All things G1176 - the new "repost" thread.

[stitch-o]

and may have errors.

This I know  ;D

Thank you for your input!

 

[trapiche2]

Hi everybody!... this is my first post!...
I would appreciate if you would help me with this problem i have: It is almost imposible that i can get BC 107, does anybody knows if i can use Bc 547 intead? thank you very much...

 

[gswan]

Yes, BC547 is an acceptable substitute, and more readily available than the old BC107.

 

[user 37518]

Ok i just finished my 2nd 1176s, both featuring the well-known Purusha racks, the blue one is the electronically balanced version, while the black one has an OEP in the input, both have Lundhal in the output. Just wanted to show you guys to give me your opinions. (No inside pics sorry...) BTW doing these things is a real pain in the ass!!!! Anyway, both sound great, and they both took a little piece of me...

 

[rooster21]

You'd better check orientation and health of Q7 and Q8 (and maybe Q9).
Do they get hot?
Check soldering and components around here as well.

Orientation is fine, Q8 gets the warmest, but I wouldn't really say hot. I had a chance to do the gain stage test and here are my results

Input Signal 0.125 Vrms
Signal at (2) 0.25 Vrms
Signal at (15) 0.131 Vrms Gain stage 1 -5.61337426 dB FAIL
Signal at (17) 0.132 Vrms
Signal at C15+ 0.489 Vrms Gain stage 2 11.37469856 dB PASS

this is with input and output at max!

I did find 2 resistors so far that are the wrong values, I'll get them replaced asap they are R60 R61.

 

[Dr-Mbogo]

Hi there!

I finished my dreamteam using mnats boards (thank you mnats!) Panel work still has to be done... Both of the 1176´s are working exacly the same. The problem is the length of the release time. After calibration I made the following experience with the units:

Using the longest release time the VU Meter needs more than 10 seconds to get back from -20 to 0 on the VU meter. Using the shortest release time it takes about 1 second. I even tried to lower the value of c22 with almost no success. Another thing is - the longer the release time - the more gain reduction occurs on the VU meter. Does anyone know how to face this problem?

Please help!

 

[Biasrocks]

Another thing is - the longer the release time - the more gain reduction occurs on the VU meter. Does anyone know how to face this problem?

VU Meter's are slow on purpose, how does it sound?

An 1176 is a speed demon if you want it to be, mine generally stay near the fastest release setting.

Mark

 

[Dr-Mbogo]

Mark - thanks for your quick reply.

VU Meter's are slow on purpose,

Yes - its due to the inertia. The devices sound good. But in this case I think something must be wrong - but I am not sure. Unfortunately I never had the chance to experiment with the original or even to compare to mine. Is there a way to measure the release time?

Maybe the meter does not correspont correctly to the gain reduction itself?  :-\

 

[Biasrocks]

Is there a way to measure the release time?

Maybe the meter does not correspont correctly to the gain reduction itself?  :-\

You could put a tone through it and record the output in your DAW and then look at the timing info or you could use a ac meter on the output to view the voltages.

Have you done the meter calibration properly?

Mark

 

[Dr-Mbogo]

I re-checked the calibration of the units. Everything is fine.

I have lent a storage oscilloscope and did some tests using a looped kick drum sound and a 1kHz sine signal with -10dB. I played those sounds with the fastest release time with -6dB gain reduction and the meter shows -6dB. I discovered there is aprox. half of the input signal at the output. The world is ok! As soon as I increase the release time from 5o´ clock to 3o´clock and more, the VU Meter reads more than -20dB and does not "want to come back to 0 dB" even when the kick drum signals occur all 3 seconds. When the signal is switched off, it takes about 10 seconds to read 0 dB again.

It seems my 1176´s are doing fine except the VU meter.

Does anyone know what the device called "UA4706" exactly does? The schematic says something about "factory set value". Perhaps a "go back to zero in time" trimmer?

Any ideas where to start my "signal-flow investigations?" What about a matched pair of FET´s. Mine have not been matched...

How do the VU meter of your 1176 clones behave?

Thanks in advance.

Chris

 

[Chrome Heart]

I re-checked the calibration of the units. Everything is fine.

I have lent a storage oscilloscope and did some tests using a looped kick drum sound and a 1kHz sine signal with -10dB. I played those sounds with the fastest release time with -6dB gain reduction and the meter shows -6dB. I discovered there is aprox. half of the input signal at the output. The world is ok! As soon as I increase the release time from 5o´ clock to 3o´clock and more, the VU Meter reads more than -20dB and does not "want to come back to 0 dB" even when the kick drum signals occur all 3 seconds. When the signal is switched off, it takes about 10 seconds to read 0 dB again.

It seems my 1176´s are doing fine except the VU meter.

Does anyone know what the device called "UA4706" exactly does? The schematic says something about "factory set value". Perhaps a "go back to zero in time" trimmer?

Any ideas where to start my "signal-flow investigations?" What about a matched pair of FET´s. Mine have not been matched...

How do the VU meter of your 1176 clones behave?

Thanks in advance.

Chris

Hey Chris
The UA4706 is the resistor value that Im trying to figure out in the post above yours. It can control the point at which the compression starts. Im pretty certain it has nothing to do with the meter behavior. And to answer your question about the meter, mine behaves like the original 1176. I do not experience any lag with regard to the meter being able to zero itself. It seems to me your problem is related to something else.
There are users here with way more knowledge than I have who can probably help you find the problem. But I would suggest going through everything and looking for a simple mistake. Thats usually where I find my problems. Something easy getting overlooked.  

 

[Dr-Mbogo]

...for a simple mistake. Thats usually where I find my problems. Something easy getting overlooked. 

Yes! The same experience that I made before, when I built my first pair of green preamps  ;D

Today I will start to check all the resistor values and capacitors. As soon as I know more, I'll let you know.
In the meantime - during my walk through "the lab" is discovered, we shoudn't pay too much attention to the part "UA4706".

Have a look here: http://www.groupdiy.com/index.php?topic=415

 

[Chrome Heart]

With regard to the T&C on the schemo, Ive seen in several posts here that this point on the ratio pcb controls the point at which compression starts. So, does it or doesnt it? Anyone have a definitive answer?

 

[gswan]

It does, and is selected at test/calibration time to an appropriate value that suits the operating characteristics of the manufactured circuit.

 

[Chrome Heart]

It does, and is selected at test/calibration time to an appropriate value that suits the operating characteristics of the manufactured circuit.

Well, alrighty then.

 

[pedroplanet]

It does, and is selected at test/calibration time to an appropriate value that suits the operating characteristics of the manufactured circuit.

does anybody know a close value for this resistor?

 

[gyraf]

Our four Rev#F units has nothing there. I've always considered it smoke-screen.


Jakob E.

 

[Dr-Mbogo]

Ok! I checked all values of the components. C28 and C35 had 10nF instead of 100nF. They have been replaced to the right values. I think in GR-Mode - the needle of the meter goes back to zero a bit quicker now.
Unfortunately the release pot still has a denpedance on the gain reduction which is shown on the meter - not on the circuit itself. It compresses and the unit sounds fine. Switched to +4 the metering acts as it should.

I keep you updated.

 

[gyraf]

Unfortunately the release pot still has a denpedance on the gain reduction which is shown on the meter

Have you been through this thread? I think we've had that before.

Jakob E.

 

[Chrome Heart]

Our four Rev#F units has nothing there. I've always considered it smoke-screen.


Jakob E.

OK. So we have a disagreement about the actual purpose/function of this schematic point. If someone can give me a ballpark value for this componant, Ill put it in and post the result.