| Musical Fidelity offer
their own path of upgrades for the X-DAC. For example, the supplied wall-mart
PSU can be upgraded to the X-DAC PSU. The X-DAC can be partnered with the X-10
V3 tube output buffer, these upgrades will cost you in the region of £300.00 a
piece. This is by no means the end of the road for the X-DAC, to contrary, it
is only the beginning. By modifying the X-DAC’s circuits, masses more
performance can be released. All this can be done cost effectively and the end
result is a DAC that truly shines.
Essential X-DAC Upgrades.
Based upon a similar
upgrade concept we have developed for the 21 DAC, the X-DAC is seriously
improved by replacing general purpose components used for the stock unit. Our
level-1 upgrade starts by replacing the general purpose Jamicon SK electrolytic
capacitors throughout the power supplies, bypassing and local de-coupling. The
Jamicon SK capacitors are a general purpose type, no low E.S.R. and audio grade
properties with a mediocre sound to match. Replace these capacitors with a mix
of Rubycon ZA & OS-CON capacitors and the improvements are
striking. Background noise is immediately quieter; you hear more music and less
noise, details, subtle tonal shifts previously veiled are audible adding an
element of ‘life’ the music.
Moving on, we next
address the +5V digital & analogue regulation for the DAC. The stock unit
uses the industry standard 7805 type. The problem here is these 3-terminal
regulators are quite noisy in the audio band. For a 7805 (5V) typical
Ripple Rejection Ratio (PSRR) is 80 db (f = 120Hz, load = 100 mA), and noise is
in the region of 40µV. Move upwards of 120Hz and the PSRR worsens considerably,
at 10 KHz PSSR drops to 60 db, 100 KHz TO 50 db. What this means for any audio
circuit using these devices is noise riding on the DC rails and arriving at the
inputs of the DAC chip, etc. The sonic result of this is a loss in resolution,
dynamics, smeared detailing, unwanted glare, edginess and compression to the
sound. We replace the generic regulator
with a specially selected low noise type which reduces noise by 30db. The
improvements are immediate, background noise is reduced, bass has extra grip
and solidity, music gains detail and clarity.
Beyond the high spec. DSD1792, the X-DAC uses industrial standard components to
perform audio functions like current-to-voltage conversion; a transformation of
the signal voltage from the DAC; low-pass filter; a reconstruction filter which
removes harmonics above the frequency of 22050 Hz. The filtered
output then passes a buffer stage before the output. All these tasks
are performed by active op-amps, in the case of the X-DAC the NE5532 is used.
The 5532 op-amps were a great workhorse in there day but can now easily be
bettered for modest outlay. Spending further on the op-amps is beneficial,
replace the 5532 used for I/V conversion with the new LM4562 and the
improvements are very impressive. Bass gain weight, definition, there is less
grain, improved detailing and dynamics. For filter op-amps we use the Burr
Brown OPA2604, the 2604 is a true FET input stage, this provides superior sound
quality and speed for exceptional audio performance.
Level-2 is a more
comprehensive upgrade and certainly reveals oodles of undiscovered sound from
the X-DAC V3. In the level-2 modification we upgrade the system clock, a simple
TXCO oscillator and replace it with the ultra-low jitter Superclock 4-S. A low
phase jitter and noise clock is required for the DSD1792 DAC for optimum
performance and exploit all there is to be had from this 24 bit /192 KHz
chipset. The gains here are truly awesome. We have singled out the Superclock 4
upgrade by taking a stock X-DAC V3 and replacing the master clock. Without any
other modifications completed this clock modification betters every other
modification combined, it’s that good. Immediately on listening with the
Superclock 4-S installed you are aware of detailing and nuances glossed over by
the stock oscillator circuit. Imaging snaps into focus, bass notes carry greater
weight, definition & agility, the sound-stage is deeper, wider with
improved spatial qualities. Timing & coherence are also markedly improved,
the music flowing in a more natural, effortless manner.
Next up with the level-2
modification is upgraded DC regulation for the +5.0V DAC analogue supply and
+3.3V DAC digital supply. We replace the 3-terminal regulators with the Invisus
2 series, a discretely designed ultra-low noise, wide bandwidth regulator which
reduces noise to negligible levels. With the new discrete regulated power
supplies installed the sense of openness and detailing is incredible; the
leading edges of instruments are precisely defined and focused without any
blurring. Bass depth and speed is captivating with low and upper bass never
becoming muddled through sudden dynamic changes. The final phase of level-2
upgrades the analogue low-pass filter op-amps to AD825 devices on Brown Dog
adapters. The AD825 has excellent resolution, spatial qualities, superb
dynamics, and is tonally accurate.
The level-2 modified
X-DAC V3 delivers a spectacular sound, one that places it as a serious high-end
achiever in the sound stakes performing way beyond its modest price tag. |
