Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it.

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More on Accuphase

Posted by Charles Hansen (M) on September 28, 2008 at 21:25:03

In Reply to: More on digital inputs posted by Charles Hansen on September 28, 2008 at 21:00:47:

I was so curious about the way Accuphase implemented their clocking scheme in their DP-67 one-box player, that I thought I would look at the rest of their models. To recap, from an engineering standpoint it would seem that they are making a product that is the worst of two worlds.

Essentially they have put a complete transport box and a complete DAC box into one chassis, connecting them with the S/PDIF interface, that is known to increase jitter. So they have the higher jitter associated with two-box solutions, along with the problems of introducing RFI from the transport section into the DAC section.

I looked at their other models, and the DP-57 is built the same way. On the other hand the DP-500 appears to be built in a more conventional fashion, whereby the digital audio data from the internal transport is fed directly to the DAC chips without turning into S/PDIF first. In this model, I would expect there to be an audible difference between playing a disc through the internal transport versus using an external transport and the digital input. (The best way to verify this would be to use two DP-500s, so that the transports would be the same. There is still the thorny question of which digital cable to use, however.)

The block diagram of the DP-700 is a bit unclear to me. However, it appears that all sources, whether fed via external digital inputs or via the internal transport, use the same "Ultra Jitter-Free Plus PLL", so I would expect that the external sources might sound similar to the internal transport.

Again, one must be careful not to reduce things to the lowest common denominator. No matter how good the Accuphase players sound, it would seem that at least some of them could be improved if they used a different clocking scheme.

Edits: 09/28/08

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