4
Unique Technology - the past and the future
In the 1980’s early DACs were all 16 bit ladder DACs, with a precision laser-trimmed resistor
creating the appropriate analog level for each of the bits. The DACs worked well and sounded
good. They were quite expensive as very accurate resistors were required. Then along came
the “single bit” DACs. Rather than using a resistor to create an analog level, pulse width
modulation was used. Basically each bit was created by turning a switch on and off for the
appropriate length of time. The resulting square wave pattern was filtered to create a smooth
output. The expensive resistors were gone, and so was the good performance. Next came
the Delta Sigma DAC. It used the same pulse width modulation but rather than creating a
single large pulse for each data point, the data point was created with many small pulses. This
allows the pulses to be smoothed with a less radical filter, and improves the sound. As you
can see, upsampling the input signal to a higher frequency reduces the filtering requirements
and thus improves the sound.
The DAC IV draws from the older, superior ladder technology, but with incredible
improvements. The Basic Platinum contains four 24 bit MSB DAC
modules (seen below). The Platinum is fully balanced so there is
a matched pair of 24 bit DAC modules for the inverted and non-
inverted signals on each of the right and left channels. Finally, each
DAC module contains one R2R ladder DAC with a 23 bit negative
sign and one R2R ladder DAC with a 23 bit positive sign. Together
this makes a true 24 bit DAC. This design allows the quieter moments
in your music to be true to the music, without the linearity errors
near zero that plague normal ladder and delta-sigma DAC designs.
With a dual 24 bits of combined resolution, a 24 bit source gives a
true 24 bit resolution without the losses and errors that make your
normal 16 or 24 bit DAC perform far less than their actual resolution
(normal 16 bit DACs only muster a meager 12 bits of resolution).
The DAC IV is carefully designed so as to require no DC correction
in the output stage. This allows direct DC coupling on the output
stage for pure, uncolored sound -- with no output filtering to muck
up your high end or smear your bass attack.
Another major difference in the DAC IV is the type of output.
Essentially all ladder DACs produce a current output. This is
converted to a voltage output with a current-to-voltage converter.
This problematic circuit colors the sound and introduces non-
linearity. The DAC IV is a true voltage DAC with a voltage output
right from the source. All amplifiers have slew rates greater than
1000 Volts/microsecond. The output impedance of the DAC IV is
53 ohms.
Original Platinum DAC module
Second Generation Platinum DAC module - Smaller but mor bits!
Balanced Out
MSB DAC Module (Non-inverted signal)
23 bit positive sign DAC
23 bit negative sign DAC
23 bit positive sign DAC
23 bit negative sign DAC
Coaxial Out
MSB DAC Module (Inverted signal)
B
LoCk
d
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Right Channel
Toggle Switch
The Dual Signature DACs
produce 25 bits of resolution,
twice the number of steps as
the 24 bit Platinum.
Special Features
The DAC IV has many special features. The following sections discuss these features and how they work. As MSB Technology has
developed, so has our DAC architecture. Our advanced digital filter now replaces the asynchronous upsampling of earlier models. The
32X Digital filter goes way beyond our older 16X filter and 4X upsampling. To play a 32 bit/384 kHz file the Platinum only needs to be
plugged into the MSB Data CD IV player and a DVD with a 32/384 .wav file needs to be played. The new reclocking feature dynamically
buffers and re-clocks all the data and clock signals to provide a virtually jitter-free source directly to the DACs.
Summary of Contents for DAC IV plus
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