All things G1176 - the new "repost" thread.

[ChrioN]

I have 2 problems with my 1176, the first is, the waveform is not centered around "0" when the input pot is used to gain up the signal. Its no biggie, but still a bit annoying.

Here is a screendump of the waveform, you can see that it's clearly "unbalanced":

The second problem is a bigger one, the unit lacks bass!
I've checked the in and output wiring, everything is good.
I'm using a LL1521 input and a JLM111DC wired as 1:2 on the output.
I don't know where to look :sad:

Here is an audiosample, the first part is the source and the second is the source through a bypassed 1176.

http://hem.bredband.net/b237697/1176.mp3

 

[khstudio]

That doesn't sound right :?
I don't have any answers though, sorry.

 

[Arrigotti]

I hate to start another troubleshooting thread in the middle of an already existing one, but here it goes.

I am building a Dual Channel G1176. Both channels pass audio just fine. One works perfectly. The other one does not compress, nor does the meter show anything at all. It will swing all the way right if I turn it to GR mode, and all the way left if it is in Bypass or +4 mode, but the zero adjust does nothing.

I am using the cheap Modutec/Jewell meters from Mouser with the mod than one of the Lab Members described.

I think the problem may be the little goo-covered bridge rectifier that comes with the meter. In the mod described somewhere in this thread, you have to run the rectifier from the X and Y points on the main board to the X and Y on the meter.

So my question is, if the X and Y weren't hooked up correctly, would you see the symptoms I am having (i.e. no compression, and meter not working)?

Thanks,

Arrigotti

 

[ChrioN]

Here is how the low end rolls off. (check my previous post)

I deleted the somewhat nada saying picture and replaced it with a proper frequency respose diagram, some posts down in this page.

 

[gyraf]

.."roll of point" is somewhat undefined. Comparable figures should rely on -3dB or -6dB points..

 

[ChrioN]

this was a ******** post

 

[Arrigotti]

I hate to start another troubleshooting thread in the middle of an already existing one, but here it goes.

I am building a Dual Channel G1176. Both channels pass audio just fine. One works perfectly. The other one does not compress, nor does the meter show anything at all. It will swing all the way right if I turn it to GR mode, and all the way left if it is in Bypass or +4 mode, but the zero adjust does nothing.

I am using the cheap Modutec/Jewell meters from Mouser with the mod than one of the Lab Members described.

I think the problem may be the little goo-covered bridge rectifier that comes with the meter. In the mod described somewhere in this thread, you have to run the rectifier from the X and Y points on the main board to the X and Y on the meter.

So my question is, if the X and Y weren't hooked up correctly, would you see the symptoms I am having (i.e. no compression, and meter not working)?

Thanks,

Arrigotti

Well, I guess I'll answer my own question, which I am actually glad that I can do.

......No silly, look at the schematic! The X and Y are taken of the main output just to give you signal for the +4 reading. When the meter is in GR mode, the X&Y are not connected.

(So I say to myself, "Hmnnn, what could be the problem then?"

After probing through volatges, I was able to trace a voltage problem back to the -10V section. I actually started with the meter selection switch, and worked my way back from the 28 pad, which had a different voltage than my other 1176.

There ended up being a pad that pulled up right after the rectifier section connected to the -10V. I fixed the disconnect and all is well.

So I guess the moral of the story is, check all your solder joints, and build up the circuit is sections.

Hope this little issue might help someone else.

 

[khstudio]

:thumb:

 

[muz]

Most of the circuit is working correctly - only you have a problem with the FET at the audio attenuator, or the components just around it.

Jakob E.

Thanks for this...

So I replaced Q1 and Q10...it seems that I am now getting compression of audio...but only at maximum compression ratios (all buttons in) and input on full and using my neve pre to hit it with a hot signal...

It seems to me that I need more from the input..?

Ive tested the voltages from scematic...and they seem good...
replaced some resistors...

Im obviously missing somthing...what exactly do you mean by audio attenuator? is this the Q bias trim pot?

Im learning at 100mph...but dont quite know enough to isolate the problem furter...

 

[muz]

OK...Ive hooked up a wire so I can touch on points on the board and listen to audio being passed into the input of my 1176...
Should the audio at 1* be about half the volume than before LL1540?

Is the input transformer bung?

anyone?

 

[ChrioN]

I've switched the JLM111DC output transformer for an OEP, and now the bass is back. Problem found. This clearly shows that there are components that needs to be changed in order for the JLM111DC transformer to work correctly.
The question is just which component or components. Could this be a load related issue? Maybe change the zobel network resistor?

 

[ChrioN]

Note: +2.5dB at 5000hz, and -5.5dB at 100hz. Thats almost 9dB.

Note: I've found the sourse of this wierd frequency response. It is my input transformer, LL1521. I've used the same load resistors as with a LL1540 (12k ohms)

 

[living sounds]

Hi everyone,

I was just starting to hook up the controls for the 1176 and wondered if there is any need to use shielded cable. I couldn't find anything in search or Meta and I'm not a good enough reader of schematics (yet), so: Is there passing audio through those wires or is it only "control data" (like in the GSSL)?

Thanks alot!

Gregor

 

[astrovic]

There is audio passing through at some points - have a look at mnats' wiring guide, http://www.geocities.com/m_natsume/1176-wiring.html where he talks about where shielded cable should be used.

FWIW, I used shileded cable on my first build, and didn't on my second, and I have not noticed any appreciable difference.

 

[living sounds]

Astrovic,

wow, that was quick! Thank you very much!

 

[syn]

Could this VU be used with germanium diode bridge+resistor for the 1176
project?

Sensitivity (±20%)- 0-500uA
Resistance (±15%)- 600Ω
0VU- 270microA

http://www.anders.co.uk/meters_products.asp?prodFamID=2042

thanks

 

[gyraf]

..probably, yes..

 

[syn]

thank you

 

[ChrioN]

This might be a pretty obvious question, but should I calibrate the unit before or after this "mod"?

[quote author="gyraf"]
Look at the schematic - find the place where signal is tapped off for use in the sidechain (around the top of the output level pot). At that spot, simply install the 100K trimmer as a voltage divider to ground, taking sidechain signal off the trimmer's wiper.

Jakob E.[/quote]

 

[gyraf]

..it shouldn't matter at all..

Jakob E.