I'm scanning your online catalog and seeing 20mm/27mm and 41mm piezo sizes. What are
the differences..are there any differences tonewise?
Also..you show a 250K pot and a 500K pot. I have used a piezo tune-o-matic bridge on my homemade
Les Paul types and the volume control supplied by LR Baggs is 5 meg ohm. Piezos are high impedance
devices according to my understanding and tube amps have typically 1 megohm input impedance.
Now a 500k for a humbucker pickup or 250k for a SC (single coil) sounds right, but I would think
that if the piezos are wired directly into a volume control, it should be around 1megohm at least.
Am I correct in this assumption?
What about wiring the two piezo's in parallel. Someone stated that two piezos will sound louder than
1 piezo or two wired in series. Again this appears to be the result of the transducer's very high
input impedance.
Tags:
MichaelS said:As far as 2 in parrallel that is how I use them and to me they don't sound louder, just better to my ears and they reduce the feedback from the amp, I don't know how, it just works. I use 2 of CB Gittys 20mm piezos.
Well if the soundboard vibrates and creates pressure on one, and you get a electrical
a/c signal from that which represents those vibrations, then
two in phase... should add more electrical signal. The impedance lowering is
another thing that
I can't quite understand how it works on piezos. It' certainly works that way on
copper wire pickups.
Ohms law I suppose..if you take two resistors of equal value (10Kohm + 10kohm)
the net result
measured with an ohmmeter is 5kohms.
The current splits down both paths and half goes through each resistor but the
voltage drop across both is the same. Piezos transducers are probably another math equation..but
I would think they should work in a similar fashion.
Don Thompson said:Audio or linear taper yes.
Audio taper is recommended for a volume pot, as the human ear does not respond linearly to loudness.
Carverman - the opinions on this stuff vary widely depending on who you ask, and I don't claim to be the grand oracle on any of it. I can just tell you what I have perceived to be the "average" take. Some guys say that the larger piezos have better volume and bass response, other people say there's no difference. Personally, I think there may be a bit of difference but that your placement and mounting method are MUCH more important than the size of the piezo. I cover all of what I consider to be "piezo gospel" in a two-part article on my site: http://www.cbgitty.com/content/view/34/43/
/blockquote>
Ok..I've looked at the different sizes of piezos and their resonant freq response. Now whether
that makes any difference in tone, I don't know..but after dealing with a very thin sounding
Piezo t-o-m (on one of my previous projects) and having to fine tune it with a tone control,
I'm leaning more now towards
just getting the EQ-7545R preamp, even if it takes a battery and you need a large
opening (3.75 x 1 9/16) in the top side. I still need space for the volume/tone for
the P-90, and a selector switch, so it may be a tight squeeze, but I could always
put the volume/tone selector on the bottom side with only 1 grommet and the
preamp and a grommet on the top side for balance. Does this sound like it's
feasible?
Haha - I guess the jokes on me. I thought it was hard spacing 4 tuners on a 5 inch headstock!Quite a wide variety of skill levels here.
The rod piezo can mount under the bridge, you can make a slot in the bridge itself and glue it in, you can glue it to the inside of the box, pretty much anywhere you could mount a disk.
As for the pre-amp and feasibility... I can't guarantee that it will give you the exact sound you are looking for, but it should sound pretty good! When it comes to stuff like that, about the best advice I can give is to try it and see!
I have never heard a difference in ohm ratings for a piezo volume control. Doesn't really matter to me.Audio or linear taper yes.
Don
Don Thompson said:Audio or linear taper yes.
Audio taper is recommended for a volume pot, as the human ear does not respond linearly to loudness.
The piezo electric effect can be summed up in a nut shell. The voltage output is determined by the pressure applied (sound waves) on its surface area with a fiddle factor of the piezo electric effect.
So, as the most piezos are made of the same material the fiddle factor is constant. Also the sound waves pressure are constant across choice of piezos its the size or surface area that will affect the choice. 20 and 27mm wouldn't really make much difference in the scheme of things. The 41mm piezo should be louder but there is the volume pot and the impedance matching between guitar and amp. The resonant frequency will change over the sizes but I find all piezos to be biased to the treble end compare to magnetic pick ups.
When dealing with audio there is never a linear response. Often there is an exponential response when falling in impedance, 1M to 500K appears to be 'half' the actual response may only 10% different.Whereas 100k to 1K may be as much of 60% difference in volume. Actual responses may be difference but the principal is as you approach a low impedance the effect is greater.
When dealing with parallel pick ups/piezos, I fear of going in to Kirchhoff, Thevenin and ac theorys and deep mathematics to resolve the ultimate sweet spot for whats sounds good and gives best signal transmission from ac sources (pick up/piezo) to amplifiers, effects pedals or mixing desks etc.
I think the best way to look at this, transducers in parallel will not give a louder signal than a single one if you got a volume pot over a high impedance say 250K. However that said there are reactance of capactive and inductive elements (including wires and leads) which will change over the frequency range of said tranducers.
By adding parallel transducers and the positions of the transducers you introduce phase shifts and even more possibilities for tuning to specific frequency response curves. This starts getting into mega-deep calculus and material worthy of a good Phd.
What I use is a simple rule of thumb. I never go below 47K pots for volume because the impedance mismatch of guitar output to amplifier input starts to affect the signal strength and you start getting a quieter guitar.At the end of the day I turn my volume pot to a point that sounds good for what I want at the time and if the tone is a or volume is a bit low I'll use the controls on my amp.
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