9 Volt DC Phantom Power Supply for Electro-Acoustic Guitar

[Dheran]

Yes Andy. Thank you all!

[Sam Spoons]

Yup, same ear

If you don't want to use staples then better glue for the velcro (or better velcro, the real stuff from 3M is noticeably better than the cheap stuff both WRT the glue and the actual velcro? Otherwise I'd give it to your luthier, remembering that anything he modified he can un-modify back to original spec.

[Dheran]

Just four your (possible) curiosity:

My luthier and I were talking about possibilities. Taking everything out has the disadvantage of letting too much cable length between the piezo and the preamp, so capacitance could generate signal loss, and interferences could cause noise. Some filtering should be needed, so an specific preamp it´s better for these cases. Passive pickups need good pres, in part for these kind of filterings and whatever.

So using the internal Baggs preamp doesn´t seem to be the best with long cable to the pickup, since it´s an internal preamp, not prepared for heavy filterings.

He´s ALMOST convinced that the power switching lead of the endpin works by a mechanical switch (you know, that kind of sockets with additional legs that act as interruptors) instead of shorting ring with sleeve. Actually, in this case, it´d be shorting second ring with sleeve (because first ring is proved to NOT turn on the preamp by getting shorted to ground, since inserting a TRS cable turns on the guitar while insulating ring from sleeve). Not too probable the TRRS thing.

So, if we assume that there´s a switching socket, actually we could implement a solution which would allow me to use external power (just applying +9V to the ring and desoldering-soldering internally just the way I described in a previous post) if battery is not attached in the internal clip... AND, in case of forgotten TRS cable at home, or lost, or whatever... (some emergency or odd situation, I mean) just connect a battery into the internal clip, put a normal instrument cable (TS) and get the job done.

I think I´m going to try this. Will build a box, similar to Jay´s one, and let my luthier mod the preamp-endpin. Let´s see what happens.

[Jay Menon]

I read this thread four years too late - but even though it’s late I thought I would reply. The TRRS and pin jack socket that you need is LR Baggs own strapjack plus model:

https://www.ebay.co.uk/itm/361129745116 ... media=COPY

Cheers
Jay

[Dheran]

Thanks Jay.

I ended up modifying the wiring in the preamp (my luthier just had to desolder one wire from its position and resolder in other position).

That worked, using a TRRS cable and en external little box with a 9V battery compartment and a 9V socket for an optional power supply.

It went perfect. But finally I got fed up of needing the TRRS cable and having care of not connecting the power prior to plugging the cable. I burnt the volume pot because of doing that.

So, for me, the days of active built-in preamps in guitars are over. I've switched to passive pickups (k&k style SBTs). I plug the guitar with an standard TS cable, no batteries, no danger of damaging preamps, into an external pre (which can even be a multieffetcs pedal, because 1MOhm impedance is the only thing you need to make the pickup work fine). It works great, simple, clean and hassle free.

[Wonks]

I found my K&K sounded better into a 10k line input.

[Dheran]

I'm not really surprised... I find it great sounding in 470k inputs... So I believe you!

[Jay Menon]

If I wish to install an ordinary passive undersaddle piezo transducer

and the input impedance of my first unit is 5 MegΩ

how would I make this work please?

https://imgur.com/FVDWxge



https://i.imgur.com/FVDWxge.jpeg

[Wonks]

I'm not really surprised... I find it great sounding in 470k inputs... So I believe you!

My Fishman Loudbox Mini has a 10M input for those piezos that need a really high Z. But with the K&K there was far too
much bass. Running in to a mixer line input and an active PA speaker it sounded far more natural. So I made a pre-amp pedal with a 10k input impedance for use with the Loudbox.

It may be down to the installation on my guitar, and the Loudbox does seem to be quite bassy with a lot of my guitars with preamps. It certainly won’t be ideal for all piezo installations. But if you’ve the chance to try some different input impedance devices with flat outputs, it’s worth a go.

[Wonks]

If I wish to install an ordinary passive undersaddle piezo transducer

and the input impedance of my first unit is 5 MegΩ

how would I make this work please?

https://imgur.com/FVDWxge



https://i.imgur.com/FVDWxge.jpeg

Well, you could simply wire it to an endpin jack on the guitar. Cut the 3.5mm jack off if necessary as it’s just a braided outer sheath with a central core like a lot of vintage pickup wire. That sort of undersaddle piezo normally needs a 5-10Meg input Z to give a flat response.

Or wire to an endpin jack with a built-in preamp.

Or fit a full-blown preamp into the guitar. Several preamps just stick to the under-rim of the soundhole so modifications are minimal.

[Wonks]

If there is no existing undersaddle pickup, then be aware that the pickup element will raise the height of the saddle.

So you’ll either need to lower the bottom of the saddle by the height of the pickup, or, if the saddle slot isn’t very deep and the saddle now angles forwards, you’ll need to get the saddle slot deepened.

Of course you’ll need enough depth in the bridge to be able to do this. Most guitars should be fine but I’ve come across one with a shallow bridge where the bottom of the slot was the actual top of the guitar. So no room for an extra 1-2mm of routing in that instance.

If there is some slight wobble of the saddle in the bridge slot once the pickup element is fitted, then I’d make a new saddle from one that’s thicker than the slot and sand it down to fit. It shouldn’t be too tight and needing to be forced in (or the string vibrations won’t get fully transmitted to the piezo element), but should have just enough grip so it doesn’t fall out easily if you turn the guitar upside down.