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Re: I2S chips

Hi Rupe. The short answer is "no". If interested, here's more context. CS8414 is a digital audio receiver. In the context of a Dac, its job is to receive an audio signal from a transmission line, recover the clock, and decode the signal according to an interface standard, generally spdif. The interconnect cable is the transmission line through which the digital receiver (within the Dac) receives the audio signal from the transport. It is the CS8414 within your DAC chassis that first receives this signal before handing it off to the DAC chip for digital-to-analog conversion. Although the CS8414 (and 8412) cannot receive and decode according to I2S format, it can, after receiving the signal in spdif format, transmit the decoded signal to the DAC in I2S. The vast majority of CD transports transmit the audio signal using spdif format to the DAC.

In a USB DAC, a USB Controller--like the PCM2706--REPLACES a digital receiver (such as the cs8414). It performs the same job (not to complicate matters, but the 2706 happens to have an onboard dac, but most designs I've reviewed elect to handle the d-to-a using another DAC chip). The USB controller receives/decodes the signal, and then transmits the signal via I2S or SPDIF to the Dac chip. Some commercial USB Dacs receive the audio signal via USB but then transmit it via SPDIF to the Dac chip. So SPDIF is still in the equation. It is my understanding that I2S is a superior format to SPDIF that results in reduced jitter. So if one intended to design a Dac without spdif in the chain, one would need to use a USB controller that outputs in I2S as well as a Dac chip that accepts I2S. I do not have broad familiarity with Dac chips, but I know that tda1543 and tda1541 accept I2S.

This is why we don't see more USB-to-I2S converter boxes on the market. Although a niche market may exist, there just aren't many commercial Dacs that have I2S inputs. The format just wasn't widely adopted, albeit a superior one.

The digital interface--whether it be I2S or spdif--is but just one element that affects the performance of the Dac. Clock recovery, digital conversion, power supply and analog stage all play a huge role in the quality of the DAC. So not everyone is going to run out and become early adopters of USB dacs. For those who are satisfied with their current Dac but inclined to try USB, they have the option of using a USB-to-spdif converter. This pretty much stretches the limits of my understanding of this subject and, if I've errored, I hope the engineers among us will set us straight.


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