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ludwigvan968
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Wave Audio DAC

So has anyone given the DAC's talked about in the Sept. issue of Stereophile a test drive? I was very interested in it, though I was wondering if there are any high end solid state devices as well???

mikechai
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Re: Wave Audio DAC

The Wavelength USB DACs suppose to have an advantage of having a low jitter digital signal feed to a non-oversampling DAC, and also free of electrical interterence/noise as compare to normal PCI-card's SPDIF to external DAC configuration.

Another excellent devices of this kind is the TwinDAC Plus.

Scrith
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Re: Wave Audio DAC

Claims like a USB connection having lower jitter than a toslink or coax connection really intrigue me...I wish somebody could back this up with some cold, hard facts. What about the jitter-reduction technology in something like a Benchmark DAC1? With that, is a USB connection necessary to achieve low jitter between the PC and the DAC?

And, really, what is so special about a USB connection, other than the data is getting buffered on the receiving end? Why couldn't a coax- or toslink-based DAC do the same thing (ignoring the timing of the incoming data, storing it in a buffer, and then reading it from that buffer with its own internal clock)? Perhaps this is something like what a DAC1 does?

FRANKe
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Re: Wave Audio DAC


Quote:
Why couldn't a coax- or toslink-based DAC do the same thing (ignoring the timing of the incoming data, storing it in a buffer, and then reading it from that buffer with its own internal clock)?

Well, I'm not an expert so don't quote me, but I believe with an S/PDIF interface (whether coax or toslink) the signal includes both the audio and clock information. To separate the two is no easy task. That is the beauty of the USB, it buffers and reclocks with a stable clock on the DAC.

What you might be interested in is an I2S interface. The Perpetual P-3A DAC has one, and Steve over at Empirical Audio told me he is in the process of mod'ing a "USB Off-Ramp Turbo" with an I2S interface. I found a definition of this on the web:

---
I2S (Inter-IC Sound) is a serial bus (path) design for digital audio devices and technologies such as compact disc (CD) players, digital sound processors, and digital TV (DTV) sound. The I2S design handles audio data separately from clock signals. By separating the data and clock signals, time-related errors that cause jitter do not occur, thereby eliminating the need for anti-jitter devices. An I2S bus design consists of three serial bus lines: a line with two time-division multiplexing (TDM) data channels, a word select line, and a clock line.
---

Intrigued?

-FRANKe

FRANKe
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Re: Wave Audio DAC

By the way, the new Denon AVR-4306 includes a USB port. Does anyone know if this will work the same way as the Wavelength USB DAC? In other words, will Denon include soundcard drivers to interface with computer audio output? Or is it limited to portable devices (MP3 players)? Incidently, they also include a dedicated iPod terminal.

FRANKe
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Re: Wave Audio DAC


Quote:
I think the data being transmitted in the s/pdif signal does not *contain* timing information (otherwise jitter would not be an issue with it), the timing is simply being applied based on when the data contained in the signal arrives at the DAC....I think that most DACs with s/pdif inputs are just built with the assumption that the data will arrive in a timely manner.

Again, I'm not an expert, so it's probably time for an expert to join in and clarify, but I think you're misinterpreting what the timing issue is we are talking about. It's not about a signal "arriving in a timely manner". The "clock" refers to the signal being transmitted at a certain frequency. For example, a frequency a DAC would be expecting would be exactly 11.2896 MHz. If the S/PDIF signal fluctuates between 11.4 MHz and 11.1 MHz, then it is not synchronized and creates the timing error we call "jitter".

That is how I understand it, but I could be wrong. Please let me know, anyone, if you are an expert, if this is incorrect.

-FRANKe

arnyk
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Re: Wave Audio DAC

>I think the data being transmitted in the s/pdif signal does not *contain* timing information (otherwise jitter would not be an issue with it), the timing is simply being applied based on when the data contained in the signal arrives at the DAC.

There is no other path but the data path, by which a SP/DIF device receives timing information. There are other formats such as I-squared S that have a seprate clock wire)

Therefore with SP/DIF the clock must be recovered from the timing of data bits, which means that the data can and does affect the timing of the clock signal that is simply recovered from the data.

>So, it seems to me, a DAC could just ignore the speed at which the data arrives, buffer it, and then play it back using its own clock (which is what a USB device is doing).

Well, here's the rub - some USB devices buffer and reclock the data, and some don't. Some that reclock do a good job of reclocking, and others don't.

>The point was that there shouldn't be anything inherently superior to the way the USB cable is transmitting the data...

Agreed, there's nothing cast in stone that says that a SP/DIF device or a USB or a Firewire device *must* be substandard.

>I think that most DACs with s/pdif inputs are just built with the assumption that the data will arrive in a timely manner.

The older DACs from 5-10 years ago were built pretty simplistically and did not usually buffer and reclock the data. The newer ones, particularly the ones that handle AC3 formats, pretty much have to buffer and reclock the data due to the nature of AC3 data streams. The same hardware features are generally used with ordinary stereo inputs, so buffering and reclocking have become far more common.

Some applications, such as data tranfers into a computer via just about any interface are inherently resistant to jitter, because the computer acts like a massive data buffer with reclocking.

arnyk
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Re: Wave Audio DAC

>I2S (Inter-IC Sound) is a serial bus (path) design for digital audio devices and technologies such as compact disc (CD) players, digital sound processors, and digital TV (DTV) sound. The I2S design handles audio data separately from clock signals. By separating the data and clock signals, time-related errors that cause jitter do not occur, thereby eliminating the need for anti-jitter devices. An I2S bus design consists of three serial bus lines: a line with two time-division multiplexing (TDM) data channels, a word select line, and a clock line.

I2S is also known as I squared S, and has been around for years. It's widely used inside audio devices, say between a data receiver chip and a DAC. It's also buried inside chips that incorporate multiple functions.

For example, this definition document is dated 1986:

http://www.semiconductors.philips.com/acrobat_download/various/I2SBUS.pdf

There has been very little resistance to I2S as an internal inteface, and almost zero widespread use of it as an external interface.

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