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I need help trouble shooting

post #1 of 8
12/14/11 at 1:12am
Thread Starter 

Hello all,

I recently built a distribution amp based on bits and pieces of a number of different designs. It has four outputs. Two sound spectacular, and two have a massive difference in volume between the left and right channels. The left channel is substantially quieter than the right. The volume increases on the pot in both channels, but the left is barely audible compared to the right. I have checked every connection on the board, as well as every resistance. They are all the same on all four opamps. I have checked the pots, replaced on pot, checked the connections at the pots, checked the connections at the output jacks. I am at a complete loss. Some suggestions on what might cause the level imbalance? There has to be something I missed!

 

Thanks a ton!

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post #2 of 8
12/14/11 at 1:40am

Someone much more wise than me in the ways of electronics may know off the top of their head.

 

I'm guessing a schematic may help even the very best though. wink.gif

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post #3 of 8
12/14/11 at 2:33am
Thread Starter 

That may prove troublesome. I have some board lay-outs and what not. It's getting quite late, I'll post what I can tomorrow.

 

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post #4 of 8
12/14/11 at 9:31am
Thread Starter 

Ok. Attached is the layout for the board. It's a really simple design. Left and right channels travel down the traces on the board. This is the amplifier board. Inspired largely by the CMoY/info on headwize. The opamps are TS922s, I just never changed the board designs, but that shouldn't matter.

 

render.gif

Built on radioshack protoboard.

 

The power is regulated by a 12V linear regulator, the schematic for which is identical to the AMB Sigma25. The final board is different from the one in the picture, as it would not fit in such a small space, but it is very similar:

Voltage Regulator.gif

This, I built on radioshack stripboard.

 

Finally, I took a bunch of radioshack protoboards, broke them in half, and mounted them vertically on the voltage regulator. On these, I used Tangent's schematic for a rail splitter using the noise cancelling TLE2426.

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post #5 of 8
12/14/11 at 9:44am

things I would try

 

1  if you have your opamps in sockets, try moving them around to see if the ones on the channels that work properly work on the channels that don't work, possible dead opamps.

 

2  check all the solder joints, your joints should be shiny and smooth, if they're dull and rough then you have a cold solder joint, re-heat the joint and add a little bit more solder.

 

3  the traces on radio shack boards are often not the best, when I use their boards I often have to make a jumper to replace a section of trace.  so check and make sure that none of the traces are damaged in any way.

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post #6 of 8
12/14/11 at 9:47am

Try swapping opamps and see if the imbalance follows the opamp or stays with the channel. If it goes with the opamp most likely you just need a new one. If it stays with the channel then I would say most likely you either have a bad component or connection somewhere.

 

edit: I see samsquanch beat me to my points - great minds think alike biggrin.gif


Edited by bcg27 - 12/14/11 at 9:49am
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post #7 of 8
12/14/11 at 10:03am
Thread Starter 

That was my plan for after work tonight. I'll post the result.

-Scott

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post #8 of 8
12/14/11 at 3:14pm
Thread Starter 

I FOUND IT! I forgot to check the solder points on the grounds. Oops. Two cold soldered points on the ground. I'll start a new thread with my build and pictures. Thanks, guys.

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