Pots...am I too anal, orrr.......

[SGD Lutherie]

So what is a linear pot going to give me? A curve that differs in detail but is no better or worse overall.

I'm not Walter, and I don't play him on TV, but here's audio vs. linear taper curves:

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You can see that when the pot is on 5, a linear taper gives you an attenuation of 50%. The audio taper gives you an attenuation of about 90%. That means most of the action on an audio taper pot happens on the last 10% of the rotation.

When would you ever want 90% of your signal attenuated? That gives you a very small area to use to mix two pickups.

If anything, I might prefer a reverse audio taper to an audio taper, as the attenuation is more gradual. If your volume controls didn't turn the pickup all the way off, you would have a much better experience mixing the two pickups, as it would allow more travel of the pot before it did as much.

This is why the ungrounded blend pot often works better. I think the ideal situation would be to have a pickup switch, for when you want to solo a pickup, and then when they are both on, a blend that does very little, and just changes the weight of one to the other somewhat.

The best option is a fully buffered active mixer. Then you don't have the situation where you turn down the neck pickup a little bit and it's gone.

 

[walterw]

This is why the ungrounded blend pot often works better. I think the ideal situation would be to have a pickup switch, for when you want to solo a pickup, and then when they are both on, a blend that does very little, and just changes the weight of one to the other somewhat.

i tried cutting the traces of a 250k m/n "no-load" style, so that when turned all the way over, it actually disconnected the "off" pickup entirely.

that trick worked fine; it made me want to find a 100k m/n pot and cut it the same way, so that the blending was smooth and subtle, but when the pot was turned all the way, it still switched out the "off" pickup.

 

[SGD Lutherie]

i tried cutting the traces of a 250k m/n "no-load" style, so that when turned all the way over, it actually disconnected the "off" pickup entirely.

that trick worked fine; it made me want to find a 100k m/n pot and cut it the same way, so that the blending was smooth and subtle, but when the pot was turned all the way, it still switched out the "off" pickup.

That's a cool idea. With 500k blends the pickup is almost off, but the blending action is not as smooth as 250ks when they are ungrounded.

 

[walterw]

I'm not Walter, and I don't play him on TV,

quicked-canceled show ever

here's audio vs. linear taper curves:

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You can see that when the pot is on 5, a linear taper gives you an attenuation of 50%. The audio taper gives you an attenuation of about 90%. That means most of the action on an audio taper pot happens on the last 10% of the rotation.

When would you ever want 90% of your signal attenuated? That gives you a very small area to use to mix two pickups.

like khutch pointed out, we all know that audio "curve" is really a two-segment pair of linear lines, but it works close enough to the same way.

it does indeed suck for mixing at the top of the range, but it's perfect for guitars through compressed, crunchy tube amps.

If anything, I might prefer a reverse audio taper to an audio taper, as the attenuation is more gradual. If your volume controls didn't turn the pickup all the way off, you would have a much better experience mixing the two pickups, as it would allow more travel of the pot before it did as much.

hmm...

a pair of ungrounded say, 100k reverse audio volumes, with the traces cut to disconnect the pickup at "0"?

swells from off would be out the window, but you'd have really nice mixing control at full-up.

 

[khutch]

I'm not Walter, and I don't play him on TV, but here's audio vs. linear taper curves:

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Yes, I think most of us who are still posting on this know that already. The curves above neglect two things though: 1) the non-linear response of the human auditory system, 2) when the volume pot is loaded down by the pickup resistance, tone control resistance, amplifier input resistance, etc, the results change and they change considerably in a VVT arrangement where the pots are typically used backwards of the normal arrangement.

So, picture your curves above but add a second dotted line just like the one you have but bowed up instead of down. With all the factors above considered (except that audio pots are bilinear instead of true audio tapers) the bottom dotted line is roughly how an audio taper pot responds in a VT single pickup bass and the top dotted line is how a linear taper pot responds in the same bass. The solid line is, in theory, how we would like the pots to respond. Neither one is ideal, both are close enough to please at least some people. A linear pot responds too quickly at low volumes and too slowly at high volumes. The common 10% bilnear "audio taper" pot responds too slowly at low volumes and too quickly at high volumes. A 30% bilinear taper pot is a little hard to find though they exist and gives a response that is reasonably close to the ideal line throughout its range. Some claim that years ago "guitars" (basses too?) used 30% bilnear pots.

If you want to consider a VVT setup then nothing works "right". The ultimate response of the perceived loudness to pot position is determined much more by the loads on the pots than by the tapers of the pots. All pot tapers follow the same curve in a VVT setup with only minor variation from taper to taper to taper. It is impossible to get a linear response in a VVT setup because the pot taper required to do that changes with every one of the infinite possible settings of the other V pot, and the tone pot, and the note you are currently playing on your bass. The pot tapers required are also very bizarre and totally unavailable on the market. Eh, for all that VVT basses work just fine, don't they, which is an indication that as fun as it is to talk about this the ear just isn't that picky about it.

Now Walter will only consider the results of actual experiments. I have not tried them but I have found the comments of others that say they tried linear pots and found them to have exactly the response that theory predicts. Actually guitarists who like linear pots are as common as bassists, contrary to what Walter maintains. The truth is that there are plenty of guitarists and bassists who prefer audio pots and plenty of both who prefer linear pots. Theory, my friends, is completely adequate to predict what is going to happen with a particular pot taper, it is totally inadequate to predict what you personally like.

So I say it again, for a person like myself who is perfectly happy with his audio taper pots, there is neither need nor benefit to tearing his bass apart and putting in linears just to satisfy Walter. I can see from theory what a linear taper pot will do, I just see no need to go there. Guys, I typically set my volume pot once per session and often once every few sessions. I would not get any benefit from a linear taper even if I hated the response I get from an audio taper.

From the brief internet survey I have now done it appears that most guitarists who love linear tapers also love to do "volume swells" and it is perfectly plain, from theory, why a linear pot would be ideal for that purpose. An audio taper would be the worst.

Finally I had a sad realization this morning. I sincerely hope that for most of you who prefer linear tapers that your preference is simply that, a preference, and not a result of what I am going to say next. People who have had hearing damage from operating jackhammers or playing their bass guitars in loud bands, to name but two, have hearing that responds much like a normal persons at middle to high volumes. At low volumes their hearing starts to depart from the norm and at a volume well above where a normal person still hears well they hear nothing. So a linear volume pot which increases very quickly at low volumes is going to seem quite linear to a hearing impaired person. I hate to think that any of you have that problem but I know that not everyone is careful of their hearing.

Ken

 

[SGD Lutherie]

1) the non-linear response of the human auditory system

But that's relative. And when you are mixing two pickups, it's assumed one is probably on 10, so a log response from the pots does not work well because you are attenuating one pickup while the other is not, and the attenuation drops off too quickly. Once you are past 8 your pickup is no longer heard with a typical 10/90 log taper. 20/80 or 30/70 might work better, but good luck finding them.

2) when the volume pot is loaded down by the pickup resistance, tone control resistance, amplifier input resistance, etc, the results change and they change considerably in a VVT arrangement where the pots are typically used backwards of the normal arrangement.

And this is another reason why linear works better. The loading accentuates the drop off in volume from the attenuated pickup.

As I pointed out, the newer M/N blend pots are linear by nature because that works better than the older A/C blend pots.

So the potentiometer companies have figured out that linear tapers work best for pickup blending and have started making all the blend pots that way.