PRR-176 REV 4 Build Thread ***Manual up!***1/16/14 - (chk 1st post)

[berkleystudios]

Hi guys,

I was just about do doing some finishing touches on my cheaper build and I decided I would change and try and go all out.

I have been doing a lot of research and it looks as though is is more of a 175 than a 176. because of not being able to change ratios, which if following the original 175 would be a 12:1 compression ratio. the 176 used a multi tap output transformer to achieve other ratios.

I am doing more research to see if I can implement a ratio change in my build with a multi tap transformer. I am going to be looking more into this as I would really like to have something like a 4:1 and 12:1 or 20:1 compressor/limiter modes

I will also be trying out other tubes if my new matched 6bc8's dont work out, looking at also 6BQ7A's as a possible alternative.


swapping out my current edcors for possibly cinemags ( anybody have a price on those?)  I know I want it on the interstage, still debating what I want on the input,  The output will be decided when I figure out If i can really implement the compression ratios into this design.

I think I will put in a GAR1731 on the inputs and move 2 of Abes dip8 2520s to the sidechains.  I would really like to get rid of the TLO74, or at least upgrade it to something better.  possibly even discrete.

thinking about a variable high pass filter as well.... but IDK if I will have room on the front panel because Im adding big simpson meters, 4 large dakaware style knobs on a 3U case... might be kinda tight, knew I should have gotten the 4U....


so quick list run down of the new plan/ hopes and dreams/already done
- All discrete (if possible) (6) 2520,(2) Gar1731, (2) unknown dual discrete opamp
- cinemag inputs and interstage, unknown multi-tap output for different compression ratios
-  add ratio switch on front panel
- 5M release pot for longer release times
- Orange drop in C5/C52 (done)
- Add VU meter drivers and front panel switches for input-GR-output
- remove threshold trimmer/ jumper OR add threshold pot on Front (depends on room up front and calibration difficulties
-  remove desser
- add variable HPF, (possibly), play with new cap values for best filter slope
- add high quality Input and output pots. not sure of what values I will go with...
- tube swap till best option is found





kinda bummed about the reports that the rest of yall have... hopefully this thing sounds pretty cool by the time im done.

Adam

 

[ilfungo]

Hi  MichaelD
"  I’ve changed the values of some of the resistors and have gained a wider area of compression and the attack and release work better"
What have you changed?
I've tried to change R39 and R86  from 10k to 5k and for me the output range is more correct ( I don't know if this can be a problem)...
Thanks

 

[gato]

The build butler is the best!

 

[anvl]

Hello everybody.  No news about this project builders?

I've built two units rev4 with RCA NOS tubes, Lundahls transformers, two op amps 2520 per channel and some modifications.  I`m really pleased with this compressor, nice sounding specially on drums busses, stereo mixes or voice channels.  Beautiful and sweet.  Middle adjustment for threshold.  No hums.

Any one knows about buying more PCB kits?  Any news from Abe?

Regards.

 

[ilfungo]

Hi anvl
what mod have you done?
I've a strange problem only with rev4 ( I've also one rev 2)...

 

[berkleystudios]

Hello everybody.  No news about this project builders?

I've built two units rev4 with RCA NOS tubes, Lundahls transformers, two op amps 2520 per channel and some modifications.  I`m really pleased with this compressor, nice sounding specially on drums busses, stereo mixes or voice channels.  Beautiful and sweet.  Middle adjustment for threshold.  No hums.

Any one knows about buying more PCB kits?  Any news from Abe?

Regards.

Good to hear! Glad to have a success story on here. A list of mods would be nice too

Adam

 

[ilfungo]

My unit sounds very good in bypass, but, when I insert compression, everything becomes smaller and edgier ...
The thing I notice is the inability to control some  frequencies
Sorry I am not a technician but when I try to compress some loops drum machine (also happens with real drummes) some high sounds are not compressed, regardless of the time of the attack and release (slow or fast is the same).
The result is that some frequencies or elements with certain frequencies come out...
The impression is that the unit tend to compress more the low frequencies...
I've checked all the componets ,and all is ok!!!
Help!!! There is something that  don't understand.
There is for my likes too much hiss...
Sorry and thanks!!!

 

[anvl]

A couple of examples

Kick L & Snare R - No comp
https://dl.dropboxusercontent.com/u/58834579/Kick%20%26%20Snare%20no%20comp.wav

Kick L & Snare R - Comp PRR176
https://dl.dropboxusercontent.com/u/58834579/Kick%20%26%20Snare%20comp%20176.wav

Drums stereo - No comp
https://dl.dropboxusercontent.com/u/58834579/Bus%20Drums%20no%20comp.wav

Drums stereo - Comp PRR176
https://dl.dropboxusercontent.com/u/58834579/Bus%20Drums%20comp%20176.wav

 

[anvl]

Hi ilfungo, do you have the same problem in both channels?  It's very strange, listen to my upladed samples.  Have you tried different 6BC8 valves?

 

[anvl]

My PRR176 Rev4:

· DonAudio PWR transformer
· 2 Lundahl transformer per channel
· Balanced output (no transformer option)
· 2 gar2520 op amp per channel (U5, U12, U22, U30) mounted at the bottom, using 150pF caps (not 22pF)
· PAD resistors used
· Second option for stereo linking wiring (RMS Summing)

Important points already suggested by Abe

· Ensure 100V rail as exact as possible (I'd say between 95V and 105V is good)
· Use PAD resistors
· Ensure to add Jumpers following Abe drawing
· Ensure to use star ground connections following Abe schem
· Ensure to use stereo linking connection (at least use the second option).  If not, right channel doesn't work properly.
· Use IC op amps first until the unit is working perfectly.  Then go ahead with discrete op amps.
· Ensure tube connections, they are inversed and can't be mounted on board (look at the pin 1 and pin 9 marks)
· Start with middle threshold adjustment.  Ensure to adjust thump also.

My mods

·  On PSU I changed to    R111 3K 5W,    R110 1K5 2W,  R112 2K2 2W  to reach 100V
·  Heaters connected in parallel (not in series).  12,6V rail changed to 6,3V and wiring changed.  It works much better matching both channels.
·  Linear pots on Gain In and Gain Out (much better than Log pots)
·  Lundahl transformer pin E (ground/shield) connected to star ground
·  Lundahl transformer jumpers needed on primary (pins 2 and 4 need to be jumpered)
·  470R PADs resistors changed to 700R (better signal level inside the unit)

I hope this will be useful.  Regards.

 

[ilfungo]

Thanks anvl
i will try different tubes...
Thanks!

 

[berkleystudios]

nice anvl!

will look into some of these mods for my own unit

adam

 

[prh]

My PRR176 Rev4:

I hope this will be useful.  Regards.

Anvl, this is highly useful!  Thanks for taking time to summarize your build so carefully.

Cheers, Paul

 

[manulaf]

Hi everybody

My unit sound good too. No hiss, no hum. I have built it with cinemag interstage trafo, carnhill output trafo and Abe's op amp. But it was very difficult to me to find good matched tube (RCA nos) And I think it's one of the most important thing.

My mods:
I add a plate balance trimpot.
I also used the T-pad option because I had a self-oscillation issue with input opamp !
With Middle adjustment treshold like anvl.

I will post some sample soon.
Regards
Manu

 

[anvl]

Good news !!!  It looked like this thread was dead.

Any one of you knows something about Abe?  I'd like to buy another PCB kit.    I've written him several times but no answer.  Maybe on black market?

Salud !

 

[geotone]

Hi All,

I very much hope this thread isn't dead, as I'm about to start my build and might need some advice! I went through the whole thread and picked up ideas and hints, let's hope it works out.

Abe's site seems to have been offline for a few days at least now. Hope all is fine over in Utah...


Merry Christmas to you all and thanks for sharing all the expreience,


G

 

[mitsos]

Hi all,
The links in the first post aren't working for me.  Can't download the latest BOM. 

I've searched through the threads for the different versions but I can't find which Cinemags people are referring to for the interstage.  I've seen both posts about both 4:1 and 1:1 ratios, has there been a consensus on which works best?

thanks in advance!

 

[berkleystudios]

Hi All,

I very much hope this thread isn't dead, as I'm about to start my build and might need some advice! I went through the whole thread and picked up ideas and hints, let's hope it works out.

Abe's site seems to have been offline for a few days at least now. Hope all is fine over in Utah...


Merry Christmas to you all and thanks for sharing all the expreience,


G

this thread is not dead as long as I'm still building haha!

 

[berkleystudios]

Hi all,
The links in the first post aren't working for me.  Can't download the latest BOM. 

I've searched through the threads for the different versions but I can't find which Cinemags people are referring to for the interstage.  I've seen both posts about both 4:1 and 1:1 ratios, has there been a consensus on which works best?

thanks in advance!

Yes the links were not workin for me as well  but the cinemag transformers should be the 15/15 line input versions

 

[anvl]

Adam, in which conditions is your build? Is it working?  Which problems?

Mitsos, which links do you need?  I could upload again.