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Audio Research HD220 Review by James Leahy
Introduction This amplifier is a benchmark in Audio Research's line up of products as the first to use transistor based output devices in the output stage and valves in the gain stage. The input is JFET with which is identical to the REF110's frontend. The tube component is a 6922 dual triode gain stage, which in turn feeds a 6H30 dual triode cathode follower.
The HD220 is rated at approx 220 watts into 8 ohms and 400 ohms into 4 ohms. The chassis size is identical to the VT100 series and the REF110 and weighing in at 27kg this is a product that would be able to be placed in most compact locations. Supporting a huge 300K ohms Balanced input impedance this amplifier has potential for massive drive and dynamics that can really be felt as well as heard even when driven with under powered line stages. Because of the lack of 6550C output tubes this amplifier runs much cooler then your typical all tube Audio Research amplifier of similar power rating.
There are twelve Thermal TrakŪ bipolar output devices per channel thermo coupled to massive heat sinks with added dual fan cooling.
Special proprietary coupling capacitors make a welcome appearance (first used in our REFERENCE 3 Line Stage). As can be seen quality of construction is first rate.
The tube component of the HD220 is comprised of one 6922 dual triode gain stage, which in turn feeds one 6H30 dual triode cathode follower per channel. Again dual tube dampening rings are supplied for all 4 tubes and are designed to cut microphonic vibrations to low levels.
The rear panel shows there is provision for Balnaced (300K ohm) as well as Single Ended input (150K ohm). There is also the added benefit of 12V trigger (not shown) for On/Off remote control operation via one of A.R.C. line stages.
A 20-amp IEC-connector is used for the best possible power supply. Identical to all of A.R.C.'s REFERENCE amplifiers.
Tube changing is no longer a matter of guess work with the latest models. Tube hour counter is now provided for easy tube changing reference. A really nice touch, thanks guys.
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.
Sonic Evaluations Now let us see where all the hype stops and when the real world listening results begin. Using my much loved copy of Bob Seger & The Silver Bullet Band - Stranger In Town (Capital Records Inc, 1978) to evaluate this new product I began in great anticipation. For me to fairly review this product objectively we must look at the HD220's design parameters and who the intended buyer is.
I understand the HD220 was designed to be of a compact size and minimal weight that most general applications will withstand as well and being easy to place in locations that require low heat generation. The output power also had to be substantial with a minimum of 200 watts into 8 ohms for owners of inefficient loudspeakers that fully wanted to drive them to within an inch of their life all day everyday. Also solid state output had to be used in this unique design to cater for the above requirements. With these design restrictions in mind I will evaluate my findings as accurately as possible. My findings have been substantiated by another experienced audiophile that came over to sit in on the review and pass his comments both positive, negative and other wise. Before I start, there have been wide spread reports going around that this amplifier takes considerable break-in time to really perform. I cannot either confirm or deny this as I have time constraints that I must adhere to. At the time of review the HD220 in my system had been running for approx 100 hours straight. I can however say that other Audio Research products have not taken any break in time to sound their best and straight out of the box they always perform amazingly. This amplifier, my friend and I both agree does not sound like your typical big solid state designed amplifier but nor does it sound like an A.R.C. all valve amplifier. To describe the sound to be on the right side of neutral with a hue of warmth would be how it sounded in my system. For the low frequency bass freaks it will be a match made in heaven with power and headroom in abundance for the taking. The high frequency was both extended and vibrant with plenty of detail in every track. The overall drive of this amplifier is huge with it's 300K ohm (Balanced) input impedance being the main determining factor. The soundstage is massively wide and full with a dynamic presence that can only be described as awesome. There is a wall of sound that fills the room with power and grip when this amplifier is asked the question and pushed. Playing at elevated listening levels I in no way found it to run out of steam and puff. But; and you knew there had to be a 'But' in there somewhere didn't you? To me this is not what makes an enjoyable listening experience, many will however disagree and consequently the HD220 might suit them down to the ground. I am sure this is the very person the HD220 was designed for. For my ears as I am used to listening to some of the all time best full valve amplifiers Audio Research have ever made and as such directly comparing the HD220 to them would be wrong and like comparing Compact Disc to Vinyl. Yes they both sound totally different but which you will prefer is impossible to say. I will say that the HD220 in no way replicates the sound of Audio Research's all valve based offerings. It would be foolish to buy this product if it is your intension to replicate rich depth of field, natural tone, smooth midrange and multi-dimensional layering in all musical passages. Wide spread reports going around that it in fact does sound tube like do not correspond with my findings at all. It would be really a long stretch of the imagination to try and suggest they sound similar. I have a large number of other ARC amplifiers on hand to compare with while writing this review and the differences are night vs. day. There is nothing for nothing in this world, only valve amplifiers sound like valve amplifiers. Even if you throw all the technology on earth at it. This amplifier however does have many advantages over valve amplifiers such as the ones I have discussed and I am sure potential buyers will find these points most welcome and indispensable. If you like vice like grip and extended bass response with a top end that is not overly bright and in your face and a midrange that has a touch of warmth about it and fully intend on turning it on and off like a light switch for a H/T set-up I would recommend it. If you need 200 watts of grunt in a compact and low heat dispersing modern design that will require minimal running costs again I can think of nothing better. If you like solid state designs with power in abundance at a modest price compared to their valve counterparts, and many customers do but with a more natural tone then your typical transistor amplifier the HD220 will deliver. Just make up your mind on which type of sound you like or how many compromises you wish to make.
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