MV abrupt taper change
Moderators: pompeiisneaks, Colossal
MV abrupt taper change
Hi all,
I tacked this on to the end of the thread about CTS pots, but hadn't heard back from that, so I thought I'd try giving it it's own thread:
I've got an issue with the master volume on my D'Lite build. The taper is quite even right up to about 1:00, which in my band ends up being about gig level (competing with another loud guitarist and a loud drummer on tight stages). At that point, the control gets as touchy as a rattlesnake. Tiny movements make big differences in volume. So at a gig, when you're trying to make changes while playing, it can be a real problem.
Not sure what pot in there...it's what was supplied by Brown Note.
Any suggestions for a taper or pot that might behave a bit more predictably at reasonable volumes?
I tacked this on to the end of the thread about CTS pots, but hadn't heard back from that, so I thought I'd try giving it it's own thread:
I've got an issue with the master volume on my D'Lite build. The taper is quite even right up to about 1:00, which in my band ends up being about gig level (competing with another loud guitarist and a loud drummer on tight stages). At that point, the control gets as touchy as a rattlesnake. Tiny movements make big differences in volume. So at a gig, when you're trying to make changes while playing, it can be a real problem.
Not sure what pot in there...it's what was supplied by Brown Note.
Any suggestions for a taper or pot that might behave a bit more predictably at reasonable volumes?
-g
- martin manning
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Re: MV abrupt taper change
I believe the "log" taper in some pots is actually made up of two linear taper sections joined together. You may be sitting right at the point where it changes slope.
Re: MV abrupt taper change
Yup...I'd had the same thought, because that is exactly what it feels like. If so, any recommendations for pots that do not apply this technique of generating a taper?martin manning wrote:I believe the "log" taper in some pots is actually made up of two linear taper sections joined together. You may be sitting right at the point where it changes slope.
-g
Re: MV abrupt taper change
George, after finding out I had several defective pots in my new 100w build I don't take anything for granted anymore.
I had bought some NOS pots and although I did measure the total resistance on the outside lugs, it was when they were adjusted that I found something was wrong.
These were two Allen Bradley pots and a NOS CTS pot.
For instance the pre gain pot was an Allen Bradley 1M pot that after about 1/4 rotation it was at max resistance.
I was not getting the clean head room that I should have been getting and after comparing notes with a couple other builders I dug into the pots.
Really scratched my head on that one until I pulled it out and measured the sweep and found the problem.
The pot I had for a master was the same way.
I had bought some NOS pots and although I did measure the total resistance on the outside lugs, it was when they were adjusted that I found something was wrong.
These were two Allen Bradley pots and a NOS CTS pot.
For instance the pre gain pot was an Allen Bradley 1M pot that after about 1/4 rotation it was at max resistance.
I was not getting the clean head room that I should have been getting and after comparing notes with a couple other builders I dug into the pots.
Really scratched my head on that one until I pulled it out and measured the sweep and found the problem.
The pot I had for a master was the same way.
Tom
Don't let that smoke out!
Don't let that smoke out!
Re: MV abrupt taper change
Thanks, Tom. Yeah, nothing quite that off-spec here, but it isn't what I'd call a smooth taper.
So short of spending $15 on Alessandro's pots, is there a good alternative?
-g
So short of spending $15 on Alessandro's pots, is there a good alternative?
-g
-g
- David Root
- Posts: 3540
- Joined: Fri Aug 04, 2006 3:00 pm
- Location: Chilliwack BC
Re: MV abrupt taper change
PEC pots $9.95 at AES. 2W RV4, MILSPEC, short shaft for amplifier use.
Never had a bad one. Stainless case, you can't solder to it, other than that they're as good as it gets in my book. Oh, except 15% taper, not 30% like the old A-B J-types.
Never had a bad one. Stainless case, you can't solder to it, other than that they're as good as it gets in my book. Oh, except 15% taper, not 30% like the old A-B J-types.
Re: MV abrupt taper change
I've bought the expensive PEC pots as well as others and I keep coming back to Alpha pots.
Sure they are cheap but they are also pretty consistently good.
I do like the locking pots that PEC makes and I use those for adjusting bias current.
Because you can lock them down and the shaft won't drift.
But I have had a couple PEC lemons.
The tolerance on Alpha's isn't the greatest of all the pots but generally they are within what we need and you can always weed through a few if you need a tighter tolerance.
And for around $2 each, you can certainly get quite a few of each value to sort through.
Sure they are cheap but they are also pretty consistently good.
I do like the locking pots that PEC makes and I use those for adjusting bias current.
Because you can lock them down and the shaft won't drift.
But I have had a couple PEC lemons.
The tolerance on Alpha's isn't the greatest of all the pots but generally they are within what we need and you can always weed through a few if you need a tighter tolerance.
And for around $2 each, you can certainly get quite a few of each value to sort through.
Tom
Don't let that smoke out!
Don't let that smoke out!
Re: MV abrupt taper change
Thanks, all.
Have you found the Alpha and PEC pots to both have smooth tapers, rather than stacked linear tapers?
Have you found the Alpha and PEC pots to both have smooth tapers, rather than stacked linear tapers?
-g
Re: MV abrupt taper change
I have read about that but I don't really feel that in my pots.
I suppose it depends where your sweet spots are and if it happens to land where those two elements join.
For the most part I find the Alpha pots to work great and I see quite a few amp builders using them.
I have to say that while I also like PEC pots, I have had one get scratchy in short order and no way to clean it.
And I had at least one that was defective in the way it tapered. (an abrupt shift in resistance)
So in comparison a PEC costs $10 and an Alpha costs <$2 in most cases.
I suppose it depends where your sweet spots are and if it happens to land where those two elements join.
For the most part I find the Alpha pots to work great and I see quite a few amp builders using them.
I have to say that while I also like PEC pots, I have had one get scratchy in short order and no way to clean it.
And I had at least one that was defective in the way it tapered. (an abrupt shift in resistance)
So in comparison a PEC costs $10 and an Alpha costs <$2 in most cases.
Tom
Don't let that smoke out!
Don't let that smoke out!
Re: MV abrupt taper change
PEC is a good pot, but still a 10% taper. I regretfully used them in MM ODS and I'm pulling them all out. I should have used Alpha. I like CTS, but I find you have to go through so many to get closer tolerances and they still don't have the correct taper.greiswig wrote:Thanks, all.
Have you found the Alpha and PEC pots to both have smooth tapers, rather than stacked linear tapers?
Re: MV abrupt taper change
So when are we going to have a pot buying party and get the correct taper pots available to everyone?
To get a large order we need the buying power of TAG members.
Mark
To get a large order we need the buying power of TAG members.
Mark
Re: MV abrupt taper change
M Fowler wrote:So when are we going to have a pot buying party and get the correct taper pots available to everyone?
To get a large order we need the buying power of TAG members.
Mark
Count me in.
Re: MV abrupt taper change
Soon to be contacted by the DEA...M Fowler wrote:So when are we going to have a pot buying party ....
But seriously, I'm interested in that as well. I've heard others say that the potentiometers really do make a big difference in the sound and behavior of the amp. And clearly I've got at least one issue that I'm aware of.
-g
- David Root
- Posts: 3540
- Joined: Fri Aug 04, 2006 3:00 pm
- Location: Chilliwack BC
Re: MV abrupt taper change
If we could get 30% taper I would be prepared to try Alpha or CTS again.
Re: MV abrupt taper change
I agree and would like to try some 30% taper pots in a build.
Mark
Mark