pot as resistor

[school]

how can i wire up a pot to be a variable resistor, and what value would you recomend as a bias pot instead of a resistor thats supposed to be 330k?  also, what would you recomend as a pot intended to mix feedback?

[maximee]

erm i don't really know what you are looking for...
a pot _is_ a variable resistor...
what do you mean by feedback?
what are you trying to build?

[school]

alright man, how would i wire it in in the place of a resistor?

[sir_modulus]

Aighty, you take the wiper (mid lug) and wire it to one of the outer lugs. That becomes one end of the variable resistor. The remaining untouched lug becomes the other end.

For a 330K...wait a sec...bias for what? If it's for something that will not handle a short (usually what it's needed for) I'd go with a 250K pot, and a 82K (? closest to 80K you can find) resis. Wire the pot like the variable resistor above, and connect the 80K resistor in series with it. That'll give a nice broad range, and give a threshold, so the resistance will never drop below 80K.

For a feedback pot...I dunno...depends on the circuit...what do you have in mind? A generic one I've used in the past is 500K...

Cheers,

Nish

[school]

the bias pot would be for a J201 in the punch in the face circuit

[school]

for the second JFET

[school]

oh, and the bypass pot is gonna be behind an SPST bypass switch.

[sir_modulus]

hmm..I confused here...isn't the trauma control a bias for a Fet? The bias is usually a 100K trim from +9V to the drain, and is usually adjusted to get 4.5V. For a feedback...I'd say replace the 300k resistor in the style of the T.M.K. (500K).

Cheers,

Nish

[school]

i dont want to bias it, i want to mis-bias it.  ive messed w/ differant values for that resistor w/ interesting effects, so i was wondering what pot could i use that would be able to achieve both the original value of resistance, but other values?

[school]

really need your help guys!

[Hal]

I'm not totally sure what else you're looking for...I think your question was already answered.  Tell us what range of values you want - experiment with fixed resistors.  I also recomend making a minimum with a series resistor, and then just add taht to the pot value to find the max...

[school]

thats about what i needed, thanks. i just didnt know how the whole pot value/resistance relationship worked.

[sir_modulus]

yup, oh and btw, the trauma control is a bias, so the circuit can get that "nice" misbiased sound with that. You can try biasing the first transistor to get some more ugly tones...but that's all I can think of..

Cheers,

Nish

[NaBo]

People is confuseded by what yous askin, man.

Not that I'm an expert, but like sir mod said, the 100k trauma pot and 470 ohm resistor to Drain are responsible for biasing your J201.  Thus, the PITF already has a pot for all your biasing and misbiasing needs.

Tweaking the 330k resistor from Q1 base to Q2 source is a different matter.  If you want a pot to mess with that value, I imagine you want something that includes 330k in its sweep and has a decent range on either side, thus 500k.  You might end up with a useless range near the bottom and top of the travel, but you can mess with series and parallel fixed resistors to influence the taper and range of the pot.

Of course, you could always experiment for 2 minutes and try a few different pots yourself and figure it out...  :wink:

[Hal]

thats about what i needed, thanks. i just didnt know how the whole pot value/resistance relationship worked.

resistors in series add values.