TEAC USB Interface

Updated 4/30/13

The new Teac UD-501 DSD capable DAC has received good reviews everywhere. Was curious about its USB interface. Here is a photo taken from a French site, qobuz.com [link]

There is a TMS320 chip and an unidentified chip. It is possible the unidentified chip is the USB receiver or the TMS320 is doing receiver function and the unidentified chip is a microprocessor to control the TMS320 chip.

The TMS320 is a DSP chip [link]. It is a “C67” series, an up to 1GFLOP 32-bit floating point DSP (the XMOS are rated at 500-1500 MIPS, likely equivalent performance). This family of DSP products was introduced in 1983 and new models have been introduced along the way.

The “C67” series is a current product and an EVAL kit, in particular for the C6748 chip,  is available from TI [link], [link]. According to the documentation:

…The
TMS320C6748, a low-power dual-core applications processor based on a fixed-point C64x+™ instruction set and the floating-point C67x+™ instruction set. It provides significantly lower power than other members of the TMS320C6000™ platform of DSPs and provides both floating-point precision and fixed-point performance in the same device. With a wide variety of standard interfaces for connectivity and storage, the C6748 development kit enables developers to easily bring audio, video and other signals onto the board.

… Included in the C6748 development kit is all the hardware and software needed for two demonstrations, a fingerprint-recognition demo and a face-detection demo.

Here is the block diagram for the eval kit:

Looks like a very capable and general purpose processor for not just audio but a lot of other things not even related to audio. You can take a look at the WIKI for all the available libraries for the DSP [link]. The DSP can even implement audio decoding and filtering.

In addition, the USB-2 interface is provided by the FT232 chip (and thus the unidentified chip is  likely not the USB interface chip; however, there are no FT232 chips in 48-pin package).

Further, the DAC has an upsampling feature and is provided by the Cirrus CS8422 chip on the main taking the I2S output from the USB board.

Thus the USB board, I believe, it is just moving the bits  to the DACs. It looks kind of overkill; perhaps in some future Teac will add other capabilities such such as PCM to DSD conversion and different upsampling algorithm on the DSP chip. It is also likely that Teac is just reusing hardware from their TASCAM proline. A device such as the TASCAM US-366 is a “USB interface with DSP Mixer”

This design from TEAC gives credibility to what Musiland is doing in their upcoming “SuperDSP” chip. The good thing about the Musiland product is that the DSP is dedicated to audio, and the chip will have native support for USB 2 and USB 3 interfaces.

UPDATE

Appreciate Mr. Daussin, the reviewer of the TEAC DAC, providing additional information in the comments section. The unidentified chip is the TPS65070. Readers would recognize “TPS” being power chips. The TPS65070 is a single-chip with multiple voltage outputs. Here it provides the different voltages required by the DSP chip. It is a convenient, integrated solution to provide the power to the main chip instead of using separate regulators.

The TMS320 DSP chip has implemented USB 2.0 capability in s/w and there is no need for a FT USB receiver chip (In the block diagram the USB 2.0 receiving capability is provided by a separate chip because (I think) the DSP chip is already burdened with many different functions).