A few questions regarding Piezo loaded bridges and circuitry

Texas07R8

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Hey guys,

I just got a Graph Tech Ghost Acousti-Phonic Preamp kit and have a Resomax bridge coming any day now.

The guitar it's going in is a custom build I'm close to finishing now. It's patterned after my 59 DC LP Jr. I've got two P90s like a Special in it and the control cavity is the same as a LP Std.

I'm still undecided on how I want to complete the system. I have some ideas on what I want but don't know if it's the most practical or best methods.

Ideally, I'd like control over both P90 volumes, I don't mind a master tone for the magnetic pickups. I want some form of volume control for the piezo pickups.

I found that Stewmac has a 6-way toggle switch that caught my eye. I was thinking that I could setup the guitar up with the following setups:
6-way switch positions:
1- Neck P90 no Piezo
2- Neck P90 and Piezo
3- both P90s no Piezo
4- both P90s and Piezo
5- bridge P90 no Piezo
6- bridge P90 and Piezo

I like this setup allows me a lot of tonal control, I still have the ability to swap my magnetic pickups from front P90, both P90s and the bridge P90 like a regular Gibson. The exception is having a common master tone control.

The other option I considered was a center detent blend control pot. This would let me blend the magnetic pickups and the piezo in a way that the blend acts like a master volume for both mags and piezo. If I went with this design I'd probably want a standard 3 way switch to toggle my magnetics separately then whatever the magnetic signal was from the 3 way switch that would go into the blend control and there I could dial in more or less Piezo or Magnetic pickups.

I read that if you use a 3 way toggle for switching between magnetics, piezo or both, the standard Gibson 3 way toggle won't work to mix piezo and magnetics. I think the Graph Tech 3 way mini toggle for piezo and magnetic switching is a SPDT type switch, does anyone know if that's the case? I don't know that I need this for my setup but I'd like to be clear in my head what type of switch I need if I wanted to toggle between mags and piezo.

Also, I've read that I can use a 250k or 500k std. pot for piezo volume control. OK, which is better? Seems like the 250k may be a better pot for the piezo volume. Also, I'm assuming you want a linear pot rather than an audio taper?

Going back to my first choice, the StewMac 6way toggle setup, I want separate volume controls for each P90 and a master tone control. Then a 3rd pot for piezo volume control and the 4th position in the control cavity would be for the 6-way switch. Does anyone (Jonesy maybe?) have a wiring diagram that will do what I need for this setup.

Also, any ideas on using a blend pot instead of the 6way toggle. Again, I want separate volume controls for each P90, a third pot for blending piezo and mag volumes and in the forth pot for master magnetic tone. Then I need to fit in a mini 3 way toggle to switch my magnetic pickups before the signal gets to the blend pot/master volume.

thanks for any tips or suggestions. BTW_ I'm using a stereo jack out, it's a smart system than senses a mono or stereo plug and if it's mono it will blend piezo and magnetic signals together. If it senses stereo the piezo and magnetic signals are discrete and will go to two amps.
 

H.E.L.Shane

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ummmmmm i'd need to actually draw that out...

but.. for me... I like the idea of the blend pot.. but it presents some other problems that the 6 way switch and seperated volume controls do not....
 

Texas07R8

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Well, if you can design a plan that is the tits please post it. I'm having a hard time finding much info about custom wiring of these piezo systems into mag systems.

I've got mine working with the piezo bridge and the two P90s are controlled by a blend pot then a master volume with a master tone then the preamp. The piezo has a volume as well but that harness is separate and all three wires go straight into the board.

While the mags and piezo is working and sounds good I know somethings not right. I have a 3 way mini toggle switch for switching from mags/both/piezo and I'm not getting a discrete signal for some reason. No matter what position my 3 way is I can still get sounds out of my Marshall and Fender amps at the same time, it should only do that in the middle position.

The tone is good and I am surprised how strong the piezo circuit is, compared to the P90s it's got almost as much signal to drive the amp near the same volume. I thought I'd have to tweak the pot on the preamp to dial up or down the signal strength of the piezo compared to the magnetic side but in this case I think I'll leave it unless I find other issues when I figure out my current issue.
 

Texas07R8

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thanks Jonesy, you da man.... I'll check the links you posted and if I have any general questions I may pick your brain a bit. thanks again and peace my brother!
 

jonesy

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Your welcome Sir ;)

That 6 way toggle switch from Stew Mac requires routing some wood in the switch cavity, but maybe you already new that? :hmm:

I have used push pull pots to switch on the peizo pu to the passive pu's but some peizo's like the Fishmans require an active boost for that.
 

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