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Best Bass Pots?


michaelfpearce

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Hi, I am taking a Mexi P Bass and replacing the pickups and pots. Does anyone know which pots I should buy? I want pots that have good physical resistance, you know - a nice creamy feel. Should I use 250k pots for the pbass pickups? I am looking for a classic pbasss sound. I just bought semour duncan 3/4 pounders as a replacement pickup. Many thanks in advance!

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I don't anything about pots/electronics really but why does the resistance matter for sound? What does it do?

 

 

Resistance between signal and ground acts as a volume knob - the higher the resistance, the more signal makes it to the target, the lower the resistance, the more signal is drained away to ground (and the lower the resulting volume). When the path to ground involves a filter (like a capacitor or inductor), then it acts as a tone knob - whatever frequencies the filter allows to pass through are cut or not depending on the potentiometer setting. So a pot with a filter cap is like a volume knob for just those frequencies affected by the cap - when pot resistance is set low, frequencies above the cap's "resonant" frequency (not the proper term, just using for this example) are drained away to ground and you get a bassier, "darker" signal; when pot resistance is set high, those frequencies are not drained away to ground and you get a brighter signal.

 

In typical wiring, higher pot values retain more of the signal, it's that simple. When used as a typical tone knob, with a capacitor to ground, higher pot values result in more high frequency volume (a "brighter" signal) at the high end of the knob. This is why single coil pickups typically use 250K pots while humbuckers typically use 500k - single coil pickups are inherently brighter to begin with (no phase cancellation of higher frequencies like a humbucker has), and so aren't thought to "need" the extra brightness that the 500K pot offers for humbuckers.

 

Personally, I'm inclined to use 500K for both types anyway, I don't see much point in intentional signal loss. I don't really see any downside to higher values. In fact, I'm considering doing mods to convert my pots on some basses to "no load" types, where, at one and of the travel, rather than having the rated resistance value (500K), it's an open circuit, or infinite resistance - that way, the "full open" settings are just like the pickups being wired straight to the jacks, with no path to ground at all.

 

(This is all assuming a passive setup - the same principles apply for active setups, but the typical values are completely different.)

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I believe the P Bass, MIA, MIJ or MIM are 250K pots.

 

 

That's the normal setup for P and J pickups, both considered single coils (the P isn't really, it's a humbucker, but it doesn't have the same high frequency phase cancellation issues as other humbuckers because the 2 coils don't sense any of the same strings).

 

I know of no downside to using 500K pots for single coil pickups, though.

 

Just another matter of preference, nothing wrong with trying both and keeping whichever sounds better.

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Resistance between signal and ground acts as a volume knob - the higher the resistance, the more signal makes it to the target, the lower the resistance, the more signal is drained away to ground (and the lower the resulting volume). When the path to ground involves a filter (like a capacitor or inductor), then it acts as a tone knob - whatever frequencies the filter allows to pass through are cut or not depending on the potentiometer setting. So a pot with a filter cap is like a volume knob for just those frequencies affected by the cap - when pot resistance is set low, frequencies above the cap's "resonant" frequency (not the proper term, just using for this example) are drained away to ground and you get a bassier, "darker" signal; when pot resistance is set high, those frequencies are not drained away to ground and you get a brighter signal.


In typical wiring, higher pot values retain more of the signal, it's that simple. When used as a typical tone knob, with a capacitor to ground, higher pot values result in more high frequency volume (a "brighter" signal) at the high end of the knob. This is why single coil pickups typically use 250K pots while humbuckers typically use 500k - single coil pickups are inherently brighter to begin with (no phase cancellation of higher frequencies like a humbucker has), and so aren't thought to "need" the extra brightness that the 500K pot offers for humbuckers.


Personally, I'm inclined to use 500K for both types anyway, I don't see much point in intentional signal loss. I don't really see any downside to higher values. In fact, I'm considering doing mods to convert my pots on some basses to "no load" types, where, at one and of the travel, rather than having the rated resistance value (500K), it's an open circuit, or infinite resistance - that way, the "full open" settings are just like the pickups being wired straight to the jacks, with no path to ground at all.


(This is all assuming a passive setup - the same principles apply for active setups, but the typical values are completely different.)

 

 

 

Good post...

 

 

 

- georgestrings

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That's the normal setup for P and J pickups, both considered single coils (the P isn't really, it's a humbucker, but it doesn't have the same high frequency phase cancellation issues as other humbuckers because the 2 coils don't sense any of the same strings).


I know of no downside to using 500K pots for single coil pickups, though.


Just another matter of preference, nothing wrong with trying both and keeping whichever sounds better.

 

 

 

 

Agreed on all counts...

 

 

 

- georgestrings

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What would be appropriate replacement pups for a P bass, then?

 

 

The original values are likely to be 250K, so you could go with 250K or 500K to get a bit more volume and high end when volume and tone are maxed.

 

A good brand of pot is best - CTS is well regarded.

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Good posts bholder. I'd argue semantics with you and call a Pbass pickup a split single coil with reverse wound coils but it would simply be an argument of definitions and not one of substance. (Single coils having one coil per string and humbuckers having two coils sensing the same string. In return, you could easily make the argument that a single coil has a SINGLE COIL and therefore can't be split like a pbass is. Whatever. ;))

 

I personally like 250k CTS pots in pbasses, but if you have access to Bourne pots, they are my favorites.

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What would be appropriate replacement pups for a P bass, then?

 

 

 

I don't know about "appropriate", but the Schaller P pups I bought off the bay have my vote - got 'em for well under $20 per set(I bought 4 sets), and they sound great - IMO, and everyone else who's heard my Ps with them in... The Schallers give a hotter signal than the stock MIM pups, have tons of lows that are plenty punchy, yet are clear, bright, and articulate - with 500k CTS pots and a .022 cap, I get a great modern sound for hard rock/metal, but can roll the tone pot off a bit and get a classic Precision sound - works for me... If you could still get the Reverend 10k's, I'd also recommend those - but AFAIK, they aren't available anymore...

 

 

 

 

- georgestrings

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Thanks for the pot explanation. Hypothetically, if I change all my pots (bass, mid, treble, volume and tone from bridge pickup to fretboard pickup) to the highest values on my active bass, I will have the cleanest, most true tone of my bass? Will I open more tonal options? Or will the extra frequencies make tone shaping more difficult?

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There's a little more to it than signal strength, though that's a factor.

 

The lower the resistance, the more the pickups are loaded down, and that causes a change in frequency response. Single coil pickups normally have plenty of highs, so the 250K works fine with them. Put a 250K on a humbucker, and you're likely to get nothing but mud. HB's need the higher resistance to prevent the frequency rolloff they'd have with a 250K pot.

 

The flip side is that higher resistance results in the amp's input impedance having a greater effect on the tone. Or effect pedal, whatever you feed the signal to first. If it's high, as most modern effects and tube amps are, no problem. Older solid state input stages can have significantly lower input impedances, and that can affect the tone. I used to make buffer amps to use in between my basses and my amps to fix this.

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