Changing pot values

[Cliff Schecht]

Does anybody know of a way to change a pot value, say from 100k to 50k, without affecting the tonal response of the circuit. This is easy if one of the pots outer lugs is connected to the wiper but if the pot is truly being used as a three terminal device then this doesn't work correctly (I don't think..). If one of the outer lugs is the signal input and the other lug is going to ground (wiper is the output terminal), then simply placing a resistor in series with the outer lugs will affect the value that the wiper sees as the pot is swept, right? I don't necessarily care that the taper is changed, I just hate that I occasionally run into this problem and never have found a definite answer.. Would using a very high value pot, say 500k, and placing the appropriate resistor across to make a 5k pot work better than using a 10k pot to make a 5k one?

For the record, I want to use one of my higher value AB pots to make a 5k pot for the presence control. It seems that AB either never made a 5k value or I just can't for the life of me find one.

[Sonny ReVerb]

I believe it's possible. Here's the skinny:

http://www.geofex.com/article_folders/p ... tscret.htm

Do you have a drawing of the presence circuit you're using?

[Andy Le Blanc]

The AB are getting harder to source, 15- 20 years back there was a range at a
reasonable $$$. Its getting to point where your screwing your self to use
parts you can't replace. You can still get JA1N brand new for $45 ea.
Instant rebate on the boutique, yank the pots, make a few hundred,
resell the amp same price. Watch out buying any high dollar used amp.

Bourns are good in the low values, the Vishay pe30 is 3w 20%,
Honeywell 380, RV4N, 53C3....and JA1N
ETI systems makes a product rated to 50,000,000 revolutions

[Cliff Schecht]

I believe it's possible. Here's the skinny:

http://www.geofex.com/article_folders/p ... tscret.htm

Do you have a drawing of the presence circuit you're using?

I was hoping nobody would post that link. I've been there and read the article a dozen times at least, on top of the fact that I know R.G. pretty damn well..

And sorry, should have mentioned that this will be going in an Express.

Andy: I'm not worried about sourcing them, especially the 10k and 250k, I have at least 50 of each of those values brand new in box. It's the 5k pot that I just haven't been able to find. I can find 2.5k and 10k in abundance but no goddamn 5k AB/Ohmite examples .

[67plexi]

I have used this in the Express builds.
PEC-5K 2 watt Mil. Spec.
http://ampbuildersparts.com/store/index ... ucts_id=82

[Andy Le Blanc]

Honeywell markets a 5 k JA1N carbon, pricey, Allied i think.

yep....

Honeywell / Clarostat
Pot; Carbon Comp; Rest 1 Kilohms; Panel; Linear; Pwr-Rtg 2.25W; Shaft Dia 1/4in

Mfr's Part#: JA1N056S102UA
Allied Stk#: 753-2203

Part type is important, Its not AB, but its made to the same requirement.