USB Audio and Computers

Using a Computer as Digital Audio Source.

We have carefully evaluated the top possible quality achievements when using a computer as digital source. The result is that a simply slaved CD player (not even synchronously re-clocked by LessLoss) outperforms even the most scrupulously slaved computer soundcard running directly off of the DAC 2004's SuperClock frequency of 11.2896 MHz. Using this SuperClock frequency, the 44.1 kHz audio sampling rate derivative is achieved through dividing this clock frequency by the exact round value of 256. Yet even in this mathematically 'clean' configuration, here is a list of known parameters inside the computer which all still have influence on the audible Jitter amount to be heard after D/A conversion, even using the top-quality LessLoss digital cabling and the syncronously slaveable LYNX soundcard.

The computer was P4 Northwood 3.4GHz, 512x2 MB DDR2 @ 400MHz, PCI CLOCK 33.3 MHz, ASUS P5AD2 925XE mainboard, Antec 550 PSU. Using Wavelab 5 with ASIO output at native 16 Bit 44.1 KHz playback, and Foobar 2000 player with Kernel Streaming output. Using only 44.1 KHz 16 Bit original files in the form of Wav PCM.

We made a custom Clock / SPDIF cable which was 30 cm long and went straight from the LYNX input/output pins directly to Eichmann Bullet RCA plugs. It was shielded in tightly double-wound large diameter silver plated copper. The original LYNX adapters were not used and there were no other cables dangling out of the LYNX connector.

Lightened Windows services:
Audible.
Probable reason -- less time-splitting of system operations

Increased memory timings to maximum smooth operation:
Audible.
Probable reason -- more consistent data transfer

Changing the card's DMA buffer size:
Audible.
Probable reason -- more consistent data transfer

Changing the audio software's buffers:
Audible.
Probable reason -- more consistent data transfer

Change the CPU frequency from 3.4 to 2.8 to 1.8 GHz:
Audible.
Probable reason -- less parasitic HF radiation

Changing the memory timings inside the BIOS:
Audible.
Probable reason -- more consistent data transfer

Playing the file from USB RAM drive instead of from Hard Disk:
Audible.
Probable reason -- less power supply spikes from Hard Drive

Playing the file from a deeply embedded folder instead of from top of directory:
Audible.
Seems to have same effect when file path name is maximum length, regardless of directory structure. Probable reason -- buffering issue, since the music playback software takes considerably longer to load the data prior to playback in these cases.

Filtering the PS of the computer:
Audible.
Reason -- Avoiding parasitic power supply fluctuations. This is just as important and audible in CD players and DACs.

Turning off the CRT monitor:
Audible.
Probable reason -- less HF radiation within the computer's schematics, and hence the audio card.

Unplugging all external devices, i.e. mouse, keyboard, monitor, etc:
Audible.
Probable reason -- less antenna effect, hence less HF radiation within computer schematics.

Even after all of these tweaks, the computer as source could not compete in clarity and low Jitter performance with a synchronously slaved run-of-the-mill NAD CD player. The DAC in all cases was the DAC 2004 with integrated volume control feature and all audio cabling and power filtering was LessLoss.

Further discussion regarding the audibility of computer parameters.

It is often falsely believed that parameters regarding only the digital domain do not affect the analogue results of the D/A process due to the fact that digital errors are neither introduced nor corrected by tweaking these parameters. The famous slogan for this school of thought is "Bits is Bits."

This train of thought is founded on the absence of direct experience and personal analysis of what Jitter at the D/A process sounds like. Nevertheless, we believe it is possible to appreciate the importance of Jitter reduction when seeking the highest quality digital-source playback even without direct experience with tweaking all of these parameters. We provide the reader with several thoughts about why these parameters do indeed lead to different discernable levels of quality after A/D conversion:

• A compact disc played back on different CD players which use different schematic layouts but almost identical parts can sound disctinctly different. Here we can appreciate the influence of a different schematic layout on the amount of Jitter-related distortion of the resulting analogue signal.
• CD players which use substantially different parts in only the digital schematics, but the same converter chips and schematic solution in the analogue schematics, also exhibit differences in analogue sound after conversion. Here we can appreciate the influence of the digital componentry on Jitter-related distortion.
• Desktop computers contain several sources of high frequency radiation. There are high frequency oscillators on the motherboard, on the soundcard, on the video card, and elsewhere depending on the specific computer configuration. All of these oscillators act as transmitters, transmitting HF electromagnetic radiation into the aether surrounding all the circuit paths located in the computer, and indeed into the very power supplies of the computer.
• The adjustable parameters such as memory allocation, buffer sizes, CPU speed, etc. are analogous to changing the physical componentry inside a CD player's digital schematics. Because most of this componentry is not programmable, the CD player is said to have "this" or "that" sound. CD players with SHARC processors are pre-programmed to manipulate the digital data streams in a specific way according to specific algorithms, resulting in the sound that the manufacturer of the player deems desireable. In this case the average user still does not have access to all parameters known to the manufacturer. Hence, again the CD player is deemed to have "this" or "that" sound.
• In a desktop PC situation, the computer is first and foremost a flexible platform for manipulating data streams. In this way, the user may wish to experiment with as many parameters of the streaming system he or she desires to. There are several discussions published on the web by experienced audiophile enthusiasts who have spent years tweaking their computers to obtain the sound they deem desireable. It is generally known in these circles that the deeper you delve into these parameters, the more one is struck by the audibility of their effect on the converted analogue signal.
• The only possible explanation to this phenomenon is that the timing of the data stream (Jitter) is being manipulated. It is known through attempts to quantify Jitter through mathematical statistical analysis of the converted analogue signal that the ear can hear Jitter amounts that on paper appear initially to be very insignificant. This shows clearly that it is not merely the amount of peak-to-peak Jitter that is significant to our ear's perception of its audible effect, but that its presence as an ongoing unstable phenomenon lends it its great distortive audibility.
• Also, throughout LessLoss's extensive experience with battling Jitter, it can be stated with authority that Jitter comes through a plethora of sources, and that this leads to a certain layering of the effects of Jitter, such that, when one successfully anihilates one source of Jitter, other sources with a lesser distortive effect become more apparant.
• Through the development and use of high-quality audio cabling, high quality power filtering, and customized electrostatic full-range loudspeakers, it is also known to us that several of the least significant layers of Jitter are not audible when one uses standard cabling or impure power supply voltages.
• We provide this information to those seeking the highest performance digital to audio conversion. It is the result of our experience and analysis, using the LessLoss DAC 2004 converter in Digital Master Mode, and using exclusively our signal cabling and power filtering technology.

USB Audio with the DAC 2004

We have developed a USB to S/PDIF converter for use with the DAC 2004 in slave mode to it. This device consists of a matchbox-sized connector, one end of which has an RCA connector to be plugged into the SPDIF input into the DAC 2004, the other end which has a USB cable which connects to your computer's USB output.

How does USB Audio sound with the DAC 2004?

It sounds much better than the standard CD Player / DAC setup when the DAC is slaved to the CD Player. It does not sound as good as a slaved (and synchronously re-clocked) CD player, but the sound is indeed musical and can be enjoyed even using very high quality electrostatic loudspeakers. There is little or no harshness, just that some of the true recorded detail goes astray. It is a very flexible solution for those seeking a quick and easy computer audio solution.

What sampling rates can be played back?

88.2 kHz or higher sampling rate is not supported. Anything lower is supported and no adjustments need be made, since the DAC runs in slave mode and locks to anything you send to the USB out.

What about software issues?

No driver installation required. You just plug the USB cable into the computer and the computer sees a new USB device. You can choose this device as playback device from your audio playback software.

The Price for the USB to SPDIF adapter?

195 Euros.