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Icon Audio HP8 Mk II Headphone Amplifier Review

Product Description

The HP8 Mk II is a tube-based headphone amp designed in England by David Shaw. It uses an ECC83 tube in the first gain stage which then drives 6SN7 tubes (valves if you prefer British English). The 6SN7s then feed through a multi-tap output transformer. This is a nice feature because it allows front panel switchable output impedance to match different headphone impedances from 8 ohms to 1000 ohms.

The form factor is quite compact for a tube amp in my experience, measuring a bit over 6” wide and 10” deep. In standalone headphone systems, the HP 8 accepts analog inputs from your DAC or streamer or phone preamp, and also can be configured at a small extra cost for Bluetooth operation if you’ve recently lost your hearing sensitivity. Icon points out that in standard in-room stereo systems the inputs can be connected to the “Record Out” or the preamp out, so that you have input switching as needed.

I tested the David Shaw Signature edition, which has special Mundorf capacitors and upgraded tubes. The Signature edition is priced at $2250, a $300 upcharge.

Sound Quality

This amp does some sonic things that I believe will make it an ideal partner for many headphones. As a reference, I listened to headphones from Focal, Meze, DCA and HiFiMan, all of which are in the $2000 to $6000 range. I went through a bevy of tracks from Bill Frisell, Pearl Jam, Taylor Swift, Santana, Bebe, Shostakovich, Eivor, The Black Keys, Daft Punk, Waxahatchee, Charles Lloyd, Herlin Riley, Samantha Fish, Bruckner and SZA. I like to imagine hosting a party for all these artists.

Back to reality.

To understand the HP8 Mk II, let’s start with our frenemy, the Harman curve. Assuming the Harman curve is right, tracking this frequency response target is just plain hard for headphone makers, at least without DSP. What this often means is that headphones designed to be reasonably flat above 2khz will probably have a few peaks in the upper-mid to treble range where tracking is imperfect. This will lead to an occasionally or often bright sound on some instruments on some recordings. And, for some listeners, this brightness will be a cause of consternation. This is especially so for those headphones that otherwise are engaging and compelling. So close and yet…

The big thing about the Icon HP8 Mk II is that it smooths out some of these peaks without making the music dead or even that noticeably altered. Maybe the bevy of solid-state amps I have in the lab are transiently imperfect and I’ve just gotten used to them? Or maybe the HP8 has some brilliant tone-shaping.

Now there are limits to what the HP8 can do. Some headphones have peaks in the treble that are 10 db off the Harman curve. I would say those are headphones you simply should avoid. But if you take a superb headphone, like the Dan Clark Audio E3, the Icon takes the E3’s slight treble tilt and makes it more musically right. At the same time, the HiFiMan Susvara seems to lose none of its prized treble definition and sweetness.

Next up, the Icon seems to have more than ample drive for any headphone I tried. It is rated at over 800 mW into each of its three switchable impedance ranges. If we take 90db@1mW as a low sensitivity, then the Icon should have plenty of drive for just about anything.

And it sounds like it does. The nice thing here is that the HP8 mk II sounds naturally dynamic. Music is punchy and lively without being piercing or strident or confused. The E3s and the Susvaras seemed to come alive.

I do think many excellent products have a quality that is make or break, and by that I mean a quality that divides listeners into “lovers” and “haters” or maybe more accurately those who think “that’s great” and those who think “nice, but I have reservations”.

In the case of the HP8 Mk II, I think that is the rather “analog” sound of the amp. The HP8 is quite clear and has good instrumental separation, but it doesn’t quite deliver the micro-detail and sense of so-called black backgrounds and openness that you find with the best current digital signals (and to some degree with optical cartridges playing vinyl). Some listeners view this hi-res digital level of clarity as “cold” or “artificial” while others prize its revelatory nature. In the case of the HP8 mk II, the sound is distinctly analog in character, something I think many listeners will love.

Summary

Well-designed headphone amplifiers shouldn’t vary too much, and yet they do have their distinctive qualities. The Icon Audio HP8 Mk II is musical and dynamic and expressive in a way that I think will satisfy many listeners on almost any good dynamic headphone they choose, either now or in the future. That is quite an achievement. I also think the Icon HP8 is an impressive value. I know $2000 is real money, but many great amps are 2 to 4 times as much. If you want an analog-oriented amp that is flexible and engaging and powerful, this is one you need to try.

Tags: AMPLIFIER HEADPHONE ICON AUDIO PERSONAL AUDIO VIDEO

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