• cupakm
  • AES/EBU artist
  • Offline
  • Registered: 2014-04-03
  • Posts: 101

Topic: UCX II 7th input channel hissing sometimes

Hi all,

I'm using an UCX II + QuadMic II combo for a month or so and I notice sometimes I get around -50dB-ish well audible hiss on 7th channel. QuadMic connects its 1-4 outs to 5-8 ins on the UCX. Tried switching cables and mics to QuadMic's 3rd channel, which is being fed to UCX's 7th, even turning off/on P48 does no effect, the hiss just gets back.
The only remedy I've found so far is power-cycling the UCX, then it goes away and CH7 behaves back to normal like the other ones.

I didn't yet notice when exactly does the hiss appear, happened like 3 times in a month of sporadic usage. But it still ruins recording and having to stop, reboot the UCX and start over isn't nice. I wonder if I'm doing something wrong.
Any ideas apart from sending the unit back to retailer?

The UCX runs in CC mode with the latest to date FW 104.

Best regards.

cupakm's Website

  • From: Haimhausen
  • Registered: 2012-04-02
  • Posts: 239

Re: UCX II 7th input channel hissing sometimes

If you disconnect USB and reconnect again, without restarting, during a hiss? Is it also gone then?

Regards,
Audio AG Support

Audio AG Support's Website

3 Reply by cupakm (edited by cupakm 2023-11-03 11:54:18)

  • cupakm
  • AES/EBU artist
  • Offline
  • Registered: 2014-04-03
  • Posts: 101

Re: UCX II 7th input channel hissing sometimes

Many thanks for your answer!

It didn't occur since my last report. If it happens again, I'll try unplugging, waiting a few seconds and reconnecting the USB cable then.

cupakm's Website

  • cupakm
  • AES/EBU artist
  • Offline
  • Registered: 2014-04-03
  • Posts: 101

Re: UCX II 7th input channel hissing sometimes

Audio AG Support wrote:

If you disconnect USB and reconnect again, without restarting, during a hiss? Is it also gone then?

It didn't take long for the issue to reoccur.
Answer to your hint is: no, it isn't.

But, in addition to swapping cables connecting QuadMic's OUT3 with UCX IN7, I've tried inserting QM OUT3 to UCX IN5, 6, then 8 - the hissing signal follows, so the problem is not in UCX inputs, but QuadMic output. I checked by connecting headphones directly to QuadMic's outputs 1 to 4. Only OUT3 shows this, but sadly I'm clueless when under what circumstances does it start to hiss.

What did not help: turning P48 off and on again, changing gain, engaging low-cut filter or swapping phase, even power-cycling the whole QM
What helped: plugging out QM IN3 (a SDC mic) and inserting it back again in after a while, same microphone and same cable

I consider it very strange this time it didn't help to turn the whole QM off and on again, only if I physically disconnect the mic cable from IN3 for several seconds, or I use another microphone cable and then return back the first one. (Hence I think both mic and its cable are fine, as other preamps never made any problems.) Previously I power-cycled both UCX and QM at the same time (they share switchable power socket) and it did help, probably...

QM IN1, 2 and 4 do not behave like this, they're just fine. No matter if I leave the P48 button engaged when powering down/up the unit, or I enable phantom power after powering the QM first.

Any ideas?

cupakm's Website

  • cupakm
  • AES/EBU artist
  • Offline
  • Registered: 2014-04-03
  • Posts: 101

Re: UCX II 7th input channel hissing sometimes

Audio AG Support wrote:

If you disconnect USB and reconnect again, without restarting, during a hiss? Is it also gone then?

The issue reoccurred. Having it narrowed to the mic - QuadMic part of the chain, I've tried swapping microphone (means unplug-plug cable on the mic side), nothing, unplugged and plug back cable to the QuadMic - the hiss went away that moment.

What exactly happens if I unplug and plug back again an XLR cable to a QuadMic's input?
It makes the hiss disappear. Only input to channel 3 shows this behaviour.

cupakm's Website