Denon AVP-A1HD Product Review page 6

Denon AVP-A1HDCI Surround Sound Processor and POA-A1HDCI Power Amplifier - Page 6
THD+N vs. Output shows that somewhere
close to 3 volts RMS is the maximum output.
An average listening power output with
reasonable volume would be about 500 mV
on any one channel of the SSP, and a typical
power amplifier has an input sensitivity of
about 1.5 volts to drive it to full output.
I measured the frequency response with the
CD input configured as CD Stereo. This let
me turn Audyssey processing on or off (not
available when the input is set to CD Direct).
It is flat to 20 kHz at 1 volt but the high
frequencies begin rolling off above 7 kHz at 2
volts output. I suspect this was deliberate to
protect speakers and your ears if you tend to
crank things up too much in action movies.
The blue graph line shows the response with
Audyssey processing turned on. I had run
the Audyssey setup with 5.1 speakers being
electrostatic, and the resulting graph shows
the EQ that has been applied (this is the left
front channel). You can see where it rolls off
in the bass to crossover to the subwoofer.
Audyssey uses filters rather than EQ bands,
and their website states that hundreds of
points in the spectrum are measured and
corrected. The resulting response is a result
of the speaker's natural frequency response
and also changes induced by the room. I have
to say that I love the changes that Audyssey
made. It all sounded so much more natural.
This is really a terrific feature.
Now to the power amplifier.
At 1 kHz and 20 volts output into 8 ohms,
THD+N was 0.005%.
And at 4 ohms, it was 0.01%.
IMD, with 60 Hz and 2 kHz sine wave
inputs, 20 volts output into 8 ohms, was
0.006%.
At 4 ohms, IMD rose to 0.011%. With IMD
measurements, the calculations are based
on the peaks 250 Hz on either side of the
fundamental (2 kHz). However, there are
other areas that have obvious IMD peaks (4
kHz, 6 kHz, 8 kHz, etc.) This is why it is
important to show graphs rather than simply
report the IMD number.
© Copyright 2008 Secrets of Home Theater and High Fidelity
www.hometheaterhifi.com
For THD+N vs. Frequency, shown below at
20 volts output into either 8 or 4 ohms, the
distortion rises above 300 Hz. This will make
for a forward sounding midrange and treble.
THD+N vs. Power output indicate that the
POA-A1HDCI outputs 175 watts RMS
(one channel) before going into a sharp rise
to clip (1% THD+N) at 215 watts, while at
4 ohms, it outputs 230 watts RMS before
the sharp rise to clipping at 320 watts. Each
amplifier module has its own power supply
capacitors, so I just measured the output
with one channel being driven.
conclusIons
The Denon AVP-A1HDCI SSP and POA-
A1HDCI power amplifier represent the
next level in surround sound flexibility. The
SSP will decode anything, including SACD
and the new high def movie soundtracks.
It sets up easily, in spite of a very complex,
powerful set of menu options, and with its
on-line firmware update capability, will