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Review: HeadAmp GS-X (single-ended)

post #1 of 23
Thread Starter 
Primer on the GS-X

For those unfamiliar with the HeadAmp GS-X, I'll preface this by saying that there are solid-state amps, and then there are top-tier solid-state amps. The upper echelon. The amps with huge price tags, built to last a lifetime. The ones you always think about upgrading to. The ones at the very top.

Released in February 2006, the HeadAmp GS-X is one of those such amps. Physically it dominates a lot of other amps with its dual-chassis configuration, one each for the amplifier and power supply section. Each of these chassis is 14.5x8.5x2. Together they combine to form a formidable stack of black. Oh, you guys want a picture?

(click for larger version)

Equipment Used

- Arcam DiVA CD73
- Arcam FMJ CD33
- Audio Aero Prima 24/192 (2005 model)
- Primare CD31 (1.5 hour audition time at local dealer)

Power cord on sources:
- Signal Cable Silver Res Reference
- generic 18 AWG IEC

Comparison Amplifiers:
- Eddie Current EC/SS
- HeadAmp Gilmore Lite v2 w/ DPS
- HeadAmp GS-1
- Heed Audio CanAmp

- Audioquest Python
- Signal Cable Silver Res Analog w/ Eichmann silver bullets

- AKG K701
- Audio-Technica ATH-AD2000
- Sennheiser HD650

Evaluation CD Tracks

Alison Krauss - Now That I've Found You - "Oh, Atlanta", "Sleep On"
Jewel - Spirit - "Enter from the East", "Life Uncommon"
Eva Cassidy - Songbird - "Over the Rainbow"
Howard Shore - Lord of the Rings: Return of the King [OST] - "Ash and Smoke", "The Grey Havens"
KT Tunstall - Eye to the Telescope - "Other Side of the World", "Through the Dark"
Massive Attack - Mezzanine - "Inertia Creeps"
Neotropic - Mr. Brubaker's Strawberry Alarm Clock - "Gutted", "You're Grinding Me Down"
Porcupine Tree - In Absentia - "Blackest Eyes", "3"
The Crystal Method - Vegas - "Keep Hope Alive", "Vapor Trail"
Thievery Corporation - Richest Man in Babylon - "Facing East"

Features & Build Quality

An itemized list of the features the GS-X offers:
- dual-mono topology (two monophonic amplification modules per channel)
- balanced XLR input and output
- single-ended RCA input and output (active at the same time as XLR, hence the front-panel switch)
- loop outputs for both XLR and RCA
- pre-amp outputs for both XLR and RCA
- a total of three headphone jacks: two for single-ended headphones and 1 for balanced headphones
- three-position gain switch - Low is 1 (unity gain)
- DACT stepped attenuator with 24 soft-clicking positions
- modular in design - the monophonic modules can be user-replaced. HeadAmp's new custom modules are still in the works. The current modules are still Gilmore-based. These are fully discrete and do not use op-amps.
- the separated chassis for the amplifier and power supply sections are both vented for heat dissipation. HeadAmp has confirmed the new modules will release more heat and it would not be recommended to block the vents.

(click for larger versions)

Build quality on the GS-X is very high. The two chassis are entirely brushed aluminum so they're tough enough to withstand any abuse they might go through. Everything is plated together in a rigid frame that feels tough too - no wobbles, no flimsy plating. It looks and feels like a machine off a factory press. Very, very sleek looking indeed. It's clear that HeadAmp prefers to keep things visually simple, and the GS-X is an exemplary achievement of that ideal. The black color is visually almost breathtaking in its dominance, but the silver switches and the white lettering add just the right touch to help offset things. It all comes together in a look that gets right to the point. Simple and direct. A nicely coordinated look. But how does it sound, right?

The HeadAmp/Gilmore Sound

In its current iteration from 2006, the modules in the GS-X are still based on Dr. Kevin Gilmore's "Dynalo" circuit, so technically the amp can be called a Dynamid, as it's a proper implementation of a balanced Dynalo. The Dynalo is a discrete circuit as it does not use op-amps.

So then a logical question is, what are the advantages of the Dynalo? While I can't speak for its technical advantages, I can speak for its sonic attributes. Through the ownership of now the Gilmore Lite v2 (with and without the DPS), GS-1, and GS-X, I can personally attest that there is a kind of "house sound" to the HeadAmp amps. This "house sound" is derived primarily from the use of the Dynalo. So what's the "house sound," right?

Before I try to answer that, I'd like to state first that the HeadAmp/Gilmore sound is an acquired taste and firmly for people who fall into Team "Source First." It's always been said here on Head-Fi that your system hinges around the quality of your source, and if there's an amp brand that ruthlessly adheres to that principle, it's the HeadAmp amps. These are amps that sink their claws into your source and scream "FEED ME, FEED ME MORE!" Yes, they can sound good on any source. But they won't sound great - nay, SUPERB without a source of equal or higher quality.

Synergy is also a key issue with these amps. Their sound is such that if your source is warm and analog-sounding, you'll get a warm and analog-like sound. If your source is cold and clinical, you'll get a cold and clinical sound. That's just how it is with these amps. Naturally that means you won't be able to fix a bad source, or a source you're unhappy with - these amps will just magnify the situation more. But if you have the right source, music can explode with color and taste, with a huge palette that you never knew existed.

Hence, essentially the HeadAmp/Gilmore sound is one of transparency and precision. A Windex-polished window, if you will, to make you hear, more than anything else, your source. Another way to put it is that they get out of the way to make you forget you're listening to an amp.

Window On The World

I've always felt that one can't fairly review an amplifier without having two sources to alternate between, in order to gauge its transparency. However, once you get intimately familiar with a source, I can concede that it's certainly possible to review an amp on that one source.

With that said, the highest compliment that I can give to the GS-X is that I discovered four sounds with it. That's right, four - because I've heard it with four sources. A transparent amp should give you a different sound with every different source you pair it with, right? And indeed, that's exactly what I got. On the Arcam DiVA CD73 it sounded warm and lush, but unrefined. On the Arcam FMJ CD33, ultra-refined, and laidback and cool. On the Audio Aero Prima, intensely focused and forward, with a small loss of detail but lots of analog shimmer. On the Primare CD31, lively and restrained at the same time with subdued bass. Those are brief comments for sure, but it sounded that different with each CD player. So how do you gauge an amp like this, if it's that transparent?

It creates a predicament, that's what it does.

I can't with any real certainty provide "final" impressions of how the GS-X sounds, because I haven't heard it with more sources. If I could that would be great, and that would provide a fantastic picture of how well it'd scale up with increasingly higher-end sources. Because of this, I'd have to conservatively rate its level of transparency at 99%, simply because I haven't heard the amp with more sources. If I could rate it at 100% I would, but I can't. And then of course there's the question, can there be an amp that's more transparent...? o_O

Yes, a predicament. The only real certainty I have about the amp is that if your source is high-end, its virtues will shine. Oh yes, they will shine, forever and ever.

But Can You Say How It Sounds?

Oh I can certainly try to take a stab at the amp's innate sound signature, if it had one, even if it really doesn't IMO. But rather than try to limit it too much to say what it sounds like, I'll instead say what it's capable of sounding like, and what it sounds like on my preferred CDP right now, the Arcam FMJ CD33.

First is the soundstage. Oh the soundstage. There are two words that succinctly describe the soundstage of the pairing: holographic and peerless. Holographic in that there's a huge, black sense of space, not just here, nor just there, but everywhere. Like sound is coming at you from all angles, attacking you from the far left, or the far right, or mid-center about 10 degrees to the left, or from way back. Truly surrounding. Peerless in that everything in the music can be linearly placed in space. There's absolutely no fuzzing, no blur. Solid, pure tones. You want to track an instrument moving around in the mix? This pairing allows you to do that exactly that - subtle shifts between left and right pop with vibrancy and clarity with absolutely no gaps anywhere. All the elements come together to form an absolutely coherent, cohesive mix in front and around you. Never any loss in distinction, always clear and precise.

Next is the attack and decay. Oh, the attack especially. Super-fast on the timing, the pairing retrieves details I previously didn't know were possible. From rat-a-tats on wood to light scratches on metal to half-clinks on cymbals to the woosh of air around physical movements, it's all there - so much so that it's eerie and surreal. And the decays - long and full, and drawn out if it's there on the CD. From the wahh of cymbals to reverb to bass post-shakes, that's all there too.

The frequency response is more evened out than on the GS-1. Where the GS-1 sounds a bit hard and grainy in the upper regions, the GS-X is completely smoothed out - graceful, refined, and delicate. No treble sparkle per se, but if sparkle is on the recording, it brings it out. The slightly warm mid-range touch on the GS-1 is also not here. Clear, fluid, with no discernible emphasis anywhere. It's more relaxed than the GS-1 which makes it sound more laidback and reserved, but that's more a criticism of the GS-1 than the GS-X. Laidback and reserved is good - that's what it's supposed to sound like on this CDP. And finally the bass. Deep, tuneful, and realistic describe it best. It sinks deeper than any headphone probably can go, with a very well-integrated response that's never flabby or muddy. Simply clean and clear with a snap and verve that can be called out depending on the recording. And the most realistic bass yet. An x-factor there as it simply sounds REAL, as if finally for the first time an instrument is producing this bass, and you can tell which instrument it's coming from. Very directional.

In short, it's what you could say is The Ultimate Solid-State Sound. Sounds sparking off everywhere like there's an explosion of fireworks, or like an explosion of taste in your mouth from mouth-watering food where there's so much going on, you just don't want it to stop. So much sound, and it's all pristine and holistic - so finely detailed, just so much sound that it overwhelms the senses. And it's not just that there's so much sound, it's all clean and clear at the same time. And not just that it's clean or clear either - you can also distinctly hear where there isn't sound. That's right. The pairing renders silence impeccably black and dead - whenever the music stops, or pauses, or whenever a certain element disappears, it easily catches that too.

Oh, and the sweet, sweet dynamics. Sound flares up in volume when it's called for but can also instantly fade when it's not. Subtle cues are truly subtle, from soft whispers to female vocalists singing their heart out in sad songs to a sad violin or a wide-ranging guitar part - both the loud and the soft parts are crushingly alive.


In short, there is no question. It is uneqivocal. The HeadAmp GS-X is one of the finest solid-state amps in existence for dynamic headphones. And it's also a major plus that once you get to this range, there are almost no more amps to find because the competition is too few! If you find yourself in this price range, the choice is obvious if you favor a truly transparent, keenly solid-state sound for your dynamic headphones on your high-end source. Because doing anything less would be an insult to your source.

I tip my hat off to both HeadAmp's Justin Wilson and Dr. Kevin Gilmore for this stunning achievement in sound. They are both to be commended on a job extremely well-done.

(This review is for the amp in single-ended mode. Apologies for not being able to cover its balanced operation.)

Post #4,092
post #2 of 23
Nicely done.
post #3 of 23
Getting me even more curious, I'd like to hear this thing. Can't wait till 8/25.
post #4 of 23
Wow. Stunningly good job, Asr!!!!
post #5 of 23
yea, great review. the GS-X's only downfalls are that it doesn't sound like a tube amp, and it can't turn a HD650 into a K1000.
post #6 of 23
great review. you should do this professionally.

(i hate those eye-winks. look horrible.)
post #7 of 23
Thread Starter 
Originally Posted by MaloS View Post
Getting me even more curious, I'd like to hear this thing. Can't wait till 8/25.
Sorry, not going to have the GS-X after next week.
post #8 of 23
Originally Posted by Asr View Post
Sorry, not going to have the GS-X after next week.
post #9 of 23
Just how much of this amp can be called a Gilmore anymore?

How does it compare with a RudiStor of equal value?

post #10 of 23
Originally Posted by slwiser View Post
Just how much of this amp can be called a Gilmore anymore?

How does it compare with a RudiStor of equal value?

In another review here on head-fi, there was a suggestion that GS-X is comparable to Apache in value, although they have vastly different tonalities. GS-X is extremely transparent according to both reviews, so my guess is that basically you are tuning between headphones and a source (in which case a high-end tube DAC or CDP, or good turn-table will really pay off while GS-X just stands there to serve as an amplifier rather than coloring machine).
post #11 of 23
Hrmm well there isn't a balanced Rudistor of equal value so its a tough comparison to make the closest balanced Rudistor is the RPX100 (New) which is 1k more.

If I compare my amp to it then I'd say that the GS-X is definitely more analytical and transparent in the amp = "wire with gain" sense. Though of course a dynamid won't have as much power as a dynamight or a beta22. While Rudistor amps, to my experience, have a bit of a fuller/warmer sound though not to the extent that Ray Samuels solid states have.

Edit: Yeah I guess "coloring" machine is one way to put it. Of course all such components including the GS-X (Though it is more transparent than most) have some coloration.

Keep in mind when people say transparent they mean in two difference senses. It gets confusing esp. when referencing Gilmore designed amps and DIY amps that were designed to test well vs manufacturer in-house designed amps. One sense of transparency is transparency as it related to source. To maintain the purity of the signal that the source provides etc. The other sense is transparency as related to the actual musical event that the whole set up is trying to reproduce... this is of course much, much more subjective from person to person. Like some feel that a nicely balanced uber HE90 rig is transparent, they mean in this sense, as anyone who listens to an HE90 will agree that it is anything but neutral (As a source transparent headphone should be).
post #12 of 23
Thanks Asr. A very well-written piece; very readable and informative.
post #13 of 23
Yes coloration is inevitable, and the transparency of he90 comes through in the sense that it is so fast that it can catch any single momentary jitter in the single and bring it to be audible, while hd650 for example is slow and won't pick up minute changes in the signal. But speed is technically already a feature of quality solid-state amplifiers, as transistors used these days are far faster than we are capable of perceiving, so amps that are less transparent are the ones that either roll-off, not letting small jitter through, or those that place more emphasis on the audible range...(this is extremely simplifying it, there is waaaay too much going on with our perception and what amps do for it). Coloration is inevitable, but I am guessing GS-X should by design be extremely neutral, effectively not changing the tonality of the headphone in any way but providing even power delivery at all frequencies.
post #14 of 23
Another killer ASR review. Thanks for spending the time and going into great detail, as you always do.
post #15 of 23
Great Review, i hv owned GS-X since the Pre-order program, it's the one of finest solid-state amps for dynamic headphones.

But we are still waiting the next modules for upgrading the GS-X.
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