Re: [LAU] OT: Phantom power and my acoustic guitar

From: Jörn Nettingsmeier <nettings@email-addr-hidden-hochschule.de>
Date: Sun Jan 25 2009 - 23:51:38 EET

Andrea Del Signore wrote:
> Hi all,
>
> sorry for the off-topic post, but since I'm a linux audio user from a
> long time
> this is the only audio group that I know ;)
>
> My question is: can I connect an Ibanez AW40ECE-NT guitar to a mixer
> with
> phantom power switched on? The guitar has a fishman pickup and an Ibanez
> SST
> preamp and I'll connect with the mixer using the XLR output, so the
> connection
> will be XLR to XLR.
>
> Best regards,
> Andrea
>
> P.S.
> I'm asking it here because searching through the various guitar and
> homerecording forums I found contradictory responses: someone says that
> I can
> damage my guitar pre or mixer and some other that it safe to connect
> with an XLR
> cable on both sides ("phantom" power).
>
> My mixer manual says only that I can't connect "unbalanced" equipment
> while
> phantom power is switched on.

that depends on how your cable is wired. i assume that your guitar is
unbalanced, i.e. it has a 2-pin connection.

phantom power works because pin 2 and 3 of an XLR connection are both
48v. if you connect your guitar to pins 2 and 3, both are at 48v
potential, i.e. no current flows (hence "phantom").

but if you connect your guitar to pin 1 and either 2 or 3, then the 48v
will cause a current through your guitar's electronics. if its impedance
is high, no problem, but if it is significantly lower than a few hundred
ohms, you will get a heat problem and possibly damage your equipment.

both ways of wiring will work, but the 2/3 scheme requires balanced
inputs, otherwise you will hear nothing.

the mixer's phantom power should be short-circuit-resistant, so it will
not take damage even while it's frying your external gear. but since
most mixers should have a current-limiting resistor in series with the
phantom power rail, most types of gear should be safe. i wouldn't bet on
it, though.

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Received on Mon Jan 26 00:15:04 2009

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