Has anyone built the CM Plexitone?

[Galego]

I fell for the "true bypass is not the best way" marketing from CM, and did my clone according to the schematic. Well, the switching sucks, there's popping when the boost is activated and there's a lot of bleeding though. You can hear it with the drive off, and you can hear it when the volume is at 0. Seems like i'll have to start from scratch on this one.

If anyone has some ideas on how to solve these issues, please chime in. If not, at least it's a warning to whoever tries to build it.

[Galego]

Here's the schematic, in case you can't find it...

[slacker]

The pop when switching in the boost is probably because unless you use a make before break switch there's a brief period when the connection is broken and the opamp has nothing  in its feedback loop. I would rewire it so lug 1 of the boost pot connects to pin 8 of the opamp, and put the switch so it shorts out lugs 2 and 3 of the pot. That will switch the boost on and off without breaking the feedback loop.

[Galego]

Yeah, that makes sense, thanks!

[Galego]

No one has any ideas on how to stop the gain section from bleeding into the bypassed signal? 

[slacker]

Try looking at the Marshall Guvnor, that's a vaguely similar circuit and grounds the point between the gain and tone sections to shut it up in bypass. The schematic is over at General Guitar gadgets. Another thing to try would be shorting out R3 when the effect is bypassed, that should shut it up.

[Galego]

Try looking at the Marshall Guvnor, that's a vaguely similar circuit and grounds the point between the gain and tone sections to shut it up in bypass. The schematic is over at General Guitar gadgets. Another thing to try would be shorting out R3 when the effect is bypassed, that should shut it up.

Thanks, i used the second half of the DPDT to switch the GND between the led and R3/LF347 pin3/C9. Hard to believe the guys at Carl Martin didn't do something this simple.

[asintoras]

Can you please explain me with a diagram how you solved this problem?
A friend helped me building the same pedal and I notice the same kind of noise, but I have no idea about electronics... I can just sold according to drawings and diagrams (no schematics).
My thread is here:
http://www.diystompboxes.com/smfforum/index.php?topic=90785.0

If you can send me some information to asintoras@gmail.com, that will be great. I am also looking for ideas on how to wire LEDs to my 3pdt switch.

[blackcorvo]

I think you need a cap comming from the buffer to the bypass switch, like in the Tube Screamer. The only difference I see is that the buffer here uses an op-amp instead of a transistor...

I wanna try this circuit now, but I wanna check how 2 infra-red LED's will sound there... they conduct a lot easier than most LEDs, at around 1.2v. May not be as much of a show as it would be with red LEDs lighting up, but might be cool to give it a try :3