Review: Audio Research Corporation HD 220 Amplifier

Category: Amplifiers

My musical tastes include primarily classical, jazz, folk/blues and some exceptional rock. Specific recordings can be discussed via phone @ 610-721-1304. Soundstaging, dynamics, transparency and coherence are paramount, while the correct tonality and warmth are of equal concern. In other words I need it all to be right or else I sell the stuff! My HD 220 has 300 hours on it at this point and it is exceptional indeed. My recent decent into Krell evo solid state gear left me wanting so I sold the rig and started anew.

When a system is in the "zone" for me it conveys lifelike dynamics, accurate tone, clarity with warmth and soundstaging to die for!! This amp does it like no other I've had on all types of music (taken as part of my current setup). One major note...USE THE STOCK POWER CORD!!! The HD 220 started to amaze me aftethunderousr I decided to try it's own power cord in place of my reference cords. As long as my ref 3 has a great power cord all is well. The amp conveys a sense of limitless power with explosive yet controlled is effortless but with great force and dynamic swing!! Treble is extended and full of sparkle but grainless and pure at the same time. Midrange is full and neutral with a tad of warmth, but not overdone. Bass is earth shaking and well defined with amazing definition. Focus and placement of instruments is the best I've heard. Width and depth of the soundstage is top notch as well. Palpability and presence are eerie baby...spooksville!!

Compared to the other great tube amps past and present it connects on excitement, dimensionality, dynamics and extension without the tube haze, lethargy and softness often found with their presentation. I prefer it over the 110 for real world reasons and for purely musical ones. Overall it takes one away with the music where very few other components take you!!

Money is no object for me ...the HD 220 is's that good!!

Associated gear
ARC Reference 3 preamp
Krell SACD standard V5.1
Krell Resolution 2 loudspeakers
MIT V2.1 Oracle IC's and speaker interfaces
Transparent MM power cord (ref 3)
MIT AC2 power cord (Krell SACD)
ARC stock power cord (HD 220)
Wattgate recepticles
Dedicated 20amp lines

Similar products
ARC VT100, VT200, VS110, VM220's, Ref 110, Ref 610T's
Krell FPB 600, 400cx, 350Mcx, evo 402
Levinson 336
3097f1aa e0f0 4271 969d 0ee32bdf00f7dave_b
Thanks for the review. It's very difficult to find any information on the sonics of this new Hybrid amp from ARC. It looks like I'll be buying an HD220 too, as soon as I get back to the States from Mexico. It'll be nice to have a good sounding ARC amp with only 4 tubes and no manual biasing. Esharp
Hey everyone, just wanted to apologize for the spelling mistake and the corrupted sentence..I was in a hurry!! Decent should read descent and what I was trying to convey is that after a couple hundred hours I was not in love with the sound until I decided to try the stock power cord which transformed the amp into a music maker...dynamic contrast and slam, bass palpability and soundstaging with effortless power on demand. Weird but sometimes experimentation proves something that's counterintuitive.
Hello. Thanks for a good review but do you know they (AR) sell the power cord alone ?
Give em a call etran..remember however that the power cord testimonial only applies to it's use with the HD 220!
The farther you get away from Krell gear the closer you will get to the musical truth... This review was a no brainer thanks for posting..
It may be helpful to know that I tune my system for the largest most dynamic sound possible speakers ar almost 14ft apart along the long wall of my 20 x 14 room. I sit against the far wall with the speakers facing almost directly forward with minimal toe in. My main complaint with otherwise great speakers like my wilson 6's is that they are designed to be aimed at your ears which always limits dynamics and constricts soundstaging. My res 2 speakers allow the soundstage to expand while maintaining focus and maximizing dynamics. I understand that Mapleshade has similiar recomendations. My room is filled with soft furniture, plants and artwork to break up standing waves and disperse frequency anomalies naturally without resorting to ugly room treatment panels.l
Dave_b you said in your review

I prefer it over the 110 for real world reasons and for purely musical ones.

I guess the real world issues like biasing, blown tubes etc are quiet obvious but can you please share some insight how the two compare sonically and why you preferred the 220? Thanks
Sure Rayden1972, whereas the 110 is ultimately more seductive in the midrange and lower treble on some material, the 220 retains the dimensionality and enough of the 110's traits here. Inevitably, the 110 (tube amps in geberal) soften transients a bit too much and aren't the last word in bass control. A certain tube film can permeate the soundstage on well recorded ensemble material. Microdynamics are a tad more engaging on some material thru the 110 but it is system dependant to some degree. The 220 gives me what I've always enjoyed about the best tube and solid state designs...dimensionality instead of paper cut outs and fixed images, roundness without bloat or hyper inflation of images, tonal accuracy without listening fatigue, warmth without haze or grain. Macrodynamics are explosive, bass expansive and controlled, treble pure and extended, midrange neutral but realistic and alive with action!! By the way I have had no quirks, noise, hums or problems of any kind from my HD 220 or ref is absolutely dead quiet when no source material is going thru the system. The fans on the HD 220 keep it at a nice warm but never hot state...they do make some residual noise on soft passages, but my brain has already begun to filter it out during my listening session. If the unit is placed in an open setting, the fan noise is almost inaudible...I have a custom cabinet setup so the noise is amplified a bit! When I add the CD 7 this fall I believe I will have just about all of the virtues of tubes without the headaches and drawbacks of output tubes.
Just thought I'd mention that I had faulty wiring on my Reference MM power cord (had it re-terminated for 20amps and it was wired wrong). I fixed it myself today and played the system for a couple of hours...everything good about the amp became stunning. The entire presentation has closed the gap between the HD 220 and the reference 110 and is absolutely huge, open, airy, lush and crazy dynamic..the midrange has become glorious and oh so vivid..bass is subteranean with great pitch, treble delicate and incisive without any edge or harshness. In other words the HD 220 is closer to a true tube amp than I originaly thought, but without limitaions at the extremes...power seems inexhaustable! This amp is a no brainer..I fully expect it to garner much praise in the months and years to come.
Dave, I'd be very intrigued if you managed to listen to your HD220 powered by an Elrod Statement or a Purist Anniversary PC.
Tried the purist..not my cup of tea! Have not heard anything superior to the Transparent MM or MIT Ac2's.
I revisited the stock power cords again on the amp first and then the ref 3 with currently 300 plus hours on the equipment. The ARC power cords get the dynamics and tonality dead on with exemplary transparency. My reference cord on the sacd standard provides all the purification needed for the rest of the audio chain, given my Oracle IC's also deal with signal distortion farther along the signal chain.
My paradigm has shifted as to what is possible in audio! Final tweaks are in.....Transparent MM power cord on Ref 3 and SACD Standard with ARC cord on HD 220. Changed outlets for front end...used outlet extender..big mistake!
Words do no justice to having a symphony orchestra in my listening room!!!
This will be my final comment on the system at hand which includes the HD 220...I have never heard a more realistic portrayel of a symphony orchestra via a stereo system under any circumstances. I thought I was so jaded at this point as to not be able to become enthused about audio ever again.....bottom line is a ref 3 will transform any sytem, an HD 220 and a ref 3 will deliver a living breathing organic soundstage like no other given the source is worthy and the speakers can handle the dynamic envelope of the upstream components. Good listening!!

Thanks for all the time you've spent sharing info about the HD220. I'm a 150.2 user at the moment with an SP16. Before the 150.2 I had a 100.2 but it ran too warm in my in cabinet installation. The cabinet is open in the back and in the front when the door is open. I like the 150.2 but liked my old 100.2 better--more musical, real and engaging. Should I be considering the HD220 or will this piece also run too hot in the cabinet? I know it has fans but there will be precious little side and top clearance once installed. (For a look at the cabinet and my current setup you can see my ad for the Daedalus DA-1's). So, as one of the few folks who seem to have logged considerable time with the HD220 would you mind helping me out?
I also had an ARC 150.2 and loved the ergonomics but couldn't make friends with the treble. I am currently running a 100.2 which continues to satisfy but it does run a bit warm. If anyone has been able to listen to both the 100.2 and the HD220 I hope they will post a comparison of the sound and the heat output.
The HD 220 is world class. It has a unique way of presenting the music as it is experienced in the hall. It is dynamic, pure, extended but not edgy or bloated. It is not overly lush and bloomy nor is it constrained and too well mannered. Heat is not a problem, as I have a cabinet runs barely warm (the fans really work). I have ran it all out on symphonic material the last few days and it does not seems to have unlimited reserves of power into my 89db res 2's (they go down to almost 2ohms). By the way, instrument tone is dead on and finely rendered with great transparency. The HD 220 is also very quick and agile with an enormously explosive bottom end! One caveat..I have a REF 3 preamp which allows the exceptional characteristics of this amp to shine thru!!!
Dave: Any idea what the peak current output is for the HD220? The ARC site does not give this specification. The 150.2 can deliver 15amps peak current before shut down. I'm guessing the HD220 is about double that figure but would be interested in knowing if the owners manual or some other source provides the specs.

BTW: Does anyone think I'm wasting my money on a HD220 running it with an SP16? I may be able to upgrade the preamp to a LS26/PH7 at some point but right now I'm stretching to replace the 150.2 with the HD220.

Also, any reviews of the HD220 out yet?
Dodgealum, the peak current figure aside (not in manual), your speakers will most likely be the limiting factor. What speakers are you driving and do you have dedicated 20amp lines? Power cords can have a huge effect on the capabiliites of the amp as well...trial and error best, for instance an 8 gauge pure copper pc will increase dynamics. I've pushed the 220 on my Res 2 speakers for extended periods of time using highly dynamic classical music far beyond concert levels...the 220 didn't protest nor did it run hot. System synergy and listening preferences will also determine if the 220 or possibly a VS110 would be better for you. An LS26 would certainly be a great match for the HD220 down the road. No reviews yet.
By the way, FYI...the longer I play the ref 3 and HD 220 the more exquisite the tonal shadings and dynamic contrasts become. I am going to try my last tweak by getting a cryo-hyper pure 8 gauge wattgate terminated 20amp power cord for the 220..will report results in about 2 weeks. Also, I use Caig' Pro gold on all contacts every two weeks!! This combo just may keep me happy for more than the usual 6 months (or less)!!
Thanks, Dave. I'm currently running Daedalus Audio DA-1's which are 96db sensitive, a pretty steady 6ohm load but, according to the designer, like amps that can deliver plenty of current. I have a 20amp dedicated line serving the electronics and Porter Ports outlets. Glad to hear the amp runs cool since this is most important--the amp will be inside a cabinet that vents front and rear but will have little room on the top and sides for air flow. How noisy are those fans?
Fans are very low in level and have been tuned out by my ear/brain system not unlike the grandfather clock outside my bedroom..only actually hear it about twice a day..funny how the brain can filter out what it expects or is used to hearing!! The 220 really sounds authoritative and I'm used to 400 to 600 w/ch Krell amps!!!!
One last comment. If like me, you believe that the musical truth lies somewhere between the best attributes of both solid state definition and control, with just enough of that magic which tubes provide....look no further! At this point I can safely say that the HD 220 communicates every aspect of recorded music at such an exhalted level..well, I am completely and utterly transfixed every time my system is played. Properly utilized, an HD 220 should be the last amp one would ever is that good! ARC has made a classic...again.
Hi, Dave ...

Just wanted to express my appreciation for your efforts in this thread. Prior to reading your ideas, I was leaning toward buying the Ref 110. I'm a ways off from the purchase, but I DO have the Ref 3 and the CD-7, both simply amazing products. I've been using my trusted, ARC Classic 60 and can honestly say, I had no idea just how good the CL 60 is. The next upgrade for my system will take place next month. I'm replacing the PH-5 with the Ref PH-7. Now THAT should be interesting. Are you so satisifed with the performance of the HD 220 that you feel no need at this point to change to the mono Ref amps?
Quite frankly, I am amazed at what the HD220 can do in every audiophile dimension I can think of...if it has an achilles heal, it's well concealed. Perhaps if I had a much larger space and Maxx 2's maybe I'd find heaven with a pair of 610T's??? The HD220 is a tremendous bargain and completely capable of transporting one to the venue...I'm happy!!
I almost crapped my pants today!!! Recieved an 8 gauge pure copper slam 20 amp cryo'd wattgate terminated power cord from Wegrzyn loudspeaker and cable co. Get one now for your amp(s) is sickly good. Relaxed, huge and open / transparent soundstage, powerfull, controlled, effortless, silky smooth highs and full complete midrange without glare, bass weight and definition beyond compare....get the idea!!! The HD220 can be considered a reference class offering from ARC with this power cord connected to it..that s a fact. FYI..and mean it man!!
Whatever Dave is the best...
And don't you forget it sweetheart..Jc51373!! Does my gear make you horny...Grrrr!!
Did you have a chance to compare REf 110 to HD220 at home or at the dealer's showroom ?
The ref 110 is the way to go if stickin with ARC. I gave up on my ref 3 and HD220 after extended listening...ARC it appears has entered another "High Definition" over musicality phase. Remember the bleached whitish sound of yor...only over time and after the rush of new purchases wears off can one ultimately understand a product. I give two thumbs down! Also, after having owned alot of tube gear, I must declare the 6H30 tube to be the most unmusical tube made by man!! I have tweaked a Krell 400xi, SACD Std and Res 2 speaker system to the point of sounding like vinyl without the drawbacks..see my 400xi review.
You seem to change your mind 180 deg quite ... well, often.

You had written:

"The 220 gives me what I've always enjoyed about the best tube and solid state designs...dimensionality instead of paper cut outs and fixed images, roundness without bloat or hyper inflation of images, tonal accuracy without listening fatigue, warmth without haze or grain."

And now you are saying:

"Remember the bleached whitish sound of yor...only over time and after the rush of new purchases wears off can one ultimately understand a product. I give two thumbs down!"

Most of us are puzzled, to say at least !
I am as well, it seems that the more the 220 broke in the harder sounding it became..I can only respond from experience over time. At first the definition and sheer grunt factor floored me. Their is palpability and roundness and great soundstaging but after re-visiting my collection it became obvious that what I was hearing was not state of the art nor musical enough for my tastes. The Thermal Traks appear to have a lean sound once fully cooked. It's subtle stuff but completely frustrating when you hear it over time. The baby krell stuff sounds more like my record player without the drawbacks..go figure!!
Now it makes sense. Thanks !
I am glad that I followed this whole thread. I was shocked that you went 180 I almost bought a 2220 based on your reveiw. I was wondering how a hybrid could beat anything in the Reference line after all most companies know their products and build to a price point. Plus let's face it AR is known for tubes not solid state.
Thank God you followed the entire thread...often what impresses at first blush, leaves you wanting later on:O( Ever wonder why the HD220 was never reviewed? All their other latest greatest stuff get's reviewed asap...not the HD220!
Hate to say it, but goes to show how much one should read into a review of recently purchased equipment! Sorry Dave, but I think you also recognize this.

We buy something new which presents a new or different sound, we love the excitement of listening to that new and different sound . . . then one day we realize, yeah its different, but . . .

As my suggestion goes, never buy into a review that is less than a year old and then only after contacting the reviewer to see if they even still own the equip.

Dave, I have a lot of respect for your postings and your opinions, but you of all people should know not to review a product after 300 hours of use! Though I am glad you came clean, but feel that you owe a bit more on the weaknesses you found with the amp than just the sudden turn around (I know/recognize we are now years later, but the dam internet won't ever let us forget those words we once wrote . . . ).
The HD220 delivers excessive overemphasis in the upper octaves. Overall, it sounds bright, forward lean. Still being avoided like the plague by reviewers...Hmmmm"O)
Discontinued after thermotraks are EOLed.  
I managed to try out a unit that has been refurbed by audio research.  Not forward an lean sonic signature at all compared to all the terrible sounding ones I've owned such as VT200. Will update after the unit gets a few months play time. 
Almost a year into ownership I can't find fault with it driving Avalon Diamond and YG Hailey.  No noticeable glare or emphasis of mid highs.  Sadly these things I guess are not serviceable anymore due to end of life of  Thermotraks.  I did notice there are paralleled resistors of the exact same type on the plate of the 6922 stage and 6H30 driver.   Hints to me audio research has revoiced this unit I have to a warmer sound. 
Cant help myself but to revive this thread after all these years.
Those who are reading this must either have a broken SD135/HD220, or got a bit annoyed with the progression from a positive "dimensionality instead of paper cut outs and fixed images, roundness without bloat or hyper inflation of images " to a negative "excessive overemphasis in the upper octaves. Overall, it sounds bright, forward lean" described by the OP.
Well, I still have my HD220 that I rotate in and out of my stash of amps.
And yes the unit has become lean and mean and despite attempts to tube-roll using Amperex pinch waist 6922s and various 6H30s, the lean and mean signature remains.
I requested a schematic from Audio Research, but zero response despite emails and phone calls.  Absolute ZERO.
I then took it upon myself to try to trace out the circuit. 
The output stage is similar to if not the same as the SD135, whose schematics are easy to find online.  My unit has the newer generation Thermaltraks and boy am I glad to discover that.   The initial attempt was made to the output stage.  I adjusted the bias drive to operate a wee bit higher current and the sound warmed up at the expense of being chesty and grainy. 

Then I spent some time looking at the tubed gain stage.  It's essentially a Diff-Amp gain stage using one plate of a 6922 directly coupled to paralleled 6H30, 230V B+ and with the existing tubes, plate V at coupling point was 115V which for a moment I thought was a nice midpoint value.  But several things stand out.  6H30 cathode follower is at 115V against 23kOhms, which means the CF is extremely current-starved.  The 6922 gain stage has a 38k plate resistor on each half to B+.  A quick simulation of this circuit shows a moderate degree of 3rd order harmonics which explains the bright and lean sound.  Power amps rarely measure poorly with a frequency range that is emphasized.  But the human brain does interpret odd order harmonics as "edgy and lean".    The saving grace of this model is that there are 2 trimpots for each channel for the tube stage, one controls the 6922 diff-amp's balance between the 2 triodes, one controls the bias.  Where I found it (not sure if its the factory-desired plate V or a symptom of aging tubes) the grid bias is at 20V giving a plate V or 115.  But simulation results tell me that in order to minimize 3rd order harmonics at a reference 1k sine wave I need a grid bias of 15V yielding a plate V of about 85.  That essentially did the trick to remove the "edgy and lean" sound.   Unless I have the schematics/service manual that describes reference voltages, I will never know whether the OP (as well as my own recent) experience is due to a gradual drift in the 6922s as they age, causing the tubes to run leaner and meaner, or it's audio research's voicing efforts right from the start.  But one thing I can see from their older models (eg the D115), the gain stage 6922 runs a lot hotter with a distortion bias in favor of even order harmonics vs odd harmonics.

Bottom line is, this unit is still a keeper.