24 bit audio over USB

This seems to be a single-channel implementation of what you're looking for. It might not be rediculous to build two.

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Reply to
Arny Krueger
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for.

The LTC2400 is not really recommended for high-end audio with its sample rate of about 10Hz...

--DF

Reply to
Deefoo

You

for

24

None. All the USB thingys are 16 bit. All the 24 bit stuff has an interface to connect to a DSP.

Meindert

Reply to
Meindert Sprang

can

TI makes some chips specifically for usb audio. Don't know which ones are 24 bit.

jb

Reply to
reddred

Right. Odds are they use the TI chipset with some glue logic between the codec and the thing.

--scott

--
"C\'est un Nagra.  C\'est suisse, et tres, tres precis."
Reply to
Scott Dorsey

AIUI, USB has some bigger issues with latency than Firewire, but unless it must be one of those, I think you should look at ADAT with the Wavefrontsemi chipsets - the PC will need an ADAT interface though.

Reply to
Clifford Heath

It appears to be a very low-speed device with a sampling rate of 50 or 60 Hz.

But there are plenty of example circuits provided by the IC vendors for audio-quality A/D and D/A converters, USB interfaces, etc.

Reply to
Richard Crowley

Probably. But you have likely specified yourself right out of an off-the-peg solution. There are 16-bit solutions because there is a sufficient market for a monolithic integrated solution.

But it seems very unlikely that there is a 24-bit solution. For one thing if you have that much dynamic rangeon the analog input side, the close proximity of the digital parts (especially something as "high-power as a USB interface) seems impractical.

Reply to
Richard Crowley

The actual dynamic range of decent audio converters is in fact in the 20 bit equivalent region. 24 bits is simply a convention based on 3 bytes.

Avoiding crosstalk from the digital to analogue section etc is simply a matter of good design.

Graham

Reply to
Pooh Bear

Which is not too difficult to achieve with separate IC packages for the A/D or D/A circuit, and another for the USB interface, separated by an inch or so of PC board.

But putting all that onto a single chunk of silicon that is likely smaller than 1/4 inch square is an engineering feat that is likely too expensive for a mass-market product. At least that seems to be the message we can get from the absense of such a product.

Reply to
Richard Crowley

Why do you think you need to do the transfer at 24bits just because it is

24bit data?
--
Aaron
Reply to
<aborgman

If that's more along the lines of what he's looking for, I'd try the sci.electronics newsgroups as opposed to the re.audio newsgroups.

Jeff

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     little temporary safety deserve neither liberty nor
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Reply to
Jeff Findley

I think that's because the original poster sent his message to a rec.audio group instead of a sci.electronics group. Different crowd, different, but fairly predictable, response.

Jeff

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Reply to
Jeff Findley

Quite possibly you don't. That would be dealt with by the device driver I guess. It would certainly make the hardware more involved though since the data stream would have to be explicitly buffered outside the USB chip.

Graham

Reply to
Pooh Bear

Both in fact but never mind.

There have been some useful snippets of info though.

Graham

Reply to
Pooh Bear

guess. It

would have

But you're only talking about 2x24bit channels at some audio sampling frequency, should be simple to do with a lot of common programmable devices.

--
Aaron
Reply to
<aborgman

Pooh Bear skrev:

something like this?

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sample code for an audio device on an LPC2148 ARM7 micro with build in USB controller, claims to be HID compatible so it shouldn't need any special driver.

It is, as far as I can tell, only audio out but it is a place to start.

-Lasse

Reply to
langwadt

Graham,

Nobody has answered your question, so I will.

a) The USB audio-class driver for Windows absolutely DOES support

24-bit audio. I have bus-analyzer traces that prove it :) So does Mac OS X's USB audio-class driver. You'll need to inform the OS that your device supports 24-bit audio, and you do that using the device descriptors. It's quite simple.

b) I haven't seen a USB high-speed audio-specific controller chip. However, the TI chips (TUSB3200A and TAS1020B) do full-speed just fine. You'll be limited to 48 kHz stereo 24 bit if you want to do full-duplex; full-speed USB doesn't have the bandwidth for 96 kHz full-duplex stereo.

c) If your design requires separate sampling frequencies for record and playback, then you'll need to use the TAS1020B, as its CODEC interface in I2S mode has two sets of LRCLK, BCLK and MCLK signals. The TUSB3200A's CODEC interface has only one set of BCLK, LRCLK and MCLK signals. A further complication is that if you wish to support more than one sampling frequency (even though both playback and record will always use the same frequency), then you need the TAS1020B and you can't use a CODEC (you need to use separate ADC and DAC devices). This is because the OS considers the playback and record interfaces to be completely separate, but if the hardware has only one MCLK/LRCLK/BCLK interface, clearly they're not separate. The problem occurs when the OS says, "I want record at 44.1 kHz" and the hardware goes, "OK," but the OS has no way of knowing that the playback interface is also at

44.1 kHz. This limitation is why TUSB3200A-based devices like the Edirol UA-5 have a front-panel switch that selects the sample frequency: at enumeration, the micro reads the state of the switch and alters the descriptors appropriately, and the only way to change the sample frequency is to detach the device, set the switch, and reattach. Again, since the TAS1020B has two sets of I2S clock lines, it has no problem supporting different sample frequencies.

Is this helpful?

-a

Reply to
Andy Peters

I was under the impression that there was plenty of speed with USB2.0 to handle far more than 24-bit 48 kHz full duplex. There are several devices that do 8 channels duplex at at least 48 kHz and some that do it at 96 kHz. Here's one:

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Reply to
Mike Rivers

You forget that USB2.0 high speed is faster than "full" speed. Go figure...

Reply to
Clifford Heath

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