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USB depth and rate limitation with Mac os lion.
Moodyalexo
post Mar 17 2013, 18:17
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Hi everyone,
First i'd like to apologize if there's is an introduction thread, I didn't see it.
and excuse me for sometimes misusing English, as i'm french and also for being a learner !

I've recently set up an audio rig with: MacBook pro running lion, audirvana plus and fidelia (trial for now), a Mav-audio TubeMagic D1 plus (up to 24/96 in USB, 24/192 for optical/spdif) and akg k701.

here's my problem : ( I also post it in head-fi, no offense meant)

With every configuration, USB input can't handle 24/96, whereas 24 / 41 or 48 is ok, and 16/96 is ok (when i set 24/96 for the input in Audi midi set up, the dac doesn't "boot" and no music can be played).
When players are set to automatic control of bit/rate, they lower bit depth from 24 to 16bit.
The spdif work fine up to 24/96 using the optical out from the macbookpro, but with sound limitation from not bypassing coreaudio.

i browsed the internet forums and i've got the impression that it might be kind of a saturation of USB bus.
The tenor 7022l (interface used by the dac) datasheet says:
- it is USB 2.0 audio class 1 FULL SPEED
- "Due to 12Mbps bandwidth limitation of the USB full speed operation, only one I2S input or output can be set for 24bit/96KHz application, under this condition, for simultaneous multiple-channel applications, rest of I2S interfaces has to be configured at the combination of 16-bit / 48KHz, 16-bit/96KHz and even lower resolution/sampling rate. In the application of USB internet telephony, lower resolution and sampling rate are needed."

When i look into "system profiler" then USB i see all USB bus. MacBook pro has only 2 USB ports. No matter which port i choose :
- maverick appears as USB full SPEED (not high SPEED) with 12mbps : So normal as i understand.
- it is always a shared USB bus (with iSight or internal keyboard or trackpad). Disabling iSight with isight disabler didn't make any change.


is it possible that, by being shared, USB bus is limiting bandwidth , leading to incapacity of habing full 24/96 ?
Is there anything to do ?

Thank you

Alex
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Ron Jones
post Mar 18 2013, 02:04
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USB 2.0 is fully capable of supporting multiple channels of 24/192 kHz (and higher), so one or two channels at 24/96 should not be an issue, assuming the device in question actually fully supports that mode of operation. There are products on the market that support sample rates that high over USB 2.0, and I've owned a couple.

Device sharing should not be an issue, so I wouldn't look to that as a potential problem point. It's more likely that 24/96 isn't actually supported over USB due to a device limitation.

I would argue that an absence of 24/96 output support over USB is not actually a problem at all, but if that's what you want, you may need a different device.
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lvqcl
post Mar 18 2013, 04:12
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USB 2.0 full speed is the same as USB 1.1
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phofman
post Mar 18 2013, 08:06
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If you want to find out real capabilities of your USB sound card, you can use any linux computer (just boot a live CD, e.g. ubuntu, or USB stick), plug your DAC and take a look at file /proc/asound/cardX/stream0, where X is number of your soundcard card (most likely 1 as 0 will be the integrated soundcard).

My multichannel card based on CM106 lists the following possible configurations (alt settings):

CODE
USB Sound Device         at usb-0000:00:1d.0-2, full speed : USB Audio

Playback:
  Status: Stop
  Interface 1
    Altset 1
    Format: S16_LE
    Channels: 8
    Endpoint: 6 OUT (ADAPTIVE)
    Rates: 44100, 48000
  Interface 1
    Altset 2
    Format: S16_LE
    Channels: 2
    Endpoint: 6 OUT (ADAPTIVE)
    Rates: 44100, 48000
  Interface 1
    Altset 3
    Format: S16_LE
    Channels: 4
    Endpoint: 6 OUT (ADAPTIVE)
    Rates: 44100, 48000
  Interface 1
    Altset 4
    Format: S16_LE
    Channels: 6
    Endpoint: 6 OUT (ADAPTIVE)
    Rates: 44100, 48000
  Interface 1
    Altset 5
    Format: S16_LE
    Channels: 2
    Endpoint: 6 OUT (ADAPTIVE)
    Rates: 96000

Capture:
  Status: Stop
  Interface 2
    Altset 1
    Format: S16_LE
    Channels: 2
    Endpoint: 5 IN (ASYNC)



    Rates: 44100, 48000


Your card based on Tenor will report different capabilities. Based on requirements from the playback chain the USB driver should switch the card to the best fitting altset. At least that is how it works in linux.
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Moodyalexo
post Mar 18 2013, 09:15
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Thank you all!
the tubemagic d1 plus IS supporting 24/96 over USB. Mav-audio support gave me a USB descriptor to Check it. I did it and it is supporting 24/96 for real.
That really is my problem.
Furthermore, i have no problem setting 96khz (with 16bit) or 24 bit (with max at 48khz).

As a palliative, listenning to 24/96 recordings, should I use 24/44(or 48) and let the system upsample or not, OR should I use 16/96 ?
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phofman
post Mar 18 2013, 13:39
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QUOTE (Moodyalexo @ Mar 18 2013, 10:15) *
Mav-audio support gave me a USB descriptor to Check it. I did it and it is supporting 24/96 for real.
That really is my problem.


Well, IMO they should have helped you to reach the real 24/96 mode, if they say the DAC supports it and their DAC is marketed as OSX compatible.
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Moodyalexo
post Mar 20 2013, 11:30
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Hi, thanks for answering.
With help from GFEC (who's manufacturing the tenor 7022l interface) I think I found the answer.

For audio interfaces ( input and output or D to A and A to digital, like in recording interfaces) USB full speed have limitations :
- 2 Inputs and 0 Outputs at 24Bit / 96kHz
- 0 Inputs and 2 Outputs at 24Bit / 96kHz
- 4 Inputs and 2 Outputs at 24Bit / 44.1 or 48kHz
- 2 Inputs and 4 Outputs at 24Bit / 44.1 or 48kHz
- 4 Inputs and 4 Outputs at 16Bit / 44.1 or 48kHz
- 2 Inputs and 8 Outputs at 16Bit / 44.1 or 48kHz (Sonica Theater)
- 4 Inputs and 4 Outputs with every other sample rate up to 16Bit/44.1kHz.

THe problem is, since os x 10.6, some audio DAC, though only having output capacity (d to a), are wrongly recognized as having both input and output. That's why I see both in and out in "audio midi settings"!!

Then the player, in hog mode, matching depth qnd rates to file played, try to equalize input and output.... Leading to 24/96 +24/96 = USB full speed saturation!!!

The same problem apparently occured with udac2 users!

I'll take you informed of new s if you want to !

Thanks
Alex
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