 PM
Hey Abe - when are you going to do another run of kits?

Soon I hope, as soon as there is enough interest.


have a problem with the psu .... i only get +6.3V but -0. I don´t find the fault ... any ideas?

Start measuring the voltage out of the transformer (carefully!) And follow it into the regulators. Also remember to trim the regulators they are multiturn, meaning about 25 turns from one end to the other. I know you probably know this but don't want to take anything for granted. That should fix it.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ethervalve on June 11, 2013, 12:00:35 PM

Hi! Yea the DRVs do seem to pass DC. They supposedly are supposed to negate it by having the caps near the output but I guess not. (from the data sheet) I would put a cap between the opamp and the DRV chip. Bi-polars are ALWAYS a fine choice when dealing with audio, or anything for that matter.


Hi all,
I just noticed that my Rev 2 also has some DC on the outputs. In my case, I'm using ne5534s rather than DOAs; as far as I can tell the DC seems to be coming from that last ne5534 prior to the DRV134. Has anyone else had this problem and successfully fixed it? Would Abe or anyone else have a suggested cap value to try?
And pardon my ignorance, but would the offset nulling application example in the ne5534 datasheet be applicable here?
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on June 11, 2013, 01:39:18 PM

Hi! Yea the DRVs do seem to pass DC. They supposedly are supposed to negate it by having the caps near the output but I guess not. (from the data sheet) I would put a cap between the opamp and the DRV chip. Bi-polars are ALWAYS a fine choice when dealing with audio, or anything for that matter.


Hi all,
I just noticed that my Rev 2 also has some DC on the outputs. In my case, I'm using ne5534s rather than DOAs; as far as I can tell the DC seems to be coming from that last ne5534 prior to the DRV134. Has anyone else had this problem and successfully fixed it? Would Abe or anyone else have a suggested cap value to try?
And pardon my ignorance, but would the offset nulling application example in the ne5534 datasheet be applicable here?

I would put a cap between the output of the NE5534 chip and the DRV chip. The DRV134 is supposed to null any DC offset as per Application data sheet, but doesn't seem to always work.
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ethervalve on June 11, 2013, 01:48:46 PM
Hey thanks Abe,
would you have an idea of a cap value I should try?
(I'd like to read up more on general troubleshooting this issue, as I also realized my DIY 169 EEQ has a little bit of DC on the outputs -- has anyone come across a good document on the topic?).
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on June 11, 2013, 06:10:57 PM
Hey thanks Abe,
would you have an idea of a cap value I should try?
(I'd like to read up more on general troubleshooting this issue, as I also realized my DIY 169 EEQ has a little bit of DC on the outputs -- has anyone come across a good document on the topic?).

10uf up to 100uf would be fine, 22uf, 47uf....Whatever you have handy :)
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: bluesbaz on June 19, 2013, 01:45:30 PM
Has anyone found a simple single transformer option to power these from US mains?
-s
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: GregNey on June 27, 2013, 03:17:59 PM
I'm looking to build a stepped, stereo only version... In this case, could I reduce on cost by:
-Eliminating the stereo switch and jump the connections as if the switch was in the 'stereo' position,
-Using only the LEFT side pots (switches in my case), and eliminating the right side controls.
-There would be no need for a second meter, correct?
-Are the HPF and Bypass controlled at all by the stereo switch? If not, I would just use a single DPDT switch for each.

Is there anything else I'm not thinking of? Are there any key components I should be keen on matching?

Thanks in advance,
Greg
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: abechap024 on June 28, 2013, 01:52:52 AM
I'm looking to build a stepped, stereo only version... In this case, could I reduce on cost by:
-Eliminating the stereo switch and jump the connections as if the switch was in the 'stereo' position,
-Using only the LEFT side pots (switches in my case), and eliminating the right side controls.
-There would be no need for a second meter, correct?
-Are the HPF and Bypass controlled at all by the stereo switch? If not, I would just use a single DPDT switch for each.

Is there anything else I'm not thinking of? Are there any key components I should be keen on matching?

Thanks in advance,
Greg

Yes I've thought about doing the same. You would need separate switches for the HPF and Bypass. IF you really wanted to save money, you could find a good mix of threshold and make up gain and only have attack and release controls and then how hard you hit it would determine the GR...but that might be to constraining, and input control would come in handy..
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: abechap024 on June 28, 2013, 01:59:25 AM
Has anyone found a simple single transformer option to power these from US mains?
-s

Yes....pretty much any....18v dual primany and dual secondary....there are lots that will work!
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: ilfungo on July 07, 2013, 08:47:17 AM
HI
any of you know recommend a toroidal for Europe?
I want to build another 176 mastering version .
In the first I used a custom toroidal bought on prodigy ..
thanks
Title: Re: PRR-176 Vari-Mu REV 2 *Updated Docs 7/31/12*
Post by: ethervalve on July 07, 2013, 06:12:09 PM
Hey thanks Abe,
would you have an idea of a cap value I should try?
(I'd like to read up more on general troubleshooting this issue, as I also realized my DIY 169 EEQ has a little bit of DC on the outputs -- has anyone come across a good document on the topic?).

10uf up to 100uf would be fine, 22uf, 47uf....Whatever you have handy :)
Hey thanks for the tip Abe! I somehow missed this message. I got very busy all of a sudden, but I'll try this out and report back.

Has anyone found a simple single transformer option to power these from US mains?
-s
I built two with this inexpensive triad model: VPT36-1390
They have them at Mouser if you're ordering other parts from there.
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: ilfungo on July 10, 2013, 08:31:37 AM
HI
any of you know recommend a toroidal for Europe?
I want to build another 176 mastering version .
In the first I used a custom toroidal bought on prodigy ..
thanks
???
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: Dr_J on July 10, 2013, 02:29:40 PM
Hi ilfungo

why not ordering another custom one from mueller (http://www.mueller-rondo.com/)?
I posted all necessary informations in the REV 1 threat.

ROCK-ON!
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: ilfungo on July 10, 2013, 03:01:10 PM
Thanks Dr_J
I can also order only 1 transformer?
Thanks
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: Dr_J on July 12, 2013, 04:13:56 PM
Hi Ifungo,

i think it shouldn't be a problem just ordering one.
Maybe take 2, one for your private stock and the next PRR176 project :)



ROCK-ON!
Title: Re: Power transformers redux
Post by: prh on August 12, 2013, 01:09:23 AM
I know this has been discussed, so I apologise for bringing this up again.  However...

I'm considering implementing the Gyraf "trick" of reverse connecting a transformer to obtain HV for the tubes, and have checked a couple of Gyraf's schematics showing this.

1  Since the centre tap of the first transformer is used in the derivation of + and - power rails, how then should the secondaries of the first transformer then be connected to the primary of the second transformer.?

2  What would be a suitable VA ratings for each transformer?

Thanks for any help.  Cheers, Paul

Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: muffy1975 on October 24, 2013, 09:14:10 AM
Hey,


1) where are the notes on calibration?

2) And....where are the AB's?

Can we hear this comp in action? The youtube clip is useless as its recorded through a room mic??????????????? whats with that?????????????


thanks in advance

Michael
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: baadc0de on October 24, 2013, 10:04:52 AM
Michael,

It's not that I'm super proud of that demo recording, but seriously, what's so terribly wrong? Where is this room mic you are talking about?

Hey,


1) where are the notes on calibration?

2) And....where are the AB's?

Can we hear this comp in action? The youtube clip is useless as its recorded through a room mic??????????????? whats with that?????????????


thanks in advance

Michael
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: muffy1975 on October 24, 2013, 10:18:41 AM
hey,

refering to this clip here right?

http://www.youtube.com/watch?v=X5KcJumut8Y

we are not talking about the same clip!!!!

where is your clip?

Have you got anything you have done recently with your prr on the mix bus?

regards

Michael
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: baadc0de on October 24, 2013, 10:27:25 AM
Sorry mate, confusion abounds!

http://www.youtube.com/watch?v=HjP2e-bq4Ao

this one has the PRR176 on the guitar, in stereo. The guitar is recorded through a pair of gefells with nickel capsules into a jensamp germanium and then squeezed by the PRR176.

I haven't used it on mix buss yet, but it's an interesting idea. We'll definitely try that!

Cheers,
B

hey,

refering to this clip here right?

http://www.youtube.com/watch?v=X5KcJumut8Y

we are not talking about the same clip!!!!

where is your clip?

Have you got anything you have done recently with your prr on the mix bus?

regards

Michael
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: muffy1975 on October 24, 2013, 10:37:17 AM
hey,


sounds great. really nice.


what are the function of the various trimmers????

how do you calibrate this thing.? No one is talking about it. I can't find it at least.

many thanks in advance


Michael
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: baadc0de on October 24, 2013, 10:51:03 AM
it was a long time ago...

but I think the first revision page does have some useful info on that, no?
http://groupdiy.com/index.php?topic=44586.0

have to catch my flight, so I'll check that later in the evening. But this is what I can find in that now:

Trimmers:
1k VR3, VR9 ....this balances the power between the 2 halves of the 6BC8 tube. Helps if you don't have a perfectly balanced tube.
100R VR1,VR4 adjust for minimum "thump"
1k VR5, VR2 Control Meters, Power on, let it warm up for a bit (10 minutes or so) turn until meters read "0" gr.

What I did was setup a 18kHz burst in the DAW that repeats every 1s or so, put it on loop mode and then adjusted VR3 / VR9 and VR1 / VR4 for minimum thump. You can "detect" thumps by lowpassing everything below 1kHz and take a look at the meter in the DAW from the compressor return after the lowpass. You want as small a signal as possible. That's it!

VR5 / VR2 is your classic zero adjust.

Hope that helps!
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: muffy1975 on October 24, 2013, 10:53:38 AM
thanks man,

that's really kind of you.

Your music sounds and is played/performed beautifully.

Michael
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: ethervalve on October 24, 2013, 03:21:19 PM
Hi Muffy,
Baadc0de's advice is spot-on. I'd just add that, if you can, try to buy 6BC8s tested for balance. If that's not possible, I'd recommend trying to get a few extra tubes (they're relatively inexpensive). I had trouble calibrating my 2nd PRR-176 to the same level of performance of the first one I built until I swapped out the tubes.
Good luck, I'm sure you're going to love this compressor. It's definitely my fav.
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: baadc0de on October 24, 2013, 04:06:12 PM
This german guy sent me a matched & balanced pair for no extra charge. I took PCC189 tubes

http://myworld.ebay.co.uk/tubeprofi?ssPageName=ADME:X:AAQ:GB:1181
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: labak on October 30, 2013, 02:49:37 AM
Hello all!

Quote
I took PCC189 tubes

Are PCC189 compatible with this compressor?

It's a real pain to have matched pair of 6BC8.
I've bought 10 pairs and still have from 1 to 5db difference of level compression.

My comp is a stereo with just one set of knobs for both channels, no link and outboard threshold pot. All built with Vishay/dale precision resistors.

Best regards.
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: ding on November 05, 2013, 12:39:33 AM
Looking forward to this build. :)

Edit: updated design.
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: who on November 08, 2013, 04:21:43 PM
Ding, if you are going to use a fender lamp or similar recheck your labeling left and right beside the lamp hole. It looks very tight and the nut/flange of the lampholder could overlap the marks  8) would be a bummer, it's looking cool  :)
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: ding on November 08, 2013, 08:02:38 PM
Good looking out. Yeah it's still a work in progress. I got the too many knobs too little space syndrome. I am definitely going to print it out and try things before I send it to the printers. I am so excited about this project. This compressor is so customizable! Once I get a final design I might want to get more people in on it to try and save a few bucks at panel express. I definitely want some nice pultec style 1.5 knobs. I'm definitely a knob guy :) hence my too many knobs problem.
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: ding on November 22, 2013, 10:50:23 AM
Trying to find a matched pair of these is proving to be a tough task. Does anyone know where to get a matched pair preferably in the US to avoid the long, bumpy trip?
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: ding on November 27, 2013, 10:16:06 AM
Final design! 1.5 inch knobs (pultec/fairchild style), chicken head or stockli on switch, vintage 1ma circular meters from evelBay. I got rid of the time constant mod because I had to make room for those knobs :) . No biggie. I am trying to source some cool SPDT and DPDT switches with the black plastic on them like electric guitar switches. Anyone have a good source? Also go with anodized natural aluminum with black letters or black anodized aluminum with white letters? Any suggestions?

Thanks all.  ;D
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: ding on November 27, 2013, 04:12:08 PM
Ok black anodized with white looks bad ass. I am still searching for those switches.  ::)
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: baadc0de on November 28, 2013, 04:26:40 AM
Hello all!

Quote
I took PCC189 tubes

Are PCC189 compatible with this compressor?

It's a real pain to have matched pair of 6BC8.
I've bought 10 pairs and still have from 1 to 5db difference of level compression.

My comp is a stereo with just one set of knobs for both channels, no link and outboard threshold pot. All built with Vishay/dale precision resistors.

Best regards.

Yeah, they work really well re: compressor action. I have a bunch of 6bc8 (from quirky channel master japanese ones, to some RCA, WE..) and these sound just as good if not better. I really like my PRR176 on acoustic guitars, bass and vocals. Can be very nice and gentle GR or quite aggressive.
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: Spencerleehorton on November 29, 2013, 02:10:38 AM
HI Guys,

i have been reliable informed that ECC180, 6BZ7, 6BZ8 are all equivalents for the 6BC8.
Can anyone verify that they will be ok?

regards

Spence.
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: berkleystudios on December 01, 2013, 04:04:06 PM
IM still waiting on the rev 4 pcbs to get in but can anyone tell me.......

1)what the compression ratio is on this guy and where in the schematic can I change it? I want to have a compress (1:5) and limit mode (1:15) if possible

2) would also like to know what tubes work the best and are easiest to find match pairs of, I have 4 6bc8s I bought in preparation of this but they are un-matched and I doubt they are very close...

3) has anyone not had and issue with Edcor Transformers and noise? I want this to be a really awesome build but the price just seems to keep climbing haha

4) I cant seem to find a lot of info on calibration. And I definitely cant find any procedure steps
never mind found them
5) Abe can the IC's (ne5524, TL072, INA134) you have on the rev 2( assuming they are still in the  rev4) can they be replaced with your discrete dip 8 kits? I think it would be awesome to make mine all discrete.
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: ding on December 04, 2013, 03:15:13 PM
Got my panel finished. In case anyone wants to in on it and get one also I started a black market thread.
http://groupdiy.com/index.php?topic=54476.0 (http://groupdiy.com/index.php?topic=54476.0)
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: JeromeMason on August 25, 2015, 03:38:09 AM
Hey guys, I know this is an older thread, but I've just built a Rev 2 and I'm getting a major ground buzz. I'm using all Edcor for input/interstage/output but the entire board is populated in case I want to switch at some point. I saw in the Rev 4 that there was some jumpers that had to be made to the board regardless of what types of transformers, just wanted to see if anyone might have a build doc describing any details on this or can help me out with tracking this down.

I have the wiring diagram, I have to admit I'm a little confused on the orientation of the pots, meaning which legs in the diagram are 1,2,3 so I can make sure I've got that right on my end. I want to believe this is something very simple. You can tap on the tubes and hear it over the hum plain as day. I'd love to get this up and running, so, if anyone has any documentation, or can point me to where it could be hiding in this thread I would be insanely appreciative.
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: JeromeMason on August 28, 2015, 03:39:51 PM
I know it's old... but.... anyone? :)
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: SIXTYNINER on May 28, 2018, 02:28:22 PM
Just for ask if this project thread is still open or closed (links at first page do not work)
thanks
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: scott2000 on May 28, 2018, 03:00:29 PM
The version 4???  has a recently finished project and some recent pdfs for that build if it helps....
https://groupdiy.com/index.php?topic=54563.msg871586#msg871586

Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: SIXTYNINER on May 29, 2018, 09:20:32 AM
The version 4???  has a recently finished project and some recent pdfs for that build if it helps....
https://groupdiy.com/index.php?topic=54563.msg871586#msg871586

Thanks for post !
started from the rev1 , then found the rev2 (docs - broken links) , now thanks to scott2000 the rev4 ,
after checked found  also there broken links ….. hmmm….little odyssey….
please any chance for the rev4 docs ?
thanks
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: scott2000 on May 29, 2018, 09:29:06 AM
Thanks for post !
started from the rev1 , then found the rev2 (docs - broken links) , now thanks to scott2000 the rev4 ,
after checked found  also there broken links ….. hmmm….little odyssey….
please any chance for the rev4 docs ?
thanks

Just click the link and scroll up ...All of the pdf files are there.....ilfungo posted them
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: jordan s on February 23, 2019, 02:13:27 AM
Does anyone have the docs from this project? I was able to find the schematics from the REV 4 thread but nothing from REV 2 and especially not a wiring guide.
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: shot on February 23, 2019, 04:06:05 AM
Here's what I have on Rev2
Just rename .txt to .zip and unpack the archive
There's a wiring diagram, schematic and BOM inside

cheers!

:)

Luka
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: jordan s on February 23, 2019, 04:30:21 AM
Thank you shot! You're a life saver.
Title: Re: PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*
Post by: jordan s on March 12, 2019, 04:06:06 PM
Does anyone have the details on the PSU board and transformer wiring? Everyone says to use a dual 18v transformer but the board has only 3 inputs for the 18v side which would make me thing they’re wired in series. I found a wiring diagram for the rev4 boards which have 4 18v inputs, 2 per each 18v secondary which makes sense to me. How does it work with the rev2 boards?