Best Pot for Spin-A-Split

[Zhangliqun]

Currently have a Jon Moore Big Dog wired up to Spin-A-Split. The pot is a stock Gibson 300k used for the bridge tone, don't know if the taper is audio or linear.

Anyway, the taper is anything but smooth -- the pickup measures 11.2k and by the time you get the pot up to about 6, it's already 10.5k which means not much goes on from 6 to 10. Not much happens between 0 and 3 either, meaning about 90% of the taper is from 3 to 6.

I'd like something with a much smoother taper. Your thoughts, ladies and gentlemen?

[Zhangliqun]

Bumpa-lumpa...

[ratherdashing]

I've been told that 500k or even 1meg is the way to go. You should also do the no-load mod on it to make sure you're getting full-on humbucker when the knob's at 10.

[larry_emder]

Hi, i'm using the spin a split in my les paul with 500k pots.

Im finding it really hard to get any sounds inbetween the full on humbucker and single coil, becouse of the ramp up (pretty much hall happens between 0 and 1).

Can someone recommend different pots? maybe a different taper? Its almost not worth it for me atm, because there is such a small area of inbetween-ness.

[Fresh_Start]

I can't speak to spin-a-split, but "dial-a-tap" turned out way different than I expected. 100k linear pot was the way to go. No load a must.

The rest of this post is Saturday morning speculation, so take it for what it's worth...

Z - what you're describing is similar to what I experienced with the dial-a-tap. With audio taper, you're still way below 50% of the 300k at "6". I started with a 500k IIRC, experimented by adding resistors across the pot's legs until the combined resistance was about 100k and found that the useful range. Since the range may be very different for a humbucker, try adding/increasing resistors until you get a useful sweep (realizing the full humbucker won't be on at "10"), then you'll be close to a useful pot value.

Another thought is that you may never want a completely split humbucker, for tone, output balance or humcancelling. Therefore, a small resistor (1k, 2k, ?) in between the series connection and the spin-a-split might be cool.

Chip

[Mojambo]

I don't think this ever got resolved. Anybody have more thoughts on what values to use, aside from no-load?

[ArtieToo]

I'm in the "not-resolved" camp myself. I haven't had it come out with any satisfactory results, but I didn't take notes, and its been awhile.

I need to sit down with one humbucker, and a box-'o-pots, and try them all.

Or someone . . .

Artie

[Mojambo]

If I'm using 500k pots for volume and tone, will using a lower value like 250k on the spin-a-split pots bleed off treble from the signal, or is it inconsequential?

[LJ King]

If I'm using 500k pots for volume and tone, will using a lower value like 250k on the spin-a-split pots bleed off treble from the signal, or is it inconsequential?

Come to think of it, that would probably be the best way to think about it.

Ok... say you are using a 500K pot for volume (ignore the tone for the moment). That means in series and without the spin-a-split, there is 500K across two coils. Which in this warped way of thinking about it, would mean 250K across one coil.

So put back in the tone control. That would be 250K loading across the two series coil and 125K across one coil. So a 250K pot across one coil would be suffiecent to remove the coil tap without bleading off any treble when it is full up or no split. Split wouldn't matter.

Does that make any sense to anyone?

[Zhangliqun]

I don't care what the pot value is, because it doesn't matter anyway. It's the TAPER I was posting about way back in those halcyon days of September 2005 AD. A smooth taper. I don't think running resistors across the pot lugs is relevant unless it can be manipulated to somehow positively affect the TAPER of the pot so that 7-10 aren't the same and suddenly the bottom falls out at 6.999, and it stays pretty much the same until 3.547 and drops off again, and so on.

You can see the taper with your multimeter. Say your pickup is 8.5k. Plug a short cord into your guitar like you're just going to measure DC resistance -- as you turn the SAS pot down from 10, you can watch the reading on the mm go all the way down from 8.5k to whatever the DCR of the remaining coil is, 4.25k if it's not a mismatched bucker.

You can also see very graphically how UN-SMOOTH the taper is.

[Mojambo]

So the taper is what matters, the value doesn't affect it. k

Is there anybody who has gotten a usable taper for S-A-S, or is this just one of those "works well in theory, not in practice" type deals?

[Fresh_Start]

I don't care what the pot value is, because it doesn't matter anyway. It's the TAPER I was posting about way back in those halcyon days of September 2005 AD. A smooth taper. I don't think running resistors across the pot lugs is relevant unless it can be manipulated to somehow positively affect the TAPER of the pot so that 7-10 aren't the same and suddenly the bottom falls out at 6.999, and it stays pretty much the same until 3.547 and drops off again, and so on.

You can see the taper with your multimeter. Say your pickup is 8.5k. Plug a short cord into your guitar like you're just going to measure DC resistance -- as you turn the SAS pot down from 10, you can watch the reading on the mm go all the way down from 8.5k to whatever the DCR of the remaining coil is, 4.25k if it's not a mismatched bucker.

You can also see very graphically how UN-SMOOTH the taper is.

Actually, a lower pot value will give you a more gradual taper. Think about it - if the full turn from 1-10 only covers 100k instead of 500k, you can zero in on the useful range. Also, a linear taper pot produces a more useful control over the full range of the pot than a linear taper would.

The downside of the lower value, linear taper pot is that you may never see the full humbucker. That's specifically why I recommended a no-load pot way back when.

Regarding treble loss, the spin-a-split (or dial-a-tap) circuit can be set up so it isn't shorting one coil to ground. If your spin-a-split pot simply shorted black with the red/white series connection, then at "1" (or "10" depending) the slug coil would be shorted out and only the screw coil would be in the circuit.

If you want to split to the slug coil, you can re-wire the humbucker as follows:

white - ground
black & green - series connection & one lead to dial-a-tap
red - hot & other lead to dial-a-tap

I apologize for not having Artie's talent for quick, clean drawings, but am reasonably sure that this works for dial-a-tap. I have re-wired a humbucker this way for different purpose and that part I'm certain about.

FWIW personally, I prefer to split to the screw coil anyway - at least on a Strat because it sounds more like a Strat's bridge single coil would, both by itself and when combined in parallel with the middle pup.

Chip

[BlueGuitar]

The Donald Brosnac book from 1980 mentions the Peavey T-60 using a rotary splitter, which did use a special taper pot. Perhaps you could order one from Peavey.

The Peavey rotary splitter when set to 10 would split the humbucker and when set to 0 was like a treble-cut tone control turned all of the way down. I tried this way back when with less than stellar results, but the real trick seems to be getting a pot with the proper taper for it to work smoothly.

Here's an idea: why not use something like an 12 position rotary switch with fixed resistors? You could design your own taper doing that, so to speak.

[ArtieToo]

The Donald Brosnac book from 1980 mentions the Peavey T-60 using a rotary splitter, which did use a special taper pot. Perhaps you could order one from Peavey.

The Peavey rotary splitter when set to 10 would split the humbucker and when set to 0 was like a treble-cut tone control turned all of the way down. I tried this way back when with less than stellar results, but the real trick seems to be getting a pot with the proper taper for it to work smoothly.

Hey Steve; Peavey did this on several of their guitars. I've got a Peavey Horizon II here right now that I'm rewiring for a friend. Its an HSH configuration with all 5 coils being "rails", and using 1 vol/2 tone. The tone controls are for each humbucker and both do that tone+split function. Both tone pots are standard CTS linear taper 250k's. With the tone pots on "10" you have singles. As you roll the tones down, they morph to humbuckers. It works pretty well.

I can post a schematic of the T-60 wiring if anyone's interested. Although, anyone can download them from Peavey's website also.

Artie

[frankfalbo]

My favorite spin-a-split was a dual pot that I got from Bartolini. I'm pretty sure it was a 500k blend pot. So it had a center detent, with both pots fully on in the center. What I did was to wire from 10-5 as a spin-a-split, and from 5-0 as a tone control. The taper from 10-5 on the spin-a-split was really good. I don't know why, but I have some ideas.

I think that those pots are audio taper "to the center" meaning the one that is from 10-5 would be a reverse-audio taper, since as you go DOWN from 10-5 you are going UP across an audio taper. So maybe try a 500k audio taper pot, but wire it in reverse. So 0 is humbucking, and 10 is tapped. I'm not incinuating that you should leave a spin-a-split reversed, but it would tell you if a reverse audio taper is what you like.

A reverse audio taper gives you way more control over that crucial 3-10 range, where the tone variance and hum levels are greatly interactive. Then 0-2 is pretty much all split, which is okay with me. My center detent pot made it's transition in half the distance, too. So that could have something to do with why I liked it, although you'd think I would prefer a longer travel. Maybe that longer travel is responsible for that wierd 3-7 plateau.

[Mojambo]

So you were still able to get a lot of good blended tones in the 3-10 range? I may have to try that out.

This may be a dumb question, but with a reversed audio taper, could it be made so 10 is humbucking and 0 is tapped?

[JarickL]

Well...you have audio and linear, so try one and if it doesn't work, try the other.

FWIW when I did the "spin-a-split" I found that I either had it on HB or SC full. So I just did the HB/SC thing. And now I think I'll just go with HB's because I don't use the SC at all.

[frankfalbo]

So you were still able to get a lot of good blended tones in the 3-10 range? I may have to try that out.

This may be a dumb question, but with a reversed audio taper, could it be made so 10 is humbucking and 0 is tapped?

Yeah the whole reason you'd use a reverse audio taper is to go 10H/0S. All that stuff I was saying about wiring the pot in reverse (10S/0H) is just so you can experiment with a regular audio taper pot, and see if the reverse one would be good for you. It's an audio taper pot that's backwards. Think of it as a "lefty guitar" volume pot. And that is precisely one of the reasons they make them.

[ratherdashing]

Now that I have a S-A-S in my Strat, I can't say it's a very useful mod to my ears. I've tried it with a FRED and a JB. I have a 500k no-load audio taper pot, and I'm experiencing a similar effect as Zhang: nothing from 10 - 6 then a big step down from there. I think it could work nicely with the right humbucker and pot, but I'll probably switch this guitar back to a good-ol push-pull split.

[Zhangliqun]

Don't get me wrong -- I still very much like the Spin-A-Split, even with the lousy taper. It's just harder to zero in on the sweet spots because they are often right where the big drop-offs are. My current SAS pot is a stock Gibson 300k that was the neck tone pot before. Must be a linear taper...