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DAC chips, but in combination with our high resolution 24 bit Second Generation, or Signature DACs the problem is very apparent. The
sound becomes muddy, veiled and un-involving when using any off the shelf digital filter. To counter this problem the MSB 16x Digital
Filter does it’s filtering in one filter stage that raises the sampling rate by 16.
FIR filters operate by multiplying each sample in the data by a set of filter coefficients and then summing the result. Most digital filters
round the result of each addition before the adding next sample. This repeated roundoff results in a similar problem to the cascaded 2x filter
approach, muddy sound. MSBs digital filter uses bit perfect accumulation in an 80 bit accumulator completely eliminating these debilitating
roundoff errors. Only as the last step do we carefully convert the audio to the 24 bits our DACs require. The high sampling rate of the
output allows us to include advanced ultrasonic dither and noise shaping techniques in this step to achieve greater than 24 bit effective
resolution.
Through extensive listening tests we have found that the choice of filter coefficients has a great impact on the tone of the music. We have
found that steep, phase perfect “Brick Wall” filters tend to sound the most neutral but are also the most difficult to implement without
problems. Improvements we have made in our digital filter, with its single stage design and 80 bit computation, allow us to use very steep
filters with no compromises.
Custom Filter Options
Custom Filter Options
Custom Filter Options
Custom Filter Options
Custom Filter Options
We recognize that different people often have very different taste in their music. For those who do not like the standard choice of filter, or
require a different filter response, we have provided a very easy method for customizing your MSB 16x Digital Filter. By playing a standard
CD containing a custom filter algorithm you can temporarily change the filter inside your 16x Digital Filter. This CD filter loading allows you
to load almost any FIR filter quickly and easily. You may also upgrade your MSB 16x Digital Filter with the latest custom software just by
playing a special Firmware Upgrade CD.
The timing of the DACs conversion clock also has a large impact on sound quality. Any
periodic frequency change or “jitter” causes a loss of focus in the reproduced audio. The
high power and large memory space of the SHARC DSP we use allows us to offer a unique
Ultra Clock to your MSB 16x Digital Filter. The Ultra Clock adds two ultra precision, ultra
low jitter TCXO oscillators and custom clock handling circuitry to your board. This custom
circuitry allows us to do much more than simply reclock the data, as other jitter reduction
boxes do, but completely replace the incoming clock!
Most jitter reduction schemes rely on Phase Locked Loops or Asynchronous Sample Rate
Converters. The Phase Locked Loop is able to reduce jitter to a significant degree but not
eliminate it because the output clock must be related to the input clock. The Asynchronous
Sample Rate Converter, which completely replaces the data and clock, seems ideal until you
realize that the complex computation involved harms the data by permanently imbedding a
portion of the clock jitter into the data. Sample Rate conversion is also detrimental to the
sound due to the complex and sub optimal digital filters involved, which must change their
filter response to track minute changes in the input to output clock ratio.
The Ultra Clock sidesteps both of these problems by storing the incoming data in an
extremely large buffer (1/2 second of audio.) The on-board clock then reads out the data without jitter. The on-board clocks are totally
independent from the input clock so that no jitter is transferred to the output. True absolute digital silences such as a track skips are
selectively shortened or lengthened by the DSP to keep the buffer synchronized. This process is carried out seamlessly by the DSP to
assure that all compatible sample rates have their clocks properly replaced. Compatible sample rates are 44.1 kHz, 96 kHz, 176.4 kHz, 192 kHz,
and 384 kHz. Other sample rates automatically use the recovered clock from the transport without user intervention. The 48 kHz sample rate
does not support clock replacement due to the large latency incurred by the buffer, which would cause audio from a DVD movie to be
unsynchronized.
The On-board Option Switch
The On-board Option Switch
The On-board Option Switch
The On-board Option Switch
The On-board Option Switch
The MSB 16x Digital Filter includes an on-board option DIP switch, which is a small multiple position
switch on the 16x Digital Filter board that allows additional configuration. With this switch you may select
the on-board Ultra Clock operation, Dither, Mute Mode, Single Ended Operation and the Motherboard
Revision.
Switch 1, Clock Replacement Mode - Switch 1 ON = Clock Replacement Mode, Switch 1 Off = Low Latency
Synchronized Mode, or no on-board clocks installed. Switch 1 allows you to enable the on-board Ultra
Clock option. When enabled this option will completely replace the incoming clock with an ultra low jitter
TCXO based clock. The DSP monitors the incoming sample frequency and detects standard sample rate signals, 44.1 kHz, 96 kHz, 176.4
kHz, 192 kHz and 384 kHz. The on-board clock then completely replaces the incoming clock. Other sampling frequencies use the incoming
clock from the source. The DSP allocates a huge internal FIFO buffer (1/4 second) that stores the incoming audio to decouple the
incoming and outgoing data streams. Long absolute digital silences in the music stream, such as between tracks and during pauses, are
selectively shortened or lengthened by the DSP to maintain data synchronization. This results in a significant delay between the audio