AXPONA 2013

Pure Vinyl & Music from Channel D

John Atkinson  |  Mar 13, 2013

Channel D's Rob Robinson was using the same combination of Joseph Audio Pulsar speakers, Hegel amplification, and a Lynx Hilo D/A processor that he used at earlier shows to show off the LP rips made with his Pure Vinyl program for the Mac, now in its v3.1 incarnation. In honor of the late Alvin Lee, Rob played me a rip from a Kevin Gray-mastered 10 Years After LP, made with an Artemis turntable/arm, Zu DL103 cartridge, and the latest version of the Channel D SETA L solid-state phono preamplifier. I have been getting increasingly impatient with the occasional ticks and pops with my LP rips, as eliminating them is too much like work. But there was no such noise on Rob's rips, a tribute to his LP player.

Though Pure Vinyl and Pure Music will play back DSD files, Rob was converting the files in real-time to 24/88.2k LPCM so he could control the system volume in software, there not being a preamp. I asked why he chose 24/88.2k rather than, say, 24/192k? He replied that it seemed a more optimal conversion.

COMMENTS
Mycophile's picture
Submitted by Mycophile on March 14, 2013 - 12:48pm

 

This choice of sample rate comes from the trade-off between time resolution (sample rate) and amplitude resolution (sample word length) resulting from the digital low pass filtering used for the conversion.

 

In the PCM conversion operation, a higher target sample rate (better time resolution) results in a smaller word length /  lower amplitude resolution. Here, the limiting case is a 1 bit word length at the native DSD sample rate, which would not be listenable as “PCM.”

 

At a lower sample rate the resulting word length is greater, which is desirable, but the time resolution / frequency response suffers.

 

I find the sweet spot, balancing time and amplitude resolution, is 88.2 kHz for 64Fs (2.8 MHz) DSD.

 

96 kHz also is a possiblity but the CPU footprint for the operation is smaller for 88.2 kHz, enabling high quality real time DSD to PCM conversion during playback. - Rob

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