USB audio codec with SPDIF or I2S out

bocka · 11th June 2005, 08:48 AM

Did anyone know a USB audio codec which has a SPDIF or I2S output? I know the PCM2902 but are there other chips? I'd prefer 24 bit and 96 kHz samplingrate if possible.

bocka · 14th June 2005, 07:59 AM

Has really no one an idea?

matjans · 14th June 2005, 08:16 AM

ti only has 48kHz 16bit stereo audio codecs with usb functionality on-chip.

bocka · 14th June 2005, 08:23 AM

Hi matjans,

thank you. I think there should be chips with higher datarates and resolution available as there are USB soundcards with 96 kHz and 24 bit on the market.

paologatto · 14th June 2005, 09:30 AM

Unfortunately 96 kHz and 24 bit chips does not exist AFAIK. All the soundcards 96/24 use custom solutions, and require drivers, with all the complications that this involves.

matjans · 14th June 2005, 09:40 AM

well of course there are, ti just doesn't have them as all-on-chip variants... Get a separates, build a board, write a driver and that's it ...

afaik, the standard usb audio drivers included with windows (nt, 2k, xp whatever) only support data rates up to 48kHz, 16 bits. (somebody please prove me wrong)

Bergrans · 14th June 2005, 09:46 AM

This is not really an answer to your question but M-audio produces a cheap USB Audio Interface (24bits 96kHz) called Transit I don't know what chip they are using. You can use this little interface as a start. Red Wine Audio do some mods on this unit to transform it into there USB select unit.

paologatto · 14th June 2005, 10:29 AM

..actually, the PCM2902/6 works also at 96 kHz, also up to 100 kHz. But its bandwidth is limited to 24 kHz. Here are some loopback tests done on a soundcard that I designed, based on the PCM2902/6.
(PCM2902 and PCM2906 are basically the same chip)

The bandwidth is obtained from the FFT of the loopback impulse response.

Loopback at 48 kHz:

(click to enlarge)

Loopback at 96 kHz:

(click to enlarge)

The bandwitdth limit is visible and measurable

I checked the SPDIF output of the PCM2906 at 96 kHz, full of hopes.. but it is limited to 48 kHz:

(click to enlarge)

The SPDIF out from the PCM2906 has been analized using the digital input of another soundcard (by RME) that allows to analyze the incoming digital data

bocka · 15th June 2005, 07:54 AM

Quote:

Get a separates, build a board, write a driver and that's it

Yes, I know using a generic USB device controller and writing some lines of code can support anything I'm looking for. Unfortunately it takes some month of work...

I just took a look to the Cypress CY7C6801x series. Seems to be possible when using an additional FPGA.

Quote:

checked the SPDIF output of the PCM2906 at 96 kHz, full of hopes.. but it is limited to 48 kHz:

Interesting that it works at least. Maybe the driver itselves limits the datarate to 48kHz?

paologatto · 15th June 2005, 08:31 AM

Quote:

Originally posted by bocka

Interesting that it works at least. Maybe the driver itselves limits the datarate to 48kHz?

I'm more inclined to think that is a limit in the firmware on the chip..
But don't have a final word.

11th June 2005, 08:48 AM	#1
bocka diyAudio Member Join Date: Jul 2003 Location: Hannover	USB audio codec with SPDIF or I2S out Did anyone know a USB audio codec which has a SPDIF or I2S output? I know the PCM2902 but are there other chips? I'd prefer 24 bit and 96 kHz samplingrate if possible.

14th June 2005, 08:16 AM	#3
matjans diyAudio Member Join Date: Aug 2003 Location: Utrecht, NL	ti only has 48kHz 16bit stereo audio codecs with usb functionality on-chip. __________________ Si fractum non sit, noli id reficere!

14th June 2005, 09:40 AM	#6
matjans diyAudio Member Join Date: Aug 2003 Location: Utrecht, NL	well of course there are, ti just doesn't have them as all-on-chip variants... Get a separates, build a board, write a driver and that's it ... afaik, the standard usb audio drivers included with windows (nt, 2k, xp whatever) only support data rates up to 48kHz, 16 bits. (somebody please prove me wrong) __________________ Si fractum non sit, noli id reficere!

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14th June 2005, 07:59 AM	#2
bocka diyAudio Member Join Date: Jul 2003 Location: Hannover	Has really no one an idea?

14th June 2005, 08:23 AM	#4
bocka diyAudio Member Join Date: Jul 2003 Location: Hannover	Hi matjans, thank you. I think there should be chips with higher datarates and resolution available as there are USB soundcards with 96 kHz and 24 bit on the market.

14th June 2005, 09:30 AM	#5
paologatto diyAudio Member Join Date: Jun 2004 Location: Italy	Unfortunately 96 kHz and 24 bit chips does not exist AFAIK. All the soundcards 96/24 use custom solutions, and require drivers, with all the complications that this involves.

14th June 2005, 09:46 AM	#7
Bergrans diyAudio Member Join Date: Nov 2004 Location: Utrecht	This is not really an answer to your question but M-audio produces a cheap USB Audio Interface (24bits 96kHz) called Transit I don't know what chip they are using. You can use this little interface as a start. Red Wine Audio do some mods on this unit to transform it into there USB select unit.

14th June 2005, 10:29 AM	#8
paologatto diyAudio Member Join Date: Jun 2004 Location: Italy	..actually, the PCM2902/6 works also at 96 kHz, also up to 100 kHz. But its bandwidth is limited to 24 kHz. Here are some loopback tests done on a soundcard that I designed, based on the PCM2902/6. (PCM2902 and PCM2906 are basically the same chip) The bandwidth is obtained from the FFT of the loopback impulse response. Loopback at 48 kHz: (click to enlarge) Loopback at 96 kHz: (click to enlarge) The bandwitdth limit is visible and measurable I checked the SPDIF output of the PCM2906 at 96 kHz, full of hopes.. but it is limited to 48 kHz: (click to enlarge) The SPDIF out from the PCM2906 has been analized using the digital input of another soundcard (by RME) that allows to analyze the incoming digital data

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