Sony S9000ES DSD Decorder, ACP System, KHz / 24-bit capable Current Pulse Converter for all discs

Fig. 18: The Low Pass Filter of the DVP-S9000ES enables usable frequency response to 100 kHz, some five times higher than previous home audio sources.

Photo 3: The heart to SACD reproduction, Sony’s DSD decoding LSI.

Audio

DVD Technical Notes

DSD Decorder

Organizing the data into left and right pulse streams is the job of the DSD decoder. A Sony-built LSI, the DSD decoder first reads the invisible watermark — a key anti-piracy feature — and then decodes the incoming data. Data on the disc originate as alternating bursts of left-channel and right-channel information. Buffer memory and master clock sync enable the bursts to be

output as two continuous, simultaneous streams. The DSD decoder also reads sub code data, including text and Table of Contents information such as track number and playing time.

To preserve the maximum accuracy of the DSD pulses, our design program identified two basic goals:

•Amplitude axis precision

•Time axis precision

Sony’s Accurate Complementary Pulse Density Modulation (ACP) system and Current Pulse D/A Converter meet the first goal. Sony’s new pulse generator in VC24 achieve the second goal.

ACP System

The Megahertz switching speeds of DSD decoding have an unfortunate byproduct, switching glitches, rough irregularities in the DSD pulse train. Sony’s Accurate Complementary Pulse Density Modulation (ACP) overcomes this by converting the DSD pulses. Instead of encoding 1 as a pulse and 0 as the absence of a pulse, ACP represents each digital 1 as wide 1 followed by a narrow 0. And ACP represents each digital 0 as a narrow 1 followed by a wide 0. In this way, ACP effectively converts the data from pulse height (sensitive to glitches) to pulse width (insensitive to glitches). So glitches are not passed along to subsequent circuitry.

Fig.17: Thanks to Pulse Density Modulation, the ACP system

disregards amplitude distortions and switching glitches.

96 kHz / 24-bit capable Current Pulse

D/A Converter ( for all discs )

Conventional D/A converters generate pulse height from the voltage power supply — a method that can expose the signal to subtle power supply voltage fluctuations. The Current Pulse Converter overcomes this limitation. The design changes the incoming train of voltage pulses to a train of current pulses. Because the circuit incorporates an extremely clean “constant current” source, the pulses emerge with the desired flat tops, flat bottoms and identical height. You get audio output of extraordinarily low distortion. The Current Pulse D/A converter operates for SACD, CD and DVD- Video sound tracks alike. The system supports the highest sound quality in DVD-Video: 96 kHz/24-bit recording.

VC 24 Plus Digital Filter ( for DVD-Video and CD )

A conventional digital filter has a fixed filtering coefficient with no user controls. Sony’s Variable Coefficient digital filter is a dramatic departure. The VC digital filter actually offers different settings, representing different filter coefficients, different filtering methods and different objectives in reproduced sound.

Separate Low-Pass Filters ( for all discs )

After current-to-voltage conversion, a simple low-pass filter is all that’s required to produce an analog output. Unlike CD, the SACD cutoff frequency is largely determined by the characteris- tics of the player’s low-pass filter. The DVP-S9000ES low-pass

filter has aresponse

curve that slowly falls in the vicinity

of 50 kHz,

enabling usable

response out to 100 kHz, some

five times higher than previous home audio sources.

Two Audio Master Clocks ( for all discs )

As an audio/video player, the DVP-S9000ES needs to generate master clock frequencies for audio and video simultaneously. Typical practice deploys a Phase Locked Loop (PLL) circuit to subdivide the video master clock for audio use. However, this exposes the audio signal to unwanted jitter, which can generate audible distortion. That’s why the DVP-S9000ES subdivides audio master clock for video use. The SACD and CD master clock runs at 44.1 kHz x 1024 = 45 MHz. The DVD-Video sound track master clock runs at 48 kHz x 1024 = 49 MHz. And the DVD-Video clock for pictures downconverts this via PLL to

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