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Re: Stuck in the Middle Problem
At 01:26 PM 2/5/00 -0800, Claude Voit wrote:
>Tim Nelson wrote:
>> I've already double-checked the wiring to ensure that the polarity is
>> copacetic and everything, the amp's mono/bridge switch is in the correct
>> position, the board's not overloading, the input levels are fine; I
>> find a problem...
>did you try it with another line source like the MD direct in the amp
>to test the amp alone ??
Good idea. I just tried it; the problem's still there, so I think I can
rule out a mixer problem suddenly having developed. It's either the amp or
the way I'm using it.
>>the amp's mono/bridge switch is in the correct position
>are u shure ??
I had visually checked the switch when I opened the box, but hadn't
physically set it, so I just pulled the amp out of the rack to be sure. It
was correct. (The switch is recessed into the bottom of the unit and is
inaccessible when installed in a rack.)
>sorry if doesnt help because
>I'm no technician just another guy with a big system that sends you some
What I'm suspecting now( yet since I'm no engineer it's only a guess) is
that the problem may in some way be related to phase, since it only happens
when the signal to the two sides is different (i.e. when there's a true
stereo source, when the pan control on a particular mono channel isn't
centered, or when the output faders are set to different levels. At
extremely low volumes, the problem disappears. I know the amp has
protection circuitry which will not allow it to operate if the load drops
below 4 ohms, and I'm wondering if that might be happening, since the
"protect" LED flickers whenever the distortion is present. I'm not exactly
sure what the load is; I'm using it to power a pair of SoundTech monitors
which each have 1-12" and a horn (the specs panel was never filled out and
I got them at least secondhand) but I can't imagine them being lower than 4
ohms. (Trying to smallerize, and not have to carry the big cabinets
around!) I suppose I should start looking for my meter...
Does anyone know if this type of problem would occur if the impedance of
the monitors were not the same? I'm assuming they are identical, since
they're the same model, but I'm not certain. They're pretty beat up, too,
so I'm not ruling out anything!
I have to pack the rig up in an hour or so to take out to play this
afternoon. I can get by without using the SR-16, and I suppose I can use an
adaptor to send the MiniDisc in mono to an unused non-stereo channel, but
there go my cool side-to-side sampled atmospheric loops! I guess I'll be
bringing the bass heads and cabs as a backup...