Switchable value pot?

[Boston Joe]

So I had this idea, and I'd love for someone to tell me whether or not this would work.

Say you had a guitar with pot values of 500K. Could you put a 250K resistor in parallel with the volume pot, and effectively get a 250K pot? If so, could you then put a switch in there, so that you could switch your volume control from 250K to 500K? Would this have the effect of creating a "tone shift" switch?

Thanks in advance,
Joe

 

[swarfrat]

No, but you could use a 500k dual ganged pot, and wire them in parallel, connected with a switch. 

Handy reading for the curious.
http://www.geofex.com/Article_Folders/potsecrets/potscret.htm

 

[Verne Bunsen]

Parallel resistance calculations being what they are [ (R1xR2)/(R1+R2) ], you'd actually want a 500k resistor (more likely a 470k) resistor in parallel with your 500k pot to achieve 250k. A 250k resistor would give you something like 166k. This is certainly do-able and is often utilized when mixing single coils and humbuckers. My Tele Special (single coil bridge, humbucker neck) uses 500k pots with a 470k resistor that is attached to the bridge pickup at the selector switch, works great. Have at it!

 

[swarfrat]

Yeah but it'll screw up the taper to parallel it with a fixed resistor.

 

[Verne Bunsen]

It does introduce a deviation that increases as you approach zero, but in my experience it's a much bigger deal on the meter than it is in application. I'm a very volume-control-intensive player myself and have never found myself having to think differently about what I do on a circuit set up like this. I still have to say 'Have at it!"

 

[Boston Joe]

Right. Yeah. I meant a 500K resistor. Need more coffee.

Parallel resistance calculations being what they are [ (R1xR2)/(R1+R2) ], you'd actually want a 500k resistor (more likely a 470k) resistor in parallel with your 500k pot to achieve 250k. A 250k resistor would give you something like 166k. This is certainly do-able and is often utilized when mixing single coils and humbuckers. My Tele Special (single coil bridge, humbucker neck) uses 500k pots with a 470k resistor that is attached to the bridge pickup at the selector switch, works great. Have at it!

 

[BigSteve22]

I actually did this on my Jazzmaster. I used a 500K fixed resistor in parallel with a 500K push-pull pot so I can switch between a 500K and 250K settings. It does change the response of the tone circuit, (read taper), but not so much as you'd really notice.

As a point of information, I used this set up with SD P-Rail pups. I also wired a second tone cap in parallel with the main cap, also on a push-pull setup. It was a lot of work to get things soldered up neatly and make the extra components fit, and everything works as planned. But what I don't see is a lot of difference either way. I was a great experiment but, IMHO, not worth the extra work.

Keep us posted with your progress!  :icon_thumright:

 

[JD0x0]

Seems like a lot of work for very little tonal change. I'd just use the higher value pots and then use the tone control to dial in the resonant peak to where you want it. If you want it switchable on the fly, you could then just put the tone control on a switch. Bypass it for the brighter sound, and activate it for your (dialed in) warmer sound.

Rolling the tone control back slightly will tame the resonant peak in the same way a 250K pot on '10' would. For this reason I pretty much inherently use 500k controls or higher and I've never been unhappy with the results. I also tend to use lower value tone caps (usually under 10nF) to give a finer control to the high end with less of the muffled muddiness when the control is rolled back significantly. To me, this makes the tone control much more usable with just about any pickup.

 

[Cagey]

Perzactly.

 

[Boston Joe]

It does change the response of the tone circuit, (read taper), but not so much as you'd really notice.

Ah, okay. This is the sort of info I was looking for. One of my amps has a "mid shift" button that changes the way the tone stack works, and I thought I might be able to do something similar here, but I guess not.

So now the question: 500K or 250K pots? I'm doing P-90s and I'm going for a fairly dark, jazz-friendly voice.

 

[Verne Bunsen]

I like 500ks with the P90s in my Les Paul.

 

[Boston Joe]

I like 500ks with the P90s in my Les Paul.

Do you normally use a fairly bright tone?

 

[Verne Bunsen]

I like 500ks with the P90s in my Les Paul.

Do you normally use a fairly bright tone?

Not for that guitar, definitely warmer/darker tones. I do use the controls on the guitar a lot and don't hesitate to have the volume and tone knocked back a bit to get where I want. This is a track I recorded a while back with the guitar in question, Lollar P90s, 500ks. It's by no means a demonstration of the pots, but it might give you some kind of a reference point that is of value...

https://soundcloud.com/vb-tunes/autumn-leaves

 

[Boston Joe]

I like 500ks with the P90s in my Les Paul.

Do you normally use a fairly bright tone?

Not for that guitar, definitely warmer/darker tones. I do use the controls on the guitar a lot and don't hesitate to have the volume and tone knocked back a bit to get where I want. This is a track I recorded a while back with the guitar in question, Lollar P90s, 500ks. It's by no means a demonstration of the pots, but it might give you some kind of a reference point that is of value...

[soundcloud]vb-tunes/autumn-leaves[/soundcloud]

The link appears to be broken, but I tracked it down.

That's a fantastic sounding guitar! Pretty decent playing too! Strong data point in favor of 500s.

 

[Verne Bunsen]

The link appears to be broken, but I tracked it down.

That's a fantastic sounding guitar! Pretty decent playing too! Strong data point in favor of 500s.

Thanks! Glad you found it helpful. It is a great guitar and I strive to be worthy of it  :icon_biggrin:  I replaced the link, thought I had the player feature figured out but I guess not....

 

[Boston Joe]

The link appears to be broken, but I tracked it down.

That's a fantastic sounding guitar! Pretty decent playing too! Strong data point in favor of 500s.

Thanks! Glad you found it helpful. It is a great guitar and I strive to be worthy of it  :icon_biggrin:  I replaced the link, thought I had the player feature figured out but I guess not....

A good Les Paul is a treasure. I've never owned one, but I've played a few beauties.

 

[lafromla1]

What about using a TBX tone control?

 

[swarfrat]

I put a TBX in my GOM strat. I like it. It's just subtle enough that all the way either direction is noticeable but never unusable.