Jump to content

Voting for March 2020's Guitar Of The Month is open - VOTE HERE!

Archived

This topic is now archived and is closed to further replies.

Paul Marossy

Great Diy Buffer/preamp For Piezo Pup Guitars

Recommended Posts

Cool, thanks for your insights. And I'm glad that it was of some use to you as well. :D

Thanks to you too. Ive got this built into my LP now, on a 0.7" x 0.7" scrap of Veroboard, tucked into a space behind the output jack. Its trouble free, it just sits there and does its job.

John

Share this post


Link to post
Share on other sites
I built this little gizmo to try out with my acoustic-electrics and my Parker Mojo Nitefly. It really works pretty well and is very easy to build. It should work well with any instrument that has a piezo - from bass to violin.

http://www.diyguitarist.com/Guitars/PiezoBuffer.htm

It won't substitute for an amplifier that is designed specifically for acoustic guitars, but it does make one sound a whole lot better when plugged into a regular guitar amp.

Thanks for posting this, Paul. :D

I'm currently running my T-Bridge into a 5 meg volume pot, through a mag/both/piezo toggle, then to an outboard f/x processor via the "ring" on a stereo cable.

It's a pretty good faux-acoustic sound, although I have to boost the lows and highs a bit to get it sounding more acoustic-ish. And I'm getting some crosstalk - magnetic p/u signal bleeding into the piezo in the "both" setting... not sure if it's a wiring problem or cable capacitance/inductance/impedance issue...??? Would a little onboard buffer like this improve the tone and possibly solve the crosstalk issue?

Thanks for your help,

Mike

Share this post


Link to post
Share on other sites
Would a little onboard buffer like this improve the tone and possibly solve the crosstalk issue?

It might help with the tone when driving long cables with an active piezo circuit, but it's really designed for passive piezo pickups. On the crosstalk issue, I'm not sure that it would help anything. I'm inclined to think that the problem may lie in the wiring somewhere.

Share this post


Link to post
Share on other sites
it's really designed for passive piezo pickups.

Hmmm... the T-Bridge is a passive piezo pickup, I didn't install a preamp (Ctrl-X or the like) with it.

Share this post


Link to post
Share on other sites
On the crosstalk issue, I'm not sure that it would help anything. I'm inclined to think that the problem may lie in the wiring somewhere.

FWIW - Found this in the LR Baggs MixPro manual:

"4.2 Crosstalk: Crosstalk is interference or "bleed" between two signals within a common shield, such as a stereo guitar cable. This common

problem is often encountered when a high-impedance piezo pickup is mixed with a low-impedance active source, such as a mini-mic. The bleed

signal from the mic mixes in the cord with the pickup signal and appears in the pickup channel. The higher the amount of amplification (gain)

required for the pickup (and longer the cable), the more of the mic signal will be present in the pickup channel. It is common to encounter 25% to

50% mic bleed into a clean pickup channel."

The mag pickup signal isn't active and is probably higher impedance than a mic, but I'm sure it's a lot lower impedance than the piezo.

Share this post


Link to post
Share on other sites
The mag pickup signal isn't active and is probably higher impedance than a mic, but I'm sure it's a lot lower impedance than the piezo.

That's true if your piezos are active. Otherwise, your piezo pickups want to see four times the input impedance that magnetic pickups want to see to keep your high end sounding good.

Share this post


Link to post
Share on other sites
That's true if your piezos are active. Otherwise, your piezo pickups want to see four times the input impedance that magnetic pickups want to see to keep your high end sounding good.

The piezo is passive, and is connected to a 5 meg pot. It's still a very high impedance signal traveling down the cable, isn't it?

Share this post


Link to post
Share on other sites
The piezo is passive, and is connected to a 5 meg pot. It's still a very high impedance signal traveling down the cable, isn't it?

Yes. I was just pointing out that non-active piezos are way higher impedance than magnetic pickups.

EDIT: Sorry, I misread that one sentence earlier. :D

Share this post


Link to post
Share on other sites
I was just pointing out that non-active piezos are way higher impedance than magnetic pickups.

Thanks... so running the magnetic and passive piezo signals through a stereo cable could cause crosstalk? If so, it sounds like I need to build that buffer!

Share this post


Link to post
Share on other sites

Yeah, I think the buffer will probably fix that. You might also be able to use a seperate shielded cable from the piezos to eliminate the crosstalk (maybe from the piezos to the buffer, too). I think the buffer kills two birds with one stone, though.

Share this post


Link to post
Share on other sites
I think the buffer kills two birds with one stone, though.

Indeed it does. Works great - great tone, no more crosstalk.

Thanks again, Paul. :D

Share this post


Link to post
Share on other sites

follow up...

We know that without the buffer the magnetic signal was bleeding into the high-impedance piezo signal. Fixed that with the buffer.

Now, with the buffer in place is it possible that I've also somehow reduced the capacitance (or some other factor) in the "other side" of the stereo cable, affecting the tone of the magnetic signal? I'm noticing a definite change - the two-humbucker sound is more Les Paul-ish (good) but the split coil Strat "two" position is now less "stratty" (not so good). Hmmm...

Share this post


Link to post
Share on other sites

If anything, the "Mint Box Buffer" should help all around. For your magnetic pickup tone to change like that is weird - that really shouldn't be happening, AFAIK. If anything, it should have helped with the mag PUPs...

Are you sure that maybe something isn't slightly miswired?

Share this post


Link to post
Share on other sites
If anything, it should have helped with the mag PUPs...

That's the thing, I'm wondering if it did "help" by reducing some sort of common impedance or capacitance/inductance (I'm not totally up on my electronics theory) that was occuring without the buffer. :D

Share this post


Link to post
Share on other sites

If it "helped", your Strat sounds should sound just the same or better (meaning more bite).

Share this post


Link to post
Share on other sites

I think I've got a little switcheroo going on :D ... now the low-impedance piezo is bleeding into the magnetic signal when I have them on together, and it affects the magnetic tone. The mags sound normal when the piezo is grounded out by the selector switch.

Perhaps a stereo cable with individually shielded conductors will reduce the crosstalk. Fishman makes one.

Share this post


Link to post
Share on other sites
I think I've got a little switcheroo going on :D ... now the low-impedance piezo is bleeding into the magnetic signal when I have them on together, and it affects the magnetic tone. The mags sound normal when the piezo is grounded out by the selector switch.

Perhaps a stereo cable with individually shielded conductors will reduce the crosstalk. Fishman makes one.

I was thinking of suggesting doing something like that whan I made my last post, but I didn't really feel like I had enough info to make any suggestions. I think that's probably what you're going to end up having to do to get rid of that problem.

Share this post


Link to post
Share on other sites

Yeah, I noticed yesterday that there's still a slight bleed from the mags into the piezo... :D

And I'm getting some distortion when playing hard - probably need to remove one of the input resistors to reduce the gain.

Share this post


Link to post
Share on other sites

×
×
  • Create New...