Mark Hammers "Choas" Question-

[jimbob]

I built this but cant figure out id the number 1 lug on the gain pot goes to anything. On Pauls Marossey's layout it doesnt show that it goes to anything as well as the ring of the input which normally has the -ground of the  battery lead--but nothing,, Is that correct? Does the input have connections on the tip and sleeve but nothing on the ring since it comes off the board? ect...

thanks


jimbob

[MartyMart]

Hi Jim,
I'm not sure but would it make sense if it went to "ground"  ? on a jack/box ground.
I would say wire the ring up as normal, to switch the circuit on when you insert the jack, it may be just omitted for neatness.
Marty.

[Mark Hammer]

My apologies for an ambiguous drawing.  The gain pot in stage 1 is wired up as a variable resistor.  That means that, in this instance, the ground side of the pot is the lug where you would normally feed an input signal if it was a conventional volume control, and the opposite lug (usually used for ground) goes to the op-amp.  The wiper is shunted/tied to the ground lug.  In this way, as you rotate clockwise, the resistance of the pot to ground gets smaller, and gain increases.

If it is used as a simple variable resistor, why use all 3 lugs?  Simple, it is traditional good practice to always use all available pot lugs to provide something less than open circuit, so that if the wiper fluctuates in the quality of its contact with the resistive element inside the pot, there is always a connection made through the two outside lugs of the pot.  Intended to reduce "chatter" from less than perfect pots.

[Paul Marossy]

The gain control is wired as a variable resistor, therefore that third lug does not need to be connected to anything. I never use the input jack to switch to the power on and off because I always use a wall wart to power all of my pedals. If you want to have the input jack switch the power, then just change the input jack arrangement to do so. The FAQ section at www.diystompboxes.com shows you how to do that.  

EDIT: Mark beat me to it...  :oops:

[jimbob]

vERY COOL.. tHANKS ALL