Author Topic: feeding I2S from a computer into a KillerDAC  (Read 3336 times)

Offline rab

  • Administrator
  • Full Member
  • *****
  • Posts: 214
  • Liked: 29
feeding I2S from a computer into a KillerDAC
« on: August 21, 2013, 10:10:09 PM »
Hi all, last week i bought an EXAU2I USB to I2S interface board to play with. This board does galvanic isolation and includes a FIFO reclocker for jitter reduction.

So the first thing I discovered before hooking it up is that it always outputs 32-bit data, even when sending 16-bit data (i.e., the data word is followed by a padding word of all zeros). There was some discussion on the diyaudio forum in 2011 about whether this would be a showstopper for the TDA1541A, with the conclusion that it "should work". However, as far as I can tell, nobody has actually tried it until now.

Much to my relief, it works. At present, I am using a late 2009 mac mini with SSD and 8GB RAM, serving audio from a NAS. As far as software is concerned, my initial testing has been limited to squeezeplay and VLC, but i have now installed a trial version of Audirvana Plus and i may also trial Amarra.

OK, so that's the background; here's my question.

In a recent telephone discussion with zenelectro, he mentioned that although the TDA1541A is limited to 16-bit data, it should in theory work with clock rates up to 4 x 44.1 kHz = 176.4 kHz in NOS mode, because it was designed to support 4x oversampling.

In a fit of blind optimism, I generated a 16-bit 88.2kHz audio file and tried to play it with my killerdac. No sound.

Now i confess up front that i have not looked at all into whether this is expected behaviour and/or what would be required to play higher sampling rates, but my guess is that the clock driving the DAC chip in the killerdac is probably fixed at 44.1kHz and some switching logic will be required to reduce the division of the (crystal) clock frequency by a factor of 2 or 4, as appropriate.

Does anyone know the answer?

- richard

Offline kajak12

  • Hero Member
  • *****
  • Posts: 2445
  • Liked: 67
    • http://killerdac.com/forum/index.php
Re: feeding I2S from a computer into a KillerDAC
« Reply #1 on: August 21, 2013, 10:48:19 PM »
Ask zenelectro
enjoy your journey
still discovering the link between electronics and audio reproduction.so much to learn and so little time

Offline zenelectro

  • Hero Member
  • *****
  • Posts: 781
  • Liked: 145
Re: feeding I2S from a computer into a KillerDAC
« Reply #2 on: August 22, 2013, 12:21:59 AM »
Hi all, last week i bought an EXAU2I USB to I2S interface board to play with. This board does galvanic isolation and includes a FIFO reclocker for jitter reduction.

So the first thing I discovered before hooking it up is that it always outputs 32-bit data, even when sending 16-bit data (i.e., the data word is followed by a padding word of all zeros). There was some discussion on the diyaudio forum in 2011 about whether this would be a showstopper for the TDA1541A, with the conclusion that it "should work". However, as far as I can tell, nobody has actually tried it until now.

Much to my relief, it works. At present, I am using a late 2009 mac mini with SSD and 8GB RAM, serving audio from a NAS. As far as software is concerned, my initial testing has been limited to squeezeplay and VLC, but i have now installed a trial version of Audirvana Plus and i may also trial Amarra.

OK, so that's the background; here's my question.

In a recent telephone discussion with zenelectro, he mentioned that although the TDA1541A is limited to 16-bit data, it should in theory work with clock rates up to 4 x 44.1 kHz = 176.4 kHz in NOS mode, because it was designed to support 4x oversampling.

In a fit of blind optimism, I generated a 16-bit 88.2kHz audio file and tried to play it with my killerdac. No sound.

Now i confess up front that i have not looked at all into whether this is expected behaviour and/or what would be required to play higher sampling rates, but my guess is that the clock driving the DAC chip in the killerdac is probably fixed at 44.1kHz and some switching logic will be required to reduce the division of the (crystal) clock frequency by a factor of 2 or 4, as appropriate.

Does anyone know the answer?

- richard

Hi Richard,

There are a few possibilities but I think you should get someone to check the integrity of the 88.2k I2S signal.

There are certain timing requirements for I2S and there are also a few different I2S flavours.

I'll check the exa website for some info on their product tomorrow.


cheers

Terry

Offline stevenvalve

  • Administrator
  • Hero Member
  • *****
  • Posts: 1489
  • Liked: 259
Re: feeding I2S from a computer into a KillerDAC
« Reply #3 on: August 22, 2013, 06:35:22 PM »
I have tried many different transports, including Computer audio, now I am listening to the digital out of a DVD player straight into the DAC, all my music DVD video's work with the DAC. But what is the sampling rate of these DVD,s.
« Last Edit: August 22, 2013, 06:39:52 PM by stevenvalve »

Offline rab

  • Administrator
  • Full Member
  • *****
  • Posts: 214
  • Liked: 29
Re: feeding I2S from a computer into a KillerDAC
« Reply #4 on: August 22, 2013, 07:24:02 PM »
all my music DVD video's work with the DAC. But what is the sampling rate of these DVD,s.

I would think that depends on how the DVD player is configured... it might be setup to output 16/44.1 on S/PDIF. Also, remember i am using I2S, not S/PDIF.

Offline rab

  • Administrator
  • Full Member
  • *****
  • Posts: 214
  • Liked: 29
Re: feeding I2S from a computer into a KillerDAC
« Reply #5 on: August 22, 2013, 07:30:01 PM »
There are a few possibilities but I think you should get someone to check the integrity of the 88.2k I2S signal.

Thanks Terry. Your response suggests that the DAC chip and its associated clock circuitry are configured to adapt to the I2S input frequency... is that correct?

Many folks are using the EXAU2I with Buffalo II and II DACS, up to 384 kHz 32 bits and DSD, so the interface should be relaxin' at only 16/88.2!

I can play the file on my computer and Audacity shows 88.2 kHz (although it converts everything to 32-bit on input).

Offline omodo

  • Sr. Member
  • ****
  • Posts: 491
  • Liked: 103
  • Green tinted glow
Re: feeding I2S from a computer into a KillerDAC
« Reply #6 on: August 23, 2013, 09:43:39 AM »
FWIW I have no trouble playing 32/88.2 through an Amanero USB module into my 1541 DAC (Pedja AYA-II), 176.4 was distorted but haven't put any more thought into it other than 'well that didn't work'..
« Last Edit: August 23, 2013, 04:22:34 PM by omodo »

Offline zenelectro

  • Hero Member
  • *****
  • Posts: 781
  • Liked: 145
Re: feeding I2S from a computer into a KillerDAC
« Reply #7 on: August 23, 2013, 07:23:03 PM »
There are a few possibilities but I think you should get someone to check the integrity of the 88.2k I2S signal.

Thanks Terry. Your response suggests that the DAC chip and its associated clock circuitry are configured to adapt to the I2S input frequency... is that correct?

Many folks are using the EXAU2I with Buffalo II and II DACS, up to 384 kHz 32 bits and DSD, so the interface should be relaxin' at only 16/88.2!

I can play the file on my computer and Audacity shows 88.2 kHz (although it converts everything to 32-bit on input).

The I2S runs the DAC.

You need to get a cro onto the I2S stream to make sure the timing / levels / wave integrity are right.

I have a feeling that the bitclock is too fast at 88.2 as some I2S interfaces run Bck at 128 x FS. If that is the case
the 1541 won't like it as it has a max bit clock spec of 6.4MHz. 128 x 88.2k = 11.2896MHz.

If you have a cro this will be easy to check.

At 16 bits the 1541 should handle I2S up to 4 x FS = 176.4kHz with a Bck of 5.6448Mhz.


cheers

T
« Last Edit: August 23, 2013, 07:25:22 PM by zenelectro »

Offline rab

  • Administrator
  • Full Member
  • *****
  • Posts: 214
  • Liked: 29
Re: feeding I2S from a computer into a KillerDAC
« Reply #8 on: August 23, 2013, 11:10:37 PM »
You need to get a cro onto the I2S stream to make sure the timing / levels / wave integrity are right.

Thanks Terry, i don't have a CRO, but i may be able to borrow one...

FWIW I have no trouble playing 32/88.2 through an Amanero USB module into my 1541 DAC

As it happens, I also have an Amanero, but i haven't even tried it yet. I will investigate and report...