[sdiy] Using tube diodes instead of LDR/lamp for tube compresor?

[René Schmitz]

anthony schrieb:
> All of the schematics I have ever seen for tube compressors use some 
> sort of photoelectric coupler. I was wondering if there might be any 
> advantage of using tube dioes like the 6AL5 and such in the 
> detector/control circuit of the compressor. One that comes to mind is 
> being able to dial in just about any attack you'd want. But I am also 
> talking about advantages over using solid state diodes in all solid 
> state compressors. I have heard that the tube diodes are more linear 
> than Si or Ge diodes. I was wondering if as compressor might benefit 
> from that in an appreciable way and I also wonder if there are 
> commercial tube compressors that in fact use tube diodes. I haven't run 
> across one yet.

I tried using vacuum diodes as control element, but the problem with 
tube diodes *is* their linearity. Ironically it is the strong linearity 
which allows a solid state diode act as a variable resistor over a large 
range. The vacuum tubes control law is roughly proportional to sqrt 
(Id), so that means you get a comparatively small range.

Cheers,
  René