This may belong to Random Thoughts, depending on how things develop. So here it goes... Besides looking at audio interface options recently (think Pete Millet), I was also looking at available options for USB/I2S bridges. In all honesty, I paid way more attention to amplifiers and DACs than I did to interfaces in the past. I was well aware of interfaces, and that they were somewhat problematic. But I never really dived very deep into it. For example, in the past, I knew NwAvGuy gave the ghost kind of right after the ODAC and in fact, did not produce a DIY DAC solution. Instead he associated himself with Yoyodyne and came up with an SMT fully integrated module with entry level performance for $100. This after criticizing some amp designs that used small SMT devices because they were not DIY friendly. I don't necessarily blame him. To some extent it seemed that the problem was not just the available selection of DAC ICs, but the USB/I2S bridge options available themselves. I also knew that many DIY designs are sampling rate limited to 44.4/48 kHz because most major device manufacturers do not offer non-NDA/COTS higher sampling rate usb bridges. In fact, I think that from Cirrus Logic, Analog Devices, AKM, and TI (all major DAC/AMP device providers), only TI has entry level USB/I2S bridge solutions in their portfolio. Though it seems AD is getting interested in this market. Instead, in this segment, we have XMOS, CMedia, and SaviAudio (there is another one, but I forgot their name). The solutions are not DIY friendly due to NDAs, IC packaging, multiple F/W configurations, and so on. I did look into the higher end TI solutions such as the TMS320C5x family (offer USB and I2S support). Though I haven't yet used the C5x family, I'm very familiar with the TMS320 DSPs, and have done quite a bit with them (the whole 9 yards particularly the old C3x and C6x families - I know very wll the C6x families can do USB to and from I2S with their eyes closed, but they are way overkill for that). Yesterday I took a quick glance at the C5x's EVMs schematics and Demo/Test code provided. This is are my comments on them: TMDX5505EZDSP (C5505 eZdsp USB Stick Development Tool): Stay away from this kit. It looks like it's got everything, but believe it or not the USB is only connected to the embedded JTAG IC for development and debugging. It is not connected to the DSP's USB interface, so sound is going to come out of the CODEC by hardcoding sound into the memory of the DSP. In other words, not really a HW or SW reference design for a bridge from what I can tell. I barely see the point of it's existence, other than checking that the DSP talks to the CODEC through I2S and powers on. TMDX5535EZDSP (C5535/C5545 eZdsp USB Stick Development Kit): Well, the USB is now connected. But guess what? The Spectrum Digital's website has no USB code test for it (reference SW). TMDXEVM5515 (TMS320C5515 DSP Evaluation Module): Much better. Like they said in their website, it offers a reference design for more realistic memory options (like Flash). But more importantly, they connected the USB interface on this one and they do offer code references for both USB and I2S libraries. It is probably doable, but not necessary stupid-simple. So of all these, one could come up with a reasonable bridge reference design and FW with the TMDXEVM5515. Maybe one could use the sample code of the 5515 EVM with the 5535 EzDSP platform for simple stuff. But again, I don't see it as a slam dunk. There is obviously a bit of elbow grease to be done here. There may be some stuff out there that may be in the works from TI along the lines with actual SOC being developed (maybe BeagleBone Black w companion daughter card), but I don't think they are ready for prime time. So all of this seems to boil down to (as far as what is readily available if you want to play around with stuff): MiniDSP streamer: XMOS bidirectional USB/I2S interface for full PCM rate support (or almost full) for $100 and no DSD. ChiFi Stuff w a mixture of random XMOS, CMedia and SaviAudio stuff which is mainly unidirectional only (or actually only), but with DSD (if you get the appropriate part from CMedia and SaviAudio that is). 48 kHz max rate constrained stuff from several vendors, including TI. Obviously forget about DSD, and likely no support for ADC. IMO, after so many years, this is truly a sad state of affairs. Feel free to discuss and contribute. We all learn good stuff that way. BTW, I did see that the widely used CM6631A has DSD erectile dysfunction. But the not-so widely used CM6632A is not. Neither is the SA9227. There is a big eBay beans spill of SA9227 + PCM5102A for like $28. The SA9227 is bidirectional, but I think most of them are F/W crippled to USB->I2S only. There are also reports that it gets hot because the cheap implementations (I like) use the on-chip rectifiers. But again, $28 is what I want to hear for no DSD and no ADC support, with at least a mediocre DAC to try to justify the mark up.