1 Topic by AviZiv (edited by AviZiv 2012-12-26 07:07:54)

  • Registered: 2012-12-26
  • Posts: 6

Topic: New UFX preamp noise question

Hi,

I'm a musician, new UFX owner, and new to recording in general. I just set up my brand new UFX (exciting!) and hearing some noises in the mic preamps that concern me. I'd like to do some sanity checks if possible. Here is what I observe when the unit is plugged into the computer via USB and nothing is plugged into the inputs. I'm monitoring via headphones. I'm not involving the DAW for this issue. Routing hardware inputs to hardware outputs.

1. If the headware input mic gain is at max, TotalMix shows about -54db (not sure what units these are exactly yet).

2. If the mic input fader (hardware input) is at 0, and the headphone monitor fader is at 0, there is a loud hiss in the headphones. I guess "loud is sujective". Not sure how to judge it. Moreover, raising the mic gain, on any of the mic preamps, results in a crackling sound through the headphones similar to the sound of a dirty analog potentiometer. This is without anything plugged into the intputs. Is that to be expected? I'm not sure if evaluating noise with floating inputs is correct or not.

3. Mic inputs 9 and 12 input has a definite delay after I raise the gain, and then it "kicks in" . It almost sounds as if it is shut off below a ceratain input level. This is audible whether I have a mic plugged in or not. If I'm not playing into the mic (quiet room) and I turn up the gain, it can take several seconds (up to usually 1-2 seconds but as long as 5-6sec) before I can hear the preamp turn on (click and then hiss). If the mic is receiving constant acoustic input then it seems to wake up the preamp and I don't hear this delay. I don't seem to detect this behavior on the other 2 pre inputs. Is this correct behavior? If I'm recording into a DAW, I can hit "record" and the DAW will record the click when the preamp kicks in. That seems to be the case if there is a delay before I start playing into the mic. Is here some sort of "voice activated" behavior here? Something wrong with the unit?

Are there any checks I can do to validate that the pres are working as they should? I'm a little concerned here

System: Mac OSX 10.6.8
TotalMix: 0.989
Firmware: v.352
Driver: v1.78

Thanks
Avi

2 Reply by MC

  • MC
  • MC
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  • From: Germany/Thailand
  • Registered: 2007-04-06
  • Posts: 24,851

Re: New UFX preamp noise question

Use DIGICheck to measure the Signal to Noise ratio of the mic inputs. Or set TotalMix to RMS, to read the value directly from the level meter.

But point is: hiss should not be there when just monitoring the mic input at 0 to 20 dB gain at the headphone output. Also the noise when raising gain should not be like you describe. I fear you need to exchange the UFX.

Regards
Matthias Carstens
RME

MC's Website

3 Reply by AviZiv (edited by AviZiv 2012-12-26 16:28:28)

  • Registered: 2012-12-26
  • Posts: 6

Re: New UFX preamp noise question

Hi Matthias,

Thanks for the quick reply. Just some clarification. The hiss is very obvious at the max gain setting and levels up. This makes sense to me although I can't figure out if it's excessive. How exactly do I measure the SNR with DiGICHeck? what gain should I set on the preamps? What numbers should I expect for the mic channels?

Still - the crackles I hear when I bring up the gain seem wrong and this delay then a pop that I get when raising the gain on a couple of channels is real. As I said, it's possible to record that pop if start recording and bring up the gain with nothing played into the mic.

I'm going to contact the store and see if they will exchange the unit. [Edit: retailer is exchanging it no questions asked. They will pay for shipping too. Good service]

Thanks!
Avi