Mold Spore Wah Tone Suck

[drummer4gc]

Hey, I just got finished bringing a Snarling Dogs Mold Spore back to life (needed new pots), and I'm getting some significant tone suckage with the pedal in bypass. I notice that it's worse when I've got the pedal plugged into 9v - if I disconnect the power supply, some of the high end comes back.

Here's the schematic:



It's marketed as true bypass, but doesn't it look like it's connected to the circuit in bypass, which would lead to some loading? Is this why it sucks worse when connected to power? Or is there something I potentially screwed up?

Thanks!

[Cozybuilder]

I'm guessing that C2 (1nF) is sucking your tone away in bypass. I'd try removing it and see if that improves your tone.

[ilcaccillo]

Hi drummer4gc,
did you remove C2 (1nF)? did the bypass improve?

[GibsonGM]

If removal of C2 doesn't help, I would convert it to REAL true bypass.   It looks from where I am sitting that the Q's are never actually disconnected when in bypass...they are always "hanging on there", if you follow the switching plan.

This would explain the tone sucking, and also why it changes with removal of battery. 

[ilcaccillo]

If removal of C2 doesn't help, I would convert it to REAL true bypass.   It looks from where I am sitting that the Q's are never actually disconnected when in bypass...they are always "hanging on there", if you follow the switching plan.

This would explain the tone sucking, and also why it changes with removal of battery.

Hello, thanks for your reply and help

what do you mean by the "Q's" ?

thanks

[bluebunny]

Q = transistor

[ilcaccillo]

Well,
it seems to me from the schematic that the signal is always connected to the wah circuit and the Ring Mod circuit, only the output of the FX is switched in or out.

So for true bypass the input signal should be switched before C1.

[bluebunny]

So for true bypass the input signal should be switched before C1.

Yep, correct.  You may also want to add a pulldown resistor to minimise popping.

[GibsonGM]

^  Yup, Bunny....

You might want to read this....you should be able to replace the switch that's in there with one that can provide true bypass.  Without a pic I cannot tell you what kind of switch would work (which would fit in your enclosure).

http://www.geofex.com/article_folders/bypass/bypass.htm

As it is built, the transistors are never truly disconnected, so it is not true bypass.  They present a load to the signal, so you experience that loss of high frequencies...

[PRR]

> marketed as true bypass

What is truth??

There are no active parts in the bypass path.

Some awful sucky effects parts hang on the guitar even when "bypassed".

Put a buffer in front.

[ilcaccillo]

> marketed as true bypass

What is truth??

There are no active parts in the bypass path.

Some awful sucky effects parts hang on the guitar even when "bypassed".

Put a buffer in front.

thanks PRR, but why not change the stock switch and wire it true bypass?

I have buffers already in the pedal chain

[GibsonGM]

It may be easier and less 'destructive' to the pedal to make up a very small 1 transistor buffer, and insert it before C1 on a separate little piece of perfboard...it would always be there, just like C1 is never really disconnected now.    This will prevent the tone sucking, as the buffer will 'source' what the rest of the circuit is trying to pull in, so to speak.

[ilcaccillo]

It may be easier and less 'destructive' to the pedal to make up a very small 1 transistor buffer, and insert it before C1 on a separate little piece of perfboard...it would always be there, just like C1 is never really disconnected now.    This will prevent the tone sucking, as the buffer will 'source' what the rest of the circuit is trying to pull in, so to speak.

Humm,
well thanks, But I really don't see how building and inserting a circuit inside the pedal, being a buffer I dont need, be "less destructive" and easier than unscrewing 1 switch, screwing another one and resolder the wiring and new wiring.
Sorry but this really seems easier and less intrusive.

thank you

[drummer4gc]

Sorry, I have no idea what I ended up doing - sounds like you got some good advice anyways though!

[GibsonGM]

It may be easier and less 'destructive' to the pedal to make up a very small 1 transistor buffer, and insert it before C1 on a separate little piece of perfboard...it would always be there, just like C1 is never really disconnected now.    This will prevent the tone sucking, as the buffer will 'source' what the rest of the circuit is trying to pull in, so to speak.

Humm,
well thanks, But I really don't see how building and inserting a circuit inside the pedal, being a buffer I dont need, be "less destructive" and easier than unscrewing 1 switch, screwing another one and resolder the wiring and new wiring.
Sorry but this really seems easier and less intrusive.

thank you

If the switch is the same size or smaller than the original, go right ahead and make it true bypass with a new DPDT.   It may not be.  I haven't seen the actual pedal, so I can't tell you it will fit.   A buffer is just one way to do it, that's all.   My thought was to make it reversible.

PRR may mean to run a buffer in front of the entire thing, instead, such as an 'always buffered' Boss pedal, which may alleviate some symptoms with no pedal mods at all.

The concern is likely that modding an old pedal (if this one is valuable) may take away from its value.  Some of these can be worth big $.

[ilcaccillo]

I see your points GibsonGM. Thanks

The Pedal box itself is really big, any switch will fit there.
This is not a vintage or old pedal, theres a lot of them around, having true bypass will not lower its value, on the contrary solving the kown china factory problems will make it more desirable.

I already have buffers in the chain from Boss pedals and alike.

here is a pic of a Mold Spore pedal with 3PDT switchs so you have an ideia of the size

thank you

[GibsonGM]

Yup, you should EASILY be able to use a 3PDT to achieve true bypass using any of the schemes out there....I suggest one that grounds the input in bypass...General Guitar Gadgets has PDF's out there that show a few different ways to do it! 

[ilcaccillo]

Yup, you should EASILY be able to use a 3PDT to achieve true bypass using any of the schemes out there....I suggest one that grounds the input in bypass...General Guitar Gadgets has PDF's out there that show a few different ways to do it! 

Thank you, I will do that.

At the moment I'm having another problem.
I fixed the Ring Modulator circuit by replacing the Max1044, that circuit is fine.

But the Wha circuit is distorting on the lower register, it sounds good but when I reach the rocker pedal towards the Low part of the sweep (toe up) it distorts, It's like and ugly gated fuzz.
I dont know what might be the culprit of this

[GibsonGM]

Can you post a sound clip of it?  I see you have another thread going....if you put it there, I (we) will come look at it!   Often this has something to do with a filter-related problem, perhaps a bad cap or something....

[ilcaccillo]

Can you post a sound clip of it?  I see you have another thread going....if you put it there, I (we) will come look at it!   Often this has something to do with a filter-related problem, perhaps a bad cap or something....

yes I can, I will record it in the next days and post it here.

Thank you so much