250k Vol Pot Post Piezo Preamp

[Johnny Foreigner]

A quick and hopefully easy question:

i know that for a piezo preamp the correct volume pot would be a 25k.

but what would the upshot be if i used a 250k instead?

[elmo7sharp9]

A quick and hopefully easy question:

i know that for a piezo preamp the correct volume pot would be a 25k.

but what would the upshot be if i used a 250k instead?

Can't say for certain without looking at the specific circuit.

It may work perfectly well.

One possibility is that the volume control will work to some extent but not actually

give you zero volume when turned all the way down.

This happens when you use regular pots instead of 25k on an EMG active pickup.

Wire it up outside the guitar to see the effect, without laborious physical installation.

Edited March 15, 2010 by elmo7sharp9

[~davie]

A quick and hopefully easy question:

i know that for a piezo preamp the correct volume pot would be a 25k.

but what would the upshot be if i used a 250k instead?

not sure. most active configurations use 25k apparently. not sure why.

but if we can apply the general effect of pot ratings, higher pot values allow more higher frequencies to be produced in the sound.

piezo pickups are somewhat thin and tinny sounding, right? i'm guessing with a 250k it'll be more shrill-sounding, or somewhat icepicky? lol

[Hank McSpank]

but if we can apply the general effect of pot ratings, higher pot values allow more higher frequencies to be produced in the sound.

piezo pickups are somewhat thin and tinny sounding, right? i'm guessing with a 250k it'll be more shrill-sounding, or somewhat icepicky? lol

Unfortunately, within an active preamp scenario, you can't apply the same rule.

The preamp buffers the piezos and to all intents & purposes converts their (very) high impedance characteristic to an output signal that has a low impedance.

It's not clear where you are thinking of changing the pot? As Elmo says, we'd have to see the specific circuit you're talking about to see where the pot lays in the overall signal path, but in all likeliehood, within an active preamp circuit you'd not hear a whole lot of difference between using a 25K pot and a 250k pot.

[ansil]

A quick and hopefully easy question:

i know that for a piezo preamp the correct volume pot would be a 25k.

but what would the upshot be if i used a 250k instead?

Can't say for certain without looking at the specific circuit.

It may work perfectly well.

One possibility is that the volume control will work to some extent but not actually

give you zero volume when turned all the way down.

This happens when you use regular pots instead of 25k on an EMG active pickup.

Wire it up outside the guitar to see the effect, without laborious physical installation.

with all due respect what monkey crack are you smoking. using any pot in an emg will give you actual zero volume i do this all the time if you get a pot doing that it is because the pot is sheit my friend.

btw instead of 25k using a 250k you will get more output thats about it. it changes the output impedance tries to make it look more like a passive system. i add 500k-1M on my bridge emg pickups all the time for my customers and they just slay. found that trick out in my ibanez with a barcuss berry passive neck and an active emg 81 in bridge. set up so that the middle position cut out the emg and added a cap to filter out some of the bass end on the barcuss so it was like having three separate settings.

[elmo7sharp9]

with all due respect what monkey crack are you smoking. using any pot in an emg will give you actual zero volume i do this all the time if you get a pot doing that it is because the pot is sheit my friend.

No crack involved, Ansil.

I have, right behind me, an EMG-EQUIPPED bass with regular-value pots.

The last owner was too lazy to switch the pots and the current owner (me) never uses the volume controls.

The volumes don't go down to zero and the tone control didn't roll off as much as it should (till I dropped in a 25k).

[Johnny Foreigner]

btw instead of 25k using a 250k you will get more output thats about it. it changes the output impedance tries to make it look more like a passive system.

okay, to clarify, I'm going to have two humbuckers on 500k pots.

then i'm also going to have a piezo pickup, run through the preamp ripped out of one of these:

the preamp already has a volume control, but it's going to be tucked away in the control cavity. I want a pot after the preamp that is accessible. and obviously i want the output of the piezo to be comparable to the mag pups.

[elmo7sharp9]

the preamp already has a volume control, but it's going to be tucked away in the control cavity. I want a pot after the preamp that is accessible. and obviously i want the output of the piezo to be comparable to the mag pups.

That's clearer.

That preamp is designed to go into a high-impedance amplifier input,

so you can treat the preamp's output just like you would a regular pickup.

Go ahead and use an identical pot to the pots you're using for the humbuckers

(You're effectively building a passive mixer).

Use the (hidden) existing preamp's volume slider to trim the volume from the piezo to match the maximum volume from your humbuckers.

[Johnny Foreigner]

okay, makes perfect sense.

thank you!

[ansil]

with all due respect what monkey crack are you smoking. using any pot in an emg will give you actual zero volume i do this all the time if you get a pot doing that it is because the pot is sheit my friend.

No crack involved, Ansil.

I have, right behind me, an EMG-EQUIPPED bass with regular-value pots.

The last owner was too lazy to switch the pots and the current owner (me) never uses the volume controls.

The volumes don't go down to zero and the tone control didn't roll off as much as it should (till I dropped in a 25k).

ok now you are talking bass which i have no experience with their pickups and pots so i have no comments on that. but the guitar pickups do not do that. mines on the wall behind me and the other in the case. hmm you know thats interesting i will email rick at emg and ask him he is sort of my email buddy

[Paul Marossy]

with all due respect what monkey crack are you smoking. using any pot in an emg will give you actual zero volume i do this all the time if you get a pot doing that it is because the pot is sheit my friend.

No crack involved, Ansil.

I have, right behind me, an EMG-EQUIPPED bass with regular-value pots.

The last owner was too lazy to switch the pots and the current owner (me) never uses the volume controls.

The volumes don't go down to zero and the tone control didn't roll off as much as it should (till I dropped in a 25k).

I wonder if the volume control is wired as a variable resistor instead of a volume control. A volume control should go to zero to full volume if it is wired correctly, no matter what the value of the pot is. Does one of the lugs go to ground? If it has a lug soldered to the pot body, but the body isn't connected to ground, it will just be a variable resistor instead of a volume control.

Edited March 18, 2010 by Paul Marossy

[elmo7sharp9]

I wonder if the volume control is wired as a variable resistor instead of a volume control. A volume control should go to zero to full volume if it is wired correctly, no matter what the value of the pot is. Does one of the lugs go to ground? If it has a lug soldered to the pot body, but the body isn't connected to ground, it will just be a variable resistor instead of a volume control.

I've wired more guitars than I've had free beers,

so I knew my wiring was right...

I had thought this was down to cheap pots not zeroing correctly,

with residual resistance, insignificant on a 0-500k scale,

that's significant on a 0-25K scale

Although I didn't actually consider this an operational problem,

I took the backplate off, found the controls wired correctly,

but the tone pot's nut had loosened,

the tone pot had rotated away from its fixed position,

stretching the ground wire from the pot casing to the socket,

breaking the solder joint.

So it's fixed and operating normally, now.

But I have lost my right to never turn the bass down.

See what Project Guitar does to the unwary?

They've got me fixing things I didn't even consider to be broke!

[Paul Marossy]

Aha, I knew something sounded fishy.

[Johnny Foreigner]

See what Project Guitar does to the unwary?

They've got me fixing things I didn't even consider to be broke!

You're welcome!

[ansil]

lol good to know i forgot to email rick and ask him i got busy playing nazi zombies lol. yeah i was a little cornfused about that one. i have been in heaven since i switched out my emg's pots. i used to have the active ones i dont' rem which ones but one was based around craig andertons one knob eq it was a direct copy of it. but they changed it on the newer version.

ed