Tuesday, October 11, 2011

Behringer DCX limited malfunction

I've noticed that from time to time my Behringer DCX 2496 goes into a wierd state where the input and output level lights don't display and the controls don't operate.

It still produces output in the mode, however.  But I had been wondering if the output was compromised either by crossover not operating (all outputs might be full range, for example) or whether the infamous high frequency cutoff of the digital input ASRC starts happening.

This is not related to a powerline cutout, though I leave my Behringer (and the Tact RCS 2.0 which feeds it AES/EBU) turned on all the time.  I have my whole system (except power amp) now running from a Belkin PureAV AVU 1500 power conditioner and sine wave UPS, which kicks in seamlessly (I've watched it do so without any noticable glitch) except that the backup power is balanced mode.  And recently (strangely enough for my neighborhood) there haven't been any power outages anyway.

So when nevertheless I noticed the Behringer go into control lockup state, I decided to leave it that way until I could get around to doing a set of comprehensive measurements.  I listened to it in lockup state for weeks, even auditioning some new Nordost Baldur balanced interconnects for my Oppo BDP-95 to Lavry AD10 connection which allows me to play SACD and DVD-Audio discs from the uncompromised analog outputs of the Oppo into the digital processing that forms the core of my system.  I decided I liked the old version and sale priced Baldur better than the Belkin 1800F balanced wires I was using previously.  That was obviously some serious listening, but I didn't notice any defect in the sound like a HF cutoff, it was sounding better than ever with the Baldur interconnects.  On the other hand, I did worry just a bit that some HF cutoff might be romanticizing the sound somewhat.  I've heard some systems with obvious HF cutoff sound romanticized, though when I deliberately low pass my own system it actually makes it sound flat and harsh.

Finally I got around to doing the measurements.  Everything seemed to be working normally.  Frequency response was essentially flat at 22kHz (actually, it measured about 0.3dB down, which could be mostly or partly due to rolloff in my Fluke 8060 true RMS meter and/or the analog inputs of the Tact which I rarely use) through the midrange outputs.  The supertweeter outputs rose sharply above 16kHz, peaking at 20kHz, and falling down a bit at 22kHz, as intended (I actually shelve high frequencies slightly to protect my supertweeters from spurious high frequencies found on some discs).  Anyway, there was no evidence of either a 10kHz cutoff or malfunctioning of the crossovers.  I also verified the high pass filter on the midrange outputs, but didn't bother verifying the subwoofer outputs.

So now I know the lockup state has nothing to do with ASRC or crossover malfunction.

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