Hairball 1176 rev D - input is very loud

[focusonsound]

Hello everyone,

the last days, I've builded my first Hairball 1176 rev D and now I have a little problem.
The input XLR is fed with a 1kHz Sinus tone from the daw with 0,775VAC (meassured), but trimming the Input pot on the front up from lowest to 40 lets the VU Meter (+4 mode) goes to Maximum and the Output transformer buzzes extremly. It doesn't matter where the Output pot stands, the Output XLR has about 26VAC in this case. Also, the Output pot doesn't work correctly because it can only trims 4dB up or down.

I've checked twice everything but can't find any problems :-( Does anyone has an idea?

Greetings from Germany,

Daniel

 

[dmnieto]

oscillation:
http://mnats.net/1176_FAQ.html

Also, please use the thread http://groupdiy.com/index.php?topic=20058.0 for questions about your build.

Check the following too: Put the output pot half way and try again... does the same issue happen? It if does not, you may have wired wrongly the output potentiometer.

 

[SSLtech]

Sounds like your output pot doesn't have a ground connected to the counter-clockwise terminal, as it should.

Fix that, and try again.

 

[focusonsound]

I've checked the ground of the Output pot and put the cables away from the signal preamp section but the Problem still exists.
I will check every voltage next week and hope to find anything, but are there any other ideas?