[sdiy] Quad 405 and Behringer

[Charles Bisaillon]

Hi guys,
 
Maybe someone will be able to shine a light on amplifiers output voltages.

Here goes, I bought a kit of components to renew my beloved Quad 405 amp
because the right channel was unstable and distorted. So I changed a bunch
of capacitors, the opamps, inputs and outputs connectors. Put it back
together and start testing the sound, which in my opinion, was of different
amplitude from channel to channel (because of the monitor mixer I found out
later).

So I thought, do we mesure amplifier outputs with a voltmeter to get a
quantitative result? Well, I ran the same saw wave in both channels and came
up with amazing data. The right channel of my 405 is at most 0.7V lower than
the left channel across the whole amplitude range. Can anybody tell me if
that¹s a problem, or is it so low it can be ignored?

Second thing I found is ³why Behringer has a bad reputation². I heard a lot
of people saying that the products are not so good etc, but never knew why
and how drastic things can get. I use a Eurorack UB1002 for monitoring
purposes only to have instant access to multiple audio formats (cpu, CD,
reel to reel, cassette, etc). When I was running the mono saw wave through
it to test my 405, I got potential differences of 5 to 10 volts from channel
to channel (that¹s what had me starting the test in the first place). I then
tested more and found that the Control Room potentiometer is made of jell-o;
and since this is the only pot I¹ve tested, I¹m now pretty sad to think that
this mixer has 25 pots total :(

In the end, I can now join the club and have my very own Behringer story to
tell.

Thanks

Charles



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