All things G1176 - the new "repost" thread.

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orson whitfield

Well-known member
Jun 3, 2004
South Florida
Tadgos, are you here? Well, if you are, please excuse me. It's time for a new "1176 Repost" thread and I'm taking the honor of being the one to start it. (All complaints to Gyraf - he inspired me) :green: .

I used a color code chart to check the values of all resistors on the Printed Circuit Board of my G1176. I found one incorrect resistor - the 82R, right below Q3; it was a 1.8K :? As I have stated elsewhere, I had high voltage at the collector of Q2 ( 2.83 instead of something close to the posted 1.76 on Jakob's schematic). Well, apparently, this 82R made a difference. The Voltage is now right on the money. Now I'm gonna check the rest of the voltages Jakob posted.
Are these tolerable?
Q2 ---1.76V --.501V -- .997V
Q3 ---11.70V - 1.76V -- 1.16V
Q4 ---29.9V ---11.7V---11.11V
Q5 ---28.19V --4.82V---4.38V


Q13--- ----14.71----14.13
Q14--- ----2.85------3.39
Q15--- ----16.66----16.12

According to notes I took from the old "FEEDBACK FOR GYRAF 1176LN (repost)" thread , "a rule-of-thumb is around 0.6V less on the emitters than on the bases." I think I might have written down some numbers in the wrong column but my ratios appear on track with this statement.

Also, here is a list of DC voltages that some one who had a working unit posted in the "FEEDBACK FOR GYRAF 1176LN (repost)" thread ,

Q2 0.54 1.05 1.77
Q3 1.16 1.77 12.4
Q4 11.83 12.42 30.3
Q5 4.54 4.96 28.59
Q6 29.12 28.56 14.63
Q7 29.75 29.12 14.62
Q8 14.01 14.61 30.29
Q9 13.94 13.33 0.002
Q12 4.03 4.59 15.12
Q13 14.5 15.12 30.28
Q14 2.9 3.508 17.28
Q15 16.7 17.28 30.3

Here I noticed my voltages are all a little lower than his. Is this O.K.? The voltages I get at Q2 are very close to Jakob's so i think Q3 might need replacing.
Hi Orson,

If the unit is working and sounding kinda okay, you shouldn't worry about how the transistors are doing. If one messes up, you will surely find out very soon.

Is the unit working as it should?

Jakob E.
Well, I haven't listened to it yet because I know I have to still calibrate it. From what I have read around here, you need to calibrate it to be able to tell it's working correctly. Where can I find the instructions for calibrating. Deanp920, are you here? You were helping me out b4 the switch.
(..) (from old RO answer)
.. first you should check id you have the FET "bias" pot set roughly correct:

This is the 2K2 trimmer pot, marked "Q BIAS", located in the "GR Control amp" section. Try turning this with signal through, and see if something happens.

The proper adjustment of this trimmer is made like this:

Input a weak signal, around -10dB or something, and measure the AC output level without gain reduction:

Set the attack and release controls fully clockwise, the ratio to 1:4, and the output level to max. Turn the input level so you get something readable, like 100mV on your voltmeter on the output.

Now adjust the "Q Bias" trimmer untill you have a 1dB drop in output level. That's it. This control makes sure that the FET is set just in the beginning of it's cut-off range prior to actually beginning gain reduction.

The low input voltage is to make sure that no gainreduction should occur when you're doing this adjustment.

If its initial position is set to a larger drop, you have to readjust the input level control.
Hope this helps...

Jakob Erland
Gyraf Audio
Ok good news. The unit is working and sounds perfect. :shock: :razz:
THe problem was A) one wrong resistor(1.8k Ohm instead of an 82 Ohm), B) two burned out resistors (the two right before or after the BD517 and BD 518), C) needed to replace the BD517 and 518 and C) needed to replace the voltage regulator (7824). The unit sounds dramatically better than it did before i droped the pcb one inch inside the chasis while testing voltages two months back. So even though droping it broke a few parts and caused me a detour, the end result is better.

Calibration time. Some one gave me an old Leader LAG-125 Low Distorion Audio Generator for free. I guess this is useful for calibrating? It's cool because on it's meter it shows R.M.S. Volts and dB with "0db=0.775V" written on the left side. I guess when you say to back off the signal till you get a 1 dB drop, I could do the formula or just look at the meter. THanks to Deanp920 big time for getting me through this. Ofcourse, I thanked everyone who ever helped me at anystage of this project over the last 15 months at the old location (Tech Talk ) I wish I had a record of that post but there were about 12 of you who helped (Jakob, SSltech, Mark Burnley, Frank Rollen, Kev, Deanp920, Chris V, and others) I can't remember at the moment. THanks again guys. No cracking open the bottle till i get it calibrated, though. THen I'll get plastered. :wink: :sam: :thumb: :grin:
Alright I think I figured it out BUT ...

"4: "GR meter Trck" (tracking). Set ratio to 1:20, set Meter to bypass. Input a 1kHz, 50mV signal. Set input level to ~12'oclock. Set output level so you get 50mV at the output also (now you have unity gain)."

I can't get anything higher than 20.9 mV at my output. Whats wrong? Also, I amchecking voltages using AC setting on my multimeter. thats ok?
Ok there are some weird things happening here. First off the unit is not working as it should, I spoke too soon. :cry: The release knob does nothing and the Attack knob is controlling the release. hmm.. maybe I just mislabled? Nah just checked the Gyraf site attack is on top as I have it. So I guess I wired it incorrectly. The never ending project continues.
Okay, I have a question that I know has been addressed on the old forum.

I have two 1176 PCB sets courtesy of Gustav. I would like to build both of them into a single 2U chassis. Now, although it would still be spiffy to have two units in one box, it would be even spiffier to have them linkable to work in stereo. I remember reading on the old board that this is possible, but I can't remember how or what the link was. Can anyone point me in the right direction? I do know I'll need to hand-match four FETs, which will be tedious but not really impossible.

Thank you all for the help!
I have 4pdf schematics about a stereo compressor based on urei 1176. I download them some months ago, but i dont remember where i found it. I can send to you by mail if you want... The title in schems is "JH .FC2 Stereo Compressor based on Urei 1176 J.Haible 2001"

Ok I simply had the switches in the wrong holes. And I think the attack is working but I really can't tell much. How do you know if the attack is working? Is it a dramatic thing? Also, after a while of being on I get intermitent noise and low frequency pops;/crackling, kinda sounds like a dirty pot turning. If I move the unit it seems to go away a bit but not consistantly. I checked the voltage regulator heatsink and, man, it was hot! I know this is not good. It supposed to be hot but not to a temperature where you can't keep you finger on it, right? I am thinking there is a connection between the voltage regulator getting hot after time and this noise. I am testing out to see.
I'm sure there would be plenty of people interested in seeing that.

Go ahead and shoot them to me! consul [at] studioconsul [dot] net (just replace the bracketed words with the usual symbols.) :wink:

I can post them to my web space if anyone else is interested. Thank you very much, Apache5!
I received them just fine, Apache5.

For the rest, I have uploaded these to my webspace, but I want to make sure it is okay to post links to these. Any issues with that, Apache5?

Thank you again!
There is no problem for me, but i dont know very much about copyright laws in these situations, and the schems are not mines. If its for my wishes id like that you will post links to them ofcourse and these links are only to informative purposes, not to lucrate with them, i think that its ok, isnt it?