RCA-4 Bass wiring

[JimC]

JimC,
I agree with you, for what little I know about wiring. I'm clueless on what pots to use with this configuration.
All I understand is a 250K pot will give more treble, high end, where as a 500K pot will be more midrange/bass.
Given my choice of pickups, and their positions, would there be a proven choice of pot values, along with your question, the cap values?

@Simon Barden knows about twenty times more about this stuff than me. I can read a circuit diagram and work something out, but the subtleties are beyond me. I have a feeling its the other way round, that 250K pots give less high end, so are a better match with single coils, whereas humbuckers need all the treble they can get. Bearing in mind three volume pots anyway I'd be inclined to use 500s on all three, and reverse the in and out wires on the individual volume pots so its more like a jazz bass. But I claim no expertise.

Tone circuits are not my thing at all. If you twisted my arm I'd note that AIUI JBs have a ~.047 cap on the tone control, and Gibsons a ~.022, so maybe it would be worth having the two different values, and I'd use 500 pots but almost anyone would be a better guide than me.

[OctoberBassRCA-4]

JimC.,
Yes I further researched some Simon posts and I was wrong, 250K bassier, 500K treblier.
My kit came with 500K pots. Whether I use them or find some others, I guess I'll go that route till I choose later to change.
I do want to hear this combination of pickups, but things may change as I go along.
Just trying to understand the wiring process, and by doing that, I get the basic setup starting to formulate in my feeble mind.
Was just recounting the wiring process in my head during a mundane chore. That's a good thing?
I keep researching.

[fender3x]

The rule of thumb is that you use 500K pots with humbuckers and 250K pots with single coils. It's just a rule of thumb, and not a bad one in my limited experience. Single coils can have a fairly harsh top end, and 250K pots take some of the edge off. 500K pots also take off some of the high end, just not as much.

Neither pot does much of anything to lower frequencies. The same pickup may sound a little bassier with the 250K pots but that's just because it's taking a little more off the top so you're hearing a little more bottom, or at least hearing it more clearly.

You can play with these values. The only really good way of doing that, though is through experimentation. I wrote something in the wiring forum about the "resister trick" which is helpful for seeing how different value pots will sound when dimed if you want to try it.

In my experience with single coils (like lipstick tubes for example) you may want a lower value like a 100K because they pump out so much treble that they can be fairly harsh without a fair amount of resistance (lower number, higher resistance).

Humbuckers are the opposite. The same property that takes out the hum can also take a fair amount of the highs. So, it's not uncommon to see higher values, like 1 meg pots, on humbucker volume controls.

Gibson uses some values lower than 500K on their humbucker basses, and I have no clue as to why. They have a reputation for muddiness and lower values only seem like they'd contribute to that rep.

Tone caps are a different story. The volume pot will take some high end off your pickup's tone whether or not you turn the knob (unless it is a no-load pot). But tone caps only come into the circuit when you turn the tone knob. So if you dime the tone knob, the cap does not effect your sound.

Tone caps have a similar "rule of thumb" .047 uF for single coils, and .022 uF for humbuckers. I think the rule may be good for guitars, but in my experience values lower than .047 don't really roll off much treble. On the Bill Lawrence humbuckers on my last build .022 did very little to role off tone, and .033 didn't do enough. .68 meant most of the turn of the tone knob was too dark for my taste, so .047 is what I went with. There are basses with tone caps that are lower than .047, and it may be good with some pickups, but I have found that humbucking pickups on basses mostly like a cap that is a little lower than their guitar counterparts. I have limited experience, however.

So...a lengthy way of saying the diagram is probably a decent starting place, but you can also experiment to see what sounds best to you. You can also always change things later ;-)