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Lumbermatt 29th June 2013 08:53 AM

Studying the Denon DCD-810

Iím actually studying the structure of the dcd-810 looking at some improvements I could do, and Iím facing some interrogations.

The DCD-810 is basically constituted of an SM5807 low pass filter (4 fold oversampling filter). The serial stream is directed to 2 PCM56H (one for each channel) DACs. On the output of each DAC, thereís a sample&hold circuit.

The S&H is constituted of a demuxer which loads a styroflex capacitor (470pF) with the current output of the DAC. The demuxer is driven by the deglitch signal of the SM5807.

As far as this is a dual DAC architecture, I canít figure out why this S&H circuit is needed. On an mono-DAC (both L and R samples are alternatively proceeded by the DAC) I can understand the need of S&H when a sample of the other channel is proceeded.

The PCM56 datasheet is clear about this :

The obvious solution to the phase shift problem in a two- channel system would be to use two D/A converters (one per channel) and time the outputs to change simultaneously. [Ö] It should be noted that no deglitching circuitry is required on the DAC output to meet specified THD performance. This means that when one PCM56 is used per channel, the need for all the sample/hold and controls circuitry associated with a single DAC (two-channel) design is effectively eliminated.
So why Denon kept the S&H circuitery even if not needed ?

Many thanks in advance.

canvas 9th July 2013 07:03 AM

That's a very good question. My Monarchy Audio 18b DAC is based on 2 x AD1860. It does not have deglitching circuitry.

guido 9th July 2013 04:41 PM

i have a dcd-800, which has just the one pcm56.
Bought it cheap long ago for it's dac. If you would like to compare, you can have it cheap too. Maybe you live near me (bit north of Aachen).

I did not use the dac, as i needed a pcm54 or 55. The dac lists on the net are incorrect for the dcd-800. :rolleyes:

wa2ise 11th July 2013 10:16 PM

Sure that that S&H circuit isn't really just an op-amp low pass filter circuit? In any event, I did this vacuum tube circuit in a CD player that used PCM56's. Sounds quite good.
And everyone I guess by now has seen my web page
Modifying CD player DAC circuits

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