Hey everyone. I jost got a kit from my local DSE store. It is an LM833 opamp based audio control board which has volume, treble, bass and balance controls. Attached are the photos of the finished product, as well as the schematic.
So far, I have tested it - and to some degree, it works. The volume, bass, trebble and balance controls work well on the LEFT chanel. They also work on the right chanel - but there is a lot of buzz. There is also buzz on the left chanel as well. There is also a bit of hash noise as well.
I have tested it so far for a couple of things. Firstly, I checked my solder joints. I resoldered most of them. It didn't fix it, so i prodded them all with a non conducting pen and couldn;t find any bad joints.
Next, I had a look at the voltages on the audio out pins. It is my understanding that they should be under 50mV or so.
When I switch the system on, the output voltages begin at 3v max, then reduce to about 8mV after a few seconds. - To my understanding, this is OK.
Next, because it is buzz, I checked the AC voltage at the outputs. A few volts at the start, as with the DC, but then goes out to zero.
Last in my thinking is the power supply. Yes, it is icky and the ground is a bit dirty, but I know that (by using the supply with 2x 20W amps) it doesn't cause too much of a problem.
So, what to do? Any help, suggestions or tips much appriciated. Thanks.