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so I got a piezo buzzer from Radio Shack...

#21
xyllion said:
You know that you guys could easily build your own high impedance preamps.
Click to expand...

you betcha... for just a couple bucks in parts.

Phatcactus, running a RS buzzer piezo element through a Bartolini circuit seems like asking too much from this mod. Not sure what you mean by "cheap piezo material big enough to fit under a bridge", might not be such a thing when you're considering raw piezo material. You're talking $2 for a buzzer (about the size of a quarter), and the next step up would be something like a Martin Thinline undersaddle transducer for around $60. Then there's some more involved to create a space for the transducer to sit and still get the bridge down tight to the body. Unless you could take apart a stick-on transducer for any acoustic instrument w/o destroying the element. That way at least the piezo is going to be suited for this type of application.

Keep in mind the pre-amp can only work with the signal it's getting fed, and I suspect the buzzer mod is far inferior in signal to anyhting you'ld want to run into a Bartolini circuit.

Although I could be wrong... :eyebrow:
 
#22
could someone help me out here??
Im looking to do this mod to a Yamaha BBG5s that I own.
What Id like to do is insert the piezo(s) under the bridge, and then wire it as a stereo output.
I dont really care about running the electronics through the body, I'd almost prefer not to mess witht the cavity given how I might not care for the results.
Can someone detail how I can build a preamp that will allow me to better match the outputs on the two systems?

Thank you for your help
Pat Mahoney
 
#23
Pat, in order to get the bridge back on to the body good and flat, you need to run the piezo's wires to the control cavity somehow. I know it seems like a hassle, but you should be able to use the hole for the string/bridge ground. Assuming there is one, that is. If not, then it's drill time. Don't do that unless you're 100% confident you can wield an 18" long 1/4 drill bit at that shallow angle and not come out the back of your bass...

You'll already have the bridge off and be swapping out your mono jack for a stereo jack, may as well run the wires too. I definately wouldn't recomend leaving then hang out from underneath the bridge. It won't sit flat (bad), the wires are fragile and tightening the bridge down may cut them (bad), and it will look bad (bad).

A super quick and easy alternative to all this (albeit with much less dramatic results) would be to just stick a surface-mount acoustic guitar pickup somewhere on your bass near the bridge. You *will* get a signal. It may be pretty faint, but it'll be there.

As for the pre-amp, a quick web search for "acoustic pre-amp schematic" and "impedance matching" ought to get you started. ;)

-Ryan
 
#25
And installed 2 of them on my 5string rogue, and I'll tell you what, those combined with all nickel roundwounds has bite to beat the tar out of you...You roll on the piezos a little and man alive does it add the sparkle....roll 'em on full and the slappin time she comes...Pik sound is good, the brightness of the new Vinci light special 5s(.35 - .110, tuned BEADG) the lighter string is alot easier on the bends...I'm lovin this bass now...I may start doing it to all the basses I buy...Be careful when you break the case off of the buzzer...it'll scratch it up pretty bad...But as far as I could tell it still worked(hooked bare wires up to a 6" cable into a headphone amp) This is a poorman's piezo setup...2 buzzers was about 6.25 at my radioshack(I bought the cheapest ones they had...30V Piezo buzzers)...I just wired it through the bridge ground, and into the cavity(I wired the 2 elements in series) and wired them to a volume pot, and straight to the jack...and it's a neat addition to my array of tones...This is a 189.99 rogue LX205B and 6.00 in piezos...I didn't even have to touch the EQ...It sounded great without it....I don't need impedence matching...It sounds fine to my ears....Good thread...made me wanna try it...And it kills!!

DWB
 
#26
Yeah. I just got mine all setup the way I like it. I just scrapped my tone knob, because I never used it anyways. So I've got a split-P and dual bridge piezos, each set with it's own volume knob, and that's it. I didn't bother with impedence matching, either. The whole point of this (for me anyways) was a cheap mod, so nothing fancy. I really like the sounds that I can get out of this bass, now. The response is SO much better now, too. I really should do some clips of it.
 
#27
Here's a couple of links in order to give credit where credit is due...

[Invalid or Expired Link Removed] I found this searching for EUB info, and ran across the
"un-official" site for Azola's Baby bass Link Removed. The link to Vintage Baby Bass info is to blame for all this. :rolleyes:

Once my curiosity was going, some more surfing turned up this page from Harmony Central. Scores of folks who tried the piezo buzzer mod (as a surface mount acoustic pickup, actually) and loved it.

And finally, in an effort to address the issue concerning the piezo's extremely high impedance, you can build your own active circuit like xyllion suggested. If you're really adventurous, go here to get a schematic for a simple FET (field effect transistor) preamp. High input Z, low output Z, and a touch of gain. Just the thing for a high impedance piezo, in fact it can allow you to run the piezo alone. Building your own would definately keep this mod in the el-cheapo-DIY-but-with- :D -results catagory, since the parts cost (assuming you already own a soldering iron) would only be a few dollars.

I'm still trying to track down a supplier for raw piezo material...
-Ryan
 
#29
Thanks for the link phatcactus!!!!! I'm on it. In the meantime, I'll be experimenting with a passive approach to the impedance issue. There has to be a simple approach in order to use the piezo alone. Any EE's out there, feel free to jump in.

I really should some get sound clips up soon, comparing mags to mags + piezo, and just piezo.
 
#30
okay here's my own experiment
My samick bass is now: bender! (from futurama)

this is the main bass(the only one), and i don't like the j pup that it had, i never use that, so i took it off, and i know that this buzzers are like microphones so i put them in that place, wired them in parallel (i think)
and how does it sound?
well it sounds like s**t
it sounds like a bass amplified by a microphone, no low end, lots of bright noises, that's it.

i'm gonna ask for some help to someone.
 
#31
Hey FractalUniverse,
piezo pickups are not like microphones. They function by translating presure or movement into electricity. By putting them under the strings like a pickup, you will only get the slight reverberations of the body.
Put the piezo buzzer under the bridge, where vibration translates into varying pressure and you will have a better result. Upright basses use piezos, and still get enough low end, so it can be done.
Later and good luck
Pat Mahoney
 
#32
You're also going to have to take the piezo element out of the black casing. Inside, there's a white disk, which is the actual piezo crystal, attached to a metal disk, which you can see through the hole in the casing. That's the part you want to wire up. Be careful with the thing, because while it's sturdy, the wires attached to it love to come off.

Edit: Actually, piezo elements are a lot like microphones. Unfortunately, a microphone wouldn't pick up the string either when it's just nearby it. It's just not loud enough.
 
#33
The reason for the lack of low end is that piezos are a capacitive source, and so they form a high-pass rc filter with the input impedence of what they're driving.
1 / 2*Pi * R * C Will give you the frequency (in hertz) of the -3db point, remember C is in farads not microfarads, R is in ohms.
 
#34
lol, i mean come on, it was an experiment.

i'm now working in the original version (putting the piezos under the bridge)
the only problem i have found is that the piezo has 3 red little cables and i don't know what to do with them(3 cables attached to the green buzzer thing)..... i unsolded one of the piezo and started experimenting.... i attached a cable to the jack of the bass, and then i did some interaction between the piezo cables and the jack.... i think i have the answer, but i'm not sure, i'm going to achieve what i want maybe tonight, i'm working with my dad he studied something with electronics.
and the other thing is that i'm not an engligh speaking person so my english sometimes looks good but it can lack of sense.(that's why i'm always a thread killa :hiding: )


edit: i finally have the piezo under the bridge of my bass, it's connected in parallel and it has good gain, but i don't know well how it sounds cause i'm trying it in a little guitar amplifier so it sound distorted, i'm going to try it in my bass amp maybe tonight.
 
#35
What have I started... :rolleyes:

OK, let me first clarify something - I don't know what I'm doing. Well, sort of. Soldering skills and common sense, yes. Electrical theory, not so much. (Ahhhh, I feel much better.)

FractalUniverse, I forgot to say before that the piezo is a 2-wire version. Good experiment, you found out less pressure = less signal. Let us know how it goes for you!

"inbrednedd - piezo pickups are not like microphones. They function by translating presure or movement into electricity."

Hmmmm. yes and no. Even though they do it very differently, both piezo material and a dedicated "microphone" function by translating vibration into electricity (wait a minute, isn't electricity a vibration? aaaaaaaaahhhhhhhhh!). Check out basic mechanical piezo theory Invalid Link Removed. More akin to a condenser than a dynamic mic.

Tim__x - Does the piezo's "buzzer mode" resonant frequency correlate to it's function as a transducer? (A quick glance at RS buzzers shows them rated any where from 300Hz to 4.5kHz.) Maybe that question is over my head... I think I'm already in way over my head, but that's beside the point... How's about really getting into some shop talk, though, for those who *do* get it.

My main goal now is to grasp the concept of the piezo's source impedance given it's capacitance (same thing?), and how to get a useable signal that can get along with the magnetic pup's output. Not to mention how the sum output changes when the piezo is parallel to or in series with the mags. I may try wiring the whole thing (P neck, J bridge, piezo under bridge) so the signal is entirely in series from top to bottom and the output jack can see any combination of the above by switching them in an out of the signal path. As soon as a functioning buffer is in there, that is. Hmmm, opamp or transistor? Hmmm........

Oh yeah, what about this. If the bridge is still grounded and the piezo is in direct contact, wouldn't that be a dead short? Come to think of it, I guess not since the disc is coated.

Keep in mind, this isn't an attempt at designing state-of-the-art musical intrument piezo technology here, that's already been done. In the meantime, it's fun to experiment and hopefully lean and understand something new.
 
#36
RyanHelms said:
Tim__x - Does the piezo's "buzzer mode" resonant frequency correlate to it's function as a transducer? (A quick glance at RS buzzers shows them rated any where from 300Hz to 4.5kHz.) Maybe that question is over my head... I think I'm already in way over my head, but that's beside the point... How's about really getting into some shop talk, though, for those who *do* get it.
Click to expand...
First of all, let me say I'm not exactly an expert on piezos so I may be wrong.
I think the resonant frequency of a buzzer is partialy determined by the casing and will be different when you remove it. As to it's effect on response, I might expect a small peak at the resonant frequency but other than that I don't know.


RyanHelms said:
My main goal now is to grasp the concept of the piezo's source impedance given it's capacitance (same thing?), and how to get a useable signal that can get along with the magnetic pup's output. Not to mention how the sum output changes when the piezo is parallel to or in series with the mags. I may try wiring the whole thing (P neck, J bridge, piezo under bridge) so the signal is entirely in series from top to bottom and the output jack can see any combination of the above by switching them in an out of the signal path. As soon as a functioning buffer is in there, that is. Hmmm, opamp or transistor? Hmmm........
Click to expand...
If you put all of your pickups in series like that you'd need a high impedance buffer or the low cut I mentioned earlier would occur on ALL of your pickups. As for Opamp VS Discrete (transistor) I strongly reccomend opamp, they're easier to use, generally give better performance and are only slightly more exspensive.

If you're building the buffer yourself I suggest a TL062, or if you're not worried about battery life/are willing to use 2 Ni-Cads in series I suggest a OPA134. You can get free 'Samples' of these from http://www.ti.com

P.S. A piezos output impedance varies with frequency getting lower the higher the frequency although it will never get that low within audio frequencys
 
#37
Thanks Tim__x! Maybe the straight series wiring isn't a good idea anyway, I *like* the P and J in parallel. Would they really be much hotter in series? The piezo will still probably switched in and out in parallel as well, just to keep things simple.

I had read that opamps offer much lower output imedance, tens of ohms compared to hundreds with trannys. Why the TL062 BTW? I'll pull the data sheet to do a comparison with a TL071 which is what seems to show up frequently. Jack Orman's "Simple Buffers" over at AMZ looks like a good place to start.

I still have to say that even wired straight to the jack w/o buffering the disc I'm using opens up the tone so much. (loads it down alot too...)
Seems to me there should be a way the piezo could be handled passivley. edit: resistors in parallel to lower the Z? Hardwire a lowpass filter? Am I anywhere near reality here?

Maybe just a piece of wire wrapped quartz crystal epoxyed to the body would be cool...couple it to the strings and have an AM receiver at the same time.


I'm kidding. :D
 
#38
i played last night with the piezo........ by itself it doesn't have too much gain, i mean no more than the magnetic one, but the piezo and the mag sound really cool blended together.
the mag has lack of clearness, but it has lots of gain(a bad MM copy wich only feature is that it's earth shaking ) and the piezo just put in the mix some clear notes... i think it's a really good tone for recording. uh.... i forgot to say that if i get a bit trebly with my eq then some people of the audience will notice that their ears have exploded. awfull reverberance!.
(it's not good for live situations) the good thing is that i can blame the singer. :D :hiding:
 
#39
RyanHelms said:
Thanks Tim__x! Maybe the straight series wiring isn't a good idea anyway, I *like* the P and J in parallel. Would they really be much hotter in series? The piezo will still probably switched in and out in parallel as well, just to keep things simple.

I had read that opamps offer much lower output imedance, tens of ohms compared to hundreds with trannys. Why the TL062 BTW? I'll pull the data sheet to do a comparison with a TL071 which is what seems to show up frequently. Jack Orman's "Simple Buffers" over at AMZ looks like a good place to start.

I still have to say that even wired straight to the jack w/o buffering the disc I'm using opens up the tone so much. (loads it down alot too...)
Seems to me there should be a way the piezo could be handled passivley. edit: resistors in parallel to lower the Z? Hardwire a lowpass filter? Am I anywhere near reality here?

Maybe just a piece of wire wrapped quartz crystal epoxyed to the body would be cool...couple it to the strings and have an AM receiver at the same time.


I'm kidding. :D
Click to expand...
The TL071 is a fine opamp too, the reason I suggested the TL062 is because although it's worse in every other way (:p ) your batterys will last longer with it (0.25ma draw). The OPA134 is the exact opposite, has amazing specs but draws a wopping 5ma, the TL071 is a fine middle ground, good stats, 2.5ma draw, fairly low noise etc..

I can't think of any good way to passivly "buffer" the piezo without expensive custom transformers or the like. Although it might be a good thing that the piezo doesn't have much low end response, kind of a passive treble boost when you dial it up.
 

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