• Registered: 2010-12-29
  • Posts: 17

Topic: Loud noise when switching on and off the fireface UC

Hi RME,

First of all, thanks for a great product, which I have been using for over a year now.

Since the beginning, the UC produces a loud pop followed by two or three seconds
of high frequency static when I switch it on.
When switched off it produces a loud pop.
I connect the UC direct to a power amp, using a standard balanced to unbalanced
(cinch) cable.
(I do not want to use an extra passive switch or attenuator between UC and power amp.)

I hope this is not normal/expected behavior for unbalanced connections...

Thanks for any insight,

John

ps. If necessary I can record the sound with a portable recorder, but I guess you get the idea :-)

2 Reply by jwork123nl (edited by jwork123nl 2011-01-07 13:09:06)

  • Registered: 2010-12-29
  • Posts: 17

Re: Loud noise when switching on and off the fireface UC

Hmm, no reply yet.
Vacation should be over now, even in Germany :-)

Let me know if I perhaps should  enter a support ticket or something?

  • From: Germany
  • Registered: 2007-04-10
  • Posts: 9,776

Re: Loud noise when switching on and off the fireface UC

A certain pop is normal, but I'm not sure what "high frequency static" refers to. Make sure to switch the amp on last and off first.

Regards
Daniel Fuchs
RME

Regards
Daniel Fuchs
RME

RME Support's Website

  • Registered: 2010-01-07
  • Posts: 54

Re: Loud noise when switching on and off the fireface UC

Hello,

same loud pop here, no static noise. Ok for speakers and ampli, but same happens in headphones. Is it safe for headphones integrity?

Or should I disconnect / connect headphones before / after turning it off / on ?

Thanks,
  Mario

i7700k@4.2GHz/16GB RAM/RME FFUC/1.25TB SSD/4TB HD/Win10x64
http://www.reverbnation.com/errepici

5 Reply by jwork123nl (edited by jwork123nl 2011-01-10 18:03:43)

  • Registered: 2010-12-29
  • Posts: 17

Re: Loud noise when switching on and off the fireface UC

I recorded the sound I described (sony PCM10 digital recorder)

http://www.vanspaandonk-koks.nl/fireface pops on_off.MP3

Switching on: there is DC on the output since my bass speaker slowly moves a good cm to the front and back
(I have a DC-coupled mains amplifier)
The digital noise is caused by the USB cable being connected while switching on. It is louder on Windows
and not as loud on Linux (this was recorded while Linux was running on the laptop).
Switching off produces a quite loud pop. I am concerned about my speakers...

As noted, I use a standard TRS unbalanced connection cable which has a cinch plug on the amplifier side.

Thanks for any advice

6 Reply by MC

  • MC
  • MC
  • Administrator
  • Offline
  • From: Germany/Thailand
  • Registered: 2007-04-06
  • Posts: 25,599

Re: Loud noise when switching on and off the fireface UC

It seems that you need passive attenuators in front of your amplifier as it is a bit too sensitive. When you listen to music what is the setting of the TM output fader then? Pulled down to -20 or more?

Regards
Matthias Carstens
RME

MC's Website

  • Registered: 2010-12-29
  • Posts: 17

Re: Loud noise when switching on and off the fireface UC

Hello Matthias,

I disagree.
I use the fireface UC as a pre-amp to directly drive a 2x400W Hypex UCD amp.
I regularly listen below -20dB, once in a while on a higher level.

My whole point of using this setup is to use the UC as monitor controller.
Without extra attenuator between it and the monitor.
For me it is less  suitable for this appliation due to the pops/DC when toggling power.

In addition, how do passive attenuators help protect a plugged in headamp?
See above post by mabian.
Can you confirm it is safe to let the headphones plugged in?

Now I also have the following question:
Does the Fireface UFX also show this problem?
Or does it have a proper switch on/off muting implemented?

Thanks for your time and help.

John

8 Reply by MC

  • MC
  • MC
  • Administrator
  • Offline
  • From: Germany/Thailand
  • Registered: 2007-04-06
  • Posts: 25,599

Re: Loud noise when switching on and off the fireface UC

Well, you can disagree but as long as you confirm my statements... :-)

Fact is that the pops are no problem if you match the FF's output levels to the input levels of the following device. If you listen at full volume and still have the fader at -20 then you can easily reduce the pop by 10 dB (which is really a lot) via the passive attenuator, and still have enough headroom for the next trance or metal party. There is no other way to fix it.

The UFX has an improved mute circuitry for power on/off, but it still doesn't work like a relay in a Hi-Fi amp, and in your setup I can not predict how much it will affect you.

How can headphones be damaged by a signal that is magnitudes lower volume/level than the maximum output level in normal operation?

Regards
Matthias Carstens
RME

MC's Website

  • Registered: 2011-01-19
  • Posts: 1

Re: Loud noise when switching on and off the fireface UC

Common practice to prevent dangerous pops/noises when turning interconnected audio devices on/off:

- ON: first the mixer/fx/interface, second the poweramp/active speakers

- OFF: first the poweramp/active speakers, second the mixer/fx/interface

hth
Blechi