Micromega CD 30 MM CD30SILVER User Manual
Product codes
MM CD30SILVER
The drive mechanism
The MICROMEGA team’s wish was to be innovative in this field, and it was the case for some very
good reasons. Due to the success of DVD, DVD mechanisms produced today are of top, reliable
quality, simply because they are mass produced and therefore subject to extremely tough quality
control procedures inherent to mass production. It is for this reason that we took the wise decision to
equip the CD30 with the latest generation SONY KHM313 or SANYO SFH850 DVD mechanism.
The mechanism control is ensured by a Philips SAA78247 circuit and a MICROMEGA proprietary
software program featuring error correction algorithms which are particularly efficient and designed for
audio reproduction. At present and in many cases, CD players are optimized to read CD ROM.
Indeed, audio CD is read at nominal speed, whereas in the case of CD ROM, some players reach up
to 52 times nominal speed. It’s a different aspect but it is not the most significant. When reading CD
ROM, it is possible, if a batch of data contains errors, to go back and to re-read the passage, before
choosing the best remaining error interpolation strategy. This solution is absolutely unthinkable in
audio terms, because in the event of errors the aim is to privilege continuity of the musical message so
that the listener doesn’t realize that the player is correcting inaccurate data. Obviously, it’s impossible
to stop the reading and to repeat a passage several times to remove a scratch, a finger mark or
anything else which could have triggered the error correction system. In light of this, we can see how
important it is to adopt a specific strategy to audio reading and why the MICROMEGA team invested
so much energy and time into developing the most appropriate solution in terms of musical
reproduction.
good reasons. Due to the success of DVD, DVD mechanisms produced today are of top, reliable
quality, simply because they are mass produced and therefore subject to extremely tough quality
control procedures inherent to mass production. It is for this reason that we took the wise decision to
equip the CD30 with the latest generation SONY KHM313 or SANYO SFH850 DVD mechanism.
The mechanism control is ensured by a Philips SAA78247 circuit and a MICROMEGA proprietary
software program featuring error correction algorithms which are particularly efficient and designed for
audio reproduction. At present and in many cases, CD players are optimized to read CD ROM.
Indeed, audio CD is read at nominal speed, whereas in the case of CD ROM, some players reach up
to 52 times nominal speed. It’s a different aspect but it is not the most significant. When reading CD
ROM, it is possible, if a batch of data contains errors, to go back and to re-read the passage, before
choosing the best remaining error interpolation strategy. This solution is absolutely unthinkable in
audio terms, because in the event of errors the aim is to privilege continuity of the musical message so
that the listener doesn’t realize that the player is correcting inaccurate data. Obviously, it’s impossible
to stop the reading and to repeat a passage several times to remove a scratch, a finger mark or
anything else which could have triggered the error correction system. In light of this, we can see how
important it is to adopt a specific strategy to audio reading and why the MICROMEGA team invested
so much energy and time into developing the most appropriate solution in terms of musical
reproduction.
132 kHz oversampling: Listening rather than figures
For some time, many players arrive on the market equipped with this technique which is so attractive
on paper and commonly called SRC. These three letters, Sample Rate Converter are like magic and
manufacturers were fast to adopt this technique allowing them to publish amazing figures to impress
consumers. And how important is actual listening in all that? Before going into detailed explanation
about what motivated MICROMEGA to make this choice, it’s important to explain briefly without too
much theory, how a SRC functions and the reasons for which this type of component came to be
developed. With the advent of digital techniques in the professional audio field, it quickly became
necessary to convert signals which had different sampling rates. The most outstanding example is that
of the difference in sampling rate between the DAT and CD. The former is sampled at 48 kHz and the
latter at 44.1 kHz. Other frequencies appeared since, for example 32 kHz for digital radio, then 96 kHz
and more recently 192 kHz for DVD Audio. It is therefore important to establish a bridge which makes
it possible to convert in any direction a sampling rate to another. It is what we call ASRC Sample Rate
Converter or Asynchronous Sampling Frequency Converter. Asynchronous means that the sampling
rates that are converted are not multiples of one another. In this way we can convert a sampled signal
at 44.1 kHz into a sampled signal at 96 kHz and even 192 kHz. Obviously at first glance, that seems
fantastic but if we dig a little deeper we quickly discover that the disadvantages far outweigh the
advantages and that despite the figures which could mislead a novice, it’s not the best solution.
Indeed, to convert 2 frequencies which are not multiples of one another, you need to have 2 clocks.
The first clock is a multiple of the first frequency and the second a multiple of the second. The circuit
will operate multiplications then round-offs until it reaches its goal. However, the two clocks will create
beat problems, which will be extremely difficult to eliminate and which inevitably will have harmful
effects on the quality of the musical message. For all these reasons the MICROMEGA team decided
to opt for a synchronous conversion. By choosing the frequency of 132.3 kHz also expressed as 3 x
44.1 kHz, MICROMEGA succeeded in taking advantage of the undeniable advantages of a sampling
rate conversion without having to deal with the problems of asynchronism. The ratio of 3 between the
two frequencies was selected intentionally after long hours of listening which proved that an odd order
had advantages over an even order. This system therefore makes it possible to have only one clock
for the two frequencies because they are multiples of one another. Hence, this clock is to be treated
with the greatest of care, in particular in terms of phase sound level and its spectral distribution, which
on paper and commonly called SRC. These three letters, Sample Rate Converter are like magic and
manufacturers were fast to adopt this technique allowing them to publish amazing figures to impress
consumers. And how important is actual listening in all that? Before going into detailed explanation
about what motivated MICROMEGA to make this choice, it’s important to explain briefly without too
much theory, how a SRC functions and the reasons for which this type of component came to be
developed. With the advent of digital techniques in the professional audio field, it quickly became
necessary to convert signals which had different sampling rates. The most outstanding example is that
of the difference in sampling rate between the DAT and CD. The former is sampled at 48 kHz and the
latter at 44.1 kHz. Other frequencies appeared since, for example 32 kHz for digital radio, then 96 kHz
and more recently 192 kHz for DVD Audio. It is therefore important to establish a bridge which makes
it possible to convert in any direction a sampling rate to another. It is what we call ASRC Sample Rate
Converter or Asynchronous Sampling Frequency Converter. Asynchronous means that the sampling
rates that are converted are not multiples of one another. In this way we can convert a sampled signal
at 44.1 kHz into a sampled signal at 96 kHz and even 192 kHz. Obviously at first glance, that seems
fantastic but if we dig a little deeper we quickly discover that the disadvantages far outweigh the
advantages and that despite the figures which could mislead a novice, it’s not the best solution.
Indeed, to convert 2 frequencies which are not multiples of one another, you need to have 2 clocks.
The first clock is a multiple of the first frequency and the second a multiple of the second. The circuit
will operate multiplications then round-offs until it reaches its goal. However, the two clocks will create
beat problems, which will be extremely difficult to eliminate and which inevitably will have harmful
effects on the quality of the musical message. For all these reasons the MICROMEGA team decided
to opt for a synchronous conversion. By choosing the frequency of 132.3 kHz also expressed as 3 x
44.1 kHz, MICROMEGA succeeded in taking advantage of the undeniable advantages of a sampling
rate conversion without having to deal with the problems of asynchronism. The ratio of 3 between the
two frequencies was selected intentionally after long hours of listening which proved that an odd order
had advantages over an even order. This system therefore makes it possible to have only one clock
for the two frequencies because they are multiples of one another. Hence, this clock is to be treated
with the greatest of care, in particular in terms of phase sound level and its spectral distribution, which