| I have no knowledge or experience of piezo transducers on a double
bass, but using the analogy of a guitar having more than one pickup,
I would guess that your idea would increase the output by a small
amount ( providing they were in-phase). However, because a double
bass is "acoustic" and reliant upon low frequency resonances to
get it's sound, you MAY find that some frequency cancelling occurs.
This may change the tone ( better or worse, I would not know!).
My approach to your problem would be to invest in a higher output
transducer, or go active and use a small op-amp booster inside the
bass itself. This will get you the extra gain, and give a lower
output impedance thus removing hum and noise.
regards
Dave
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I agree that a preamp is really your best solution. A piezo elelment
is very high impedance, so it is going to pick up lots of (electrical)
noise so you're best off with a short lead run to a preamp and then let
the preamp drive your mixer.
I'm not sure what brands are available in Europe, here in the U.S.
Fishman and Barcus Berry (both transducer makers, BTW) offer such
preamps and there are units from DOD and TC Electronics (they're
Scandinavian) that will do the job for you.
Brian
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| If you have access to Radio Shack, go out & buy thier small
Piezo buzzer, it has a similar element in it & it will work
quite well (all for only a few dollers) . Placing 2 in series
will increase the output voltage. You will also see more voltage
if you add mass to the other side of the piezo. The transducers
that I've seen are usually the size of a nickel (about 5/8 inch
in diameter) & have a piece of maple glued to the top with silicon
adheasive. This is to add the additional mass to get greater output
(these are pressure sensative). You might want to experiment with
different amounts of mass (try double stick tape & a coin) to see
how it affects the sound. Also try for placement. You can get
some cancellation if the transducers are far apart. In most cases
they sound best mounted under (if on the inside of the instrument),
on top of (if on the outside of the instrument) or near the
bridge. Since they tend to favor BASS, you might want them nearer
the treble strings, or one transducer in the middle of the bridge
and the other just off of the bridge on the treble string side.
If you use the small Radio Shack element (be careful when soldering
these, they are easy to ruin), you can add a cheap but very clear
and effective piezo transducer system to any acoustic musical
instrument (I even have one on my banjo!!). Preamps will help as the
output level is not that high, but they are not always necessary if
you are careful about the placement. Double stick tape (the stuff
with the foam core) is excellent for final attachement, as is
silicon based adheasive.
Jens
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