This Week on the Breadboard: OKKO Diablo v3

I had an Okko Diablo way back and quite liked it. I remember it being very good if a little polite. I tried building one when Robert first came out with a PCB but couldn't get it to work - probably the only pedal I have had not work from here.

I'd love to build a working one. Mr @szukalski if I ask nicely could I get some gerbers from you or should I build a Vero version? I have a DCA55 transistor meter which I didn't know could do JFETs. I just tried it but the battery is low - it says "Drain and Source not identified" and that's all it wants to say. But it will tell me which pin is the Gate. :)
 
comradehoser said:
Just so I'm clear, the final schematic also
*changes C5 to 470nf from 100nf
*changes body spdt on-off-on switch to c50k pot
*deletes r7, R8, and r25,
*adds c22 100nf after c13 10uf
*subs 1n5817s for the 1n4148 diodes at D2 and D3?
*Volume pot changes from b100k to a100k
*R19 is replaced with 50k trim pot

I have a j201 that measures 1.33 idss. Adequate?

Or would you still suggest the 2n5457? My through hole 5457 register 1.3-1.7, but my batch of SMD 5457 all register between 3.8 and 5.3. I don't know if that means I should worry about my measurements, but I'm guessing we're going for 1.3-1.7 and not 5.3.
Click to expand...
The Final Schematic in post #19 is the Final Schematic. As much as I could, I kept the ref des from the PPCB Build Docs dated 3/20/24.

The Idss spec for J201 is 0.2mA to 1.0mA. Any part that measures outside that range is suspect.
SRPP circuits like this are very sensitive to Crs (gate-drain capacitance). One of the attractive features of J201 is the low Crs. Most other JFETs, 2N5457 included, have greater Crs and will cut off some of the treble. The issue with using JFETs with higher Idss is they will also have higher Vp, which affects the biasing. Best bet is to stick with J201 and arrange them so Q2 & Q4 have higher Idss than Q1 & Q3, respectively.
 
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