[sdiy] improved dynamic range diffpair-vca

[np]

Thanks everyone for answering. Now I got the idea why it works.

I've done a plot of the base voltage vs. the output of my differential 
amplifier. The circuit wasn't trimmed, and my differential amplifier is 
inverting so the curve is mirrored. You can estimate the amount of 
distortion based on the base voltage drive though:

http://torus.untergrund.net/vca_improved_trace.gif

Regarding noise: My primary source of noise is hum and rf stray-ins. I 
doubt that the extra np-connection will contribute that much, but beeing 
able to drive the base harder was a win SNR-wise. At least for me.

Nils