LAB REPORT
44 Australian Hi-Fi http://www.avhub.com.au
-140.000Hz 9600.00 19200.00 28800.00 38400.00 48k-120.00-100.00-80.00-60.00-40.00-20.00dBFS0.00 .EWPORT4EST,ABS-140.000Hz 4000.00 8000.00 12000.00 16000.00 20k-120.00-100.00-80.00-60.00-40.00-20.00dBFS0.00 .EWPORT4EST,ABSGraph 8:THD at 0dB 44.1kHz/16-bit test signal.
Questyle CAS192D.Graph 7:mpulse response, 176kHz oversampling (see
copy). Questyle CAS192D.-140.000Hz 4000.00 8000.00 12000.00 16000.00 20k-120.00-100.00-80.00-60.00-40.00-20.00dBFS0.00 .EWPORT4EST,ABS-3.00 10Hz 100.00 1000.00 10000.00-2.50-2.00-1.50-1.00-0.500.000.501.001.502.002.503.00dBr .EWPORT 4EST ,ABS-140.000Hz 4000.00 8000.00 12000.00 16000.00 20k-120.00-100.00-80.00-60.00-40.00-20.00dBFS0.00 .EWPORT4EST,ABS-3.00 10.00 Hz 100.00 1000.00 10000.00-2.50-2.00-1.50-1.00-0.500.000.501.001.502.002.503.00dBr .EWPORT4EST,ABS-1.0020Hz 100.00 1000.00 10000.00-0.500.000.50dBFS1.00 .EWPORT 4EST ,ABS-140.000Hz 9600.00 19200.00 28800.00 38400.00 48k-120.00-100.00-80.00-60.00-40.00-20.00dBFS0.00 .EWPORT4EST,ABSGraph 1: Frequency response at 1 volt out. [Questyle
CMA 800P]Graph 2: THD @ 1 volt out. Questyle CMA-800P.Graph 5: Frequency response of the Questyle CAS192D
˹ǔǜǒƞǔǏƬʁƬȭǜǞǚǜƬʁʊƬǜǜǔȭǷʊɤȭɁɁ˸ƬʁʊŘȧɡǚǔȭǷƙʊƬƬƋɁɡ˿ɦƖGraph 3: Frequency response at 1 volt out. [Questyle
CMA 800R]Graph 4: THD at 1 volt out. [Questyle CMA 800R]Graph 6: Impulse response, no oversampling (see
copy). Questyle CAS192D.Newport Test Labs measured the frequency
response of the Questyle CMA800P as extend-
ing from less than 1Hz to 69kHz ±0.5dB and
from less than 1Hz to 110kHz –3dB. Across
the audio band, the response was 20Hz to
20kHz ±0.1dB. Channel separation was more
than 100dB right across the audio band,
measuring 116dB at 20Hz and 1kHz and
still an excellent 106dB at 20kHz. Channel
balance was equally good, with the lab meas-
uring 0.054dB at 1kHz.
Distortion was extremely low, as you can
see from Graph 2, with a second harmonic
at –110dB (0.00031%), and second and third
harmonics at around –115dB (0.00017%). A
few other harmonics are visible above the
noise fl oor, but they’re all more than 120dB
(0.0001%) down. Overall THD+N, as shown
in the tabulated results, was measured at
0.0009%.
The noise fl oor across the audio band was
extremely low, as you can see on Graph 2,
where it’s more than 140dB down. There was
some low-frequency noise (the spike at the
extreme left of the graph), but the overall
signal-to-noise ratios measured by Newport
Test Labs were exceptionally good: 101dB
unweighted and 107dB A-weighted.
The frequency response of the CMA800R
was almost as extended as that of the CM-
A800P, but within the audio band rolled off
slightly earlier, to be 0.4dB down at 20kHz,
then 1dB down at 35kHz as you can see in
Graph 3. The results of Newport Test Labs’
measurements of the CMA800R’s distortion
are shown in Graph 4. You can see a second
harmonic at –108dB (0.00039%), a fourth
harmonic at –116dB (0.00015%) and a sixth
harmonic at –120dB (0.0001%), but that’s
it. All are so low as to be totally inaudible,
but even if they were, the fact that they’re
even-order harmonics (as opposed to odd-or-
der) would tend to make the sound seem
‘richer’ than if there were no distortion at
all. The noise fl oor of the CMA800R across
the audio band is shown on Graph 4 to be
tracking at –130dB, but some low-frequency
noise (visible at the extreme left of the graph)
resulted in the overall signal-to-noise ratios
being measured at 91dB unweighted and
97dB A-weighted.
LABORATORY
TEST
REPORT