Missing output cap causing problems?

[HeavyFog]

So i just finished putting together a preamp that's made up of a modified valvecaster (only in part values) with a fender brownface 2 band tonestack after it and a zvex super hard on after all that for a bit of boost. The valvecaster+tonestack and SHO each have their own bypass switch. The SHO works perfectly fine on its own but the valvecaster makes a very loud pop when engaging an disengaging. The volume pot and treble+bass controls also cracke loudly when turning. Even weirder when the SHO is engaged and the valvecaster is engaged after it, the valvecaster fades and out instead of a just turning on and off instantly and is its itself a bit noisy. This also happens in reverse order to the SHO when it valvecaster is on and the SHO is turned on after it. Iv'e checked all the grounds and leads to check for anything wrong and i can't seem to spot anything wrong.

When i built the valvecaster i got rid of the 1uf output cap since the output of the valvecaster goes straight into the tonestack and i'm starting to suspect that that's why i'm having these issues. The valvecaster sounds fine but the the poping, fading, and noise makes it unsuitable for any live use. Can anyone confirm that getting rid of the output cap would cause these kinds of problems? I can post schematics if needed.

[GibsonGM]

Can you post a schematic to what you built?  May well be a DC level affecting your next stage, yes.  Or maybe you need a pulldown resistor that's not there, or something like that...

[HeavyFog]

Here's the schematic for the build. (sorry for the huge picture size)



And for the power supply i used (the lm7809 has a heatsink on it)



The differences between this and what i built is the way the volume controls are wired and the mute switch (which works fine without poping). The volume for the SHO stayed the same but the other one was actually wired to be directly after the treble pot. I also got rid of the trimpot coming off pin 8. Tried this pedal with a 12au7 and a 6211 and both work, but have the exact same issue with unwanted noise. Iv'e had no issues with the power supply voltages.

[antonis]

IMHO, you have to move 1M resistor after 100nF cap in front of it and (optionally) place another diode facing from Gate to +9V..
(SHO Input cap left side is floating when effect is disengaged..)

That 1M resistor confuses me a bit 'cause is actually placed in parallel with lower 10M resistor of feedback divider bias pair..
(probably it's a wrong drawing placement and you actually have placed it on the left side of 100nF cap..)

Deleting 1μF Valvecaster output cap leads to DC leak to Treble & Bass pots through 35k and first left tonestack resistors (can't discerne its value - 100k..??) and also to Volume pot, when engaged..

I also can't see if there is any pull-down resistor in front of input cap...
(if not, place one..)

[GibsonGM]

^^  Yes!   What Antonis said.   You have DC on your 250k bass pot...see?  That will make the control sound scratchy as the wiper makes/breaks contact inside the pot.   

Placing an 'arbitrarily large' cap before it (above and to left of 100k)  will prevent this..use a poly or mica type for best results, oh .68u or something, even smaller is probably fine.   And maybe 1M to ground before input as he said.   Tell us what happens.

Have you tried a Mosfet boost to fix this issue?   <inside joke>

[antonis]

Have you tried a Mosfet boost to fix this issue?   <inside joke>

To keep it <inside> see post #6 : http://www.diystompboxes.com/smfforum/index.php?topic=117908.0 

[HeavyFog]

Thanks for the help, il try adding a cap around .68uf after the valvecaster and before the tonestack to see if that will fix it. Iv'e never had this problem before with any of the valvecaster iv'e ever built so it seems to me that this is the likely culprit. The SHO isn't quite built the same as the schematic shows. I used a layout that i know and use often and the SHO is working just fine. It definitely sounds though like this cap is my problem.

[HeavyFog]

UPDATE

I added a 1uf cap before the tonestack and now its working perfectly! No switch poping or unwanted fading at all. Thanks for all the help!

[GibsonGM]

Great!