exaU2I - Multi-Channel Asynchronous USB to I2S Interface

[exa065]

Originally Posted by Bunpei

Yes, a DSD256 source converted from PCM sounds definitely better than its original PCM as long as I use Sony "DSD Direct" software for the conversion.
I guess an upsampling FIR filter and a delta-sigma modulator employed in the software might be superior than hardware implemented ones in DAC chips.

1. Is the conversion PCM -> DSD256 lossless?
2. Is there an objective proof that it is lossless?
3. Can you convert back to PCM and get an identical binary file image?
4. If not how do you know if it is sounds "better" or "different"?
5. How much fidelity is lost on the lossy conversion, to have an non-quantifiable gain based on the guess that "an upsampling FIR filter and a delta-sigma modulator employed in the software might be superior than hardware implemented ones in DAC chips" ?

[exa065]

Sorry, I had to delete your post. Let's not go off topic promoting other projects.

[Bunpei]

Dear exa065,

I think it's meaningless to stick to "lossless-ness" of PCM to DSD256 conversion because PCM -> DSD256 and DSD256 -> PCM conversion are not mutually reversible mathematical processes. (If you can't agree with my opinion, I hope you will read this book " Understanding Delta-Sigma Data Converters")
ES9018 DAC chip converts PCM input signals to 6-bit delta-sigma modulated signals before applying internal DAC section. Do you stick to "lossless-ness" of the process in the DAC chip?

Anyway, I wish the new exaU2I board maintains the capability of DSD256 & DSD512 play. I think no consumer or DIY products other than exaU2I support a DSD512 play. Your exaU2I is obviously a world-record holder on this point and I think it is very valuable feature. Just recently, my Japanese friend purchased one exaU2I because he wanted to try DSD512.

Best regards,
Bunpei

[exa065]

Thanks, we will preserve DSD256 and DSD512.

[MoonUnit]

Originally Posted by exa065

We can have the same hardware supporting the PCM1704 input format with an alternative firmware. It can be offered as a separate product. There will be no oversampling, you will have to use a third party software or hardware oversampling filter.

Thank you! One of the advantages of your device (as opposed to other ones that only handle 192kHz) is that I can do 8x oversampling of CD audio in software with the PCM1704. That's a huge benefit for me. I'm looking forward to your new hardware.

BTW, there are a lot of people who run the PCM1704 is NOS (non-oversampling) mode as well, with either a first or third order analog filter. I'm sure they'd be candidates for purchasing a board with alternative firmware as well.

[Telstar]

Originally Posted by qusp

the fifo main problem is
A. no multichannel at this stage
B. no DSD
C. the delay

These problems are irrelevant for most users.

[hochopeper]

Originally Posted by Telstar

These problems are irrelevant for most users.

I guess that is qusp's point

[exa065]

Sorry qusp, I had to delete your last two posts because of the disrespectful tone. They were on display for a while, so people can see them. Going forward I intend to keep the discussion here focused on the support of our users and the development and the improvement of the exaDevices products.

[avian]

Originally Posted by Telstar

These problems are irrelevant for most users.

But not for all users. As an exa owner I've used the DSD, appreciate the low delay (infact Ive used it with Logic on osx quite a few times), and have considered using the multichannel aspect for a pc based crossover. Different strokes for different folks.

[exa065]

Here is again an updated list of features for the next generation exaU2I:

• Just about 1ps jitter
• Two sets of clocks for synchronous and asynchronous operation with ES9018
• 8 channel DSD
• 8 channel DXD / 384 kHz PCM
• Individual LEDs for all PCM and DSD sampling rates
• Easy elimination of USB power
• Macro USB connector
• Header for connecting external USB connector
• Connectors for external power sources
• New ground isolation technology
• Micro BNC output connectors
• Elimination of the USB daughter board
• No need to rewire the outputs for DSD and PCM (ES9018 only)
• I2C header for ES9018 volume control - if we can make it.
• Multichannel support for PCM1704. This option will rewire alternative firmware, and it may be a separate product.

Attached is an early version of the PCB. Please post to this thread if you think you are interested to buy one. Indicate your preferences:

• ES9018, PCM1704 or a third party DAC.
• Let us know your priorities - all in one board or multiple specialized products for lower cost
• Asynchronous operation (only two clocks) or all clocks installed.
• Two channel only, PCM only etc.

Cheers,

exa065