Newbie in Need of Advice

[Dom Phenom]

Hi all,

So, I'm trying to build my first pedal.  What I would like to build is an A/B switcher that provides an attenuator for each line (I switch between electric bass and synth bass, so I'd like to be able to adjust for the fact that synth's out is way hotter than my passive bass). 

I bought an A/B kit from general guitar gadgets, and I figure that all i have to do is wire a potentiometer of some sort into the circuit for each line. (please forgive me if my nomenclature is totally wrong, like I said i'm a complete newbie).  What I'm looking for is advice on how to do this - i did some searching on line could not find advice for what kind of potentiometer i'd need to provide a volume control on this kind of circuit.   Also, where should the potentiometer be wired in... before or after the switch? 

Advice would be greatly appreciated. 

Thanks,

D.P.

[Drake120]

The pots had to be before the switch, cause after it you have only one signal coming out So:

- connect the tip of 1st input jack to lug 2 of a pot
- connect lug 3 of a pot to the switch (the lug which you will normally connect to the tip of the 1st input jack)
- connect lug 1 to ground
- solder a 1nF capacitor across lugs 2 and 3

and do the same for second input jack

Potentiometer should be audio taper, value 100k ro maybe higher.

(JD)^S

[Dom Phenom]

Thanks!  I'll give it a try, and let you know how it turns out.

-D.P.

[dano12]

- solder a 1nF capacitor across lugs 2 and 3

Curious, what does the 1nf cap do in that configuration?

[Mark Hammer]

If it is simply a matter of bringing a hotter signal down to approximately the same level as a not-so-hot one, then really you only need one pot to attenuate the hotter signal.  Just make sure that the synth is always plugged into the to-be-attenuated input and the bass is plugged into the other one.

So, the switch is wired up as an A/B input selector, with the output going to a single jack.  We'll stick a 100k pot hardwired to input jack A, with its wiper going to the A side of the switch, and input jack B wired straight through to the B side of the switch.

You can either use an SPDT stompswitch without a status indicator LED if you'd rather sidestep installing a battery and all the stuff that goes with that.  Or you can make a more "deluxe" version using a DPDT switch.  Realistically, you'll probably use the same darn switch in any event, just wire it up in more and less complex ways.  My guess is you don't need an indicator LED to let you know if you're playing bass or synth.  I figure you'll probably have all the indicator status you'll need once you put one down and pick the other one up.

[Drake120]

If I didn't make a mistake, this cap should prevent from losing treble when you turn the pot down.

And Mark is right - you should consider if you want two pots, only one for turning down the sunth bass a bit also is a good idea.

Correct me if I was wrong with the cap, though.

(JD)^S

[ayayay!]

Dano, I can smell it from here...:  You're cooking up one of your awesome Visio drawings for this guy aren't you?  You at least have to admit you entertained the thought.   

And, Welcome Dom Phenom! 

[Dom Phenom]

Think I'm going to go with just one pot - i was originally thinking that two would be more useful, but since neither will be a boost, there would never be a reason for two volume adjusters. 

At risk of really showing how green I am - what type of 1mf cap should i get?  seems like there are a ton of different kinds.  Also, i'm assuming mf = uf??   

thanks again

-D.P.

[petemoore]

  1nf...nanofarad.
  Don't let me confuse anyone, go to a capacitor conversion chart and figure that nano is super small, picofarad is smaller...that's it for now.
  Film is what I'd get..polyester, mylar...had great capacitor experiences, and haven't felt any need to use anything more 'special' than that, though I have tried some metal films. I tend to stay away from brownie caps.
   

[dano12]

Dano, I can smell it from here...:  You're cooking up one of your awesome Visio drawings for this guy aren't you?  You at least have to admit you entertained the thought.   

And, Welcome Dom Phenom! 

holy crap, am I that predictable?

Yeah, the thought had crossed my mind