Berhringer UltraAcoustic AT108: PA system hookup issues

[n***@gmail.com]

Recently purchased a Behringer UltraAcoustic AT108. Amp sounds fine
when used alone, I have no issues with it. However, when I connected it
yesterday to a sound system at a gig, going from the headphone out jack
into a mixer, there was a terrible buzzing noise. The only way around
it was to set the volume on the amp very low -- near 1 or 2.

To make sure it wasn't the guitar, cords, mixer, speaker, or anything
else that was causing it, we substituted a similar sized and wattage
Peavey combo amp and everything sounded perfect -- it was obviously the
Behringer.

My question is this: is something wrong with this particular Behringer,
with all Behringers, or am I doing something wrong when I hook it up? I
am following the connection example from the user manual directly, so I
don't think that is it.

I bought it only because it was an "acoustic amp", and I figured I
would get a nice sound out of my Ovation Celebrity with it, but when I
used my friend's Peavey yesterday, it sounded identical, if not better,
and it has no issues when plugged into a PA system.

Should I return this amp?

[m***@yahoo.com]

Post by n***@gmail.com
Recently purchased a Behringer UltraAcoustic AT108. Amp sounds fine
when used alone, I have no issues with it. However, when I connected it
yesterday to a sound system at a gig, going from the headphone out jack
into a mixer, there was a terrible buzzing noise. The only way around
it was to set the volume on the amp very low -- near 1 or 2.
The headphone out is a stereo jack(3 conductor). by pluging

a mono plug (2 conductor) into this jack, you are shorting
out one channel of the headphone amp to ground. This accounts
for the buzzing noise. If you have not blown out the headphone amp
by doing this (you may have already) you need a "Y" cord with 3
conductor stereo plug on one end ( headphone jack end)
and two mono plugs on the other two ends of the "Y". one of
these mono plugs can go to an external mixer. however dont you
have a mono line out on the AT108? This is what you SHOULD be
using. You can buy a Y cord at radio shack or other electronic
supply. Hold on let me check the AT108 spec sheet.........

[m***@yahoo.com]

here is a link to the on line manual:
http://www.behringer.com/AT108/index.cfm?lang=ENG
there is a mistake in this manual that tells you to
hook a mono plug to the headphone jack, dont do
this. you can only connect a 3 conductor stereo (TRS)
plug to the headphone jack, buy the "Y" cord from
radio shack as I have said, and this should solve the
problem. There is a picture of a Y cord like this
on page 7 of the manual. Only instead of RCA plugs,
you want 1/4" phone plugs on all three ends.
your Y cord should be 1X stereo plug (TRS)
to 2X mono (TS) 1/4" plugs. OK so if the circuitry
has not been shorted out, this should work ok.
no its not the amps fault, the instructions have a
mistake written in them, which you followed,
not your fault at all.

[n***@gmail.com]

when I connected it yesterday to a sound system at a gig, going from
the headphone out jack into a mixer, there was a terrible buzzing
noise.

you need a "Y" cord with 3 conductor stereo plug on one end and two
mono plugs on the other two ends of the "Y".
however dont you have a mono line out on the AT108?

No, the AT108 didn't have a mono line out. Shortly after you posted
your reply, I was contacted by a tech at Behringer who suggested I use
a Behringer ULTRA-DI DI20 box to eliminate ground loops.

Short story: I bought the DI20, it didn't work. Not only that, the
Behringer AT108 amp "blew up" (there was a lot of foul plastic-smelling
smoke emanating from it) and completely fried itself shortly afterward.

Not sure if the DI box was the cause of it, but in any case, I'm now in
the market for a new amp for my acoustic. Any recommendations?