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Description:
HD220 Hybrid Drive Stereo Power Amplifier
Whether tube or solid-state, power amplifier designs from Audio
Research have always emphasized the key criteria of musicality,
lifelike dynamics and realistic soundstaging. Whichever technology
was used was intended to serve these priorities in the music reproduction
chain.
Recent advances in solid-state output devices and other components
have opened up design possibilities as never before, allowing
Audio Research engineers to combine the strengths of two different
technologies in a completely new power amplifier: the new Hybrid
Drive HD220 stereo power amplifier.
We call it "Hybrid Drive" because that's how it works.
As in the Reference 110, a JFET input (for low noise) feeds a
6922 dual triode gain stage, which in turn feeds a 6H30 dual triode
cathode follower which drives the outputs through our proprietary
coupling capacitors (first used in our Reference 3 preamp). This
vacuum-tube input / driver arrangement sets the stage for superbly
musical performance and a nuanced, lifelike character at the front
end of the amplifier.
The output stage is comprised of twelve Thermal Trak® bipolar
output devices per channel, producing 220 WPC into 8 ohms, and
nearly 400 WPC into 4 ohms. These new devices have the unique
ability to automatically adjust their internal bias in response
to operating temperature, thereby assuring extremely consistent
output performance no matter how hard the amplifier is pushed.
Low-noise fan cooling of the output stage keeps the output devices
within their operating range. Power supply regulation is all solid-state
to assure stability and consistency under high-current-demand
loads, and power supply energy storage is a startling 200,000
mF capacitance for explosive dynamics and rock-solid bass impact
and control. One look under the cover tells you that the HD220
is all about performance.
But the HD220 offers livability as well, with all of the dual-triode
front-end tubes being run very conservatively within their operating
range for longer life. We have even included an easy-to-read meter
to keep track of tube hours. And, needless to say, there are no
output tubes to replace, ever. Both balanced and single-ended
inputs are provided, as well as a detachable 20-amp IEC-connector
power cord. Output connectors are our proprietary gold-over-copper
binding posts. The chassis dimensions of the HD220 are identical
to those of the Reference 110.
In performance, as always, your own ears will be the final judge.
But we honestly believe that this unique amplifier represents
the highest level of sonic performance we have yet experienced
from any solid-state or hybrid design. Its musicality is superb,
with a degree of transparency and grainless purity that is nothing
short of eerie, thanks in large part to extremely low distortion
and a low noise floor. Dynamics and bass control are thunderous
and controlled, whether driving dynamic or planar-type loudspeakers,
thanks to the Thermal Trak® output stage. In short, the HD220
gives you the finesse and nuance for which tube amps are famous,
with the consistency and speaker control under high-current-demand
conditions that solid-state amps excel at. This HD220 simply goes
and goes and goes.
If you are a demanding music lover who wants ultimate sonic performance
without the periodic burden of replacing amplifier output tubes,
you now have a new choice - one that opens a new chapter in the
Audio Research High Definition® story.