Help! Piezo volume difference between JP guitars....

[leplaidn]

Hello,

I have a little question for you guys...
I own 3 "Petrucci" music man :
- A JP6 Piezo, bought second hand. I think she comes from the amercian market.
- A JP 7 Piezo, bought from Thomann (Germany).
- A JPX (Piezo), bought from France.

I use a stereo cable, plugged into the magnetic/stereo output of each guitar.
In this case, the "mix" knob is not usable.

I have found a big piezo volume difference between these guitars :
- the JP6 and the JPX have the same piezo volume output.
- the JP 7 has a lower volume, about -8db !!!!

Treble and bass knobs are set the same way.
Batteries are new.

It s quite boring when you have to change guitars, i have to change the volume of the PA...

Have you heard about this ?
Is there something i can do ?

Thanks in advance...

 

[Iperfungus]

Hi there!
I do not know for sure and I would wait for suggestions from more experienced people, but....did you check already if there's an internal gain/level trimpot for piezo output adjustment??
In that case, different settings could explain the difference among JP6/JPX and the JP7.

 

[leplaidn]

Hi,
Thanks a lot for your answear.
Your statement is quite logical. So i take a look at the piezo system : i did not find anything...

The only thing i ve found is an inscription on the piezo "motherboard" : "EBJP REV 2.0".
It is the same on both JPX and JP 7 (did not check the JP6).

Such a mistery...

 

[Iperfungus]

I had a look to this schematic:

John Petrucci 6

JP6 is the original Music Man John Petrucci signature model. The basswood body features a high gloss durable finish with stylish lines and an ergonomic scooped arm contour. The smooth action floating tremolo allows for raising and lowering of the pitch with impeccable tuning stability and piezo...

www.music-man.it

If I'm not wrong there, the piezo board should have trimpots/controls for volume, treble, bass and mix of magnetic and piezo pickups, the volume being the dedicated pot on the guitar's top.
You should have access to mix, bass and treble controls on the back of the guitar, on top of piezo board external side.
I would check if all the trimpots have the same settings on all guitars...
Then...if boards are the same on all guitars and settings are as well, I would check saddles...

 

[leplaidn]

The piezo board do have trimpots :
- treble and bass which works.
- mix (between magnetic and piezo) which is inactive because i use a stereo cable (piezo and magnetic are separated, magnetic goes to my amp, piezo to a PA).
The volume knob for the piezo is on the guitar body (after the tone knob), and is at max.
May be it has a different impedance, but at max this should not be a probleme... I'll take a look to confirm that.

All setings are the same on all guitars. I try different settings to compensate for the volume drop, but it does nothing.
About saddles, i can't check anything, no access possible..

 

[Iperfungus]

The piezo board do have trimpots :
- treble and bass which works.
- mix (between magnetic and piezo) which is inactive because i use a stereo cable (piezo and magnetic are separated, magnetic goes to my amp, piezo to a PA).
The volume knob for the piezo is on the guitar body (after the tone knob), and is at max.
May be it has a different impedance, but at max this should not be a probleme... I'll take a look to confirm that.

All setings are the same on all guitars. I try different settings to compensate for the volume drop, but it does nothing.
About saddles, i can't check anything, no access possible..

I've to give up then...
The question needs some more experienced/skilled people on JPs with piezo.

 

[leplaidn]

Thanks again for your time ;-)

I have taken some measurements on the volume knob, for both the JPX and JP7.

For the JPX, i have 3 differents values possible (knob at min and max, between the 3 connectors):
0 Ohm, 16 kOhm, 23 kOhm.

For the JP7 : 0 ohm,15 kOhm, 22 kOhm.

There is a difference about 1kOhm between the 2 guitarts.
I dont think this could be the probleme, but i dont know ...

 

[Iperfungus]

Thanks again for your time ;-)

I have taken some measurements on the volume knob, for both the JPX and JP7.

For the JPX, i have 3 differents values possible (knob at min and max, between the 3 connectors):
0 Ohm, 16 kOhm, 23 kOhm.

For the JP7 : 0 ohm,15 kOhm, 22 kOhm.

There is a difference about 1kOhm between the 2 guitarts.
I dont think this could be the probleme, but i dont know ...

Measurements are quite the same.
I don't think that's the problem.

 

[DrKev]

Bonjour!

Have you contacted Music Man customer service and asked them? Make sure to include the serial numbers of your guitars and if there are version or revision numbers on the ciruit boards include them too.

Maybe it's possible the circuits and outputs are deliberately different because Petrucci wanted it that way. Music Man make the guitars that the artists actually want and use, so if Petrucci wanted a change at a particular time or for a particular version of his guitars, that's what they make.

 

[GoKart Mozart]

I seem to recall some discussion on the MM Guitar FB page recently about differing outputs in the newer piezo transducers & preamp vs. the older ones. Seems like @PeteDuBaldo had some insight on that.

 

[PeteDuBaldo]

I would contact Music Man customer service first, as they are best suited to help you.

That being said, sharing photos of the saddles for each guitar and the serial numbers will help. Also, each preamp is labeled on the circuit board with v. 2.0 or v. 3.51 etc.

The preamp versions are particular to the old/new still saddles. The newer saddles have a lower output than the originals (for manufacturing consistency of output), and the newer preamp compensates for that.