• Registered: 2014-08-14
  • Posts: 29

Topic: iPad SPDIF output => UCX SPDIF input

My iPad is becoming more and more part of my RME UCX based piano rig : music sheet reader, OSC Totalmix control via Lemur, music player... For the latter purpose, I use the iPad headphone stereo output, which of course doesn't play in the same category than the UCX. So I came to the idea, that I could use a cheap SPDIF converter (e.g. PHIREE U2S) to benefit from the high quality DAC of the UCX. But in the digital world, things are always a bit more complicated and having read the SPDIF part of the UCX user manual I am still confused.

1) Has the sampling rate of my piano VST Host software (currently 24bit 192kHz) to match exactly the one of the iPad SPDIF output ?
2) What is the typical sampling rate of an iPad when using an SPDIF converter ?
3) Can I set the sampling rate of the iPad SPDIF output in iOS ?
4) Do I have to think of audio codecs used and/or sampling frequency of the music files I play ?
5) What would happen if I use my iPad AND my iPhone with SPDIF converters at the same time with the UCX ? (I am thinking of possible word clock issues)

Thanks for your advices.

2 Reply by MC

  • MC
  • MC
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  • From: Germany/Thailand
  • Registered: 2007-04-06
  • Posts: 25,444

Re: iPad SPDIF output => UCX SPDIF input

In this scenario the iPad will be the clock master for the UCX. Therefore iPhone plus iPad reuire at least one additional sample rate converter. What you can control or not depends on the app used in the iPad, the iOS itself doesn't give you a way to change sample rate etc.

Regards
Matthias Carstens
RME

MC's Website

  • Registered: 2014-08-14
  • Posts: 29

Re: iPad SPDIF output => UCX SPDIF input

MC wrote:

In this scenario the iPad will be the clock master for the UCX. Therefore iPhone plus iPad reuire at least one additional sample rate converter. What you can control or not depends on the app used in the iPad, the iOS itself doesn't give you a way to change sample rate etc.

Thank you for your explanation.

1) If I understand well, the iPad sample rate settings will define the sample rate settings of the UCX, and I thus will have to setup the ASIO settings for my VST Host accordingly.

5) I can forget the simultaneous SPDIF use for both an iPad and an iPhone, because I won't be able to synchronize them (no idea how to realize the additional  sample rate conversion).

3) So, no way to setup the sample rate in iOS, it depends from the apps...

hummm... why doesn't this Apple Inter-Application Audio stuff make things more clear? My iPad can play music files of different formats and I guess of different sample rates (I suppose typically 44.1 or 48) in the background, together with some Garage Band or Korg Module VST. And at the iPad output, there is only one DAC, with one unique sample rate, for all running applications. Things are perhaps more "open" regarding  the SPDIF sample rate, but I have difficulties to figure out, that one of the running audio application, could implicitly define it for all other apps. Moreover, I think I never used an application that makes it possible to set its sample rate...