Home Computer Audio Asylum

Music servers and other computer based digital audio technologies.

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ Computer Audio Asylum ]
[ Alert Moderator ]

RE: cMP - the open source high-end Memory Player

I think this area is the weak part of cics's hardware design: The need to make the computer slow to (potentially) reduce problems with the DAC. Removing the DAC is a beter solution for many people.


DAC can be placed internally (as in soundcard providing analogue outs) or externally (via USB, PCI/e soundcard, firewire, ethernet). External DAC would probably require SPDIF interface. In both scenarios, you'll want to minimize electrical interference to improve sonic performance. For example, high speed clocks generate high energy RF spikes which is detrimental to sound output. Hence lower clock speed is desired. RAM settings have remarkable impact on sound: the more aggressive, the greater the noise.

PCI is a shared bus. PCI-e is a dedicated serial-like connection.


Yes PCI is a shared technology BUT the design applied results in a single PCI device (the soundcard) - no sharing. Other PCI devices like onboard sound is disabled. Also a dedicated interrupt is used. PCIe may not be a better choice given its large latencies. Its implementation is a challenge for sound as PCIe prefers large data chunks against smaller transactions. PCI together with ASIO suggests a better combination.

Using an external USB DAC. If the computer provides bit-perfect USB data to the DAC, all the computer case concerns about heat and radiation go away. ... It's a fairly trivial task to provide perfect data to an external DAC, if it has a small buffer and a good clock.


USB is an option for outputting sound and by design has a buffer and clock. USB however requires proper audio drivers to ensure bit perfect delivery and these are not readily available.

Achieving bit perfect delivery (which is also achieved using other interfaces like PCI, Ethernet, etc.) is one important aspect to good sound. The remaining aspects are jitter and correct upsampling. Using SRC ensures upsampling is correct.

Jitter requires both hardware and system software optimizations. This is an ongoing challenge with less jitter yielding better sound. DACs are hugely susceptible to master clock (aka work clock or sample clock) jitter. Periodic jitter (sine or square wave) is most offensive giving ahamarmonics whilst random jitter deteriorates DAC SNR. Given the ultra low levels of jitter (~ps) required for high quality sound, subtle changes can make a difference.

Do this experiment: set TRRD on RAM to 2T (instead of 3T) - with this simple hardware change, sound is harsher and over time its unpleasant. Let me know what you get...

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

Follow Ups Full Thread
Follow Ups
  • RE: cMP - the open source high-end Memory Player - cics 23:08:20 02/28/08 (0)
FAQ

Post a Message!

 Forgot Password?
Moniker (Username):
Password (Optional):
  Remember my Moniker & Password  (What's this?)    Eat Me
E-Mail (Optional):
Subject:
Message:   (Posts are subject to Content Rules)
Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:  Automagically notify you when someone responds.

[ Top 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 ]