PT2399 based delay. Decrease delay output

[nonost]

A DPDT. There's one free pole right now.

Let's see if I got it. The source of the new FET would go to the drain of the bypass FET. The gate of the new fet would receive 9v/GND (in reverse regarding the bypass FET) and the drain of the new FET goes to ¿? That's what I don't understand. You said "AC ground", which makes nonsense to a n00b like me.

[anotherjim]

Yes, use the opposite wiring of the other switch pole so when one gate switches to ground, the other switches to 9v.

AC ground. Basically means a path to ground via a capacitor. Both De Profundis and Small Time have a capacitor in the path from the input amp to the delay. The output of the amp is electrically a "virtual ground" and the repeats path "sees" that virtual ground through the capacitor. Since the capacitor can only pass AC, it is an AC ground.

The extra JFET would replicate the dry input path but instead of starting from the input opamp output, use the VR voltage. That will represent an AC ground since it has a capacitor to 0v on it and behave like an opamp doing nothing and also at the same DC voltage as the opamp. It ought to be enough to join the bypass JFET connection to the PT2399 input capacitor. So you have one JFET feeding in the dry signal or the other JFET feeding in the AC ground.
I hope - I pull these ideas out of a void you know.

[nonost]

Thanks a lot Jim. I appreciate the info. It makes more sense now and I'm sure it will make even more in the future when I had a more solid knowledge.

I'm using the FET buffer at the input posted before. So I have no VR there. Can I make an AC ground point with this arrangement?

[anotherjim]

The problem with that is the bypass JFET has some DC voltage that comes from the buffer.  The extra JFET switch needs that same DC voltage, but that voltage depends entirely on the buffer JFET parameters and it isn't present without any input signal added to it. An opamp buffer would output the same DC as the VR reference supply. If a different voltage was used, there will probably be a click/pop when the voltage to the input cap to the PT2399 changes.
Is it going to be impossible to change the buffer to that of the Small Time input?  Or add it between?

[nonost]

I see...

I did try a thing. Taking a look at my input buffer posted before...I've added a 4u7 cap to ground at the 1M junction with the 1k & 2k2 resistors. And so I've taken this point as AC ground. And as you said there's a pop. The pop becomes part of the repeats and that's a problem. Also, there's a slight bleed in bypass. I guess that's also for the voltage different. At this point the voltage 3.7v, whereas voltage at drain is 5.5v (FET input buffer drain, I mean).

Now, if I take the 9v and make a voltage divider so I get 5.5v and I put a bypass cap as well...Would that work?

For the last build I will definitely use an opamp as input buffer. For this current built I'm keeping the FET. If the previous idea doesn't work, I will leave it at peace.

[anotherjim]

What you could do is use a trimmer pot (around 20k, not too critical) across the power supply to make an adjustable VR. Add a 47uF cap from its wiper to 0v. Then measure the DC voltage out of the JFET buffer (the source end) and adjust the trimmer voltage to equal it.
A single JFET switch in series with a signal path usually does let some signal bleed through when it's supposed to be turned off, however, the second JFET switch will tend to shunt any bleed-through to AC ground. This is just how Boss bypass switching works - one for the FX output and one for the clean with toggling gate control, only here you want the clean to be silent.
RG's article may be helpful...
https://www.premierguitar.com/jfet-switching
Note that the Slow Time tails switch does without the bias resistors to each side of the JFET. The input bias comes from the preamp and the output end probably hangs on to that voltage well enough when the JFET is off.

[nonost]

Yes. A trimmer is a much better option. I was going mad with resistors.

Yeah. It works! There's a subtle "pop" when pushing the footswitch. It's subtle, like a faint heartbeat. This pop sounds sounds with the next repeat after the FS is pushed. I've set the trimmer to the exact same voltage, but it doesn't want to vanish. I guess the opamp version would not have that problem. Even tough, it's not annoying at all.

Thank you so much Jim!

[anotherjim]

Good. Yeh, the trimmer and buffer are not perfectly matched sources so I wouldn't be surprised if there is a little disturbance, besides, when the input signal cuts off then the buffer voltage at that instant is its bias DC + or - the signal voltage so there is a sudden discontinuity which only a fade-out to zero of the signal in advance of the switching can cure - but that would be complicated to achieve.