I have an order for a uke bass. The guy is a big McCartney fan and has a full size Hofner but wants to fill out his collection with a nylon stringed Titchenbacker mock Rickenbacker 4001.
I build a lot of ukes and I had a good look at a Kala UBass and a Boulder creek bass uke so I feel pretty confident about what I need to do for neck sizes and frets action height and all the regular stuff I do on my ukes.
I am a little bit nervous about whether I will need a preamp on the under bridge Piezo to give sufficient volume or if just fitting volume and tone knobs will be fine.
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Yeah titch, I used a 9v powered pre amp on my u bass build and it helped the tone and volume a lot. Ebay has the rod piezo/pre amp combinations for less than 20 bucks and the added plus is a built in tuner on many of them..
A "normal" passive guitar tone control (potentiometer with a capacitor) doesn't work with a piezo. From what I have read my understanding is that the arrangement of components form a high pass filter (= the high end you are trying to remove passes through and you lose the low end you are trying to keep). To my ear it just doesn't do anything.
How loud it will be will depend on the type of piezo. What I find is:
Discs (highest volume, can use ok without preamp)
Rigid piezo rod(ok but you need to crank up the amp volume)
Flexible piezo cable (low volume needs a preamp)
Others may disagree.
Preamps are really cheap so I tend to always add them. If you don't want to add it to the uke you could build it in a separate box.
Wired correctly, the tone control is a "Low Pass" filter, RC parallel to the pickup, and shorts the high frequencies to kill the "trebble tones" and passes on the low frequencies. The bigger the capacitor, the lower the frequency it starts killing tones. The variable resister (POT) controls how big of a slice of tone-killing is served.
If 'the guy' wants to pay for an on-board eq/preamp, give it to him.