LUMIN - Audiophile Network Music Player

[Miska]

I think different UPnP server shouldn't affect sound quality, as long as the renderer (LUMIN player) gets the original audio file data.

 

Only in case there's match of content type capabilities, UPnP demands server-side transcoding in cases where the recipient is not capable of the exact source format. Some servers may do it anyway.

 

Good example of such transcoding media server I've been using is PS3 Media Server - allows playback of almost any content, even though the PS3 itself has really limited capabilities.

[Miska]

As you say the parts aren't similar - doesn't the LUMIN use Burr Brown / TI DAC and the Linn use Wolfson (IIRC).[/s] Okay they use the same DAC chip' date=' and have the same output transformers - but the rest of the board doesn't really look similar (IMO)[/quote']

 

Out of curiosity, does anyone know if they use the Direct DSD mode offered by Wolfson (assuming it's either WM8741 or WM8742)? Or does it go through the PCM conversion? If there's digital volume control with DSD, then it is likely going through the PCM conversion, since Wolfson offers digital volume for DSD only through PCM conversion.

[Miska]

If you know the designer, you know. Well, I know! We tried very hard to implement the real DSD native mode (called DSD Direct in Wolfson terms). One of the difficulty is the handling of "mute" operation, because unlike PCM mode which works by fade out the volume and feeding zero into the DAC, DSD is total different. In DSD everything is relative...

 

So did you succeed and it is using DSD Direct?

 

I know, but it's all implementable, I know because I've implemented soft-ramped digital volume control for DSD...

You definitely don't want to feed zeros to DSD DAC because it would generate maximum negative DC, but you can feed "DSD silence".

 

In my PCM+DSD DAC I have output mute relays anyway for a true mute.

[Miska]

Is the Wolfson Direct DSD mode really direct? The filter graphs in the data sheet make me think some processing is being done (not natural to have such sharp nulls)

 

 

See the connections from "AUDIO INTERFACE" block to the "PCM/DSD MUX" block, this is the Direct DSD mode. Similar to the Direct DSD mode available in CS4398 DAC chip I'm using:

 

 

Reason for the filter graph is that the D/A conversion stage itself is one kind of (analog) filter. Main difference between the two chips is that for volume control option the CS4398 has a "DSD Processor" stage that operates with straight DSD at original rate, including DSD128.

[Miska]

JRIver asks "can LUMIN support SetNextAVTransportURI"? That is what is needed for JRiver to do gapless.

 

Note: don't shoot the messenger..I have no idea what the command above even means.

 

That's the thing so many UPnP devices miss, it instructs the playback device to begin pre-buffering for upcoming next URI before the previous one ends. So when the current song is over it already has issued HTTP request for the next song and fetched bunch of data ready for playback of the next track...

 

(just think UPnP playback as series of HTTP GET -requests for each track)