diode-compression opamp (updated)

[Joe Davisson]

http://www.diystompboxes.com/analogalchemy/pedals/diodeopamp.html

Also added a better circuit description to the Easy Drive and changed the description of the 5-part opamp to "opamp-workalike" as to avoid confusion with traditional opamps.

The parts count with the new discrete opamp is high, 10 parts per opamp. So use the discrete opamps in audio gain/distortion stages, but regular IC opamps in tone controls, etc. Maybe I'll whip up some small modules sometime. The question is, to SIP or DIP?

[petemoore]

Shocktave is too Cool... . I love that sound !!
 GREAT Site !!!

[aron]

DIP is what I was thinking.

AWESOME! I am going to try it Joe.

THANKS!!!!!!!!!!!!!!!

Aron

[Ghandi]

No need for selected PNP transistors with the Diode-Compression Opamp, right?

[StephenGiles]

......and I've just had a delivery of opamp samples! Thanks Joe.
Stephen

[Phorhas]

http://www.prodigy-pro.com/forum/viewtopic.php?t=4903

like this one?

[bwanasonic]

I'd be interested in hearing an A/B with this circuit and an IC in something like a Tube Reamer. I would imagine it would *feel* different as well.

Kerry M

[ragtime8922]

This is great. Before I started building JD stuff every distortion/OD unit i've built had an IC except the fuzz stuff of course. Then I fell in love with working with discretes as it gave more of a sense of fine tuned control. Now with the discrete opamp stuff the possibilities are endless. Great stuff Joe!

[RLBJR65]

Awsome site Joe! I was just checking it out before loging on here. The Electronic Math Helpers are a great addition as well

[Joe Davisson]

http://www.diystompboxes.com/analogalchemy/pedals/diodeopamp.html

Resolved a gating problem (a trivial fix, luckily), and the schematic now shows dual-supply rails. I also added a "deluxe" version of the circuit. Both seem to behave pretty well now, hopefully this will do it.

More testing was done, both circuits can operate over a decent voltage range, between about 6 - 18 volts. I tested TS9-style circuits with both circuits, and a Shredmaster distortion section with the basic version. Pretty
decent overall.

I guess the downside is the parts count, but the flexibility is kinda neat. (All-germanum opamp, anyone?) Yep, the diode can be Ge too Some things can't come on a chip...

[Joe Davisson]

Circuit is ok, had to add a 10k resistor on the negative input to prevent the diode from turning off. I briefly yanked the page, but it's back now. Might need to reload images.

-Joe