post #16 of 16
10/12/05 at 5:11pm
Quote:
Now with all that said: how does the potentiometer play into this?
A potentiometer is no more than a variable resistor voltage divider so the amount of voltage "divided" depending on where the ground referenced "wiper" resistance is.

where selection comes in is with the input resistance of the pot which if it is a 10K pot means the amp will have a 10K ohm input.
In order to "drive" this 10K input the source needs to have a low enough output impedance or the high frequencies can end up attentuated,the nore is 1:10 though 1:5 should be fine so your source would need to be at worst 2K ohms output Z and bettrer if lower.

If that driving source is a single ended tube stage there is a chance the output will be higher so the "fix" would be to bump up the pot size but even this has limits.As you increase the input impedance you also increase the possiblility of a DC offset appearing at the opamp output (if opamp based) AND you run the risk of picking up RFI and amplifying it just as if the sateg was a radio so everything is a tighrope balancing act.

http://hyperphysics.phy-astr.gsu.edu...ic/voldiv.html

http://hyperphysics.phy-astr.gsu.edu...ic/vdivac.html

http://www.yadtel.net/~ccp/potdesign/

http://www.platenspeler.com/backgrou...enuator_1.html

http://www.goldpt.com/compare.html
Reply