DIY HiFi Forum Welcome! Need support, you got it. Or share your ideas and experiences.

---

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ DIY HiFi Forum ]

---

[ Alert Moderator ]

---

RE: "Properly Done USB" is like the Unicorn

Posted by bcherry (M) on November 10, 2009 at 02:10:39

In Reply to: "Properly Done USB" is like the Unicorn posted by Jon L on November 9, 2009 at 11:30:05:

Not sure why is that.

asynchronous:

"In a synchronous system, operations are coordinated under the centralized control of a fixed-rate clock signal or several clocks. An asynchronous digital system, in contrast, has no global clock: instead, it operates under distributed control, with concurrent hardware components communicating and synchronizing on channels."

So either it is or it isn't. The Musiland uses an onboard local clock and its own driver instead of an MS driver. I'm not sure that is an issue relating to sound quality.

The key here is how good the audio clock is. Being asynchronous means its output jitter depends on how good the Musiland audio clock is.

In the Musiland a simple 24MHz clock generator is used that runs off the main powersupply, which is fed directly from the PC's USB power line. This will create a very jittery reference clock for starters.

This clock forms the reference of a "fractional division PLL". Such a PLL is used to make non integer multiple clocks from a reference clock. It can never be any better than the reference clock. The DIYHFS EZ Clock with a 0.5ppm clock generator provides as close as possible to the ultimate as reference clock, eliminating this issue.

There are many varying PLL implementations, however a crucial thing here is that the PLL will contain another clock generator which is MUCH more subject to jitter from power supply noise. So by feeding this PLL a clean supply, jitter is minimized.

Purely from a viewpoint of potential jitter (which we cannot verify as having been achieved or not) the Musland system (the chips used) seems to be capable of sub 100pS jitter results, something the Musiland guys also claimed (but their actual design does not achieve it).

All that said, the common Cirrus Logic (Crystal) Receivers and most others add over 100pS jitter of their own, so I should think the SPDIF Receiver would be the limit in the DAC.

If receivers used have low jitter of their own and equally good suppression of external jitter, all of this is moot anyway.

The Musiland is cheap and the mods done do not cost the earth either (there are more expensive USB2SPDIF boxes out there that do less). So I think one can easily defend the Musiland USB to SPDIF converter with modifications as a good way and economical way to make a computer transport for a pre-existing SPDIF DAC capable of 24/192KHz. That's all.

regards
Brian

DIY - Done Right!

Edits: 11/10/09 11/10/09

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

Atma-Sphere Music Systems, Inc.

---

[ 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 ]

---