Which volume pot for passive pickup?

Ok, I think this belongs here and not in building/luthier...

I’m planning ahead and was considering adding a volume wheel to a passive pickup when I install it, mounted at the edge of the sound hole. Similar to the upgrade option for the JJB Prestige pickups. I found some volume knobs online, but they come in several “flavors”. It’s been 20 years since I took an electronics course and had to think about these things. How many kOhms do I want? I think they came in 1k, 10k, and maybe one other.

I have a K&K volume wheel on mine. I saw one today with both volume and tone. They're really hand for controlling volume between lead and rhythm.

Do you need a preamp between the piezo and pot?

Barrytone said:

Do you need a preamp between the piezo and pot?

Click to expand...

I originally thought so. But looking at the JJB, it doesn’t appear they use one. And the unit I found online has a review that says it works with passive pickups. I don’t trust online reviews as gospel, which is why I’m asking about it here.

I did some more digging. It looks like a volume knob would work just fine on a passive pickup (to reduce volume, not amplify), but you need a pre-amp to use a tone knob. And I think I would want a 10kOhm potentiometer with a logarithmic resistance curve. Can anyone confirm or correct?

Here’s a new thought... use a separate wheel for each piezo on a multi-head pickup. This would be less helpful in using the volume control mid-performance since you’d need to fiddle with multiple wheels. However, it would give you a way to balance the output of the pickups in relation to each other to refine the quality of the sound. This might be especially true on a low-G linear tuning. With one piezo installed on the bass side and one on the treble, you could change volume by turning both wheels, or tone by turning just one. Of course this is all theoretical since I don’t actually know how much of a real-world difference the placement of the pickup makes on overall tone. I may have to try this just so I can play with multiple configurations.

I think the VC wheel controls the impedance between pickup and preamp. If using a passive pickup and an amp without a preamp built in, you'll need a preamp between the instrument and amp. If one is built into the amp, you won't. I have a Phil Jonees Double 4 that has both active and passive modes. I still use a preamp with it though for a cleaner sound and because I know very little regarding amps and electronics.

My Pono solidbody has a passive setup with a volume knob. I'll try to remember to dig out that assembly and look at the pot sometime today (I replaced it with an active setup). Should be just like an electric guitar I'd think...

I prefer not to mount any electronics into or onto the ukulele body.
Obviously, the piezo element must be an exception here.
It is far easier to run the passive signal to a belt mounted preamp that can be modified, upgraded or exchanged, depending on your electronic talents and/or the size of your wallet. Circuits are freely available with fixed or adjustable controls for volume, tone and filtering.
The biggest advantage of this approach is that all of your instruments can benefit from the one investment. This is also beneficial in removing the need for fiddly work inside the instrument body when chasing problems in the sound chain, as once you have found the right position and mounting method for the pickup/s (I find that this is the challenge) you are virtually guaranteed of no further revisits. The only {insert expletives here} exception to this rule that I have experienced has been a separation of a signal wire from the piezo wafer.
A bonus of this approach is that, apart from a strap button jack, the instrument appears aesthetically unadulterated.