1Meg Ohm Volume Pots and swells

[Butch Snyder]

All,

I just installed a 1 Meg Ohm audio taper pot in my T-style guitar. Let me go through the set up.

Alder body, maple neck/fretboard
Duncan (SM-1) 59 humbucker in the neck position
Fender Tex Mex Strat pickup in the middle position
Duncan Little 59 Tele bridge pickup in the bridge position.

I have the guitar wired like a Strat, with a 5-way blade switch. I have a 1 Meg Ohm audio taper pot for the volume and no tone pot. Wiring seemed to be okay; but I'm noticing a strange thing with the volume pot. Seems I can turn in up and it sounds ok. Then, when the pot gets all the way up, the volume increases quite a bit. Not really a result that I want. Anyone have any thoughts about this?

 

[ItsaBass]

Re: 1Meg Ohm Volume Pots and swells

Try linear taper instead. IME, audio taper pots act that way. That's why I dislike them. There is so much change crammed into the very upper area of the pot's rotation; it's too sensitive up there. Meanwhile, the rest of the pot is less sensitive. The fact that it is 1M is just exacerbating this characteristic, by making full-up brighter than with 500K or 250K. Linear taper allows very fine adjustments in the upper range, which I highly prefer.

 

[SoPhx]

Re: 1Meg Ohm Volume Pots and swells

Ummm, guitar builders figured this out in the 1940s----you want a reverse audio pot.

 

[Clint 55]

Re: 1Meg Ohm Volume Pots and swells

Audio sux for volume.

 

[Downrazor11]

Re: 1Meg Ohm Volume Pots and swells

...Then, when the pot gets all the way up, the volume increases quite a bit. Not really a result that I want. Anyone have any thoughts about this?

Not to double-check your work, but are you sure that you put in an Audio taper pot (also called LOG, companies often use the letter "A" in their product numbers to designate (xx...253A for example)), and not a Linear taper (often with a "B" letter designation (xx...253B))?

.. Here is a discussion covering that:
Audio Taper vs. Linear Taper

Choosing audio (log) vs. linear depends on what you will be using the pot for. You should always use audio pots for volume control, otherwise you will find that the volume does not change smoothly as you turn the pot up and down. With a linear taper pot, you will find that the volume increases slowly from 0 to about 60 or 70 percent, then increases rapidly from that point on. This is because there isn't a direct relationship between resistance and volume in a passive circuit (which is what a guitar with passive pickups is). Audio taper pots compensate for this, and give you a consistent volume change throughout the sweep.

A tone control, on the other hand, works best with a linear taper pot. The role of a tone control is to feed part of your signal to a capacitor that bleeds the treble to ground. In order to have a smooth transition from bright tone to mellow tone, the pot has to be linear. You can use an audio taper pot in a tone control, but you won't find the tone roll-off to be as smooth as it could be....

EDIT: Correction posted below.

 

[Clint 55]

Re: 1Meg Ohm Volume Pots and swells

^ Wat are you talking about. Audio turns up more slowly and down more quickly not linear.

 

[GuitarDoc]

Re: 1Meg Ohm Volume Pots and swells

Ummm, guitar builders figured this out in the 1940s----you want a reverse audio pot.

No.

 

[Butch Snyder]

Re: 1Meg Ohm Volume Pots and swells

Thanks for the replies guys. I removed the pot, which is indeed an audio taper. I bought an audio taper because my guitars have always come with them installed from the factory. I'm reinstalling the Fender Vintage Noiseless set with the control assembly that came with them - 1 Meg Ohm audio taper vol/tone pots.

 

[Artie]

Re: 1Meg Ohm Volume Pots and swells

Hey Butch. Long time, no see.

I wonder if it might be because of using a 1 meg pot? With an audio taper, you'd be close to 500k close to the end. The, as you went to the end, you'd have a virtual no-load pot. Just morning speculation.

Btw, the SM-1 is a mini-humbucker. The SH-1 is the 59.

 

[Downrazor11]

Re: 1Meg Ohm Volume Pots and swells

^ Wat are you talking about. Audio turns up more slowly and down more quickly not linear.

Thank you for the kind correction, it seems the post I cited was incorrect and my analytical reasoning skills are rusty..
This is a chart from Bourns' PDB181GTR line of pots:



So.. possibly the curve of the audio pot was more "backwards-L" shaped as opposed to the "half a parabola" it was supposed to be..

FWIW, I almost exclusively use pots that utilizing conductive plastic instead of carbon traces as I find them to be way more consistent in both curve and specified resistance..

 

[Clint 55]

Re: 1Meg Ohm Volume Pots and swells

Thank you for the kind correction

lol

 

[devastone]

Re: 1Meg Ohm Volume Pots and swells

^ Wat are you talking about. Audio turns up more slowly and down more quickly not linear.

That's the way audio is percieved, hence why it is called "audio" taper. Hearing is not linear, and yes, volume pots should be audio taper so they seem to function more linearly.

 

[Clint 55]

Re: 1Meg Ohm Volume Pots and swells

AUDIO SUX FOR VOLUME

 

[devastone]

Re: 1Meg Ohm Volume Pots and swells

"wat"?, just because you like it better doesn't mean it "sux" I couldn't tell you "wat" is in my guitars right now, pretty sure the one in my Solo Custom is linear, it comes on way too fast.

Unfortunately I don't have useful info for the OP so I'll check out. Seems like 1M pots with single coils would be almost painfully bright, IIRC the lil' 59 (and all the single size hbs) were designed to work with 250K pots so they could be direct drop ins.

 

[Jacew]

Re: 1Meg Ohm Volume Pots and swells

^ Wat are you talking about. Audio turns up more slowly and down more quickly not linear.

Exactly. I've never managed to get audio taper work for me. Way too sensitive.

 

[Jacew]

Re: 1Meg Ohm Volume Pots and swells

That's the way audio is percieved, hence why it is called "audio" taper. Hearing is not linear, and yes, volume pots should be audio taper so they seem to function more linearly.

Does the audio pot need to be wired the modern way? Because I always wire pickup to wiper, and for me audio never works correctly. It's way too quick drop from 10 to 9 or 8.

Linear drops volume much smoother and slower. With half volume being where it should be; around halfway.

 

[devastone]

Re: 1Meg Ohm Volume Pots and swells

Does the audio pot need to be wired the modern way? Because I always wire pickup to wiper, and for me audio never works correctly. It's way too quick drop from 10 to 9 or 8.

Linear drops volume much smoother and slower. With half volume being where it should be; around halfway.

You have me questioning myself. The guitars I have now still have the stock pots in them. The Solo Custom comes on way too fast from zero, pretty sure it is a linear pot but I could be wrong. I guess a lot of it is personal preference too, as long as it's on 10 when it's all the way up, other than that I like to have have more movement adjustment in the "cleaner' range below ~5 or so, I don't like to have to have a small adjustment range to have to feel for. Same thing with old Marshalls (JCM800s and earlier), where 3/10 is pretty much full volume. When I got my first JCM900 I didn't think it was as loud as the 800, but the volume pot just had a better taper and you actually had to turn it up more to get the same volume.

As far as wiring, I think I usually have the middle lug going to the output jack, but it's been a while. Not sure what "modern" wiring is, sorry.

 

[Jacew]

Re: 1Meg Ohm Volume Pots and swells

You have me questioning myself. The guitars I have now still have the stock pots in them. The Solo Custom comes on way too fast from zero, pretty sure it is a linear pot but I could be wrong. I guess a lot of it is personal preference too, as long as it's on 10 when it's all the way up, other than that I like to have have more movement adjustment in the "cleaner' range below ~5 or so, I don't like to have to have a small adjustment range to have to feel for. Same thing with old Marshalls (JCM800s and earlier), where 3/10 is pretty much full volume. When I got my first JCM900 I didn't think it was as loud as the 800, but the volume pot just had a better taper and you actually had to turn it up more to get the same volume.

As far as wiring, I think I usually have the middle lug going to the output jack, but it's been a while. Not sure what "modern" wiring is, sorry.

With "modern wiring" I was just referring to the usual way of wiring output in the middle.

My partscaster currently has log pots in it. Gain falls really quickly turning the volume down. It's probably halfway around 8.

I might try to first switch the output and pickup wires just to check how it differs before switching to linear. I like to have separate volumes so I can blend pickups.

 

[Zombiwoof]

Re: 1Meg Ohm Volume Pots and swells

What is needed is a pot with a vintage audio taper, which many of the modern custom taper audio pots are trying to achieve. There are different audio tapers, and the pots in vintage guitars had an audio taper that was more gradual. There are a bunch of these custom taper pots on the market, try those to get a better taper for volume swells and such. I don't think you'll get it with linear, that's what has come in many Gibson guitars for volume pots for many years, and they do almost nothing from 10 down to around 2 or so, and then abruptly cut off.
Al