Temporary Fix for Missing 1M Pot in Bassman Clone?

[The New Steve H]

Apparently, I'm stupid. I only ordered 2 1M pots for my Bassman clone. I should have bought 3.

I figure the volume pots are pretty crucial, so I will want to put my 1Ms there. The other one is a bass pot, which isn't a big priority.

What's the best way to rig it up until I get a third pot? I have all sorts of 500Ks lying around. What if I put one in series with a resistor about the same size? Or I could just bypass it. Gerald Weber says it doesn't do much anyway! I know how everyone here trusts Gerald Weber and considers him the Oracle of Gain.

[Cliff Schecht]

I'm sorta the other way. Messing with the value of the bass pot will change the tonestack frequency response and going smaller isn't necessarily desirable.. Volume OTOH is not significantly different feel wise from 1M to 500k (bright cap might need adjusting)..

[tubeswell]

What Cliff said - a 500k pot will be slightly more 'lossy' than a 1M pot (but on the other hand, the TS in a tweed bassman is driven by a cathode follower so you might not notice it too much) and it will change the freq response. If you put 470k in series with it, it will be like having the bass pot turned up a bit.

Technically, if you wanted to run with pots that were 1/2 the value and caps that were 2 x the value of the original circuit, you will get the same freq response, albeit with more signal attenuation (which will mean that the LTP will not be driven as hard).

[The New Steve H]

I guess I'll just stick a 500K in there with a 470K resistor. I'll add a 1M to my next Mouser order.

[Jana]

I would put the 500K in the bass spot. With a 500K pot substituted for a 1M audio pot in the bass spot it will be like you have numbers 0 through 8 or 9 instead of 0 through 10 on the bass.

Don't put the 470K in there.

If you want to be sure, call up GW and see what he says.

[The New Steve H]

He will say, "Did you pay your tech support fee?"

[pdf64]

I always use a 500k audio for the bass control in that tone stack; even then it's only ever in the '1-4' range of the control.
Check it out on Duncan's TSC; with a 1M log bass control, the upper 30% of the range is only affecting subsonic frequencies.
Whatever, putting a 470k resistor in series would make the bass control useless. Pete.