Mark Levinson No. 390S Compact Disc Processor
No. 390S Compact Disc Processor
We’ve watched the No.39 CD Processor sales continue as strongly
as ever, with the rather poor CD playback performance offered by the
majority of the DVD machines on the market. Our customers have been asking
us if we would ever consider taking the No.39 to that "S" designation
found on several of our Mark Levinson separates, allowing even higher
performance in a one box CD playback solution.
We have completed design of an update for the No.39 that delivers a remarkable
improvement in sonic performance over our original design. The "S" version
is based on the original, updatable chassis. It features a complete re-design
of the No.39’s DAC/analog output module. Borrowing heavily from
the design of the No.32 Reference Preamplifier and upcoming Audio Processor
portion of the No.40 Media Console, the No.390S incorporates our latest
advances in D-to-A converter design, output buffer and volume control
technologies, all implemented on a four-layer Arlon® 25N circuit
board. We’ve decided to take the No.39 to an entirely new level
of performance and provide an upgrade path for our No.39 owners in the
process.
No.390S as CD Transport
The first task performed by the No.390S is that of a high performance
digital transport. The characteristics of an outstanding CD transport
are simple to define: it must recover the correct data from the disc
and deliver it to the digital processor with exacting precision. As simple
as this sounds, in reality achieving it has been extremely difficult-as
evidenced by the significant sonic differences among various transports.
Recovering the correct data is not difficult. Modern CD transports include
powerful error correction systems, making uncorrectable errors quite
rare. Even badly scratched discs can often be played without difficulty.
Since compact discs operate with a 44.1 kHz sampling rate, there should
be exactly 44,100 error-free samples transmitted each second. Moreover,
each such piece of musical information should exist for exactly 1/44,100th
of a second before being replaced by the next piece. Inconsistencies
in this respect account for most of the sonic variations heard between
transports, and are referred to as jitter.
Digital audio depends on the proper signal being reconstructed at precisely
the right time. An early (or late) digital sample distorts the audio
waveform, causing it to sound harsh and unnatural. One of the greatest
challenges in digital audio is delivering these samples with adequate
precision. Without achieving precision measured in picoseconds (trillionths
of a second), the full potential of the system cannot be realized.
Traditional transport designs seek to retrieve the digital audio information
from the disc itself at exactly the correct rate. A "clock" mounted
on the laser pickup mechanism determines the "tempo" at which
the musical information is recovered. If a discrepancy exists between
the tempo of this clock and the flow of digital information, the transport's
motor attempts to adjust its speed.
Unfortunately, the performance of this important clock is limited by
cost and by its environment. Typically, a 1000 part-per-million oscillator
is used in an extremely noisy electrical environment, adjacent to the
motor that spins the disc and to other circuitry. The resulting electrical
noise introduces timing errors in the oscillator. Mechanical limitations
such as friction, vibration, and inertia introduce additional inaccuracies
of their own.
Subsequent handling of the digital audio signal within traditional transport
designs cannot improve upon this "jittery" signal. To the
contrary, the various stages of signal processing between the laser pickup
and the final output can only contribute additional jitter of their own.
A New Generation
The Mark Levinson No.39 CD Processor, the predecessor to the new No.390S,
went beyond conventional digital audio playback technology by employing
a proprietary, Closed-Loop Jitter-Reduction (CLJR) system. Simply put,
the No.39 separated the recovery of the digital data from the task of
maintaining a consistent, jitter-free output. This separation allowed
each task to be performed more accurately. The No.390S continues with
this design approach.
As in the No.37 CD Transport, the No.390S derives its reference frequency
from a custom made, temperature-compensated crystal oscillator that acts
as a "clock" with better than five part-per-million accuracy
(a two-hundredfold improvement over the standard oscillator). This oscillator
is removed from the noisy environment of the laser mechanism and placed
on a quiet, independent digital circuit board. With its own dedicated
power supply and electrical isolation, this clock provides a far more
stable reference frequency than in any traditional design. Significantly,
the all-important reference clock is located in the most critical area
of the design, adjacent to the digital processor section and the digital
outputs-where it belongs.
Each bit of the digital audio signal is stored momentarily just prior
to its transmission to the digital processor. The reference clock determines
the precise moment when each bit is released from this memory buffer.
This purely electronic process virtually eliminates transport-related
jitter, whether of mechanical or electrical origin. Of course, another
bit must be ready to be loaded into the buffer as the current bit leaves
on its way to the processor. For this reason, the same crystal oscillator
that controls flow of information out of the memory buffer also directs
the digital servo that sets the rate at which data flows into the buffer.
By placing the all-important reference clock in the final stage of the
transport section, and slaving the mechanical subassemblies to it rather
than the other way around, the signal presented to the digital processor
section of the No.390S is uncontaminated by electrically- or mechanically-induced
jitter. The sonic advantages of this design are immediately apparent
in the stunning clarity, warmth and dynamic contrasts exhibited by the
No.390S.
Sonic Summary
The No.390S successfully builds on the strengths of the popular No.39
CD Processor. The name change is intended to convey the level of sonic
improvement that you can expect. It doesn’t sound like a better
No.39 – it sounds like a completely new and significantly better
product.
Many of the improvements have resulted in a further reduction in noise.
Low-level musical details that were previously masked are now revealed.
High frequency clarity and extension are improved. Low frequency detail
is improved. Imaging and spatial information are substantially improved,
with a greater sense of depth and width. There is an almost holographic,
wrap around quality to the presentation.
All of this musical information was obviously always present on the CDs.
Once again, significant sonic improvements were attained by better implementation
of an existing technology. We encourage you to compare the new No.390S
to other digital products, including separate D/A converters and SACD
players. We are confident that you will agree with us that the No.390S
is an outstanding value.
