Simplest way to add a gain pot to an AMZ Mini-Booster

[afrogoose]

Hey All,

I've recently built the above Mini-Booster and I like it a lot.  I also purchased the lab notebook that Jack sells which details a bunch of mods to the pedal.  I have to be honest and say that much of the packet is over my head, because I either can't understand the underlying theory or I can't figure out how to implement the ideas with a combination of off and on board wiring.  At this point, I'm still basically a paint by numbers DIY'er (and I'm ok with that).  So my question is... what is the most dead simple way of adding a gain pot to this board?  I've tried subbing both R1 and R2 for a pot, and it doesn't work.  To the initiated, I'm sure it is obvious why this wouldn't work so I won't even give more detail.  I would appreciate any and all help!!!

Thanks!
andy

p.s. here is the Mini-Booster schem
http://www.muzique.com/amz/mini.htm

p.p.s R1 is not represented in this schematic.  What I'm referencing as R1 is a resistor right after the input but before C1 and what I'm calling R2 is R1 in this schem.

[petemoore]

  The Source's AC bypass cap, smaller or put none there, or put a pot to ground on it, 25k I guess.
  Make the source resistor larger value.

[Jered]

  Make R5 a 10K pot. Simple enough?

[afrogoose]

Pete, Jered,

Thanks for the advice!  I will give that a shot.  I'll have to experiment with both values (10k and 25k) to see which one works out better.  I have another beginner's question.  When subbing the pot for a resistor that is going to ground, I'm curious how to wire the pot.  It seems that you would just wire the two outside lugs, one from the circuit and one to ground.  However, it seems like I usually see the middle lug bridged with one of the outside lugs in this sort of application.  Would it be the case here?  Also, why is that?

Thanks!
andy

[petemoore]

  From the wiper, center lug:
  to One outside lug is a variable resistor.
  To the other outside is a variable resistor.
  One sides R value rises as the other sides R value falls as you turn the shaft.
  If you start with a linear pot, it's symmetrical, for use as a variable resistor, all that is needed is a wiper and outside lug connection, connecting the wiper to the other outside lug is just a 'failsafe', if the pot should fail, instead of an 'open'...the  pots value is the default value.
  GEO: "Secret life of pots".

[afrogoose]

Thanks Pete.  I can see now that I was viewing the pot anatomy incorrectly.  I can't wait to give it a try!

[afrogoose]

Ok, so I finally had a chance to give the gain pot a go and it seems to work ok, except I notice another curious problem.  When I turn the volume pot up, the signal gets louder, yet cleaner.  When I turn the pot down, the signal get quieter, yet more distorted.  Does anyone have any ideas why this might be so?  I've disconnected the drive pot from the circuit so I know that isn't part of the issue.