• Registered: 2020-07-15
  • Posts: 15

Topic: Fireface UC.. Using as DAC: SPDIF input sounds better than USB input

Ok this is prob going to be controversial..

I'm playing back audio from my Macbook.. It has an optical out and USB.

I gain match the inputs and outputs and toggle between the Optical input and USB to the Fireface UC.

It's material I know very well and I'm playing back over a Kv2 Audio system which has good resolution - 30kg tops each and 100kg double 15" sub in my lounge. My fav playlists.

Output from the SPDIF input has crisper highs and firmer lows. It does.
I can make out vocals I did not understand before. I can hear the slap of the skin of the toms. The bass growls and has deep pitch that I've not heard before.. The system feels faster and has better spacial imaging. The layers and subtle aspects of the backgound elements in the mix stand out more. The high hats, a shuffle on the shaker I had not noticed before..the kick slams. The is a modulation in a synth line and touch of snare I had not heard. I can hear the vocal line underpinning the vocoder.
Vocalist have regional accents I have not quite noticed before.

It sounds very, very good. Better than anything I have heard before.

I'm just mentioning it.. I love it. It is not particularly subtle. Do others find this? Maybe there is something going on with my USB?

2 Reply by ramses (edited by ramses 2020-07-24 08:20:45)

  • ramses
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  • Registered: 2012-10-14
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Re: Fireface UC.. Using as DAC: SPDIF input sounds better than USB input

This is not possible, digital is digital, ensure that playback levels are equal, as "louder" sounds better to our ears.

BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub13
  • Registered: 2020-07-15
  • Posts: 15

Re: Fireface UC.. Using as DAC: SPDIF input sounds better than USB input

Interesting.
I see you know what you are talking about.
And I knew someone would say exactly what you have said.

I'm a sound engineer, musician and audiophile from way way back.
I wasn't expecting a sonic difference and wasn't listening for one.
I was very surprised by what I heard. 

Somewhere something is different - and it is volume independent. 
Digitial is Digital but SPDIF and USB are not exactly the same signal paths are they..
Like I say this is material i have listened to many, many, many times at lots of different volume levels through my home system. I know it well. I'd say the balance of the music is quite different.. on my hardware.

  • ramses
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Re: Fireface UC.. Using as DAC: SPDIF input sounds better than USB input

I noticed you are using Apple, I can not refer to Apple.

In the case of Windows I would have asked you questions in terms of the signal flow. Depending on what driver you use in Windows the signal flow can be very different and Windows Sound infrastructure might alter the signal by EQing, Windows Mixer, Volume settings below 0dB in the application or the mixer, etc etc.

But I would definitively check your signal flow.
Also I would check your SPDIF source ... on my new Panasonic OLED TV I noticed that there are settings for the output of the SPDIF channel and if I remember right the default was at -6 or even -8 dB !

BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub13
  • Registered: 2020-07-15
  • Posts: 15

Re: Fireface UC.. Using as DAC: SPDIF input sounds better than USB input

Thanks I will dig around.

6 Reply by MC

  • MC
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  • Registered: 2007-04-06
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Re: Fireface UC.. Using as DAC: SPDIF input sounds better than USB input

You should have done that before posting. How did you manage to send out the exact same signal unaltered and identical via USB and SPDIF from your computer, plus doing this in parallel so you can easily switch at the ADI to check for differences? Unless you describe your setup in detail you have no point.

Regards
Matthias Carstens
RME

MC's Website

  • Registered: 2020-07-15
  • Posts: 15

Re: Fireface UC.. Using as DAC: SPDIF input sounds better than USB input

Ok.... MC?  Should have done WHAT before posting?  How do I know where to look? I'm a user. One of RME's customers. I'm not an electronics hardware or audio software engineer.

>> How did you manage to send out the exact same signal unaltered and identical via USB and SPDIF from your computer, plus doing this in parallel so you can easily switch at the ADI to check for differences?

So....
I connect the optical cable to the headphone jack of my MacBook and the SPIDIF In on the Fireface.
I also connect the USB to the Fireface.
Both are left connected.

I set the faders on AS 1/2 (optical) and on Software Playback AN 1/2 (USB) to full: O db

I play a test signal from a tone generator at some arbitary freq say 440hz and input level.

To switch to SPDIF In I set the OS X Sound menu to use Digital Optical Out.
To switch to USB in I set the OS X Sound menu to use Fireface UC Mac.

I look at Total mix. When I switch output channel in OS X I instantly see the signal switch in Total mix. There is no click pop or pause. The signal levels reported in TotalMix for SPDIF and USB are exactly the same to the 00.1 resolution of the display at the top of the channel strips there.

Now I play music instead of the tone generator.
The SPDIF sounds better to my ears as described above. It feels like it has had some subtle multiband mastering applied to it.. or that the information content seems clearer. IDK.

I have been having issues with the Fireface dropping its USB. So I thought that for gigs I could try the optical out instead. So I plugged it in and tried it. And I noticed a change when I wasn't looking for or expecting to hear any difference.
My ears? Just that I was listening more closely?  I don't think so.

An analogy:
You know how in the analog world some pre-amps sound better than others? Or some cartridges- You plug your Linn turntable in with the best MC cartridge you can buy and you hear stuff you didn't hear before and suddenly you are digging out old favs and re-listening. Your whole record collection. (Maybe you don't know this).
Well it's a bit like that.

Look- its RME:  It sounded great over USB. It just seems to sound better over SPDIF to me given my computer and signal chain.
Make of that what you will I guess.

  • From: Germany
  • Registered: 2007-04-10
  • Posts: 9,549

Re: Fireface UC.. Using as DAC: SPDIF input sounds better than USB input

Fact remains there is no possible way the UC could "sound better" over SPDIF than via USB with identical signals (!). There is no "information content" that could be "clearer" or the like. And f the UC were to apply "some subtle multiband mastering" to an input signal, that would mean it would actually alter it, which ist's certainly not meant to do. With that in mind, I'd suggest you look for differences in the signal path or playback. You did not mention the playback software, for one. What alternatives did you test? Also try resetting Totalmix to make sure nothig changes there (although in the absence of an effects section, the only thing that could change would be  balance or level...)

Regards
Daniel Fuchs
RME

Regards
Daniel Fuchs
RME

RME Support's Website