stereophile.com n August2019 89
AESTHETIX AUDIO MIMASmeasurements, continuedwhen, later, I schlepped the Mimas to the house of my friend
Gary Forbes, a musician and physician, to hear how it would
fare in a system closer to the Mimas’s price range (see below).Opening the ears
Using the Mimas as an integrated amplifier to revisit Paul
Lewis playing the first movement, Allegro ma non troppo, of
Schubert’s Piano Sonata in B, D.547 (24/96 WAV, Harmo-
nia Mundi HMM 902324), I found the sound appealingly
musical and involving with realistically round piano notes.
As Schubert’s music tugged at my heart, I noted the lovely
liquid ringing of the piano’s high notes and the beauty of the
sound overall. But the music lacked transparency and the
space between notes was less silent than I’m used to.
Next, I checked out the Mimas’s ability to reproduce
vibrant tonal colors by listening to two recordings of cham-
ber music by the master colorist Debussy. The sound of his
Cello Sonata, performed by cellist Edgar Moreau and pianist
Bertrand Chamayou (24/96 WAV, Erato 565142) was
not as deep and rich as I know it can be, with tonal colors
that were muted. The period instruments of Jean-Guihen
Queyras and Javier Perianes performing the same work
(24/96 WAV, Harmonia Mundi HMM 902303) sounded
extremely natural, with a lovely glow. But with both, I felt
I was listening to a recording rather than the sound of realMimas plugged directly into the wall, and then with AC
conditioned by the Niagara 5000. Through the AudioQuest
I heard a smoother top and tighter bass.
One of the reasons I invite local audiophiles to join me
for listening sessions is that they invariably break me out of
my classical ghetto with some very different music. A few
weeks after I began listening to the Mimas, Port Townsend’s
Peter Schwartzman came over and proposed that we stream
“John Taylor’s Month Away” from King Creosote and Jon
Hopkins’s Diamond Mine (16/44.1 FLAC, Deep Six/Tidal/
Qobuz). This lovely track is ideal for evaluating gear. It
begins with an emotionally evocative man’s voice, progres-
sively backed by guitar and what sounds like a harmonium,
a very deep bass rumble, and layered women’s voices—then
segues into a long, ambient, room-filling, New Age–ish
postlude in which sounds of water and birds are layered
with synthesizer and female voice.
I first listened to this track with the Mimas plugged into
the AudioQuest Niagara 5000. When we switched to wall
power, the recording lost some of its arresting ambience, the
bass was less clear, and the sense of total immersion at the
end was so diminished that the track basically lost its magic.
After repeating this comparison with several other tracks, and
noting how the Niagara 5000 helped bring out natural color
contrasts and details, I stuck with the Niagara 5000—save
from the unbalanced jacks, 200 ohms
from the balanced XLRs. The output im-
pedance at the speaker terminals was
0.25 ohm at low and middle frequen-
cies, rising to 0.26 ohm at the top of the
audioband. As a result, the modulation
of the Mimas’s frequency response with
our standard simulated loudspeaker^2
was ±0.3dB (fig.1, gray trace). This
graph was taken with the volume con-
trol set to its maximum; commendably,
there was no change in response or
channel balance at lower volume-con-
trol settings. The Aesthetix’s frequency
response at the speaker terminals is
down by 3dB at 120kHz; as a result, a
10kHz squarewave was reproduced
with very short risetimes (fig.2), and
there was no overshoot or ringing with
a resistive load. A 1kHz squarewavewas perfectly square (not shown). The
response from the headphone outputs
was down by just 0.4dB at 200kHz.
Channel separation was superb
below 2kHz, at >95dB R–L and >100dB
L–R, though at 20kHz these ratios re-
spectively decreased to 72 and 78dB.
The unweighted, wideband signal/
noise ratio, taken with the unbalanced
inputs shorted to ground and the vol-
ume control set to its maximum, was
a disappointing 46dB (average of both
channels), this improving to 57.5dB
when the measurement bandwidth
was restricted to 22Hz–22kHz, and to
61.2dB with an A-weighting filter in
circuit. These ratios improved at lower
settings of the volume control and
are related, I believe, to the Mimas’s
higher-than-usual preamplifier gain.Spectral analysis of the low-
frequency noise floor (fig.3) indicated
that the AC-supply spuriae were at
60Hz and its odd-order harmonics,
which suggests that they were due
to magnetic interference from the
power transformer perhaps being
picked up by the tubes’ steel pins. The
spectra in fig.3 were taken with the
volume control set to “88” (blue and
red traces) and to “68” (green, gray).
Though the levels of the random noise
components remain the same, lower-
ing the volume reduced the levels of
the AC spuriae, particularly the 60Hz
component in the right channel (red
and gray traces).
Aesthetix specifies the MimasFig.4 Aesthetix Mimas, distortion (%) vs 1kHz
continuous output power into 8 ohms.Fig.5 Aesthetix Mimas, distortion (%) vs 1kHz
continuous output power into 4 ohms.Fig.6 Aesthetix Mimas, THD+N (%) vs frequency
at 20V into: 8 ohms (left channel blue, right red), 4
ohms (left cyan, right magenta).2 See http://www.stereophile.com/content/real-life-
measurements-page-2.W Hz Hz% % %