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Not really. I wouldn't want to use a charge pump in this case because it adds more circuitry and cost. Plus, it already has plenty of headroom at 9V.

So the order came in and I've done some more experimenting. 1. The TL052 doesn't work in the application at 9V. Damnit 2. You can't use half a dual opamp for a servo and the other for audio. Noise with my opamps on hand 3. J201s I got will not bias correctly with a 5K6 drain resistor. Had to go...

Sweet! That sure simplifies things. I've always been able to gate bias, so I guess I hadn't considered that problem.

So here's what I'm talking about for biasing at the JFET gates. Of course I just altered the drain resistors on my build and it sounds great. This is a solution for keeping the drain and source resistors stock.

The more I think about it, the more I think the whole idea is a little %$&^ed-up in the head. Feels like I'm on Mouser shopping for the right $200K supercar someone can leave parked in their garage just in case their 1987 Chevy Corsica needs a jump start. In practicality, I think it could be...

Also, looks like in the picture, if that's the pin 8/power side facing us, pin7 isn't connected to the JFET source - just the cap to pin 5.

Hmm. What's the voltage at pins 3 & 5 of opamp? Junction of R8/R9?

Supply voltage?

That fish is a whopper! How the drain voltages looking?

If you're going by the schematic above, use 18K for R8 and 24K for R9. That should give you about 5.3V on the drains with a 9V supply. Also, I used 2u2 for C3 ad C7 because I had those laying around. Those caps could probably drop to 100n without running into trouble.

Wow! I don't think I even have a shipping notice yet on mine. Ordered from Digikey. I'm also planning on trying a non-inverting servo bias on the JFET gates and possibly just a simple voltage divider on the gates. You can bias up a Black 65 with trimmers that way without changing the Drain or...

Overdrive. Sounds great at low and med-high gain. Highly recommend.

Agree with Chuck, but I have a bit of an out-of-the-box suggestion: Try 1N5817 you use for polarity protection. You probably have some around and they're hella leaky like a D9-Russian whatever.

Good catch. Totally whiffed on that. I've already got a few coming, so we'll see if they start up with 9V. I think there's a pretty good chance.

No sweat! I love this stuff. The TL062 won't give the best results. I tried an 072 today and it couldn't keep up. Looks like the trick is a Fet-input, rail-to-rail opamp for this.

It's a good one. I was heavily into JFET ODs for years and the Black 65 is easily in the top 3 for me in that category. If I build this out, I'm most likely going to leave off the bonus boost stage. There are a lot better boosts to hit it with, especially a good ol' Klone. Might look into...

Nope. those are pretty much the 358. Only other rail-to-rail I've got on hand is a 2272 and it works fine (mosfet-based). It's through-hole, but they're $5 each these days. OUCH! If something comes of this, I'd like to make it through-hole capable so you guys can build one if you want, and I...

Spent a little more time playing around with this today. Unfortunately, an LM358 doesn't perform well. Think I'll look around for a cheaper JFET-input rail-to-rail opamp. Also confirmed it's easy to raise or lower the value of the drain resistor to dial in the amount of gain while maintaining...

You'd reduce C1. Going to 100n, even, would make a pretty noticeable difference.