Center-Tap (4 lug) potentiometers?

[bwanasonic]

As a follow up to this post:

http://www.diystompboxes.com/sboxforum/viewtopic.php?t=28314

A whole mess of these pots are  Clarostat 30k, with a "center-tap" lug opposite the usual 3 lugs. Anyone familiar with this type of pot and it's uses?

Kerry M

[Nasse]

with a "center-tap" lug opposite the usual 3 lugs

Some loudness control circuits in hi-fi are done with center tapped pots

[Paul Perry (Frostwave)]

A great (though obscure) use is when you have two different modulation sources, you run the mod sources to opposite ends, then earth the centre, now as you go from one side to another the first mod source goes from full to zero, then the second goes from zero to full.
ALSO: if you have two audio sources, and dont want to mix them, but want to be able to choose A or B at various volumes (eg. if you have 2 guitars plugged in, or 2 FX).
I wish I had a steady supply of 100 or 200K centre tapped!!!

[MartyMart]

A great (though obscure) use is when you have two different modulation sources, you run the mod sources to opposite ends, then earth the centre, now as you go from one side to another the first mod source goes from full to zero, then the second goes from zero to full.
ALSO: if you have two audio sources, and dont want to mix them, but want to be able to choose A or B at various volumes (eg. if you have 2 guitars plugged in, or 2 FX).
I wish I had a steady supply of 100 or 200K centre tapped!!!

Is that how the Tech21 DoubleDrive pot mixes from A/B distortion then ?
But near the "centre" you have an equal amout of both, hows that done ?
Nice, I could use a few of those !

Marty.

[Paul Perry (Frostwave)]

Is that how the Tech21 DoubleDrive pot mixes from A/B distortion then ? But near the "centre" you have an equal amout of both, hows that done ? Nice, I could use a few of those ! Marty.

You can make an A through to B blend, by leaving the centre tap ungrounded (or using an ordinary pot). (where A and B are the low impedance outputs of two effect stages or whatever) BUT, you will always have a tiny bit of the other side bleeding through at the extremes (because the A and B sources have some impedance). You wouldn't notice anything mixing between two distortions, though!

[MartyMart]

Is that how the Tech21 DoubleDrive pot mixes from A/B distortion then ? But near the "centre" you have an equal amout of both, hows that done ? Nice, I could use a few of those ! Marty.

You can make an A through to B blend, by leaving the centre tap ungrounded (or using an ordinary pot). (where A and B are the low impedance outputs of two effect stages or whatever) BUT, you will always have a tiny bit of the other side bleeding through at the extremes (because the A and B sources have some impedance). You wouldn't notice anything mixing between two distortions, though!

Thanks Paul. I've just learned something very useful here AGAIN !
What a "cool" place this is

Regards,
Marty.