pots for Volume / Tone pedal?

Doug Beaumier · Post by **Doug Beaumier** » 1 Mar 2002 8:17 pm

I know that the Clarostat 500K Type J pot has been standard in good volume pedals for some time now. My question is about volume/tone pedals such as the Fender and Bigsby. Is is necessary to use Type J 500K for both tone and volume?

I have an old Bigsby V&T pedal that has an A&B Type EJ (extra-life) pot for volume, but it's missing the tone pot. Is it advisable to use a Type J 500K pot for tone too, or would a regular 500K pot be okay for tone?

------------------
My Site | Doug's Free Tab

[This message was edited by Doug Beaumier on 01 March 2002 at 08:21 PM.]

Ken Fox · Post by **Ken Fox** » 1 Mar 2002 9:14 pm

Doug, the old Fenders had 250K pots in them. I changed mine to 500K, I like the travel/action better. Audio/log taper pots are what you need. if you use a linear (non log) pot, all the change will happen suudenly at one end of the travel (great for a do-wah effect, but thats about all). For a smooth/even change use the audio/log taper pots.

Bill Crook · Post by **Bill Crook** » 1 Mar 2002 10:20 pm

Ken....

It's not often I tend to disagree with a fellow steel player, but I think you have the linear and logrithmic pot explanations reversed.

I checked my books and also pulled a couple of pots from stock to verify my findings.

If you look at a graft of a linear pot, the resistant line looks like a 45 degree,from lower left to upper right. A audio taper/logrithmic pot has resistant line that is far more than 45 degree for the first half, then tends to flatten out at about 3/4 to full on. This design was developed for/by the RIAA folks who is now fighting to keep you from makeing your own music CD's and such.

There is a bit of history behind the audio taper pot but as most people don't care about the hows and why's of how things came to be, I won't go into that here.

Please check your electronic books and manuals on this subject.

Jim Smith · Post by **Jim Smith** » 2 Mar 2002 1:26 am

Volume pots use logarithmic tapers and decibels are logarithmic as well. In order to be twice as loud the decibels are squared, so 25db is twice as loud as 5db. Thus a pot must work the same way.

Doug Beaumier · Post by **Doug Beaumier** » 2 Mar 2002 5:57 am

So the Bigsby T&V pedal that has a 500K Type J (EJ) volume pot... I should use a similar pot for tone too? Maybe not, if I want a better boo-wah effect from it? Does it matter if I use 500 or 500 Type J for tone?

------------------
My Site | Doug's Free Tab

[This message was edited by Doug Beaumier on 02 March 2002 at 06:00 AM.]

Ken Fox · Post by **Ken Fox** » 2 Mar 2002 9:34 am

The audio pot uses a log taper, that appears to be linear when the ear hears it. Try a linear pot, I have. All the change appears to be at one end. The ear hears in a logrithmic fashion, not linearly. I think we are saying the same thing here! I agree with you that the taper of a linear pot is a 45 degree line when plotted out. Unfortunately we do not hear that way! Of course, after all those years on a bandstand, I can hardly hear at all! Ain't this fun?[This message was edited by Ken Fox on 02 March 2002 at 08:13 PM.]

Jim Smith · Post by **Jim Smith** » 2 Mar 2002 1:44 pm

I've read here that volume and tone pots both use audio tapers, but as I recall, tone pots are linear. Does anyone really know for sure?

Ken Fox · Post by **Ken Fox** » 2 Mar 2002 4:19 pm

I put a linear taper in my Fender tone and volume, all the tone change is at one end. Good for do-wah but not good for a tone control.

Jussi Huhtakangas · Post by **Jussi Huhtakangas** » 4 Mar 2002 1:44 am

Doug, audio/log taper pot it is, if you search for doo-wah effect. That's what the tone control on these pedals was designed for. I guess the value of the pot is not that critical, cause I've heard different pedals with different valued pots sounding equally good ( for that effect ). I just put a 1Meg audio taper pot on my Wright Custom's endplate and it does the doo-wah tone-job perfectly. Can't remember the value of the capasitor. You might wanna fool around with different valued caps to get it right, depending on how deep you want the change on the bass.

Doug Beaumier · Post by **Doug Beaumier** » 4 Mar 2002 8:29 am

Much thanks to everyone for the replies.

------------------
My Site | Doug's Free Tab

Doug Beaumier · Post by **Doug Beaumier** » 12 Mar 2002 7:37 am

Follow up FYI: a forum member who has a Bigsby T&V pedal tells me that according to Bigsby's original diagrams that came with the pedals, a 100K ( linear taper ) pot with .1 CAP was recommended for Tone.

------------------
My Site | Doug's Free Tab