volume pot questions

[GoDrex]

I have some questions about volume pots.

I like the sound I get when I turn the volume pot on my guitars to about 9 or so. Just a hair. Is that like using a slightly lower value pot?

Also when I'm playing loudly I notice more hum when I turn the volume down. The background noise is much quieter when the volume on the guitar is up all the way. Is that normal?

And anyone else notice some slight scratchiness just below fully turned up? Like between 10 and 9 there's a little area that that makes a slight noise when you turn it.

 

[MUYFUE]

I also turn down to 8 or 9 and like the sound. For my style, it helps clean things up and takes off some of the edge.

From your description, it sounds like the pot may have some corrosion. Every once in a while I give my pots a good cleaning and it helps them stay quiet. If that doesn't help, there may be some little metal filings or a stray wire, maybe even some damage...

What I like about pots is that worst case scenario, I just replace 'em.  :icon_thumright:

 

[jimh]

What is your pot and pickup combination?

Essentially, if you had for example, a 500k pot turned down to 8, it might be the equivalent of a 450kpot fully up. This would just knock off the very high end frequencies to darken the tone a fraction, assuming you're not using a treble bleed network.

Some single coil sets are wired to buck hum in the 2 and 4 positions. It's also possible to wire a blend pot for a 4 conductor humbucker to allow you to blend from a single coil to full humbucker.  I've seen the circuit for this somewhere, for this, but I've never done it myself.
If you've got independent volume for each pup (or a blend in the above humbucker scenario), then as you wind the level of one pickup down they get a very slight phase mismatch between the coils which would allow some of the hum to creep back into the signal.

Have you got your pups wired correctly? (i'm not doubting you by the way, I'm just checking  :icon_thumright

Also, if you imagine that you have a pot turned down, what you are doing is diverting a small portion of the signal away to ground, whilst the rest of the signal flows to the signal chain.  Well....looking at it from the other direction, by turning the pot down you've created a connection from ground to your signal chain thus allowing some of the ground to 'see' your signal chain.  Therefore if you've got a noisy ground, then a small portion of that noise will get into the signal chain and get amplified.

I don't have any scratchiness in my new CTS pots in my LP (that I've noticed) although, theres a big scratchy patch in the middle of the Gibson own brand neck vol pot on my ES137.
You dont have 'no load' pots do you?  It could be where the switch occurs between true-bypass when the pot is fully up, and then where the wiper hits the track of the pot as you turn it down?


Just my thoughts.

Jim

 

[GoDrex]

ok - I just figured out that the hum when I lower the guitar volume is coming from my pedals - so I'll have to figure out out why one of these days.

the slight scratchy sound only happens on some pots and not all - on different guitars. some are brand new, some are not so new - none are very old though.

 

[line6man]

Essentially, if you had for example, a 500k pot turned down to 8, it might be the equivalent of a 450kpot fully up. This would just knock off the very high end frequencies to darken the tone a fraction, assuming you're not using a treble bleed network.

If you are using an audio taper pot, "8" should be about 250K.

 

[blue313]

the slight scratchy sound only happens on some pots and not all - on different guitars. some are brand new, some are not so new - none are very old though.

Pots can sit in open bins in the warehouse or at the resellers.  All kinds of funk can get in there.  Even brand new pots should be flushed out.

 

[MUYFUE]

Say this in the Foghorn Leghorn voice!

From your description, it sounds like the pot may have some corrosion. Every once in a while I give my pots a good cleaning (I say a good cleaning!) and it helps them stay quiet. If that doesn't help, there may be some little metal filings or a stray wire, maybe even some damage...

 

[-CB-]

There are two ways to wire up a volume pot on a guitar.

One way is end-fed, where the pickup goes into one end of the pot, and the wiper is the output.  The other end of the pot is grounded.  In this arrangement, the load on the pickup remains fairly constant - and very close to the load presented by the pot itself, because the input load on most amps is anyplace from 1meg to 10 meg ohms.  Les Paul's (and similar) and most Fender guitars are wired this way.

The other way is center fed, where the pickup is wired to the wiper, and the output is one end of the pot.  The other end is grounded.  In this arrangement, you're changing the load on the pickup as you rotate the wiper.  In essence, you ground out the source (the pickup) rather than ground out the output in this arrangement.  This will result in fairly large tone changes, and much greater interaction with the tone pots.  Jazz Basses are wired this way - it allow greater "blending" of the two pickups, and turning one to zero doesn't alter the volume of the remaining pickup (or alter it very much).  Some folks will alter their guitars to behave like this.

So to answer your question - it depends.