NEXT-GEN Digital
April Music Eximus DP1
DAC, Preamplifier, and
Headphone Amplifier
Steven Stone
hat constitutes a mid-priced DAC? There’s a
ton of room between the least expensive highperformance external USB DAC, such as the
$169 HRT MusicStreamer II, and the most expensive, such
as an $80,000 dCS combo stack. Almost any DAC that falls
between $1000 and $10,000 could be considered “midpriced” by some audiophile’s standards. So, while the $3200
April Music Eximus DP1 might be on the low side of midpriced for anyone looking at $10,000 DACs, it’s too pricey
for someone on a $2000 DAC budget. But for $3200 the
Eximus DP1 delivers a near state-of-the art DAC, robust
USB implementation, low-noise multi-input digital preamp,
excellent headphone amp, and a stylish looking retro/
modern custom enclosure.
18 March 2012 the absolute sound
What’s Inside The Box
Before we dive under its hood, let’s take a moment to
admire the Eximus DP1’s enclosure. If its carved aluminum
chassis reminds you of designs from Resolution Audio
and Constellation Audio, that’s because they were created
by the same industrial designer—Alex Rasmussen at Neal
Feay Design in Santa Barbara, CA. The DP1’s overall
look is modern and clean without being too sterile or selfconsciously retro. The figure-eight-shaped volume knob
reminds me of my first Nagra field tape recorder, and besides
being a nod to the past, the knob’s shape makes it easy to see
your current volume level from across the room.
Other niceties that I consider necessities include
provisions for simultaneously active balanced XLR and
April Music Eximus DP1 DAC, Preamp, and Headphone Amp - NEXT GEN DIGITAL
single-ended RCA outputs. I used the balanced outputs for my
main amplifiers and the unbalanced for a subwoofer. On the input
side, all six of the digital inputs fully support 192/24 format,
including USB. The DP1 also has two analog inputs, allowing the
unit to function as preamplifier. Analog devotees will appreciate
that the DP1’s two analog inputs are pure analog with no A/D
and D/A converters anywhere in the signal chain.
The front panel consists of a single on/off switch, a sourceselector button with eight options, a source-lock LED, an on/off
filter button, an upsample button with three options, a standard
¼" headphone jack, a 1/8" mini stereo input, and the master
volume knob. The filter is exclusively for headphone listening; it
engages a cross-filter circuit that’s intended to move a headphone
soundstage out of your head. The three-way upsample button
permits the user to choose no upsampling, upsampling to 96kHz,
or upsampling to 192kHz. When you insert
a headphone jack into the front headphone
connector, the output to the back-panel
outputs shuts off. While anyone who wants
to use all three outputs simultaneously may
find this feature to be a problem, I liked it. I
could leave my amp and subwoofer on while
listening to headphones. I also liked the
single volume control for both headphone
and regular listening. Couch potatoes, be
forewarned, the DP1 does not include or
support a remote control.
Most of the time I had the DP1 positioned
so I could reach down with my left hand
and adjust any of the controls without
moving my head to look at them. It took
maybe two days to be able to operate the
DP1 “blind.” In my mind that constitutes
an ergonomically well-designed audio
Under the hood, the signal chain uses
the Cirrus Logic CS8416 input chip that
can accommodate sampling frequencies
up to 192kHz, a low-jitter input receiver,
and complete galvanic isolation to reduce
external noise from external ground planes.
In past reviews of DACs, I’ve seen and
heard what a big difference the right USB
implementation can make. April Music
opted for the XMOS USB solution, which
uses a 32-bit XS1-L1 processor and 1Mb of
SPI flash memory. The digital signal then
goes to a Burr-Brown SRC4192 chip for
upsampling and digital conversion. Finally
the digital signal is returned to analog via
the dual-mono current-output 192kHz/24bit Burr-Brown PCM1794A chip, which
features less than 0.0004%THD and a
dynamic range of 132dB. For its power
supply the DP1 employs a custom-designed
toroidal power transformer, which allows
for very low output impedance. Even the
circuit board has been physically optimized
for low noise and maximum separation between digital and
analog components. Finally, the component-output analog-buffer
module and headphone-drive module are made up of discrete
components rather than an off-the-shelf integrated circuit.
Most of my listening was done at my computer desktop since
this product was designed principally for this kind of listening
environment. The signal chain was simple: USB from my Mac
Pro to the DP1 and then a one-meter length of cable from the
DP1 to a power amplifier. For some of my A/B tests I also used
the DP1’s S/PDIF and AES/EBU inputs.
The DP1’s 3V (single-ended) outputs are slightly higher in
output than the usual 2V standard, so with amplifiers that have a
higher than standard 26dB gain you could have a gain mismatch,
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April Music Eximus DP1 DAC, Preamp, and Headphone Amp - NEXT GEN DIGITAL
but none of my amplifiers displayed any problems from this
higher output level.
If you plan to use the DP1 as a fixed rather than variablelevel output device, don’t look for a button or switch to convert
it to a fixed level. Merely turn the volume control all the way
up for fixed-level use. While the first prototypes had a switch,
April Music’s Simon Lee told me he opted for no switch in the
production versions because listening tests determined that
removing the switch delivered better sonic results.
The Sound
When I listen to a stereo system the first question I ask myself
is, “Which component is the weak link?” Whichever system I
dropped the Eximus DP1 into, it was never the weakest link in
the signal chain. During the time I’ve evaluated it, the DP1 was
always articulate, dynamic, and musical.
If I had to choose a single word to
describe the sonics of the Eximus DP1,
it would be “revealing.” Especially on
higher-resolution material, such as my own
live on-location recordings, I was amazed
by the Eximus’ ability to expose even the
subtlest soundstage cues. On my recording
of a great young acoustic band, The Deadly
Gentlemen, which I made with only two mics
in a small schoolhouse, I could clearly follow
the way the acoustic bass’ energy builds up
in the corner of the room and then rolls
out into the rest of the performance space.
The DP1 portrays the three-dimensionality
of the soundstage as accurately and with as
much detail as any DAC I’ve ever used.
I’ve written before about how important
the USB interface is to the overall sonic
quality of a USB DAC. The DP1’s USB is
very good, and in the same league as the
previous generation of Empirical Audio’s
Off-Ramp 4 USB interface device. I did
some matched-level A/B tests using the
Off-Ramp’s S/PDIF output into the
DP1 compared to the DP1’s own USB
implementation. Although it was not an
ideal A/B, due to the lag time of software
changes (closing and reopening Pure Music
and iTunes as well as switching audio
outputs from the system preferences takes
at least 30 seconds), I could not hear any
consistent and meaningful differences
between the two signal chains. Sometimes
I preferred one chain to the other, but my
preferences were always source-material
dependent. The DP1’s upsampling settings
also affected which signal chain I preferred.
Shortly after the DP1 arrived the OffRamp 4 went back to Empirical Audio for
an upgrade to current specs, which will
undoubtedly change its performance for
the better.
Unlike other DACs I’ve used with variable upsampling
options, with the DP1 these different options not only made
a sonic difference, but the setting that sounded most correct
varied depending on source material. Sometimes within a
single album I found that different cuts sounded better with
different upsampling rates. On Randy Newman’s album 12
Songs, “Underneath a Harvest Moon” was best at 96k, “Burn
Down the Cornfield” sounded better at 44.1, and “Lucinda”
had the cleanest vocals at 192k. On my own 96k/24 recording
of Richard Stoltzman playing Copland’s Clarinet Concerto, I
found that the 96k upsampled rate had slightly better midrange
presence and body on Stoltzman’s instrument than either the
44.1 or 192k settings.
Anyone who’s come to the firm opinion that “upsampling is
bad” will find the DP1’s upsampling a revelation. Unless you try
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NEXT GEN DIGITAL - April Music Eximus DP1 DAC, Preamp, and Headphone Amp
all three settings on each track, you can never be sure which one
is best. Sometimes I found that upsampling to 192kHz resulted
in a tight and overly controlled sound to the point of becoming
mechanical, but other times upsampling to 192kHz delivered an
additional level of control that rendered slightly messy mixes
more articulately than lower sampling rates. As it says in the
DP1’s owner’s manual, “there are no fixed rules for the selection
of upsampling.” That proved to be an understatement.
The Eximus DP1’s headphone filter’s effects were more
consistent and less sonically illuminating. Whenever I employed
the filter, regardless of the headphones, the results were a slower,
thicker midbass and lumpier bass response. It was like going
from a good modern tube amplifier to an unrestored 50-yearold triode amp—euphony and homogenization intruded on the
signal. Perhaps for some listeners the filter’s soundfield effects
24 March 2012 the absolute sound
will make up for the losses in harmonic balance and transparency,
but I much preferred the DP1’s headphone feed without the
filter in the circuit.
I used the DP1’s analog inputs to compare the Weiss DAC
202 with the DP1. Once more A/B comparisons took longer to
switch than I would like—programs had to be shut down and
reopened along with confirming the MIDI settings. But despite
the delays it was clear that the DP1 was almost in the same
league as the Weiss. Both did a superb job of illuminating the
entire soundstage and placing instruments accurately. The Weiss
produced a slightly larger overall soundstage, but the DP1 was
equally well focused. Harmonically the two DACs were very similar,
both with well-defined low bass and vividly dynamic contrast.
At times I preferred the DP1, due in large part to its slightly
lower noise floor. But the Weiss had extensive handicaps—I had
to use its single-ended outputs rather than
the balanced analog output. Plus there was
additional cabling and analog circuitry and
connections inside the DP1. So, I wouldn’t
go so far as to say the DP1 was the Weiss
DAC 202’s equal, but it was closer than I
Comparing the DP1 with the
Wyred4Sound DAC proved to be an equally
interesting exercise. Even though the two
DACs had very similar harmonic balances
and dynamic signatures, the DP1 was a bit
more musical and slightly less mechanical.
The DP1 also had an ease to its dynamic
presentation that I noticed especially on
aggressive pop, such as Toy Matinee’s only
release. The two DACs have similar feature
sets, except the DP1 has two pure analog
inputs. Still, the Wyred4Sound DAC2 is less
than half the price of the DP1. And no, the
DP1 doesn’t sound twice as good as the
DAC2. But it does look better, with a far
more ergonomically appealing front panel.
Finally, the DP1 is more likely to transport
you to the point where you don’t care
much about the equipment because you’re
enjoying the music so thoroughly.
And how does the DP1 compare with the
Bel Canto Dac 3.5, which I reviewed in Issue
216? Unfortunately the 3.5 was returned to
Bel Canto over a month before the DP1
arrived, so I never had an opportunity for
any direct A/B testing. But I will share
this comparison: The USB interface on
the DP1 is noticeably better than the Bel
Canto 96/24 Link USB interface box. Also,
the sonic differences between the USB and
the S/PDIF inputs on the DP1 were much
smaller than they were between USB and S/
PDIF through the Bel Canto Dac 3.5.
I’d be remiss if I didn’t spend some time
using the DP1’s headphone amp. The DP1
had more than enough gain and power to
April Music Eximus DP1 DAC, Preamp, and Headphone Amp - NEXT GEN DIGITAL
Digital inputs: USB 2.0, I2S, two 75-ohm coax, 110-ohm AES/EBU,
optional, USB 2.0
Analog input: RCA, mini-jack
Analog outputs: RCA, XLR, headphone
Input sampling frequency: Up to 192kHz
Upsampling: To 192kHz (default), 96kHz, or bypass
DAC: Two Burr-Brown PCM1794A 192kHz/24-bit
Dynamic range: 132dB
THD+N: 0.0004%
Max input level: 4.8V RMS
Output signal level: RCA, 3.0 V RMS; XLR, 3V RMS Dimensions: 208 x 62 x 291mm
Weight: 8 lbs.
Price: $3195
May Audio Marketing, Inc.
2150 Liberty Drive, Unit 7
Niagara Falls, NY
14304-4517, USA
(716) 283-4434
Associated Equipment
Source Devices: MacPro model 1.1 Intel Xeon 2.66 GHz computer
with 16 GB of memory with OS 10.6.7, running iTunes 10.2.1
and Amarra 2.1.1 music playing software, Pure Music 2.0 music
playing software, Audirana music playing software
DACs: Weiss DAC 202, Empirical Audio Off-Ramp 3,
Wyred4Sound Dac2, Musical Fidelity M-1 DAC
Amplifiers: Parasound A23, Edge Electronics AV-6, Accuphase
P-300 power amplifier, Perreaux E110 amplifier, Krell S-150
monoblock amplifiers
Speakers: Aerial Acoustics 5B, ATC SCM7s, Silverline Minuet
Supremes, Paradigm S1s, Quad 11Ls, Role Audio Kayaks,
Earthquake Supernova mk IV 10 subwoofer, Velodyne DD+ 10
subwoofer, JL Acoustics F112 subwoofers
Headphones: Sennheiser HD 580, Grado RS-1, Ultimate Ears
Reference Monitors
Cables and Accessories: Locus Design Polestar USB cable,
Locus Design Nucleus USB cable, Wireworld USB cable, PS
Audio Quintet, AudioQuest CV 4.2 speaker cable, AudioQuest
Colorado interconnect, Cardas Clear interconnect, Crystal Cable
Piccolo interconnect, Empirical Audio Coax digital cable, and
Audioprism Ground Controls
drive low-efficiency headphones. I never
got more than 1/3 of the way up on the
volume knob. The sound was clean and
very well controlled, especially in the bass.
And while headphones still lack a certain
visceral power when it comes to bass, the
DP1 did a yeoman’s job delivering some
serious wallop when needed. Resolution
and low-level detail were limited only
by my choice of headphones. The best
results came with my pair of Ultimate
Ears Reference Monitor in-ear canal
Final Thoughts
When I asked Simon Lee, April Music’s
president, what the design goals were
for the DP1 he said, “I wanted to make
a DAC/preamp/headphone amplifier
that can be used as a desktop high-quality
USB DAC, high-end normal analog
preamplifier, and top-quality headphone
amplifier—all in one small box. My design
goals were for a DAC/preamp that was
internally complicated but externally userfriendly and intuitive in operation, had
natural sound, a reasonable price, and the
best-quality headphone amplifier I could
make.” I think he succeeded brilliantly.
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