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Author Topic: Why You Can't Use A No Load Pot For Volume  (Read 5388 times)

Offline Phostenix

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Why You Can't Use A No Load Pot For Volume
« on: July 30, 2010, 02:59:39 PM »
I've seen a few comments on forums recently about using the Fender "No Load" tone pot as a volume pot to get the same affect of unloading the pickups at full volume.

Unfortunately, it won't work as a volume pot.

The no load pot works by breaking the conductive element at the "end" of the pot - fully clockwise. This means several things: If you measure across the outside terminals of the pot like you would a normal pot to check its value, it will read open. The resistance from the counter clockwise (CCW) terminal to the wiper will increase as you turn the pot CW up to its 250K value right near the CW end. At the CW end, the wiper drops into a detent position & actually connects to the CW terminal. But, at this point, it "disconnects" from the CCW terminal.





By disconnecting the wiper, that effectively removes the tone control from the circuit & remove any loading on the pickup(s).

Now, if you try to take that same pot and replace a volume pot with it, you end up with this:





What you'll get is a volume control that is at maximum volume at 0 - full CCW - and gets quieter as you turn it "up" until it gets to the end & disconnects (and connects to the CW terminal which is tied to ground) giving you no output at all. I don't think that's what anyone's looking for.
 

Why You Can't Use A No Load Pot For Volume

Offline Paul Marossy

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Why You Can't Use A No Load Pot For Volume
« Reply #1 on: July 30, 2010, 04:48:38 PM »
quote:
Originally posted by Phostenix

I've seen a few comments on forums recently about using the Fender "No Load" tone pot as a volume pot to get the same affect of unloading the pickups at full volume...

...Unfortunately, it won't work as a volume pot.
What you'll get is a volume control that is at maximum volume at 0 - full CCW - and gets quieter as you turn it "up" until it gets to the end & disconnects (and connects to the CW terminal which is tied to ground) giving you no output at all. I don't think that's what anyone's looking for.


That's because all it is doing is acting as a variable resistor. With no connection to ground, it has nowhere to shunt the signal to.

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Why You Can't Use A No Load Pot For Volume

Offline Phostenix

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Why You Can't Use A No Load Pot For Volume
« Reply #2 on: July 30, 2010, 05:08:57 PM »
Well, it will add resistance in series with the guitar's output until it eventually is connected to ground. Again, I can't imagine anyone wanting this affect on their guitar (it would most likely roll off highs as the volume went down, as well) so I'd say there's no good way to make the no load pot as a volume pot.
 

Why You Can't Use A No Load Pot For Volume

Offline Paul Marossy

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Why You Can't Use A No Load Pot For Volume
« Reply #3 on: July 30, 2010, 07:10:45 PM »
quote:
Originally posted by Phostenix

Well, it will add resistance in series with the guitar's output until it eventually is connected to ground.


Oh, I see. I interpreted that second schematic as there being no connection to ground. But I looked at it again a little closer I was in a hurry to get out the door and wasn't paying attention. [:I]

Anyway, it doesn't really sound useful for a volume pot. To each his own, eh? [;)]



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Why You Can't Use A No Load Pot For Volume

Offline Phostenix

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Why You Can't Use A No Load Pot For Volume
« Reply #4 on: July 30, 2010, 07:33:00 PM »
There is no connection to ground using the no load pot as a volume - until you get to the detent at the end. And then it's the wiper that goes to ground. The resistive element of the pot never gets grounded.

No, not very useful as a volume pot. That's the reason for this post. No load tone pots can't be used as no load volume pots.
« Last Edit: July 30, 2010, 07:35:26 PM by Phostenix »
 

Why You Can't Use A No Load Pot For Volume

Offline Paul Marossy

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Why You Can't Use A No Load Pot For Volume
« Reply #5 on: July 30, 2010, 08:02:10 PM »
quote:
Originally posted by Phostenix

There is no connection to ground using the no load pot as a volume - until you get to the detent at the end. And then it's the wiper that goes to ground. The resistive element of the pot never gets grounded.


Ahh... I get it now. No, not useful at all as a volume pot. Cool, now I know how one of those things work.

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Why You Can't Use A No Load Pot For Volume

Offline 908ssp

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Why You Can't Use A No Load Pot For Volume
« Reply #6 on: July 30, 2010, 10:46:34 PM »
Try this for volume pot with no load
Alex

[IMG]http://i146.photobucket.com/albums/r245/908ssp/ThumbNails/_1010802.jpg[/IMG

Why You Can't Use A No Load Pot For Volume

Offline Phostenix

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Why You Can't Use A No Load Pot For Volume
« Reply #7 on: July 31, 2010, 12:16:50 AM »
That's certainly looks like it would work, but I wonder what kind of impact it would have on the guitar tone, since the load on the pickups keeps changing as you turn it.
 

Why You Can't Use A No Load Pot For Volume

Offline Paul Marossy

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Why You Can't Use A No Load Pot For Volume
« Reply #8 on: July 31, 2010, 09:09:32 AM »
quote:
Originally posted by Phostenix

That's certainly looks like it would work, but I wonder what kind of impact it would have on the guitar tone, since the load on the pickups keeps changing as you turn it.



Yeah, instead of being a voltage divider like a normal guitar volume, it's now a variable resistor to ground. It seems to me like it would change the frequency response somewhat as you adjust it. Might work out good for some people, though.

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Why You Can't Use A No Load Pot For Volume

Offline Phostenix

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Why You Can't Use A No Load Pot For Volume
« Reply #9 on: July 31, 2010, 02:27:05 PM »
Since I'm making some changes to my Strat today (waiting for a Nitefly to arrive next week), I decided to try the Fender no load pot as a volume control setup the way 908 suggested. It does work & does roll off the highs as you turn it down. It's not as bad as I thought it might be, but it's definitely noticeable. The no load position isn't a big volume jump, but it is brighter/edgier. I would guess that if you put an inductor between the wiper & ground so that it attenuated low frequenices more than high, you could find a balance & make it work.



BTW, this test was done with a '94 Strat Plus with Lace sensors into a Boss GT Pro (1 M ohm input impedance).
 

Why You Can't Use A No Load Pot For Volume

Offline Paul Marossy

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Why You Can't Use A No Load Pot For Volume
« Reply #10 on: July 31, 2010, 04:15:44 PM »
The inductor is an interesting idea. You might also be able to combat the highs being rolled off as you turn it down by putting a "treble bleed cap" on the pot.

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Why You Can't Use A No Load Pot For Volume

Offline Phostenix

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Why You Can't Use A No Load Pot For Volume
« Reply #11 on: July 31, 2010, 08:16:57 PM »
I tried that idea first. Since you can't get to the 3rd terminal, every other way I tried to put a cap in the circuit just rolled off highs like a tone control.
 

Why You Can't Use A No Load Pot For Volume

Offline Paul Marossy

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Why You Can't Use A No Load Pot For Volume
« Reply #12 on: July 31, 2010, 10:12:19 PM »
quote:
Originally posted by Phostenix

I tried that idea first. Since you can't get to the 3rd terminal, every other way I tried to put a cap in the circuit just rolled off highs like a tone control.



Yeah, I guess that don't work, eh? Sounds like it's more trouble than it's worth. But that inductor idea would be an interesting experiment.

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Why You Can't Use A No Load Pot For Volume

Offline Phostenix

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Why You Can't Use A No Load Pot For Volume
« Reply #13 on: August 01, 2010, 12:02:08 AM »
Paul,

I posted a couple of things today on some Fender forums that I didn't think most there would be interested in, but you might.

http://www.tdpri.com/forum/tele-technical/225573-wiring-strat-o-tele.html

http://www.tdpri.com/forum/tele-technical/225580-anatomy-fender-tbx-tone-control.html
 

Why You Can't Use A No Load Pot For Volume

Offline Paul Marossy

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Why You Can't Use A No Load Pot For Volume
« Reply #14 on: August 01, 2010, 07:39:15 PM »
Cool. If you have a Strat, that Super Switch let's you do some cool stuff. [8D]

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