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zed has the presence control right and its tied to the 1u C10 on his schematic, no need for a question mark there.

your op amp pin 2 culprit is the 1uf C11 you have circled . it runs from pin 2 to 1K resistor R12 and that runs to the positive side of a 10uf. R12 is also connected to R14 10k, R13 220K, R93 10K, R92 10K at the same cap. vref

Guys,

I just finished tracing the circuit. I am about to re-do all the references and... there's a surprise on "presence"
I will post it soon, later this evening.

Ok guys, here it is my final trace. I double check the tracks and think it's accurate.

Mind that I re-did a NEW component reference annotation. Here it is:
So, if this is correct (which I hope it is) who is interested on designing a 9mm pcb-mounted pot, 1590B-friendly PCB layout...?

Very cool! So the TL072 op-amp powered with V+ and GND?

EBRAddict wrote:Very cool! So the TL072 op-amp powered with V+ and GND?

No, just V+ (after 100R), on pin 8. GND doensn't power anything.

zedsnotdead wrote:So, if this is correct (which I hope it is) who is interested on designing a 9mm pcb-mounted pot, 1590B-friendly PCB layout...?

I should have one for you later this afternoon.

zedsnotdead wrote:

EBRAddict wrote:Very cool! So the TL072 op-amp powered with V+ and GND?

No, just V+ (after 100R), on pin 8. GND doensn't power anything.

The pedant (and science teacher) in me wants to say that strictly speaking, the opamp Is powered by ground at pin 1 and +9v at pin 8: without ground, there would be no complete circuit and so no power would flow.

Nocentelli wrote:

zedsnotdead wrote:

EBRAddict wrote:Very cool! So the TL072 op-amp powered with V+ and GND?

No, just V+ (after 100R), on pin 8. GND doensn't power anything.

The pedant (and science teacher) in me wants to say that strictly speaking, the opamp Is powered by ground at pin 1 and +9v at pin 8: without ground, there would be no complete circuit and so no power would flow.

And you are right Sir!
Something like having a motor running without a gas exhaust tube. I hear you, I hear you...

Also, the battery's energy is transferred to electrons which travel FROM ground to +9v.

As requested, here's a PCB layout with 9mm board mounted pots. Mount them from the solder-side of the board. In and out pads kinda ended up in a weird place, but shouldn't really be a problem. Board dimensions are 2.1" wide, 1.9" tall in case it doesn't scale right. I'll probably do another layout for 16mm board mounted pots, but that's gonna take some re-arranging. Enjoy!

I etched my own PCB version for it but, IMO something's still not right. everything works as it should (the drive, eq, presence etc) but there's just way too much gain and the distortion gets really ugly/splattery when at 9:00 and above.

johnk wrote:I etched my own PCB version for it but, IMO something's still not right. everything works as it should (the drive, eq, presence etc) but there's just way too much gain and the distortion gets really ugly/splattery when at 9:00 and above.

Could it be a wrong cap polarity? Maybe C4 1uF ?

I really don't think so, since I used non polarized caps for the 1u coupling caps.

BTW, I just tried it with polarized electrolytics for the 1u's (installed with the correct polarity) with the same result.
even with the gain not turned up very high there's an ugly fizzy decay that i'm sure isn't supposed to be there, which to me, reminds me of opamp clipping.
it would be great to solve this since everything else works perfectly.

Talons almost behaves like a boost with gain=0, so it's almost clean.

I just re-checked the connections and values mainly on drive section, There's one minor (i think) correction: R4=4,7K, not 4,6K.
I don't really think it would make a difference, but I could be wrong..

One thing though, are you using log or linear 500K pot for gain? If you are using log, mind the lug numbering - lug1 connects to R4.

I didn't have a 4K6 so I used a 4k7. and yes, i'm using a 500K audio pot for the drive control and lug 1 is connected to R4.

NEVERMIND! your schematic is perfect.
it turns out that I had the two clear red leds facing the same direction! no wonder the clipping sucked.
I feel like an idiot.

great!!!

How does it sound?

AWESOME!