Even as digital/analog processors were becoming a hot product category in the early 1990s, audiophiles were also learning that timing uncertainties in the AES/EBU and S/PDIF serial datastreams—jitter—would compromise any improvement in sound quality offered by these DACs. Some companies therefore introduced products to reduce or eliminate jitter—in the November 1994 issue of Stereophile, Robert Harley reviewed three such products: the Audio Alchemy DTI Pro, the Digital Domain VSP, and the Sonic Frontiers UltrajitterBug. I still have Stereophile‘s review samples of the UltraJitterBug and VSP, along with two contemporary DACs: a PS Audio UltraLink and a Parts Connection Assemblage DAC-1.
As our reviews of these products were published before Paul Miller’s and the late Julian Dunn’s development of the “J-Test” diagnostic signal, I performed J-Test jitter measurements to bring that 1994 review into the 21st Century. You can see what I found here.
Enjoy!
Oh, and the heading image? This is the PS Audio’s output spectrum when fed TosLink data representing a full-scale, 16-bit 10kHz tone and corrupted with jitter at 1kHz with an amplitude of 1 nanosecond. The Ultralink can’t deal with the jitter, throwing up sidebands at ±1kHz.
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