SHO aa Piezo Preamp?

[squirrels]

I've built two cigar box guitars using piezo pickups which are pretty weak on their own. I was going to build the piezo preamp vero but I was wondering if adding a SHO or LPB would work just as well. Any thoughts?

[Neil mcNasty]

The Piezo is extremly high impedance, so having the piezo preamp first is a good thing in order to make the signal pedal friendly , before going trough the SHO.

I like your idea!
I build Cigar Box Guitars myself, and has been pondering the idea of adding effects in the guitar, when there is a battery involved allready.
But I have not done it yet, since I mainly build them solid-body style (I fill the box with hard and heavy wood) with magnetic pickups.

A push-pull pot could be great as a bypass switch for the SHO Boost knob.
Specially if you can make the pot start from unity gain CCW

Let us know how this goes, and please feel free to post pictures of your guitars.
I'm a sucker for CBG's!!!

Cheers!
Neil

[squirrels]

I guess it makes sense to have the preamp first. I was thinking for having a master volume SHO and just leave it always on, I know without a preamp, the piezo is very weak sounding when plugged in. Would the preamp alone fix this?

I thought of adding it to my CBG's when I saw a video of a guy playing a bass with an on board Phantom Octave.

I'll post some pictures of my two later. I still have a nice box with a flamed lid that I've been waiting to do something with.

[induction]

The stock SHO without a pulldown resistor at the input will have an input impedance of about 5 megs. I have read reports of people being happy with the SHO as a piezo preamp in acoustic guitars, though I haven't tried it myself. Op-amp based piezo preamps have also been used successfully.

Low input impedance in the following stage reduces bass preferentially in piezo pickups. The piezo can be modeled as a capacitor, so the piezo plus the input impedance of the preamp form a high-pass filter. If the input impedance of the preamp is too low, the corner frequency of the filter will be too high, and will strain out the bass. The appropriate resistance can't be calculated without knowing the effective capacitance of the piezo, but capacitance increases with the physical size of the piezo element, so a bigger piezo gets you more bass with the same preamp. In any case, it shouldn't be a problem to use the SHO for this application as the input impedance is very high. The only question is whether you like the way it sounds, and how willing you are to tweak it to your preference. It should be plenty loud without cranking the gain pot to the point of distortion, but some EQ may be necessary, which can be incorporated into the preamp, or left to a pedal or the amplifier.

The only thing to do is build one, and see how well you can optimize it, or build several different types, optimize each one, and see which you like best. Let us know how it turns out.

[squirrels]

Good point about EQ. My CBG's are very thin and harsh sounding plugged in. I'll have to figure something out to add some lows and miss. I could add an active EQ but it would be easier and save space by making a pedal.

[induction]

Before you experiment with EQ, I would try a very high impedance preamp like the SHO on its own. That should give you a lot more bass and mids. Then you can EQ for fine tuning. Trying to boost bass that is no longer in the signal is a recipe for mud and hiss.

[squirrels]

I haven't done anything yet but here's the pictures that Neil asked for. The skull one was painted like Hendrix did with hos Flying V... nail polish. I'll put better pictures up when i get a chance.

[squirrels]

Well I finally got around to adding a SHO to one of my CBGs (three stringer) and it works. It pretty much matches the output level to my humbucker equipped guitars while keeping the twangy acoustic tone. I'll have to play around with it tomorrow at a proper volume to make a better judgement of the tone.  The only issue I've noticed (so far) is that it's very noisy. I'm guessing it's because it is essentially an unboxed effect. The noise does go away when I touch the plug and jack. Shielding the cavity would probably be the answer, no? What about putting the board and battery inside a small metal box like an Altoids tin, could that work?

I'm thinking of maybe an LPB-1 or maybe even some type of Electra or EM-Drive (for a little more dirt) inside my other one. The four stringer has a full neck though design so it has much less feedback than the three string. The three stringer is a neck through, but it is primarily open inside so it feeds back more.

[nocentelli]

LBP-1, electra and em drive all have lower input impedance that the SHO, so would not transfer as much of the bass. You could try two SHOs in series (I.e. Supa dupa 2-in-1) so you get the high impedance input, and the first stage can drive the second stage into distortion.

[squirrels]

That's a good idea about the Super Duper, I think I may just do that. First I have to figure the noise thing out. Everything is grounded properly, so I'm guessing I need to shield the inside of the CBG, or at least get the board into some type of enclosure.

[alex.s]

A friend of mine used my SHO clone as a piezo preamp for his Autoharp and was very happy with it - sounded great through the PA at the gig! I also piezoe'd up his toy piano, this time with a Tillman JFET pre, which also sounded very good.

I say, for the time it takes to mock one up with minimal parts, it's worth making a Tillman at least to have a term of comparison, but I doubt you'll be unhappy with the SHO, as it seemed to do the Autoharp an awful lot of justice on the day in my experience! :)