Piezo and preamp into a solid body guitar/uke

[Steve Senseney]

I would like build a small bass uke with a piezo and pre amp and the Pahoehoe polyurethane strings.

I don't want to make the body very thick, and would like to find a skinny preamp.

As I look at Ebay, I see lots of designs that would work for a thicker body.

I don't want to build my own preamp, especially when they are quite cheap on ebay.

Is it feasible to buy a preamp, pull the back of the box apart and try to squeeze the components into the lesser space?

Or is there another way to accomplish this?

[Samuel Hartpence]

I'll be working in similar parameters soon. I was hopping to integrate standard electric guitar style pots for volume and tone in my build (as opposed to sliders) as well.

[Mark Swanson]

If your space is small, then you could get one of the small preamps that is meant to be used attached to the end pin jack. These are very small and have no controls on them at all, if you do it right you can take it off the jack and wire it into the control cavity and the controls. You need to do it right, and use the right value of controls so you'd need to get guidance on that if you don't know, you could ask right here.

[Steve Senseney]

Please give advice! I am not clever with electronics!

Is there a site you suggest? Which type of preamp off of the end pin jack?

I see an item on ebay called a SOHO endpin Jack.

In the discussion, it indicates to solder the Pick up or Piezo to the two leads.

What other controls would be needed? Volume?

[Mark Swanson]

Yes, I am talking about the type of preamp that is made as a part of the output jack of an acoustic pickup system, such as a Martin Thinline or a Fishman pickup. this would be a bit of a job for someone who hasn't got any experience Steve but if you can solder and feel like taking it on we'll help.
So this is for a bass? If it was a small bass I would go with minimum controls. On my electric instruments I use nothing but a volume control, being content with setting my tone and stuff like that right at the amp or the board. I think, and you may agree, that a small instrument would look cluttered with a lot of knobs.
It should be pretty easy to wire up one of those preamps and have one volume control on the instrument. I expect a 25K pot after the preamp would be the way to go. The preamp you mentioned looks like it would work just fine. You could use it as is, if you
* want to have your output jack do double duty as the endpin, that's how these are meant to be used and
* you choose to have no controls at all on the bass. Using the preamp as-is would take the control option away because the controls should only be added AFTER the preamp and never between the preamp and the pickup.

[Steve Senseney]

Thanks for your help Mark.

I will get one of these ordered, and see what they look like. I suspect I will NOT feel like figuring out where to put a volume control on the pre amp board.

[Samuel Hartpence]

It looks like Kala uses this pick up for their Sub-Bass:

http://www.shadow-electronics.com/viewp ... _id=&id=25

Looks like this is a passive system that could easily be routed through some on-board tone and volume controls.

[Mark Swanson]

Sam, that pickup is a magnetic soundhole pickup that needs steel strings, and it's large and wants six strings as well so it wouldn't work for Steve at all.

Steve, you wouldn't put the volume control on the PC board at all, but rather up near the face where the player can reach it, similar to an electric guitar, right? What you would want to do is sever the connection between the PC board and the output jack right at the jack and run shielded wire from there to your volume control. It would be small and a bit tricky but it can be done. That would be the easiest way and would allow you to use the output jack as it's meant to be used, allowing you to not need to worry about mounting the preamp or finding another jack.

[Steve Senseney]

I think I understand.

I was scanning the Ebay listings for guitar parts.

The 25 k pot is not listed with any of the instrument suppliers.

I suppose I need to order this from an electronics supply store?

[Mark Swanson]

You could use a 10K, or a 20K...Probably even a 50K, that isn't all that critical but the regular guitar pot of 250-500K is way too high. I see Stew-Mac sells a 25K pot.
Maybe Greg can chip in with a bit better info on that.

[Greg Robinson]

It's somewhat dependant on what model preamp you end up getting and it's output impedance, but 25K should be a pretty safe bet. Stewmac have 25K pots if you order from there, most other places that have much stuff for electric guitars should have them too.

Have you got a preamp chosen? When you do I can probably give more specific advice, maybe draw up a diagram to help you out if you need.

[Steve Senseney]

I haven't ordered yet. Still looking.

Thanks.

[Samuel Hartpence]

Sam, that pickup is a magnetic soundhole pickup that needs steel strings, and it's large and wants six strings as well so it wouldn't work for Steve at all.

When you go on the Shadow web-site there is a pop-up of a magnetic sound-hole pick-up. If you close out of that window, the "SH 064 4 String Bass Bridge Pickup with saddle – fits 8 mm slot" Pickup is what is on that page. It appears to be the same pickup that Kala uses for their solid body U-Basses (and they state they use a shadow pickup)

[Randy Cordle]

LargeSound sells the Ashbory preamp very inexpensively, and it should work perfectly for a solid body uke. Check the gain mods on site, as many report low volume with the pre-amp before doing the gain mod.
https://www.largesound.com/buy/

[Steve Senseney]

Could you direct me to the mods?

I did a quick look and could not find anything.

My Ashbobory preamp and piezo is a pretty quiet sound

EDIT--I found the mod--

http://www.largesound.com/ashboryarticl ... ification/

Currently the bass is not living at my house. I might mess with it if it comes home some time.

I read the article. Still I am a little hesitant to mess with the circuit board.