500K pots?... Experiment gone GOOD!

M.R. Ogle · #1 03-06-2010, 10:04 PM

Long(ish) story, but I'll try to get to the point...

I wired up an old bass with a G&L MFD split-P style single pickup, because I had it laying around and was just a bit curious about it's sound... and I never really liked the MEC soapbar that was in this bass. I put it in (reversed) with the D-G half further forward.

I've always used 250K pots in my basses, mostly J and P type pickups, but, I had two new 500K pots in the box, so... what the heck...i used those, and a big reddish tube of a tone (.2 mfd?)cap from an old Gibson bass, again, just because it was laying around. I'll post a pic in a minute...

Anyway, because of raiding the junk box, I got this astounding sounding bass... it's very loud, when I roll the tone control down, it goes into subterranean-dub lows... but, best of all...

When the tone control is full open, I got this little bit of extra "ping" on top of the notes that is not harsh or obtrusive, but I can hear it plainly and it allows me to "place" each note more precisely... hard to explain, but NONE of my other basses do this, and now I've got this one Frankenstein of a bass with the scrapings of the parts box installed in it, and every other bass I have is suddenly "lacking" by comparison.

The biggest single difference seems to be the 500K pots, I think... maybe they're just letting that top-end zing through a little more? If I try to replicate this in my other basses, should I use a 500K for both the volume and tone (like I did here) or would just switching out the tone pot do the same thing?

Also, if this is what I'm hearing, would a 1meg pot give even MORE of these highs? Again, vol and tone or just tone?

This has been an eye-opener to me, I've used 250K's for years, but this one little experiment has rendered everything else to second-string status right now, so I'm wanting some advice on how to get closer to that sound out of my other p-pickup'd basses.

I know it's a little bit of everything going on here, the heavy walnut body, Warwick Ovangkol Streamer neck, and the reversed pickup placement, but....daaaammmmn... it's working!

EthanTheHeathen · #2 03-06-2010, 10:18 PM

You sure it's not the MFD pickup? Those things are mighty zingy!

M.R. Ogle · #3 03-06-2010, 10:28 PM

Not really sure... I have a bass with a G&L MFD Humbucker...it'll take down walls, but it does not have that top end, and a bass with a G&L MFD single coil (early SB-2 pickup) that also doesn't have that, so... I did not peg it on the G&L pickup immediately.

TC2112 · #4 03-06-2010, 11:18 PM

I have nothing of any quality to add to this thread other than, D@mN that bass is hot. And now you say it sounds great too?? doesn't seem fair

walterw · #5 03-07-2010, 01:55 AM

i'm all about 500k pots on passive basses, for just the reasons you've mentioned.

be sure to use a linear volume and an audio tone, so that each control sweeps evenly through its range.

the diff between 500k and 1meg will likely not be as big, and at that point you might get too brash, and also the sweep from "10" to "0" starts to get too uneven.

M.R. Ogle · #6 03-07-2010, 07:36 AM

Thank you... that's exactly what I was wondering about. I have to go back into my other basses and try this now.

morguedoc71 · #7 03-07-2010, 07:41 AM

That is a beauty of a bass...I think I just wet my pants...

Lutuh · #8 03-07-2010, 07:46 AM

Please correct me if I'm wrong:
The resistance in ohms (250K, 500K, 1M, ...) is the maximum value for the reducement of the parameter controlled by the pot, e.g. the highs rolloff for a tone pot. So using 500K tone pots, you can roll off more highs.

This has nothing to do with the zings you get because you get them when the tone is not rolled of, i.e. the pot has zero resistance.

slyjoe · #9 03-07-2010, 08:23 AM

Not quite - the tone pot value mostly controls the height of the resonant peak where the circuit starts to rolloff. No matter the value of the tone pot, they all roll off at 6 dB/octave; the cap has the most effect on the frequency of where the rolloff starts.

What a lot of people forget is that the tone pot and cap are in parallel with the rest of the wiring, including volume pot(s) and the pickups themselves.

Changing the tone pot has less of an effect than changing the volume pots, IME with jazz basses.

**line6man** · #10 03-07-2010, 08:29 AM

Quote:

Originally Posted by walterw

i'm all about 500k pots on passive basses, for just the reasons you've mentioned.

be sure to use a linear volume and an audio tone, so that each control sweeps evenly through its range.

the diff between 500k and 1meg will likely not be as big, and at that point you might get too brash, and also the sweep from "10" to "0" starts to get too uneven.

+1 to all of this.

I've always felt it best to have the purest signal possible so that I can take out what I don't want later on in the signal chain if I so choose to do so.
With low value pots, the very first thing you do with your pickup's output is attenuate it...

Linear works best for volume controls, nice even sweep.
It doesn't work well for tone controls though, it will have little effect until the end of the rotation.

As far as the 1M pots, those would usually be desirable if you had many pots in the circuit, which in parallel would decrease in value (R_Total= (R₁ X R₂)/(R₁ + R₂)
It probably wouldn't work very well to have only one 1M volume in the circuit.
It would be closer to the "straight to jack" sound throughout most of the pot's rotation. (Linear)

**line6man** · #11 03-07-2010, 08:33 AM

Quote:

Originally Posted by Lutuh

Please correct me if I'm wrong:
The resistance in ohms (250K, 500K, 1M, ...) is the maximum value for the reducement of the parameter controlled by the pot, e.g. the highs rolloff for a tone pot. So using 500K tone pots, you can roll off more highs.

This has nothing to do with the zings you get because you get them when the tone is not rolled of, i.e. the pot has zero resistance.

No.

For a tone control, the higher the value, the less effect the tone control will have when it's at a higher setting.

Turning a tone control all the way down is 0 ohms, (capacitor fully "engaged" in the circuit.) regardless of the value of the pot.

Turning a tone control all the way up is the full value of the pot between the signal and capacitor (Or capacitor and ground, depending on how you've wired the bass.)
The greater the resistance, the less signal gets to the capacitor, which means the less high end gets cut.

M.R. Ogle · #12 03-07-2010, 08:58 AM

Great info, thank you!!!

I've done wired and re-wired basses a lot of times, I can solder and follow a schematic (barely) and I've always just used 250K pots, as they're usually "recommended" as the factory setup.

One time, out of sheer chance, I try something "odd", and I get this surprising result, and unfortunately, my electronics knowledge stops just short of understanding exactly why this is sounding the way it is.

Of course, I'm not going to screw THIS bass up, but I'll be breaking out the soldering station and switching out pots in a couple OTHER basses to try to replicate what I'm hearing.

Also, the "reversed" P pickup placement is giving me a very "EVEN" string balance. I like that, too.

koobie · #13 03-07-2010, 03:44 PM

Cool looking bass, kinda Carl Thompson-ish. The neck looks like it was made for that body. Who made the body?

M.R. Ogle · #14 03-07-2010, 04:00 PM

Me. My first attempt at building a bass body.

M.R. Ogle · #15 03-11-2010, 09:47 AM

Yep...500K pots from here on out for me... I just did an experiment with a different bass, and sure as heck, I can HEAR the little extra top end.

I wouldn't have believed it.

**zenrad** · #16 03-11-2010, 01:46 PM

Quote:

Originally Posted by M.R. Ogle

Me. My first attempt at building a bass body.

Nice job. That's a very cool bass.

RBrownBass · #17 03-11-2010, 01:54 PM

Very nice looking body. Who made the scroll for the neck?

M.R. Ogle · #18 03-11-2010, 04:23 PM

I just bought a broken cello neck and grafted the scroll end onto the bass' headstock.

RBrownBass · #19 03-12-2010, 10:12 AM

Quote:

Originally Posted by M.R. Ogle

I just bought a broken cello neck and grafted the scroll end onto the bass' headstock.

Good eye for the placement of scroll and tuners. The scroll goes well with the upper horn on the body, too.

The only thing I'd have done differently had the bass been my design is to rout the control cavity from the rear and use a soap with the D&G already forward (or a quad coil that allowed me to wire it that way). That wood's too pretty for pickguard material. Beautiful instrument in any case.

M.R. Ogle · #20 03-12-2010, 11:56 AM

Yeah, I agree... but I've had a MEC Warwick soapbar, a Gibson Mudbucker, a TeleBass single coil, and now this G&L pickup all in this bass at one time or another, so that plate covers a LOT of previous experiment's routing!