Recently I built an MXR GT-OD.
W20K is recommended for the tone pot, but I didn't have it in stock, so I made it with B25K.
I know that it is used as a replacement for the W20K in many TS pedals, and I also have a few TS pedals made with the B25K.
However, make my GT-OD with B25K, the tone was too dark when the tone pot was set to 12 o'clock.
I looked for other errors, but there were no special problems, so I purchased a W20K and replaced it.
There has been a big change. It gave me a balanced sound that I was familiar with, without being overly heavy.
The results are successful, but one question arises.
I understand that the W taper pot is the same as the linear taper pot when placed in the center.
In fact, when I placed this pot at the center, it measured about 8~9K. (The total value of the pot is measured to be approximately 17~18K)
In that case, I think we should think of it as a change not because the taper changed, but because the value changed.
Is the difference between the 25K and 20K tone pots on a TS like pedal that big?
I have used both 25K and 20K during make TS pedals so far, but I have never tried replacing the two one by one, so I never thought there would be a big difference.
Since I mainly build for 1590A cases, I use small pots, and it's not easy to find a W20K or B20K in this size.
If the difference between 20K and 25K is big, I should look carefully for a place that has it in stock.
How have you experienced the difference between 25K and 20K in the tone pot of a TS like pedal?
For pedals other than GT-OD, isn't there much of a difference depending on pot value?
I don't remember which pots I used in the other TS pedals I've made, but I've never had a problem with the tone other than the GT-OD.
TS like pedal tone pot 25K vs 20K?
-
mauman
- Cap Cooler
Here's the schematic for reference, note the change suggested by karul in the text: viewtopic.php?p=260888&hilit=MXR+GT+OD+ ... ic#p260888
Since you measured your 20kW pot, I suspect your 25kB pot was either faulty, or very outside the 20% tolerance. There should be no audible difference between a 20k and a 25k tone pot in this circuit. If you model them in LTSPice, the difference at midpoint is less than 2 dB, which for many people is not an audible difference.
The midpoints of a 25kB pot and a 20kW pot should be quite close to each other, considering the 20% tolerances. And you're right, the midpoint, 0% and 100% of same-value B and W pots are identical. With same-value pots, the B and W tapers differ only in how quickly the value changes when moving from the 50% point toward either 0% or 100%.
Since you measured your 20kW pot, I suspect your 25kB pot was either faulty, or very outside the 20% tolerance. There should be no audible difference between a 20k and a 25k tone pot in this circuit. If you model them in LTSPice, the difference at midpoint is less than 2 dB, which for many people is not an audible difference.
The midpoints of a 25kB pot and a 20kW pot should be quite close to each other, considering the 20% tolerances. And you're right, the midpoint, 0% and 100% of same-value B and W pots are identical. With same-value pots, the B and W tapers differ only in how quickly the value changes when moving from the 50% point toward either 0% or 100%.
In my experience, there were no particular problems when using the B25K with other TS pedals. I don't tend to use the tone knobs of TS pedals in such a variety of ways, and I usually set it to around 12:00 to 2:00 and use it. However, in the GT OD make this time, the difference is significant.
In fact, it is closer to a question about the difference between 20K and 25K rather than a question about taper. I haven't used the B20K in GT OD yet, so I don't know if it's a taper problem or a value problem, but the difference between when using the B25K and the 12 o'clock setting is quite significant, so if any of the other TS pedals I've made so far used the B25K, I was considering replace with W20K or B 20K. After reading your response, I'm thinking that it's not necessary, but if I get the chance, I'll consider replacing it. Thank you for your reply!
In fact, it is closer to a question about the difference between 20K and 25K rather than a question about taper. I haven't used the B20K in GT OD yet, so I don't know if it's a taper problem or a value problem, but the difference between when using the B25K and the 12 o'clock setting is quite significant, so if any of the other TS pedals I've made so far used the B25K, I was considering replace with W20K or B 20K. After reading your response, I'm thinking that it's not necessary, but if I get the chance, I'll consider replacing it. Thank you for your reply!
Information
- Posts: 1
- Joined: 28 Nov 2024, 08:46
The difference between 20K and 25K tone pots in TS-like pedals affects the tonal balance, with a 20K pot allowing slightly brighter frequencies and a 25K pot introducing more warmth and muddiness.
-
dai h.
- Solder Soldier
hi,
my understanding is (with a linear taper pot where there should (ideally) be a 'W' (also referred to as 'S' or 'G' which is half log and half reverse log taper)) if you stay around the mid-point (which is supposed to be flat but may not be due to tolerances) you can have decent control over the sound change, but once you move beyond a certain range in either (positive or negative) direction you won't have good control over the sound since the resistance change happens too quickly with a linear pot. (I suppose this could explain someone being happy using a linear taper if they don't stray too far from 12 o'clock and conversely someone else who isn't satsfied if they tend to use ranges beyond that.) Also, some 'W' taper pots may have better control than other ones due to them having more sections on the resistive track. Furthermore, maybe check out the Providence Sonic Drive schematic (should be in a thread here IIRC). They used a fixed R and a reverse log 10k.
my understanding is (with a linear taper pot where there should (ideally) be a 'W' (also referred to as 'S' or 'G' which is half log and half reverse log taper)) if you stay around the mid-point (which is supposed to be flat but may not be due to tolerances) you can have decent control over the sound change, but once you move beyond a certain range in either (positive or negative) direction you won't have good control over the sound since the resistance change happens too quickly with a linear pot. (I suppose this could explain someone being happy using a linear taper if they don't stray too far from 12 o'clock and conversely someone else who isn't satsfied if they tend to use ranges beyond that.) Also, some 'W' taper pots may have better control than other ones due to them having more sections on the resistive track. Furthermore, maybe check out the Providence Sonic Drive schematic (should be in a thread here IIRC). They used a fixed R and a reverse log 10k.