Hi-Rez Highway New high resolution SACD releases, players and technology.

---

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ Hi-Rez Highway ]

---

[ Alert Moderator ]

---

RE: Is DoP true DSD?

Posted by Thorsten (M) on February 5, 2014 at 21:54:53

In Reply to: Is DoP true DSD? posted by John PA on February 4, 2014 at 16:00:14:

Hi,

The document describing the method is a bit obtuse.

The simple way of explaining it is that DoP wraps native DSD data into a package that can be transmitted via USB Audio connections. So to the Operating System and the USB connection the signal looks for allintent and purpose like PCM Audio, but it is NOT PCM, but DSD "disguised" or "repackaged" to appear as PCM.

If you use a PCM only USB DAC capable of handling 176.4KHz and send it DOP Signals, what you get is noise. Because the DSD signal makes no sense to a PCM DAC, because it is NOT PCM.

If your DAC however supports DoP it will instead recognise it is being send a DSD signal and not PCM (by looking for the "marker" bits, which cannot naturally occur in PCM Music material) and then extracting the DSD, which can beplayed back as pure DSD datastream using any "DA Conversion" that supports DSD and that you like.

So, to the layman it is best viewed as a pipe where you stuff DSD in at one end (the Player does that) and where DSD comes out on the end. The internal workings may be safely ignored, as the data is never altered, only re-packed. This means the exact bit pattern that enters the pipe comes out at the other end.

In more detail, the starting point was that all modern computer systems support high speed PCM via USB Audio Class 2, there is no DSD support in any of the USB Audio Classes.

So to play DSD via this either Steinberg's ASIO 2.1 "wrapper" must be used and be supported by both hardware and software. As Steinberg has not made ASIO an open standard implementations generally require licencing, support and permissions from Steinberg (who are generally not interested in talking to anyone not shipping 10,000's of devices), or DSD must be converted to PCM (not the end of the world, 176.4KHz PCM at 8 Bit would be sufficient).

From this starting point it was a question if there would be any way to transmit DSD via a USB connection that would bootstrap on existing tech, and be an open standard WITHOUT altering the data or converting to audio PCM.

What is done is to take a DSD Datastream which contains 2 * 2.822 Million Bits per second and to chop it up into 16 Bit blocks. These are "chunks" of the original DSD stream, completely unaltered.

What we use as transport for these Chunks (which could also be 32 Bit long or anything we like really, as long as the transport is fast enough) does not matter.

For standard DSD, if we have 2.822Million / 16 = 176,400 of these blocks per channel, we can transmit a full DSD datastream and decode and re-assemble this data stream into the original DSD Datastream at the other end.

So,if we have a USB standard 24 Bit PCM stream at 176.4KHz we have the ability to "transport" 2 * 176400 Chunks of 24Bit of any kind of data via a USB audio connection.

What is done with DOP is to use the top 8 Bits of a "marker" which also fills the top 48dB of the PCM signal with an alternating low level 88KHz signal. The lower 16 Bits contain the DSD "chunk". At the playback end the chunks extracted and are re-assembled seamlessly into the the original DSD Datastream.

Simple in principle but a stroke of genius, that pretty much resurrected DSD from the dead.

Thor

At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need?

This post is made possible by the generous support of people like you and our sponsors:

Western Glow Tube Service

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---