I actually wanted to reply to a couple of previous posts but I'm new at this
newsgroup thing.
A number of people have had problems with the new behringer ub mixers
causing certain line out devices (ie sb live cards and vhs lineouts) crapping
out after a couple of minutes when used in the stereo line channels at the
-10db setting. I've had the same problem myself with my sb live. I exchanged
the first mixer believing it was defective, but the new one exhibited the same
problem. After a ton of long distance phone calls to behringer canada (they
don't have a toll-free number) and a couple of months, I was finally sent
another demo mixer to see if I could recreate another problem I was having.
(more on this later). This third mixer also had this problem. A number of posts
thought the problem was related to DC offset from the line out devices.
I believe however that the DC is coming from the line inputs of the
Behringer, and causing the output stage of more susceptable line outs to become
unstable, for instance my sb live. Here's why I believe this is so.
My sblive does have a very slight dc offset on the left channel of 12
millivolts, however a very cheap aopen card I have with a much larger dc offset
of about 1.5 volts works forever in the stereo inputs at the -10 setting. This
would imply that the mixer isn't distorting from the dc voltage of the line out
device. When I measured the voltage at the line inputs of the behringer mixer,
all of the voltages were 0, including the mono channels regardless of input
trim, and the stereo channels at the +4 setting. However when the -10 setting
of the stereo channels was engaged (which are the channels and setting causing
the problem), I found 2.3 volts at every input, and 5.8 volts when the phatom
power was turned on!
Another problem I've found in 3 separate ub1622fx-pro mixers is what I
believe is interference from the meters showing up at the output stage of the
fx unit. Lets suppose you want to record a track using an "insert effect" on
the mixer through the sub outs and monitor previously recorded tracks with the
main mix. With the fx return at 12 or one o'clock or so assigned to sub out,
and the control/phones monitoring the main mix with the meters peaking at +4,
you'll hear something similar to distorted crosstalk (but louder, approx -40db
at my usual recording levels) coming through the sub outputs. This interference
won't show up at the control room out or through the headphones however, which
is why perhaps no one has noticed it before. If you reverse the setup, monitor
sub and assign fx return to main, the interference shows up at all main outs as
well.
I'm just curious whether anyone else has recreated this interference
problem, and if others have similar voltages at the stereo line inputs. I find
it hard to believe behringer had no idea of these design problems.