piezo snob?

[swarfrat]

After turning up my nose at 30 years of under saddle piezo acoustic guitars... I've heard the light.
I've been incredibly impressed by the sound clips I've heard for bridge plate transducers, but just never got around to ponying up for one.

Finally bit the bullet and ordered a JJB Prestige 330 - same thing as the K&K Pure Mini at a fraction of the cost - $50 on ebay.  And after scratching my head and saying - someone ought to make one - I finally found that Schatten does sell a Phantom Powered Endpin preamp jack - the Schatten Artists II, found mine for $72 shipped on Amazon.

I've been impressed enough with the clips that - if it sounds that good for me I probably won't even bother micing acoustic guitars for project recording. Sure, if I make a real album some day I'm sure I would, but it'd probably take something nicer than my Audio Technical AT-2020 to convince me to bother micing.  Actually, it'd probably take a nicer sounding room than my bonus room to do the convincing.

I decided against thumbwheels, batteries and doodads on my guitar. Phantom power, straight into the board. My Eleven Rack mic input will also provide phantom power if I ever did that.

 

[TBurst Std]

Congrats.  My order of preference is mic, SBT, then UST.  I find that 99% of the time I'm using a blend of mic and SBT depending upon stage volume.

 

[swarfrat]

Bridge plate is really a variant of SBT. It's NOT the same thing as UST - that's a large part of why I never did it before - I was lumping all piezo in with UST.

 

[Logrinn]

SBT?
UST?
:icon_scratch:
???

 

[swarfrat]

SBT = Sound Board Transducer
UST = Under Saddle Transducer (meaning directly under the plastic saddle, as opposed to attached only to wood.)

 

[Logrinn]

Ahh, I see. Thanks for the clarification.

 

[Cagey]

Looks like a good plan. If it sounds good, that'll be great, as the whole system is so simple. I also like that the Schatten unit can be separately energized by 48v phantom power. No battery on board? Gotta love that. You just reminded me that there's been a battery sitting in my Taylor for over a year now, and the damned thing is currently sitting in storage where I can't get at it easily. I'm gonna be mega-pist if I open that thing up and the battery has puked all over things.

 

[swarfrat]

Oh yeah, I forgot - their sound clips page:
http://jjb-electronics.com/sound_clips.html


http://jjb-electronics.com/media/Carolan_s_Concerto.mp3

 

[TBurst Std]

Bridge plate is really a variant of SBT. It's NOT the same thing as UST - that's a large part of why I never did it before - I was lumping all piezo in with UST.

Yes, just using inits. I have K&K in mine. (Actually their Trinity system).

 

[swarfrat]

I'm gonna have to trash the Schatten Artist preamp on design principle alone (cause I can't evaluate it any other way - as it's now a worthless piece of garbage).

They sell this preamp and you're expected to solder to tiny surface mount pads. Which promptly lifted up. Had they used a plated thru hole, it would've been a cinch.

Rather than take my chances, I'm gonna roll my own through SEEED Studios. Just thought I could pony up a few extra bucks and avoid another project but alas.... if you want it done right. $72 down the toilet in about 10 seconds.

 

[Cagey]

Wow. I haven't seen a solder pad lift in years. Did you ask for a replacement?

 

[swarfrat]

Not one but two. I figured it was "my fault". But honestly - a through hole would have been soooo much easier (and more reliable - since it's an off board wire.)

 

[Cagey]

I agree - a hole would have been better. I was taught early on that the key to a good solder joint is a good mechanical joint. Solder just isn't that strong. But, lifting pads sounds like a faulty or poorly made pc board. Usually, you have to abuse the hell out of them with an oversized iron or repeated solder/desolder operations to do that.

 

[mayfly]

I was taught early on that the key to a good solder joint is a good mechanical joint.

This +100. 

Sorry to hear about the schatten.  Does sound like you need to just do it yourself.  Please post the design in progress.

 

[swarfrat]

http://www.zachpoff.com/diy-resources/alex-rice-piezo-preamplifier/

Looks like a good candidate. Solid design, good specs. But 30seconds of looking while falling asleep on the couch wasn't turning up a 50v matched jfet pair with the appropriate specs. It'd be my own layout though, i need to fit it inside a long 1/4 endpin shell. Probably SMT in 805 sizes with thru holes for the three pickups. The three braids twisted together is probably what killed the pads - way too much heat required and too much mechanical leverage.

 

[mayfly]

interesting design.  So that third fet is used to bias the other two?  Actually no - never mind it's those 3M resistors doing the input biasing.  Have you done an analysis of the circuit? (too tired to try it myself  )

 

[swarfrat]

I read the article, eyeballed the circuit. Haven't run it through spice yet partly because I'm not sure how to model the piezo, but mostly because it's crunchtime at work, weekend work, and the 4yo was up an hour and a half past his bedtime coming back out of his room every now and then. (The only bit of 'free' time I had).

It appears to rely on CMMR and the fact that floating at 1/2 Vpp won't hurt the piezo.

 

[swarfrat]

Trying to read up on this design, I found some improvements of interest.

http://stompville.co.uk/?p=680

 

[mayfly]

Interesting analysis.  I'd be tempted just to get the PCB/FETs from that guy.

 

[swarfrat]

His build is kinda bulky and won't fit inside, which I really wanted.