replacing volume pot in 1991 Modulus Q5: 50k vs 25k?

F

fudster

Member
Messages
3
Hey - just found this forum, looks fantastic. Cheers!

I have a 1991 Modulus Q5, that came with EMG pickups and electronics. I have to replace the volume pot, and I love the sound I get from my Q5 and my Redhead so much, I don't want to change anything.

At some point in the last 15 years or so, EMG changed this electronics system ("BTC System") in at least one way: the volume pot is a 25k instead of a 50k. I have the old system that had the 50k, and I need to know whether there will be any impact at all in my output or sound if I just swap them.

A local tech sold me one of the newer 25k EMG pots, and he said that in this low-impedance system, using a 25k instead of 50 will make "almost no" difference. However, I read here on this forum that a lower pot will result in less output and a compromised sound (this fellow also suggests seeking an Alpha replacement pot in that thread).

Seems likely that someone here would be knowledgeable or have an opinion about this - what would you do?

I also posted this question (with a little more detail and narrative)
here at the EMG forum, feel free to have a look there if you wish.

Thanks!
 
F

fudster

Member
Messages
3
Hey - thanks for your prompt reply and the link. If I proceed to order I think that's probably the one I need.

I preferred to find one locally but a 50k couldn't be found here. If I buy one online, I obviously need to know for sure that it's a suitable replacement both physically - I've seen differences in the sizes and shaft lengths. Shipping will cost well over double the price of the pot, and I may have to pay tax and duty to get it here to Canada. It's a bit more hassle.

More to the point: I forgot to mention it here, but I have the 25k EMG pot here on my desk already (they had lots of those).

I don't know much about electronics, but given an active system like this, it seems possible to me that the resistance from the pot isn't actually participating in the circuit, so much as it is controlling something else that is. If someone who is more knowledgeable than me were to be able to assure me that "there'll be no difference at all", the fastest way to move on with my life will be to put this 25k pot in, because buying one from the US on the Internet will be a bit of a hassle.

Thanks again.
 
walterw

walterw

Platinum Supporting Member
Messages
41,729
the 25k will be fine. the 50k will make for an ever-so-slightly brighter tone, but might not have as even of a sweep from 0 to 10. a 50k linear pot might be worth checking out, as it would likely have a smoother transition than the 50k audio taper.

the resistances of the volume and pan pots are absolutely "participating" in the sound of the circuit. it's just that, since the pickups are active, the resistances have to be that low for the pickups to "notice" that the pots are in there and be affected in a usable way by adjusting them. put a 500k or 250k volume in an emg circuit, and the pot will have no effect until it's almost all the way down, at which point it will shut off the output like a switch.

emg pots, even though they're little, are pretty good quality. no need to go searching for an alpha, which IMO is not as reliable.
 
F

fudster

Member
Messages
3
Thanks walterw, those are exactly the things I was hoping to learn.

Chances are I'll just put the 25k in, based on what you've said it sounds like it'll be fine. My volume is usually 100% up when I'm playing and I only use the volume pot occasionally for fades, so I'll probably be OK with either one there. If the reduction in brightness turns out to be noticeable, I'll grab one of the 50k's that test1two suggested (thanks test1two, especially for finding one in Canada), or try to find a linear one that'll fit in my guitar.

Thanks much to both of you, I appreciate your input, thanks for helping me learn about this.
 
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