Discrete preamp design

[efinque]

The perfboarded circuit didn't work properly, which is a shame.

Oh well, I had two of these Kemo M040n preamplifier modules, tested one, it worked so in the mixer it goes.

It sounds a bit distorted but it's better than nothing.

EDIT : it's potted in epoxy so I have no clue how it works.. it's been tested with an electret mic.

 

[ccaudle]

setting the gain is VERY critical in this thing..

You are using an externally compensated op-amp which is not unity gain stable. You need to understand what those terms mean before successfully using an NE5534.

The perfboarded circuit didn't work properly

Your circuit still did not include a reference to bias the output to half of the supply voltage. As drawn you are providing 9V to the non-inverting input for a circuit which runs from 9V, so the output will be stuck at the positive supply voltage constantly.

 

[efinque]

You are using an externally compensated op-amp which is not unity gain stable. You need to understand what those terms mean before successfully using an NE5534.



Your circuit still did not include a reference to bias the output to half of the supply voltage. As drawn you are providing 9V to the non-inverting input for a circuit which runs from 9V, so the output will be stuck at the positive supply voltage constantly.

I measured 2,23V bias voltage for the non-inverting input using a 10k resistor.

As to why the perfboarded circuit didn't work and the breadboarded did I have no idea. By accident I placed the perfboard on my tool box (aluminium) and discovered the circuit makes a scratchy noise when dragged around (bad solder joint or a jumper wire?)