Denon POA-A1HDCI User Manual
Page 7
7
www
.a
udioholics.coM
What I believe was happening here
was the power draw at low frequencies
didn’t allow enough time for the
capacitor bank to charge and at high
frequencies the power density is much
higher requiring a bigger transformer
to achieve these sustained power levels.
I couldn’t help to wonder just how
much more power the POA-A1HDCI
could have delivered if Denon chose
to employ one massive power supply
instead of multiple smaller ones for
better channel to channel isolation.
There are pros and cons to these
different methodologies but I believe
Denon struck a good balance here,
yielding the best of both worlds with
their hybrid mono block multi power
supply approach while also keeping the
box size reasonable for a high power
ten channel amplifier. Keep in mind
that this amp in bridged mode will yield
a HUGE +6dB of dynamic headroom
when driving a real speaker load with
music, even though sustained power
measurements aren’t all that much
higher into resistive loads driven by
continuous test tones.
Editorial Note on
Bridged Power Measurements
Keep in mind most review
publications don’t do continuous
power measurements and they usually
publish power measurements into
clipping at 1% THD + N at 1kHz. Our
measurements are very conservative
and are continuous full bandwidth.
For more info on amplifier
measurements, see:
Editorial Note
on Audioholics Power Ratings
It is clear that the POA-A1HDCI easily
hit the 150wpc power rating, delivering
MUCH more than specified into 8-ohm
loads in normal and bridged modes and
about dead on specified power delivery for
4-ohm loads for normal and bridged modes
of operation.
While the POA-A1HDCI was driving
4-ohm loads in bridged mode, I was able
to achieve the 1% power numbers at <.1%
THD + N in the above table at 1kHz
but distortion went up significantly at the
frequency extremes (20Hz and 20kHz). This
is why I scaled the measurements back to
ensure the amp delivered the measured
power at <0.1% THD + N full bandwidth
continuously.
Denon POA-A1HDCI FFT Analysis @ Full Rated Power
When testing 2 channels bridged mode
into a 4-ohm load, my APC S20 ran into an
overload condition but did manage to keep
the line regulated above 116Vrms. This goes
to show you that continuous power testing
consumes far more power than real world
usage as I was never able to get my APC
S20 to state I was using greater than 30%
capacity even when I was blasting my system
at sustained 110dB listening levels in 7.1
surround modes at my listening area.
Upon peering at the spec sheet for this
amp, it was obvious that the manufacturer
was specific about how they rated power.
They specified full bandwidth power at
< .05%THD + N for (150wpc, 300wpc bridged)
for 8-ohm loads, but only 1kHz .7% THD+N
(300wpc, 500wpc bridged) when driving
4-ohm loads. Under these circumstances,
the POA-A1HDCI delivered as promised
and then some, but as an Audioholic, I would
de-rate the 4-ohm bridged continuous
power specification by 15% or so and
bolster the fact that you’ve got roughly
+6dB of dynamic headroom.
Efficiency
With two-channels driven at full load, I
measured about 47-49% efficiency which
is good but not as great as I’ve seen in for
other linear Class A/B amplifier designs.
When the unit was idling with all amplifiers
turned on, it consumed about 275 watts. It’s
the idle power consumption of 10 channels
that kills the efficiency of this amplifier.
Too bad there isn’t a way to cut power on
unused channels.
SNR Measurement
When the POA-A1HDCI was driven to
full power into an 8-ohm load, I measured:
-117.15 dB below 31.77 dBV Reference
Level (at 0.09% THD+N) < 10Hz – 22kHz
unfiltered and unweighted. This translates
down to 94.3dB SNR @ 1 watt which is
excellent and explains why this amp sounds
so crystal clean and quite at low power
levels.
FFT Distortion Analysis