Fairfield Barbershop: Tone switch

[Rob Strand]

Good to see you worked it out.

Should i add a buffer after the volume pot, just before the output jack socket, to prevent similar behaviour to happen again ?

Up to you. 

The JFET buffer is fine.  Given there's already a transistor (BJT) at the output of the pedal why not use a BJT buffer?    I guess they are cheaper.

One thing I should point out.  You have tuned the cap to suit the input impedance of the buffer you added.   So in order to not to change that sound you need add a buffer with the same input impedance.   Alternatively you could use a buffer with a different input impedance and re-tune the bass cap to get the sound you want.

It's a good idea for the buffer to have a big output cap like 10uF and add maybe 100k to ground after that to stop "pops" when you switch the pedal.

[snk]

Thank you, Rob.
I added the little buffer circuit i posted above (and kept the parallel capacitor on a switch), and got rid of the SAG which wasn't working.
Now it's boxed, and running fine
It's a nice overdrive !

[PRR]

> with a buffer after, the sound is changed : the bass is back ! So, Rob, you were right
> - I wired a 150nF cap in parallel with C6 (100nF) : and the bass range is here again

So what sucky load are you driving??

I don't know why your plot slants, but the excess slant suggests you have 5kOhm on it.

[snk]

The Barbershop was plugged into the AUX of a mixing desk (A&H GL2400).

Plugging a buffer ( a Klon buffer clone i built a while ago) after the pedal, before going back to the mixer solved the "lacking bass issue".

[rankot]

Anyone figured out what's the optimal biasing point for JFETs here?

[snk]

From what i have read, it is 6-6.6V.

[PRR]

> the AUX of a mixing desk (A&H GL2400).

I don't see an AUX IN on the '2400.

The 2-TR IN has an astonishingly low 4k input. Pad and ST inputs are >10k. Insert Return not specified.
https://www.allen-heath.com/media/gl2400ug_ap5597_2.pdf

[snk]

Ah, indeed, sorry, i make my routing using a patchbay, so i didn't remember that
I'm routing back the out of the barbershop into a channel mixer
the signal flow is : Synth > A&H GL2400 channel 01 > AUX01 out > barbershop > A&H GL2400 channel 02