250k/500k Strat vol pot versus turning down the tone knob

[DreX]

a lot of Strat players avoid 500k vol pots claiming they make their guitar too bright. I've always wondered why they don't just roll off the tone knob a bit and allow themselves the extra brightness, should they ever want it. Someone had said they thought that the there was a difference in tone between using a 250k vol pot, and rolling down the tone knob with a 500k vol pot. That's a hard thing to witness first hand since a Strat only ever has one or the other installed. I'm not interested in proving that person wrong so much as figuring out whether I'm missing out on some awesome warm tones by using 500k vol pots and relying on my tone controls for softening the high end.

To get some data on what the difference might be, I hooked up the wiring with alligator clips, a Lollar Blackflace pickup with a frequency inducer, different tone and vol pots, and I was prepared to try a lot of different capacitors, but what I found using the first cap I tried, a generic .047 uF cap, was that if I swept a 250k vol pot full open, and then swept a 500k vol pot with the tone dial at "8", or 151k ohms of resistance, that the lines overlap completely:

The two overlapping lines on the bottom are the relevant ones, and the other three above just show how much more treble response there is using a 500k vol pot full open, and using 250k or 500k vol pots with no-load tone pots, for even less load attenuation.

This doesn't necessarily mean that there is *no* difference between the two, as an induced frequency sweep test isn't 100% the same as strumming guitar strings, but what it is saying is that for any given inducted frequency of fixed amplitude, the 250k vol, tone @10 / 500k vol, tone @8 deliver the same amount of voltage to the amp. They're pretty dang close, if nothing else.

* edited for clarity

 

[beaubrummels]

Re: 250k/500k Strat vol pot versus turning down the tone knob

A no-load tone pot on 10 should be wire-to-wire bypassing all resistance material, so 500k and 250k no-load should be the same at 10. Something seems incorrect with the graph or somewhere in the test.

 

[DreX]

Re: 250k/500k Strat vol pot versus turning down the tone knob

A no-load tone pot on 10 should be wire-to-wire bypassing all resistance material, so 500k and 250k no-load should be the same at 10. Something seems incorrect with the graph or somewhere in the test.

The test includes both a vol and tone pot, to simulate a Strat in the neck or middle position (but not bridge, or the in betweens) or a 1 vol/1 tone guitar, wired modern (non 50's). The tone pot is no-load in both cases, but the vol pots differ, so the outcomes differ.

 

[blueman335]

Re: 250k/500k Strat vol pot versus turning down the tone knob

As a few members have explained in detail, a 500K pot cannot duplicate how a 250K filters high-end, no matter what it's set on. There is a definite difference between the two. I don't care for the sound of tone pot turned down, and use 250K's on most of my bridge HB's and P-90's. That would be my recommendation. To my ears, I still get a sharp edge on top, but the tone is fattened up.

This allows me to dial in more treble at the amp than I would if I was using 500K's, and that in turn adds clarity and bite to the neck PU.

 

[Archer250]

Re: 250k/500k Strat vol pot versus turning down the tone knob

Hmm... what about 500k with normal 500k tone?

 

[DreX]

Re: 250k/500k Strat vol pot versus turning down the tone knob

As a few members have explained in detail, a 500K pot cannot duplicate how a 250K filters high-end, no matter what it's set on..

I'd love to see that explained in detail, my test results show them to be the same in the context of a frequency sweep. If the real-life performance contradicts what a frequency sweep indicates, I'd love to know how and why, if for no other reason than to modify the test to make the results more relevant and in line with our experience.

 

[blueman335]

Re: 250k/500k Strat vol pot versus turning down the tone knob

I'd love to see that explained in detail, my test results show them to be the same in the context of a frequency sweep. If the real-life performance contradicts what a frequency sweep indicates, I'd love to know how and why, if for no other reason than to modify the test to make the results more relevant and in line with our experience.

They are not the same, I can tell that much with my ears. Almost everyone that says 'they're the same' are guys that don't use 250K's in their bridge PU's, so they've never done a true comparison.

Do a search. I think one of the guys that explained how it works was RayBarbee last year. Another might have been Orpheo a few years ago. There was another who I don't remember off the top of my head.

 

[LesStrat]

Re: 250k/500k Strat vol pot versus turning down the tone knob

Do you have a graph to illustrate that point?

 

[uOpt]

Re: 250k/500k Strat vol pot versus turning down the tone knob

[never mind, though you are talking tone pot, see below now]

 

[uOpt]

Re: 250k/500k Strat vol pot versus turning down the tone knob

Nobody I have ever noticed claims that turning a 500 kOhm volume pot in a passive guitar to where it reads 250 kOhm is the same as using a 250 pot in the first place. It obviously is not if you trace the effective resistance on both sides of the path that the signal takes. There is additional load on the pickup and that lowers the resonance peak.

It is, however, true for the tone pot (as typically wired up in a passive electric guitar).



ETA: also consider that the situation is different depending on whether you wire up the vol pot "forward" like in a Les Paul or "backwards" like in a Jazz bass, with the hot-to-slider so that free mixing with one pickup off is possible in the latter case. The latter case causes even more load.

 

[DreX]

Re: 250k/500k Strat vol pot versus turning down the tone knob

They are not the same, I can tell that much with my ears. Almost everyone that says 'they're the same' are guys that don't use 250K's in their bridge PU's, so they've never done a true comparison.

I just want to point out that you're choosing to refute an objective measurement with subjective anecdotal evidence. I can understand not having 100% faith in an experiment conducted by someone else that you were no present for, but I can't understand having absolute faith ("They are not the same") in the subjective experience of others. Maybe they did have a solid reason for it's different, but it's strange that you would trust those reasons so thoroughly, and yet not remember what the reason was.

Do a search. I think one of the guys that explained how it works was RayBarbee last year. Another might have been Orpheo a few years ago. There was another who I don't remember off the top of my head.

Telling someone to do a search is like asking them to support your own argument. If you don't know off hand, then why are you backing that position to begin with?

I can give you a reason why they are audibly the same, though. .047 is a high value cap for a tone control, it's rare to see anything higher. Where as low value caps retain more mids an attenuate higher frequencies, .047 covers a wide range of frequencies. The attenuation of a 250k vol pot versus a 500k vol pot covers a similarly wide range, the the extent of perfect overlap, as shown by frequency/voltage analysis. If a higher cap is used, such as .022 or less, then the responses are likely to become divergent, since lower value caps will retain more low end than will a 250K vol pot.

 

[DreX]

Re: 250k/500k Strat vol pot versus turning down the tone knob

Nobody I have ever noticed claims that turning a 500 kOhm volume pot in a passive guitar to where it reads 250 kOhm is the same as using a 250 pot in the first place. It obviously is not if you trace the effective resistance on both sides of the path that the signal takes. There is additional load on the pickup and that lowers the resonance peak.

It is, however, true for the tone pot (as typically wired up in a passive electric guitar).

Yeah, I'm not talking about turning the volume down at all, and I understand why that's inherently different. I'm only talking about changing it's overall value.

ETA: also consider that the situation is different depending on whether you wire up the vol pot "forward" like in a Les Paul or "backwards" like in a Jazz bass, with the hot-to-slider so that free mixing with one pickup off is possible in the latter case. The latter case causes even more load.

That may be true, but the 250K/500K debate/issue usually revolves around Strats and JB equipped guitars, so that's all I'm personally invested in.

 

[blueman335]

Re: 250k/500k Strat vol pot versus turning down the tone knob



"Can't you approximate the effect of a 250k pot by just turning down the volume ever so slightly?
"

NO. For two reasons. One, a volume pot is NOT a rheostat. The load the pickup sees to ground does not change. It is wired to the hot lug, and the hot lug is not soldered to the wiper as it would be in a rheostat. Second, when you turn a pot down, it introduces a series resistance into the equation, i.e. the resistance between the hot lug and the wiper. So when you turn a 500k pot down to about 7.5, which if it's an audio pot would be about 250k from wiper to ground, the pickup still sees 500k, and there is a 250k resistor now in series with your pickup's output on the way to the amp. Not at all the same as a 250k pot turned up all the way.

I use various resistors across pots which I have measured to get a resistance I want. That goes from about 200k all the way up to 1M or more. Various pickups in various guitars sound better with different resistances. PAFs to my ear generally sound like icepicks with anything approaching 500k. 225-300k works much better. JB? Most guitars like them between 250 and 400k. Hotter, darker pickups generally need closer to an actual 500k MEASURED resistance (not just the number on the casing which means F all). On neck humbuckers, I use 1M religiously unless they are unusual types like 40ga wire, firebirds, etc.

So, since I've actually done this more times than I can count, including wiring guitars so each pickup selector switch position sees a different resistance, I'm NOT asking whether anyone thinks it's "ok" to do that.


This is from Ray Barbee on pot values.

 

[DreX]

Re: 250k/500k Strat vol pot versus turning down the tone knob

"Can't you approximate the effect of a 250k pot by just turning down the volume ever so slightly?
"

NO. For two reasons. One, a volume pot is NOT a rheostat. The load the pickup sees to ground does not change. It is wired to the hot lug, and the hot lug is not soldered to the wiper as it would be in a rheostat. Second, when you turn a pot down, it introduces a series resistance into the equation, i.e. the resistance between the hot lug and the wiper. So when you turn a 500k pot down to about 7.5, which if it's an audio pot would be about 250k from wiper to ground, the pickup still sees 500k, and there is a 250k resistor now in series with your pickup's output on the way to the amp. Not at all the same as a 250k pot turned up all the way.

I use various resistors across pots which I have measured to get a resistance I want. That goes from about 200k all the way up to 1M or more. Various pickups in various guitars sound better with different resistances. PAFs to my ear generally sound like icepicks with anything approaching 500k. 225-300k works much better. JB? Most guitars like them between 250 and 400k. Hotter, darker pickups generally need closer to an actual 500k MEASURED resistance (not just the number on the casing which means F all). On neck humbuckers, I use 1M religiously unless they are unusual types like 40ga wire, firebirds, etc.

So, since I've actually done this more times than I can count, including wiring guitars so each pickup selector switch position sees a different resistance, I'm NOT asking whether anyone thinks it's "ok" to do that.


This is from Ray Barbee on pot values.

OK, this is a difference scenario. This is asking "what if I just turn down the volume pot?" and what I tested above is "what if I just turn down the tone knob?". In the scenario this thread is addressing, the vol stay at 10 and the tone pot moves, so that explanation isn't applicable to this.

The other thing is that this explanation also only talks about the difference in terms of schematics, it's very possible to get the same tonal outcome with two different schematics, which is what I submit is happening with the tone pot @8 versus a 250k vol/250 tone; two paths to the same place. So even with respect to that other issue, the fact that the schematic is different doesn't even necessarily prove there would be an audible or measurable difference. Maybe that's something to test next.

 

[uOpt]

Re: 250k/500k Strat vol pot versus turning down the tone knob

Yeah, I'm not talking about turning the volume down at all, and I understand why that's inherently different. I'm only talking about changing it's overall value.

Uh? From your OP:

"Someone had said they thought that the there was a difference in tone between using a 250k vol pot, and rolling down the tone with a 500k vol pot. That's a hard thing to witness first hand since a Strat only ever has one or the other installed."

What kind of rolling down are you talking about then? I read that as rolling down a 500k vol pot to where it reads 250 and expect the same sound as 250. What else did you have in mind?

 

[DreX]

Re: 250k/500k Strat vol pot versus turning down the tone knob

I'll word that more explicitly, " rolling down the tone pot with a 500k vol pot".

 

[uOpt]

Re: 250k/500k Strat vol pot versus turning down the tone knob

" rolling down the tone with a 500k vol pot"

I have no idea what that is supposed to me. Are you talking about "tone" as in "tone pot" or "tone the abstract concept" now?

 

[DreX]

Re: 250k/500k Strat vol pot versus turning down the tone knob

Sorry.. the "tone pot" itself.

 

[uOpt]

Re: 250k/500k Strat vol pot versus turning down the tone knob

So you are talking about the tone pot, not the vol pot, the whole time?

 

[DreX]

Re: 250k/500k Strat vol pot versus turning down the tone knob

So you are talking about the tone pot, not the vol pot, the whole time?

The scenario involves both, bot only the tone pot is dialed differently, so to restate the two test cases which I found to produce the same output amplitude for a given input amplitude at all tested frequencies:

case A) 250k vol pot turned up to 10, 250k tone pot with a .047 uF cap, turned up to 10

and

case B) 500k vol pot turned up to 10, 250k tone pot with a .047 uF, cap turned up to 8