New project = Two effects in a box : questions...

[Lenougat]

Hi Everyone,

I've got a new project in my mind : I'd like to put a Klon Centaur and and OCD Fulltone in the same box.
The purpose is to have only one footswitch to engage both effects simultaneously.
Then, I want to add two specific controls : one switch to choose between serie (to stack the effects), and parallel (to blend both signals with a pot).
The aim is to have something like Fender's Pugilist, with two stages, and the option to stack or to blend the effects. The blend ratio will be done by a potentiometer.
I will start my project using kits, so I will use 2x "stock" PCBs, and not do any circuit by myself. The "stock/blend" switch will be a 3PDT.

Problem : If I'm confident enough now to produce some simple single effects now, I've absolutely no idea about the constraints made by these two effects, once they're paralleled.

Here's a schematic of what I think the wiring must be (I didn't draw the DC input, but I will put both circuits in serie). But perhaps I'm missing some basic notions about electronics and signal that will make this circuit not viable... I Need your help on that point !!

I've got two main questions :
- If my guitar signal goes into two parallel circuits, will it divided by two in each circuit ? = will I have a volume drop on the outside ?
- If my general idea is ok, what type and value of pot should I use to blend both signals ?

If you see anything dumb about my project, let me know !! I'm still working on blank sheets, nothing has been bought yet.

Thanks a lot for your help guys !!
Alex

[iainpunk]

welcome to the forum!!!

a quick look at your schematic and i think it should work! but if you are going to blend, i'd recommend adding a buffer to lower the output impedance. also, both volume controls can act like the mix control, so you could replace that pot with two of the same resistors because lowering one sides volume control will lower the that sides mix value. i would also recommend a summing amplifier to mix the signal without loss of volume.


cheers, Iain

[Lenougat]

Thanks Iain for these advice !

You're right on the volume thing. I've missed that. I don't want to have two volume pots on the pedal, but a single one. I must review my wiring...

On a Klon, the volume pot is 10k (or 50k on some kits), and on the Fulltone, it is 500k. Is it a big deal if I use a 250k to control both ?
What are the rules of thumb when choosing the resistance for a pot ?

[PRR]

> I didn't draw the DC input, but I will put both circuits in serie

I think that is wrong.

If you have two household light bulbs, do you put their power connections in series?

[antonis]

What are the rules of thumb when choosing the resistance for a pot ?

Exactly the same with those of choosing a resistance for a resistor..
(after all, a pot is a 2 part variable resistor..)

P.S.
Sorry but it's late Saturday night here..

[Lenougat]

If you have two household light bulbs, do you put their power connections in series?

You're right, I've forgotten my basics from college...! I'll connect both DC circuits in parallel, sounds better...

Exactly the same with those of choosing a resistance for a resistor

Right, but I mean : what will be the difference if, for a given circuit, I use a 50 or a 500k pot for the volume ? The max volume ? The sensitivity of the setting ?
I'm in France ! It's late for me too ! 

[antonis]

what will be the difference if, for a given circuit, I use a 50 or a 500k pot for the volume ? The max volume ? The sensitivity of the setting ?

No for both..

You have to take into account preceding and succeeding stages impedance (complex resistance)..

e.g a 50R source output impedance has no problem to drive a 50k pot but the later might have big problem to drive a 50R next stage input impedance..