If i parallel a 82k resistor with a 25k linear pot....

[daz]

Now that you mention it, i didn't even think about that. So it looks like it's good to go because the degree of difference isn't crazy and that's all i was worried about. Don't much care if a certain position now has to be a couple numbers away, only that the end of travel and beginning are the same and that theres no insane degree of taper change like everything happens between 1 and 3 and after that it doesn't change much. Thanks Juan.

So ?????????

The calculation you made shows two resistors in parallel, in this case a fixed one ... and another fixed one, since you are taking end to end track resistance.

Might do if you want to compare a a 20k pot set on 10 with a 25k pot, set on 10 , but with an 82k resistor in parallel .
At any other setting from 1 to 9 they will not be the same, hence my comment.

But a potentiometer is not a fixed resistor , itīs a variable one , and obviously you need a pot there or would simply use a fixed 20k resistor there and call it a day.

Do we agree so far?

So, IF adjustment is implied, letīs see what we have at different settings, and see whether they are the same or not.

Many Math problems include something called "the trivial solution", (trivial as in "silly") ,what we might call the "duh???" solution in everyday language, the one youīll say about: "hey dude , is it a joke? I already knew that!!! it does not help me" ... yet you can not say itīs *wrong* , it IS a solution even if nothing new.
As in: "what tube does replace a 6L6 and works exactly the same?"
Trivial solution: "another 6L6" .

Here both solutions match perfectly ... at 2 settings and those settings only, so they might be called "trivial solutions" to your doubt.:
a) both match on 10 , you just did the Math , both have 20k total. (wonīt complain about the tiny difference, thatīs not the point here)
b) both match on 0 ... both show 0 ohms.

so far so good, but itīs an adjustable control, what will happen if we set it to numbers different from "trivial solutions" at 0 and 10?

Ok, we might do it at every setting from 0 to 10 but to simplify letīs split the difference and calculate at 5.
You can repeat it at all other values ifnyou wish.

* A 20 k pot set to 5 will show 10k , period.

* A 25k pot, set to 5, and with an 82 k resistor soldered end to end, will show:
10 k (half track)- in parallel with - 10k (the other half track) in series with 82k=9k

Not the same. (hence my comment).

[R.G.]

Well, it's like this. I am using it as a presence and i found that i like the sound various points down to 20k resistance and don't like what happens lower than that, plus i want the end of the pot's throw to be that point i like so i don't have to guess at it and make sure it's pointed right where i like it. I can just turn it all the way down. But i DO also like to add more highs so i DO use it brighter too. I just want the sweet spot to be the stop point on the knob and a 82k across a 25kpot will yield the 220k where i like it at the end of it's travel. I might string a few together depending on the pot's actual value (haven't gotten it yet) to get exactly 20k.

Ah! That makes perfect sense! You want a stop/limit on a pot used as a tone control.

I can do better than this if I know the exact circuit, but I think you want a fixed resistor in series with a pot, not a paralleled resistor. Can you point me to an example schematic?

[daz]

Ah! That makes perfect sense! You want a stop/limit on a pot used as a tone control.

I can do better than this if I know the exact circuit, but I think you want a fixed resistor in series with a pot, not a paralleled resistor. Can you point me to an example schematic?

That could work but I'd need a 10k pot and it would give me a shorter range, plus i already ordered a 25k.

[R.G.]

That could work but I'd need a 10k pot and it would give me a shorter range, plus i already ordered a 25k.

I still don't understand what you're doing in the circuit, so I have no clue what will and won't work, I'm just guessing based on your posts.

PLEASE point to a schematic with a similar resistance/pot and I can do a much better job of helping.

[tubeswell]

I recently got stuck for a 25k pot in a home brewed amp vibrochamp style tremolo depth control. I took a 1M pot and put two 27k tapering resistors across it (one from the hot to wiper, and the other from the wiper to cold). It changed the pot taper but also changed the overall pot load. You either get a 26.3k load with the pot dimed or cut all the way, and at half rotation you get a 50k load. The taper is a bit skew wiff, but it works at a pinch because its only a trem depth pot, and in the vibrochamp trem circuit, the only parts of the pot rotation that really matter are at either end, and the trem sounds good 8-)

[Chuck H]

Something to note is that this pot is being used in a presence circuit. Which means it becomes part of the shunt for the NFB loop. Depending on how it's wired there may be tonal changes that affect the sound of the amp regardless of pot setting or it's taper.

[daz]

Something to note is that this pot is being used in a presence circuit. Which means it becomes part of the shunt for the NFB loop. Depending on how it's wired there may be tonal changes that affect the sound of the amp regardless of pot setting or it's taper.

This i don't understand. I can see it affecting the taper, but the tone? I mean, it's just being used as a variable resistor with a certain resistance at one and and a dead short at the other. facing in the back of the pot i'm using the center and right lug. Variable resistor. So i can see the taper changing but how could it affect tone?

[R.G.]

It affects tone because the capacitors in the circuit around it change the amp's frequency response with different amounts of feedback, and that depends on the resistor.

Can you PLEASE post a schematic, or even a pointer to a similar schematic on the web? I could actually tell you something that makes sense then. We're all throwing darts in the dark until that happens.

For instance - knowing that you're only using two of the three pot terminals is important. It means that the stuff I said about a series resistor giving you what you want is now extremely pertinent. If you were using all three pot terminals, the advice about an 82K across the whole pot is pertinent.

We can be a lot more help to you if we know what you're doing. Otherwise, the advice "spread cream cheese on it" is as good as any other.

[daz]

It affects tone because the capacitors in the circuit around it change the amp's frequency response with different amounts of feedback, and that depends on the resistor.

Can you PLEASE post a schematic, or even a pointer to a similar schematic on the web? I could actually tell you something that makes sense then. We're all throwing darts in the dark until that happens.

For instance - knowing that you're only using two of the three pot terminals is important. It means that the stuff I said about a series resistor giving you what you want is now extremely pertinent. If you were using all three pot terminals, the advice about an 82K across the whole pot is pertinent.

We can be a lot more help to you if we know what you're doing. Otherwise, the advice "spread cream cheese on it" is as good as any other.

[Chuck H]

Daz
If that's your circuit then the absolute only difference between a 25k pot and a 20k pot is that there will a tiny (and I mean tiny) amount less presence with the presence control at zero. With a 25k pot the presence control "looks" the same electronically to the circuit between 2 and 10 as it would with a 20k pot between 0 and 10. Knob setting will be slightly different. No matter what you think you hear there cannot be any tonal difference between a 20k and a 25k pot in this circuit except that the 25k pot is capable of turning the presence down a pinch more. If you don't want the presence down that low (I doubt you could actually hear it) simply don't turn the presence knob below 2. Other than that I promise that there is no difference to the circuit at all. Since it's a variable resistor, and not a voltage divider, the pot can only represent one value for it's setting and the 25k can represent all the same values as a 20k value would. I'll repeat, no matter what tonal difference you think you hear, it isn't there. Don't compare either value with the same exact knob setting. A 25k pot will need to be set a little higher than a 20k would. As in 2 for the 25k value instead of 0 for the 20k, with the differential increment decreasing as the knob is advanced. Like 8 for 25k instead of 7 for the 20k value. So, since knob setting is the only difference, the taper is going to be jagged when you kludge in a parallel resistor anyway, and the 25k value has more range at the lower end of the adjustment there doesn't seem to be any sane point in fussing with it.

[daz]

Daz
If that's your circuit then the absolute only difference between a 25k pot and a 20k pot is that there will a tiny (and I mean tiny) amount less presence with the presence control at zero. With a 25k pot the presence control "looks" the same electronically to the circuit between 2 and 10 as it would with a 20k pot between 0 and 10. Knob setting will be slightly different. No matter what you think you hear there cannot be any tonal difference between a 20k and a 25k pot in this circuit except that the 25k pot is capable of turning the presence down a pinch more. If you don't want the presence down that low (I doubt you could actually hear it) simply don't turn the presence knob below 2. Other than that I promise that there is no difference to the circuit at all. Since it's a variable resistor, and not a voltage divider, the pot can only represent one value for it's setting and the 25k can represent all the same values as a 20k value would. I'll repeat, no matter what tonal difference you think you hear, it isn't there. Don't compare either value with the same exact knob setting. A 25k pot will need to be set a little higher than a 20k would. As in 2 for the 25k value instead of 0 for the 20k, with the differential increment decreasing as the knob is advanced. Like 8 for 25k instead of 7 for the 20k value. So, since knob setting is the only difference, the taper is going to be jagged when you kludge in a parallel resistor anyway, and the 25k value has more range at the lower end of the adjustment there doesn't seem to be any sane point in fussing with it.

I'll leave it then, thanks.

[R.G.]

Actually, seeing that, I can provide some help.

If I understood you, you like what happens from full pot value down to 20K, did not like what happened below that. Did I get that right?

The simple thing to do is to put a ~20K more or less fixed resistor in series with a 2K - 2.5K pot where the 22k (?) pot is now. The fixed resistor keeps you from going off into the area you don't like, and the smaller pot spreads out the region you do like over the whole pot rotation. It will make for a much finer resolution on the region you do like. And it's an entirely reasonable thing to try.

[daz]

Actually, seeing that, I can provide some help.

If I understood you, you like what happens from full pot value down to 20K, did not like what happened below that. Did I get that right?

The simple thing to do is to put a ~20K more or less fixed resistor in series with a 2K - 2.5K pot where the 22k (?) pot is now. The fixed resistor keeps you from going off into the area you don't like, and the smaller pot spreads out the region you do like over the whole pot rotation. It will make for a much finer resolution on the region you do like. And it's an entirely reasonable thing to try.

Thanks, but it;s not really a big deal. I'll just use the 25k if it even matters anymore. Right now none of it matters anyways because something happened to the amp that i have been trying for 2 days to figure out and i'm out of ideas. It's reduced it to a bookend. Unusable unless hideous tone is your thing.

[Chuck H]

Thanks, but it;s not really a big deal. I'll just use the 25k if it even matters anymore. Right now none of it matters anyways because something happened to the amp that i have been trying for 2 days to figure out and i'm out of ideas. It's reduced it to a bookend. Unusable unless hideous tone is your thing.

Ugh...

You do this every time brother man!

Just rest your ears for a couple of days and try it again before you change anything, ok I don't know, but I can't imagine what "happened to it" to change it from great to horrid. Whatever it is... I don't want any of your amps getting near my amps in case it's catching

[daz]

Ugh...

You do this every time brother man!

Just rest your ears for a couple of days and try it again before you change anything, ok I don't know, but I can't imagine what "happened to it" to change it from great to horrid. Whatever it is... I don't want any of your amps getting near my amps in case it's catching

No, it;s not that. It's literally a different amp and not in a good way to put it mildly. No idea why, all i did was put in a new gain pot because the old one was cutting in and out. measured a hair under 1M and the taper measured the same as the old one. That fixed the issue but brought another thats just totally ruined the thing. No matter, just go back to the modeler. I'm not getting back into this BS again. I had 2+ blissfull years w/o all this crap using the modeler and i don't need to get back into it. I looked every inch over with a fine tooth comb but i can't find a single thing wrong. F it.