Any advice on pots & caps?

Lamont B Dumont · #1 01-13-2010, 10:06 PM

I've got this old, slab bodied beast of a bass I'm resurrecting. It's an old short-scale Kent with a single humbucker. It previously had the tone circuit removed and I can't find a diagram for it. Since it was a single pick-up, I copied a P-bass circuit (250K pots, 0.1 uf Orange Drop cap) and I now possess the World's Greatest Fart Noise Generator. The sound is sprawling, muddy, diffuse - fart noises.

Another weird aspect is that the (audio taper) volume pot is more like an on-off switch; by the time it's down to 7, there is no audible signal.

From what I've read so far, I should go to 500K pots for starters. Any votes to go to 1 meg?

I'm also thinking audio taper for the volume, linear for the tone.

I'm also thinking I need to go down on the cap value, any ideas?

The pickup reads about 7.7K ohms.

Am I in the neighborhood, or am I completely on crack?

Deathblade Eric · #2 01-13-2010, 10:23 PM

Quote:

Originally Posted by Lamont B Dumont

I've got this old, slab bodied beast of a bass I'm resurrecting. It's an old short-scale Kent with a single humbucker. It previously had the tone circuit removed and I can't find a diagram for it. Since it was a single pick-up, I copied a P-bass circuit (250K pots, 0.1 uf Orange Drop cap) and I now possess the World's Greatest Fart Noise Generator. The sound is sprawling, muddy, diffuse - fart noises.

Another weird aspect is that the (audio taper) volume pot is more like an on-off switch; by the time it's down to 7, there is no audible signal.

From what I've read so far, I should go to 500K pots for starters. Any votes to go to 1 meg?

I'm also thinking audio taper for the volume, linear for the tone.

I'm also thinking I need to go down on the cap value, any ideas?

The pickup reads about 7.7K ohms.

Am I in the neighborhood, or am I completely on crack?

I'd guess the problem is with the cap - it's twice the value commonly used. A good chunk of your top end is just leaking off - hence the MudMonster. Swap it out for either a 0.047μF & if that's too much, a 0.022μF. 500k pots are no bad thing either.

As to the Volume pot acting as a switch... could be damaged/ defective. It's quite possible to wreck a pot with excess heat from a soldering iron.

Pickup resistance sounds reasonable.

Pete.

DavePlaysBass · #3 01-13-2010, 11:27 PM

Depends on what sounds best. My favorite passive tone control is in a P bass using a 250k and a 0.1uF.

If you want more highes the 500K pots would be an option.

Stuggi · #4 01-13-2010, 11:33 PM

Technically you want linear for volume and logarithmic (audio) for tone. It sound stupid, but it works a lot better.

If you want a more controllable mud then go for the 0.047uF cap and 500k log tone knob. Stock Fenders are usually 0.047uF and 250k.

Lamont B Dumont · #5 01-26-2010, 08:31 PM

I put in 500K pots & a 0.047uf cap, which cleaned the sound up alot. I tweaked the action a bit (a new bridge was part of the resurrection) and the tone is much improved.

It's still got some mud, but that's a bass humbucker for you. But now the mud is part of the sound instead of all of the sound. Maybe I'll join a punk band.

Thanks again.

xaxxat · #6 01-26-2010, 08:49 PM

How many wires on that pickup?

Also, have you considered adding a Varitone to it?

Lamont B Dumont · #7 01-27-2010, 04:42 AM

It's only configured for two leads right now.

Would a Varitone replace the existing tone control? I'm not eager to drill any more holes in the pickguard.

I'm also OK with how it sounds now, not great, but OK. It's only going to serve as a back-up and maybe for recording some of the punkier Food Rock tunes, if we ever get arond to that. It has the right tone for tunes like 'Cauliflower' and 'Prime Rib'.

I'm probably done with this for now, at least until I get my '60-ish Hagstrom HBII back up and running. However, I'm sure this one will be in pieces again, so any ideas are welcome.

xaxxat · #8 01-27-2010, 05:11 AM

Too bad about it being a 2-wire. 4-wire humbuckers are fun to play with. Yep, a varitone could replace the tone pot. Check out this thread:

A simple varitone circuit for your bass -

R. Laevinus · #9 01-27-2010, 11:39 AM

I'd reccomend using 500k pots and a .047 cap - CTS and Orange Drop, respectively, if you can get them.

Additionally, if muddiness is an issue, you may wish to use a .022 cap. I don't reccomend 1 meg pots - if you'd like the option to have the axe wide-open, I'd vote for a control bypass switch - mounted either on a separate DPDT toggle or on a push-pull pot.

Having a switchable control bypass (pickup straight to jack) will give a wider, open-er sound even than 1-meg pots, and you also then have the ability to switch quickly and cleanly back to your controlled tone and volume - which could be useful for, say, pumping up a solo.