Piezo bridge pickups - useful for synthesis?

[Mark Hammer]

I'm picking up a Mike Christian piezo bridge pickup for Strat this weekend.  This has a separate piezo sensor in each bridge saddle.  Does anyone have any comments or experience with this as a potential source for dividing string outputs for hex processing purposes?  I realize the traditional synth method involves thin hex humbuckers near the bridge, but I gather things like the Godin synth-ready instruments use something like piezo bridge sensors.  Am I correct?

I figure that something which permits ersatsz acoustic tone AND synthesis possibilities can't be that bad.

[tommy.genes]

I don't know alot about them, but both Godin and Brian Moore use hexaphonic piezo systems from RMC.

http://www.rmcpickup.com/polydrivei.html

Graph Tech also sells the hexaphonic GHOST system for use with their piezo saddles.

http://www.graphtech.com/prodghost.htm

-- T. G. --

[Peter Snow]

I realize the traditional synth method involves thin hex humbuckers near the bridge, but I gather things like the Godin synth-ready instruments use something like piezo bridge sensors.  Am I correct?

Hi Mark,

Yes, you are correct sir!  In fact I was considering buying the same type of product from Graph Tech - a Canadian company in BC I think. Their stuff is available locally at Steve's or SongBird - maybe have to order it though. They have a number of different saddle styles to fit most types of guitars.  They also have a couple of on-board preamp products that allow you to mix the individaul signals for regular mono output or to buffer the 6 separate signals ready to be processed for MIDI or whatever.  Maybe worth a look.   Being able to process each string individually is a very attractive proposition.

When I last looked they were not *that* expensive and I had the choice of buying a set of saddles or breaking into my Casio MG-510 and trying to get separate outputs from the hex pickup.    Of course, so far I have done neither
Cheers,

Peter

[Processaurus]

Hi, a friend has something like that in his instrument, each piezo goes seperately to a breakout box (thru a multi-pin cable), then a comercial mixer.  Its neat, but the sound wasn't that great, you had to turn the bass all the way up, and the treble most of the way down to get a decent sound.  I think the bass gets cut if the piezos don't get a real high impedance preamp, kind of the opposite of magnetic pickups.  I would probably get the preamp the company that makes the saddles manufactures, if theres a way to get individual ouputs after it. 

Heres a weird idea for that setup, if two strings were tuned the same but effected differently, like vibrato one one and nothing on the other, you'd probably get a unique chorus sound.  Or an octave divider just on the low E.  Of course you'll need a seperate pedal board for each string . 

[MR COFFEE]

Mark,
What kind of hex processing do you think you want to do?

Hex overdrive\fuzz sounds great, but the cord for a hex output can be a bit of a downer. That's a lot of conductors...

If you want an overdrive sound, a LPF for each saddle with a low-medium Q and Fc between 2-4.5 khz  makes it sound a lot better IMHO. Those piezo transducers can be real splatty-sounding if you clip the natural (buffered) piezo signal. The piezo pick transient is a real zinger. FWIW

[Mark Hammer]

Hi one and all,

Pete, the guy I'm buying it from actually lives out your way (near Ogilvy and Montreal Rd).  It looks like this will provide an excellent use for all those teeny SMT TL081s you were gracious enough to give me.

Mr. Coffee, I think, given the backlog of projects, I should probably aim for mono processing at the moment.  The split pickup will allow for each note to be sensed accurately, provided there is some sort of note priority system to gate out incidental noise from other strings.

I would like to retain the capacity to blend piezo and mag sounds though.  It'll need some think-through.

[tommy.genes]

I remember seeing a release from Boss about one of their twin pedals being equipped with a 13-pin input to allow pollyphonic processing in conjunction with a GK-2 hex pickup. None of the twin pedals listed on their site today mention this feature in their descriptions. I guess there just wasn't that much demand to place a different effect on each string...

Reminds me of a producer who once told me about the concept of a "guitar choir", where a power-chord passage was recorded one string/note at a time, each to a separate track. The idea was to get a really full sound without the inter-modulation distortion between strings that happens physically within the guitar. In the same conversation, this producer also proudly stated that he, in fact, had never done such a thing.

-- T. G. --

[Mark Hammer]

The old Ripley/Kramer guitar, endorsed by EVH on the back of Guitar Player for what seemed like a few years, was intended to do just such a thing, except the guitar's output was stereo.

[Dave_B]

I don't know alot about them, but both Godin and Brian Moore use hexaphonic piezo systems from RMC.

Does anyone know about the construction of these?  Piezo discs are about $1.25US from Mouser, and they can be trimmed to the width of a string.  I've used them in drum pads and they're pretty simple to implement.  I've never seen one of these piezo hex pickups up close, but is there any reason you couldn't make one, mounting each one one foam or something if isolation is needed?

[Squeal]

cnmat

I promise you will like this better than the last one I posted. It's a paper by some guys at berkeley who made some 2 dimensional pickups. There is a part about hexaphonic processing as well as a part about piezo pickups. Their music/art tech program is called cnmat.

[H^)harry]

Hello all...

There is some difference in using the piezo and magnetic pickups for hexaphonic use.
If you are doing hex processing, it should be OK to use either if the preamp takes into
account the piezo properties. You need a very high impedance amp or you will be making
a hipass filter with the capacitance of the piezo.

Making your own bridge saddles from piezo benders will probably not work. You can't cut
them successfully and they are too big. There are Piezo films from Measurement somebody
(see Digi-key) that might possibly be used... they worked for sh!t as a drum pickup, maybe
guitar might be different.

In a non-hex configuration, you can use an encased piezo bender as a guitar pickup if you
add mass to the center to lower the resonant frequency WAY down. I used a lead pellet from
a bb gun epoxied to the center.  Stole the idea from a CLOCK MAKER who used a harmonica pickup
to listen to clockworks with. I looked at what he had (broken) and figured out what it was...crystal pickup with solder
epoxied to it
to lower the resonant freq.


H^)harry
ps: does everyone have to type at one character per second or is it just me

[Squeal]

An idea for a hex pickup: Send one or more strings to the carrier input of a ring mod, then send the other strings or all the strings to the input of the ring mod. Has this been done? Seems that some setups could give you good musical control over the output: less random crap frequencies.

[Dave_B]

Could it look something like this?  I left out the wires and guitar strings for clarity.  The white and gold part is the cut piezo, the black part underneath is foam rubber or something similar.  I've seen articles about glueing whole peizos to guitars for pickups (and tried with some success a long time ago).  If you put these close to the strings would it be enough to keep them from triggering notes from adjacent strings?

[gurutzeta]

Did anyone ever try this diy approach? did it work? any other suggestion for a diy hex pickup?

[Marcvv]

I should probably aim for mono processing at the moment.  The split pickup will allow for each note to be sensed accurately, provided there is some sort of note priority system to gate out incidental noise from other strings.

I would like to retain the capacity to blend piezo and mag sounds though.  It'll need some think-through.

Hi Mark,

I have been working with guitar synths for several years. Still own the old GR300/G505 combination.

Piezo pickups can work fine to drive a synth from your guitar. The note seperation is a pretty crucial thing. In general pitch to voltage converting (which is what we are talking about) needs to be able to detect the fundamental of the note you are playing. Any extra information creates the situation where it is not clear what the fundamental is and results in misstracking or glitches. The split pick up will only allow each note to be sensed accurately as long as it is separated from the other pickups. Any mixing of the six signals needs to be done after you take the split signal for your synth....
To pick up the fundamental the pickup should be located as close to the bridge (or in cas of the piezo in the bridge) as possible as that is where the string will give as little overtones as you can get.
Zeta released a midi guitar end of the 80's that did a lot of good things (and unfortunately some that did not work so good): they had a very elaborate system  to gate out incidental noise. Although the idea was great it did not work as good as it promised.
Any nois gives you an extra "trigger" and so an extra sounding note.... priority has too go to the fundamental.

Maybe a nice idea to look into the original GR300 design. It converts pitch to voltage and that voltage drives an analog synth. No midi. What is really interesting is the filter that is implemented per string: the filter changes as the pitch goes up. This makes the same note on a different string sound different, which is what we guitarplayers want is it not...

Marc

[Mark Hammer]

Well, since the original posting, I sort of cheated.    Last summer a guy in town sold me his GK-1 and Roland MIDI brain for a decent price, so the piezo saddles have been relegated to their original purpose, and are awaiting installation.

[puretube]

SHADOW...