Tube version?

[edvard]

This is totally nuts, I know, but here's an article on configuring tubes for op-amp operation.
I suppose the diode would have to be rated for a bit of higher voltage to work here...

http://www.headwize.com/projects/opamp_prj.htm

[blackcorvo]

i think a 1N4007 would do the trick.

[edvard]

Hmmm... yes you are correct. Those are rated for like 1000 volts or so, right?

[blackcorvo]

yep. 1000V at 1A current.

there are also other high voltage diodes like 1N5408 (if i'm not remembering it wrong thats it's code) that is rated 1000V at 3A.

if you have any program like Proteus or any other Schematic/PCB editor, just look at the list of components on the library. they usually have some info about the components models.

[Joe]

I'm looking at this circuit:
http://www.headwize.com/images2/opamp3.gif

A simpler version might be to use the input stage as shown, but after the .22uF capacitor use a single tube stage (other half could be a source-follower, tone-thingy, etc.) Bias the tube ouput to 1/2 supply.

I'm not a tube guy, so perhaps someone else can help. I think regular 12AX7's should work, and using a single supply would be easier. Seems like a waste of time to include the diode on a tube circuit, but who knows?

[edvard]

The point to using the diode was to get some crazy compression effect.
I found it fascinating that op-amp technology has been around for so long.
It would be interesting to make a low-power, two-tube op-amp circuit into a pedal and add the diode mod.