mus1k_freak

Re: PRR 176 vari-mu (check first post for docs)
« Reply #800 on: January 28, 2014, 08:35:38 PM »
Is anyone making a case for this project? I'm gonna have to build one now!   ;D


ding

Re: PRR 176 vari-mu (check first post for docs)
« Reply #801 on: January 28, 2014, 09:40:48 PM »
I know plenty of people have been posting in this thread for the Rev4 boards it has it's own thread. You might get better responds there in the future. Dan is still making a case for this project AFAIK.
http://collectivecases.com/prr176.html

Spencerleehorton

Re: PRR 176 vari-mu (check first post for docs)
« Reply #802 on: February 11, 2014, 12:16:43 PM »
Hi all,

just got my boards, looks great btw, thank you very much.

regards

Spence.
website: www.mohawkstudios.co.uk
email: [email protected]

If it hisses its probably the wrong impedance!!!
Or a snake!!!

coriolis

Re: PRR 176 vari-mu (check first post for docs)
« Reply #803 on: February 19, 2014, 04:37:47 PM »
Ahem...so back to Rev 1 boards  :)
Just finished mine today (only took me like 2 years  ::), but ack, no sound - only hum! Sounds a lot like the problem ilfungo had (his file on soundcloud sounds exactly like what I'm hearing).

My build:
- Offboard rects and filtering (I stuffed all the caps onboard as well.
- Grounded everything as per the instructions in this thread, but currently to the CT input on the main PCB - not the *G point.
- Chip inputs and outputs.
- 5534 for opamps
- Edcor pcb mount iron
- Right now, my I/O wiring is unshielded (just twisted wires) so I was expecting some hum - but NO SOUND?

Observations:
- I adjusted the heaters to around 12.5V on the first tube and the second is half that. Okidoki. But then after about a minute after I switch the comp on, the heater voltage drops to about 3.5V on the first tube (and half that on the second), with most of the hum fizzing out. Still no sound though.
- The tubes seem to be somewhat microphonic. They seem to be picking up the sound if I tap them or their surroundings.
I tried swapping them around to see if that helps with anything, but no. Not the heater prob either. I do have more tubes I can try though.

Why the heck does the heater voltage do that? A bad cap? Rifts in the space-time continuum?

A question:
- The sidechain bias ckt. I stuffed the regulator and all that. Do I leave out all the stuff in the optional box then? No resistor, jumper and LED? Or what? A bit confused about that part.

Hope anyone still reads this thread!

Update: Seems the 350 reg got too hot and shut down after a minute or so. Put a bigger heatsink on, and now the heaters stay on. It still gets rather hot to the touch. Not blistering, but still.

It seems there is a mod I need to do around the INA134, but other than that, I am leaning towards heavy grounding issues causing my problems. Had the grounding set up to Abe's instructions in this thread, but tried this http://groupdiy.com/index.php?topic=14147.0 as well. That is to say, Donnysparks last drawing combined with squibs following comment. No dice.

In this thread http://groupdiy.com/index.php?topic=46776.20 everyone seems to agree that the common regulator 0V node is what should be connected to chassis. Would this be the *G...errr...spot? :D

Thanks...
« Last Edit: February 20, 2014, 04:34:01 AM by coriolis »
- more projects than sense...or money...or time...
http://www.hzandbits.com

G-Sun

Re: PRR 176 vari-mu (check first post for docs)
« Reply #804 on: March 12, 2014, 04:08:04 AM »
What do you use the PRR 176 on?
Is it an affordable and easy build?
HJFP2, ssl9k, Harrison Ford Filters
My music

Re: PRR 176 vari-mu (check first post for docs)
« Reply #805 on: March 17, 2014, 07:19:51 PM »
Hi,

looking forward to build this one. I just tested friend's version and I like it ;)

I have one question (for now) exactly what power transformer do I need?

weiss

Re: PRR 176 vari-mu (check first post for docs)
« Reply #806 on: September 13, 2014, 10:29:08 AM »
I have one question (for now) exactly what power transformer do I need?
Just read the manual..

Quote
The power supply for the PRR-176 has 5 power supply rails. A
bipolar +/-16V power supply drawn from one 18VAC tap. A 1.5V biasing
voltage taken from the +16V rail. A 12.6V rail for the tube heaters
taken from one 18VAC tap via a voltage dropping 10R resistor. And
finally a 100V rail for the tube plate voltage

btw this seems like a nice project, i think i am going to build this in the near future :)
how much did you guys totally spend on tubes, tx's etc?

Re: PRR 176 vari-mu (check first post for docs)
« Reply #807 on: January 03, 2015, 11:14:52 PM »
I have one question (for now) exactly what power transformer do I need?
Just read the manual..

Quote
The power supply for the PRR-176 has 5 power supply rails. A
bipolar +/-16V power supply drawn from one 18VAC tap. A 1.5V biasing
voltage taken from the +16V rail. A 12.6V rail for the tube heaters
taken from one 18VAC tap via a voltage dropping 10R resistor. And
finally a 100V rail for the tube plate voltage

btw this seems like a nice project, i think i am going to build this in the near future :)
how much did you guys totally spend on tubes, tx's etc?

I cant find a power transformer with those in and outs, at least for 240v australian power.

Re: PRR 176 vari-mu (check first post for docs)
« Reply #808 on: January 04, 2015, 02:32:34 PM »
Now i'm building V1.Can i use this version's transformer for V1?

Input 10K:10K
Interstage 10K:600
Output 600:600
Age Of Leviathans

Re: PRR 176 vari-mu (check first post for docs)
« Reply #809 on: January 09, 2015, 06:46:37 PM »
 :o
Age Of Leviathans


bluesbaz

Re: PRR 176 vari-mu (check first post for docs)
« Reply #810 on: March 10, 2015, 05:28:40 AM »
Its late and I could use some help and encouragement. Signal flows on both sides but I can only get one side to compress.
I realize my main problem is I have no idea how this thing works and that would be the first place to start really. I have swapped the tubes for no difference. I have a rev 2 board and I can get compression which does not show up on the meter when jumping   r58/56 I am at a loss here and really just need to understand the circuit to know what I am missing here.  Thanks again!

Baltimore

Re: PRR 176 vari-mu (check first post for docs)
« Reply #811 on: June 19, 2017, 09:10:55 PM »
Does anyone have the original documents for this? i have a PCB i'd like to finally build.

vitopower

Re: PRR 176 vari-mu (check first post for docs)
« Reply #812 on: June 22, 2017, 12:34:21 AM »
Just emailed rev 4 manual & BOM with docs (wiring guide, schematics, jumper info, layout) to admin, should be available soon.   8)

saint gillis

Re: PRR 176 vari-mu (check first post for docs)
« Reply #813 on: December 20, 2017, 10:12:20 AM »
Is the triodes' matching as critical as in the UA 175/176 ?
Or as another way of asking the question, how much does the 1k vr3 plate current trimmer help for the triodes' matching?
Did you guys had to buy a full truck of tubes to get a suitable one or was it quite easy?

saint gillis

Re: PRR 176 vari-mu (check first post for docs)
« Reply #814 on: April 25, 2018, 03:12:13 PM »
  Hello dear friends, here's my PRR 176, it has 2 ratio modes, "compress" and "limit" :

http://sub-continental.com/partage/d%26d%20schematic.jpg

  We could use a that1246 instead of the 2:1 transformer, if you use a 1:1 transformer just change the gain of IC1 but use the unity gain compensation capacitor.
  I used a 600:600Ohm transformer before the grids, because it is driven by a low impedance source and the grids have a high impedance so a lot of transformers would work here.
  The anodes drive a LL1521, because they have a high impedance we need a good input transformer like LL1540 or any good quality line input transformer.
  If you use other transformers' ratios just change the gain of the according stages (IC1 IC2 IC3).

  The trimmer before IC2 is to ajust tube gain differences between left and right channel, you can trim to 1dB, if you need more just use a 20K trimmer with a  68K for instance.

  The deeser is not very usefull (to me), so I will modify it to get a 2nd HPF mode like 100Hz or I don't know yet..

  Well, it's an awesome compressor and thank you PRR and Abechap and everybody who provided great brain juice on the forum!

  Here are some pics of the finished unit :








« Last Edit: April 25, 2018, 03:17:19 PM by saint gillis »

scott2000

Re: PRR 176 vari-mu (check first post for docs)
« Reply #815 on: April 25, 2018, 04:20:17 PM »
Marvelous! Thanks for sharing!!!

saint gillis

Re: PRR 176 vari-mu (check first post for docs)
« Reply #816 on: May 03, 2018, 05:37:52 AM »
Also the cathode balance trimmer may not necessarily be a multiturn, maybe because I used well balanced tubes but I found difficult to really adjust the low-frequency distortion.

saint gillis

Re: PRR 176 vari-mu (check first post for docs)
« Reply #817 on: July 15, 2018, 08:08:13 PM »
Also the cathode balance trimmer may not necessarily be a multiturn, maybe because I used well balanced tubes but I found difficult to really adjust the low-frequency distortion.

Yes you are right, I didn't get any significant difference in low frequency distortion moving the trimmer...
I ordered a transformer from Audiophonics 6,3VAC  14VA - 130VAC  14VA - 34VAC-CT  35VA, the heaters are AC

saint gillis

Re: PRR 176 vari-mu (check first post for docs)
« Reply #818 on: July 16, 2018, 05:52:39 AM »
Yes, it's slightly oversised but the price was for a 63VA transformer. For the low voltage it depends which op amps you use, see the datasheets make the math and use the double power..

saint gillis

Re: PRR 176 vari-mu (check first post for docs)
« Reply #819 on: July 16, 2018, 05:56:45 AM »
If you use leds etc you need to add their current also


 

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