[LawnGnome]

So I'm wanting to eek a bit more performance out of my soundcard until I can afford a external DAC.

So I'm thinking of trying to bias my soundcards opamp into Class A. I don't think it has been done before.

I'm thinking of cascade JFETs. I have some spares from my PPAV2 build.

What would be the simplest schematic to get 3mA bias?

I want to build a little module on a bread board that I can just solder to the opamp.

 

[a1rocketpilot]

The simplest I would think would be a CRD connecting from the opamp output to one of the power rails. Don't know how effective that would be, but worth a shot. Someone please correct me if I am horribly wrong.

Aditya

 

[00940]

http://tangentsoft.net/audio/opamp-bias.html

 

[NelsonVandal]

Quote:

Originally Posted by LawnGnome /img/forum/go_quote.gif So I'm wanting to eek a bit more performance out of my soundcard until I can afford a external DAC. So I'm thinking of trying to bias my soundcards opamp into Class A. I don't think it has been done before. I'm thinking of cascade JFETs. I have some spares from my PPAV2 build. What would be the simplest schematic to get 3mA bias? I want to build a little module on a bread board that I can just solder to the opamp.

CRDs are hard to find. A lone JFET like 2N5484/86 is also a simple solution. You have to measure the IDSS of each JFET. Just add a resistor of appropriate value from G to S to get the current you like. Some opamps seem to improve with class A biasing and some don't. If you're connecting your soundcard to an amp, there's no need for more than 1 mA or so.