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Looper's Delight
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> Besides the disadvantages, is there any advantage which would
> justify 4 times the price of a Zoom H-2.???
The reason is DSD technology. To quote our own Henry Kaiser (from the liner
notes of "Yo Miles! Sky Garden"):
"We also recorded the music with a Studer 1/2'' analog two-track machine.
Everyone who listened to both recording formats in many blindfold tests
preferred the DSD recording to the analog for its amazing depth, imaging
and
greater detail.[...] Chek this out - this is a technology that needs to be
supported by more users."
DSD is a delta-sigma (1bit) conversion technology which samples at 'round
2.88MHz. So how does this work, compared to typical PCM (e.g. CD, DVD)
audio?
A usual (let's say 16 bit) A/D converter with a sampling frequency of (to
make calculations simple) 100kHz (close to today's 96kHz) will sample every
10us. That means: every 10us, it measures the voltage on the analogue
input,
which let's say can be in a range from -1 to 1V. This range is then evenly
cut up into the digital sampling steps: with 16 bits, there are 64738
possible values, so a voltage of -1V would equal 0000000000000000, a
voltage
of 1V would be 1111111111111111, and a voltage of 0V would be
1000000000000000. That means that every sample step (here, every 10us), you
can theoretically correctly sample a change from -1V to 1V (or from any
value to any value).
With delta-sigma conversion, the converter only has one bit. How does that
work. If we start at time 0 (sample point 0), the voltage is sampled. At
step 1, the voltage you measure now is compared to the voltage from the
last
step. If it's bigger, then the converter's single bit outputs 1, else it
outputs 0.
The trick here is that you greatly increase the sampling frequency. In the
case of DSD (and SACD), it's 2.88MHz, which compared to CD is about 64
times
as much. That means that every time your normal converter samples, the DSD
converter has sampled 64 times.
As in the analogue world, sudden jumps (like -1V to 1V in an instant and
back to -1V in the next) are rather uncommon while very fast changes (i.e.
faster than every 10us) are, it is argued that the 1bit conversion better
represents the analogue world the sound comes from (this may be different
for all of us electronic-noise-generators, though).
Is it worth four times the price?
It depends. First of all, I have to admit that I don't have any first-hand
experience with this new technology - I don't even own a CD player that can
play SACDs, let alone have a DSD recording medium. So I cannot judge wheter
the sound is any better (and by how much it is better).
Now why do they charge that much? Having a clock frequency and data
transmission happening at 2.88MHz can be an EMC issue, especially in an
audio device. However, this is nothing uncommon nowadays, because 1-bit
converters have started to dominate the audio market some 15 years ago -
and
if today, you look at the specs of your favourite "24bit" audio device
(let's say, TC Finalizer), you'll find that it actually uses 1bit
converters
sampling at 6.144MHz. And I'm sure that a lot of the lower-range devices
(e.g. Microtrack) use 1bit converters as well (they are even cheaper).
Sooo, you obviously pay for a technology that has been present for many,
many years, only its output hasn't been used as a data storage format.
Perhaps some of our codewarrior/soldering iron people can hack e.g. a Zoom
H2 to use DSD?
Rainer