pot value question

[daz]

I have a box with a pot and switch and relay that acts as a volume boost in my effects loop. The pot is bypassed for the boost and the lower volume when it's not bypassed is my normal sound. So it's not actually a boost, just a attenuator of the loops signal that i set a tad lower than the "boosted" volume for solos and such. This is a SS modeling amp, a fender mustang. Using a 100k pot the pots is a little sensitive, but i had no problem with that. What i DID have a problem with is the tone. (when pot is in circuit) So i figured i needed a higher value pot and that might sound better, but be too sensitive. So i tried it and sure enough it sounds better. But also sure enough it's much too sensitive. I figure the 100k pot was too low of an impedence for the loop and i guess thats why it didn't sound good? Anyways, whatever the reason a larger pot works good but is too sensitive to set right. The window where the level i need is is probably 1/20th of one number on the pot, maybe less. So it's near impossible to easily find the right level. Any ideas how i could do this? I'm thinking maybe a 50k pot with a 220k resistor from the pot's ground lug to ground instead of the lug directly to ground?

[The Dude]

The pot resistor idea is a good one. Also, what taper pot are you using?

[daz]

Just regular audio taper guitar pot pulls. The 100k was audio too, a fender SS amp pot.

[Chuck H]

You might try a 1M linear pot. A linear pot will actually adjust more slowly at the top end than an audio pot.

The other option could be to use a "bright cap" type circuit. Just a cap across the ungrounded lugs. You might need a larger value than impedance mapping would lead you to think since the pot is only going to be turned down a smidge.

And then there your idea of a pot and resistor. That's good too but doesn't offer a "full down" setting. Of course if you're playing your guitar with that pot set full down you don't really need the amp at all

[daz]

And then there your idea of a pot and resistor. That's good too but doesn't offer a "full down" setting. Of course if you're playing your guitar with that pot set full down you don't really need the amp at all

Thanks, I'm going to try what i said. Theres no need for it to ever be set full down, not even more than a tad. It will always be used for one thing only....to turn the amp volume down about 5% lower so i can use it as a lead volume boost, thats all. So pot in circuit=normal volume, pot bypassed=solo "boost".

[daz]

Ok, issue #2 now. I tried what i said with a 100k linear and a 220k resistor and it worked, but i noticed another issue so i removed the resistor and it still exists. On a side note the linear pot is all i needed as was suggested because when i removed the 220k it still was not sensitive. But heres the other issue....hum. When the pot is bypassed it's dead quiet. When the pot is in circuit it is also dead quiet with the pot on 10, but when i turn it down the further i go the noisier it gets. So what you have here is hum when a pot thats in the effects loop is turned down at all, but dead silent on 10. Any ideas? Some sort of impedence thing? Maybe i have to go back from this 100k to a 250k or even 500k? If i do it will get more sensitive but if linear maybe it'll be ok. But is that the issue, 100k is too low?

Edit: DOH!!! One of the cables was a speaker cable ! Not mine and it looks like a audio cable so i had no idea. anyways, now after ripping pots and resistors out it probably worked bine before with the resistor and 100k pot. Arg ! (thanks Al Bundy for that one )

EDIT 2: done. 100k linear and 220k ground lug to ground worked perfectly.