Quick Piezo battery question.

[puppyonacid]

Hey everyone. Long time no post.

Just a quickie about the battery power supply for my piezo on my JP6. I'm using a stereo Y-cable at rehearsals. That plugs into the same output as a normal mono cable. When I use a mono cable on the stereo/magnetic output, obviously I cant use the piezo and I'm not drawing power from the battery. Or am I? So, if I'm using a stereo cable in the same out put, am I correct in thinking that it only uses juice from the battery when the piezo is selected? Or is the piezo system always losing power as its still technically "plugged in"?

Ta very much.

[puppyonacid]

Anybody?

[beej]

I'm not sure (the jack on the JP is sealed), but the circuit is likely connected by inserting the jack, in which case the preamp will be drawing power (even though the piezo'd output is grounded out).

Check with MM to be sure, but I'd guess you're drawing power.

[puppyonacid]

Yea that's what I thought. The only thing really that I'm not sure of then is, if that's the case, why wouldn't you be drawing power from the battery if you're using a mono cable? Unless it's simply because a stereo cable, because of the stereo connection, will draw power where as a mono cable won't.

[beej]

Normally on the MM guitars when you insert a battery it connects the +9v from the battery (which is wired to the jack) to the circuit in the guitar, turning on the silent circuit, etc. I'm not sure how it's done on the guitars with sealed jacks (the piezos), but it likely connects the +9V or the ground, letting current flow when the guitar is plugged in. (There are a few different ways to do it.)

If that's the case, then any time you have a jack plugged in there will be current draw by the preamp, even if the piezo output is grounded out. (Just because you can't hear the piezo at the output doesn't mean it's not on.)

But again, check with MM- they'll know better than me.

[puppyonacid]

Ok. I'll do that.

Ta for the help Beej

[Matt Gillis]

I've quoted this from the FAQ on the MM site:

What is the battery life expectancy on a John Petrucci with piezo option?

Answer
The battery life of course will vary depending on how much your guitar is plugged in. Whenever your guitar is plugged into either jack, the battery is under load. The average battery life is about 4 months for the player who practices every day for about an hour and gigs 1-2 times a week. One way to remember is: whenever the season changes - so should your battery.

While it doesn't really explain it, it does say that when the guitar is plugged in, it's drawing power from the battery, so that gives us enough of an answer for our purposes I think. I also have another guitar (non-EBMM) that has LED side markers that are powered by a 9V battery, and you can put a cable in the jack, and it will light up the LEDs even though the cable isn't plugged into anything (like a dummy plug). Obviously the cable is just completing the circuit, and the cable has nothing to do with the power (so whether the cable is stereo or mono doesn't matter).

beej explained it pretty well (better than I, at least!) but I'll pitch in anyway and say I concur. But like beej said, ask CS as only they will know; seeing as they build the units. On a semi-related side note though, the piezos in the JP guitars are phenomenal I begin to miss mine when it's not around!

[the24thfret]

I follow that general rule. If anything is plugged in, the piezo is active. I once drained the battery without knowing it by having the cable plugged in for a week or so, even though the selector switch was on magnetic and not piezo.