On 07/01/2013 05:29 PM, Fons Adriaensen wrote: > Hello all, > > The incredible happens. > > The electronics of the 'Lampadario' at the Casa del Suono in > Parma consists of a rack with an RME ADI468 converting MADI > to 8 ADAT outputs, 8 Behringer ADA8000 converters, and 8 QSC > amplifiers of 8 channels each. The rack was wired (very neatly) > by a firm specialising in this sort of work. > > When I installed the software four years ago, I found out > that 25 of the 64 channels had their phase inverted. For one > of those it was an error in the speaker wiring, which was easy > to correct. The other 24 corresponded exactly to 3 groups of 8, > and the speaker wiring was OK. I assumed that the cables between > the ADA8000 and the amps were to blame - this is a non-standard > cable which had to be hand-made by the whoever did the wiring. > If two technicians had worked on that, they could have had > different ideas of what were the correct connections. > > Since I didn't want to take the rack apart, resolder 24 wires > and put it all back, and since there was only one SW app driving > the installation at that time, those 24 inversions were corrected > for by that software. So far so good. > > Recently I re-measured the IRs of the whole thing. There > were again 24 channels out of phase. But not the same ones. > One of the groups of 8 had turned in-phase, and another > one was now inverted. > > The only thing that has happened to the installation over > the last years is that some of the Behringers failed (power > supply blown up, one per year on average) and were replaced. > So I checked those separately. And yes, some of them had their > output phase inverted w.r.t. the others. Apparently the thing > exists in two versions, but apart from measuring there's no > way to tell which is which. So I'll have to recheck things > each time any of them are replaced again. Thank $GOD we didn't > use those for the WFS system. > > The incredible happens. > > Ciao, Wow. Tricky. I think the original Black-faced ADATs would record the audio out of phase to tape, and then correct it on the way out. So if you had tapes recorded in a Black-faced ADAT, and played it in a silver XT, or had tapes recorded in a Silver XT, and played it in a Black-faced unit, you were 180 degrees out of phase on playback. Rich... _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
