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A Review On: Audio-gd Master 9 Preamp & Headphone amp

Audio-gd Master 9 Preamp & Headphone amp

Rated # 93 in Desktop Amps
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Purchased on:
Price paid: $1,550.00
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Pros: A very natural and balanced sound, Jack of all trades (anything from C/IEMS to full-sized), Build Quality, Price, Best of all... can DRIVE the HE-6!

Cons: Slightly soft in the bass when paired with certain DACs, Flavor can be considered too laid-back, Utilitarian Aesthetics



I’m somewhat of an enthusiast at this point in the game. I don’t consider myself an audiophile yet by any means. I feel someone that is a true audiophile seeks the purist, most untainted reproduction of sound and is always tweaking and striving to better their gear. Because I don’t have the ultimate means or the hardily trained ears to be an audiophile, I’ll leave that title to others better and more experienced than I. What I do believe is that music is the #1 priority always and forever. As an enthusiast, my goal is to find gear that is enjoyable to me regardless of how accurate and/or well measured it is. Measurements are incredibly useful for both assessment and for purchasing, but I let me ears and brain decide if I like what I’m hearing or not.


With that said, my preferences have changed over time as my ears “mature”. I used to love strong, emphasized bass (not basshead bass) with a strong mid presence that is lush and warm. Detail retrieval, imaging, soundstage, dynamics… all of those things were like foreign language to me. They weren’t very important. As I’ve climbed the ranks, upgraded my gear, and started to critically listen to my music, my appreciation for the technical aspects of music reproduction have blossomed. I now have a need for excellence in all of those aforementioned areas. I’ve since partially grown out of that phase and into what I feel is my preferred sound. I enjoy something that is natural and realistic. I still love hard-hitting, accurate bass but not overly so. I know those are subjective terms, but as a closet musician, I feel I have a firm grasp on what Piano, Drums, Bass, and Guitar sound like in real life. Those sounds need to be as real as if I were playing them in order for me to want to keep something.  Overall I prefer a neutral tonality, with slight warmth. A sound that is non-fatiguing, with plenty of air and space between instruments - deep and appropriately wide soundstage, with excellent spatial cues and imaging. Last but not least, a large dynamic range. Those factors and criteria are tested every time I evaluate my gear. If they pass most or all of those subjective tests – they stay, if not they go (most of the time). 


Test Equipment:


  • Source: C.A.P.S. Carbon v3 (w/ Paul Hynes PSU)
  • Software: JRiver 19 (ASIO)
  • DACs: MSB The Analog DAC / AMR DP-777
  • Amplification: Audio GD Master 9 / HeadAmp GS-X mk2 / Rogue Audio Apollo Monoblocks (for Preamp testing)
  • Headphones: HD800 / LCD-X / HE-6 / Mad Dog / TH-600 / TH-900’
  • Speakers: Tekton Designs Pendragon


Technical Specifications:


HeadAmp GS-X mk2: Pure Class A – Solid State Headphone Amplifier / Preamp 


  • Frequency Response: 5Hz-50KHz (+/-0.1dB)
  • Signal-to-Noise Ratio: >100dB
  • Total Harmonic Distortion: <0.006%
  • Gain: 1x / 0db, 3x / 9dB, 8x / 18dB
  • Output Impedance: less than 1 ohm
  • Output Power: 1 W (SE), 2 W (Balanced)
  • Inputs: 1 XLR / 1 RCA
  • Outputs: 2 - Combo Jacks (¼” and 3-Pin XLR) / 1 - XLR / 1 - XLR loop-out / 1 RCA loop-out
  • Preamp Outputs: 1 – XLR / 1 – RCA
  • Chassis: 14.5" (length) x 9" (width) x 5" (height)
  • Weight: 12 lb


Audio GD Master 9: Pure Class A - Solid State Headphone Amplifier / Preamp


  • Frequency Response (XLR): 20Hz – 20KHz (+/- 0dB)
  • Signal-to-Noise Ratio: >130dB (Input short, XLR mode)
  • Total Harmonic Distortion: <0.002%
  • Gain: Low Gain - +14dB (XLR) / High Gain - +20dB (XLR)
  • Output Impedance: 1 ohm
  • Output Power (Balanced): 9 W @ 40 ohm / 3.8 W @ 100 ohm / 1.25 W @ 300 ohm / .63 W @ 600 ohm
  • Output Power (Single-End): 2.5 W @ 40 ohm / 1.05 W @ 100 ohm / .35 W @ 300 ohm / .175 W @ 600 ohm
  • Preamp Output Level (Max): 10V @ RCA / 20V @ XLR / 4.8MA @ ACSS
  • Inputs:  2 – XLR / 2 – RCA / 1 – ACSS
  • Outputs: 1 – 4-Pin XLR / 1 – 3-Pin XLR / 1 – ¼”  
  • Preamp Outputs: 1 – XLR | 1 – RCA
  • Chassis: 17” (length) x 17 (width) x 3.6” (height)
  • Weight: 


The Sound:


Out of the box, the M9 sounded very good. It seems Kingwa breaks-in each individual product for 300 hours or so before sending it off. I didn’t find my difference in my initial 100 hours, although some treble smoothness – and some effects of definition in the bass were noticeable. Other than that, the M9 is ready to go as soon as you set it up.


M9: Overall is slightly warm but not overly so. Initially I thought this amp was going to be brutally honest, being the most neutral amp I’d had ever heard, but I just don’t find that to be the case. It has great non-offensive sound that has excellent synergy with both my HE-6 and HD800. Bass is tight with great texture and weight. Impact and slam could be better, but that could be my DAC, which I find to be slightly rounded in the lower regions. Mids are clean and clear without a hint of grain. A non-fatiguing response that is extremely enjoyable with everything I’ve thrown at it. The treble is definitely my favorite aspect of this amp. It has great extension and clarity while only exhibiting a small bit of sibilance with poor recordings. It has a smoothness that isn’t present in comparison to the GS-X mk2. This could come down to personal preference, but in terms of overall transparency I find the M9 to be more accurate compared to the GS-X mk2. 




GS-X mk2:  In comparison more neutral although with some slight emphasis in the bass region. Bass is extremely tight, controlled and extended. This is where I find the GS-X mk2 to shine - the way it can grab a headphone by its virtual balls and control the hell out of sloppy bass, overly bloomy bass and even refine good bass. It won’t transform overly bassy headphones into well textured and refined beasts, but it will clean up and control bass to a point where you won’t recognize the sound even though you are listening to the same headphone. Mids are crystal clear, clean and up front (not as laid-back as the M9). You could say the GS-X mk2 has a more aggressive tone. Treble is where things get a little hairy. One of my few complaints about the GS-X mk2 is the treble response. I feel there was always something about the treble that was slightly unnatural. It is hard to describe, but I feel there is some etch, glare that I hear with certain tracks. It wasn’t apparent on everything I listen to, but on some tracks it was there – and it could become fatiguing especially with an ultra-revealing phone like the HD800. This is me nit-picking, and I’m sure there are plenty of people that won’t agree, but it was one of the few problems I had with the GS-X mk2. Overall a very small price to pay considering how versatile and well rounded the amp is. 




Imaging on the M9 has good precision. I was able to accurately pin-point instruments and vocals very easily. Soundstage is appropriately deep, but could stand a bit more width. In comparison, the GS-X mk2 has a more expansive, 3D staging giving the impression of more air between instruments. Detail retrieval is also very good, albeit not as good as the GS-X mk2. The GS-X mk2 is faster and more transparent. Everything sounds airier, better separated on the GS-X mk2 regardless of what headphone I used. Dynamics are also better on the GS-X mk2, although this is a closer race, and one could easily prefer the M9 in terms of dynamics over the GS-X mk2. Overall I find the M9 to be slight less proficient in the technical aspects in comparison to the GS-X mk2. Both are very good, and definitely make my top 5 SS amps I’ve ever heard in terms of staging, imaging, separation, and dynamics.



Headphone Pairings:


I wanted to include this section because I’ve been asked several times whether or not the M9 has the grunt and finesse to power the HE-6. I’ve also been asked if the HD800 has good synergy as well. There is always a reluctancy in the back of mind when I order something new with very little information in form of reviews, impressions, etc. on how it does with the wide range of headphones that pass through my house. I’m always trying new headphones, typically not with the idea to keep but just out of curiosity - how it sounds and how it compares. I’ve finally found my trifecta with the HD800, LCD-3, and HE-6. Owning these three headphones give me the range and covers all my bases. I can switch headphones depending on mood and have the versatility to compare new gear when I’m not feeling lazy. The problem becomes amp synergy and requirements. I feel all three of these headphones have different requirements when it comes to amplification. Buying something that pairs well with all three is a difficult task. I was hoping the M9 was able to at least sound decent with all three and to my surprise it does and then some.


HE-6: This pairing was the most important, and the largest risk to me. We all know the myths and exatrations that pass through these forums regarding the HE-6 - they NEED 100wpc to sound their best – blah blah. Well I don’t buy into that crap, but I do believe the HE-6 are power hungry and need lots of grunt. At the same time they need clean power that packs a ton of punch but has the finesse to soften the semi-hard treble and get rid of the etch. Well, the M9 definitely delivers. Sound signatures match up very well having good synergy, and there is plenty of headroom on the volume pot. Out of the 100 steps – I’m at 60. Over the years, I’ve come to find out that I listen to music relatively loud. Any sane person shouldn’t listen at 60 unless they want to jam all day err day like I do. The M9 DRIVES the HE-6 with authority, and I can’t say it gets a lot better. For a headphone amp, the M9 does a surprisingly good job.



HD800: Even after hearing the GS-X mk2 and M9 with the HD800, I still feel the HD800 belongs with tubes. I can’t get over the bright treble and the artificial staging the HD800 has without the realism tubes bring along. There aren’t very many SS amps/HD800 combos that my ears agree with but the M9 comes really close to be the best. It does smooth out the treble, and give me the warmth I need for the HD800 to sound somewhat natural, but there are still some missing pieces that I have yet to find in any SS combination. The upside is you get a very nice bass response with the HD800, adding a bit longer decay which in turn makes the sound more engaging. The HD800 is an uptight prude, but with the M9 – it shows some skin. Overall I like the pairing. I could definitely live with it, tweaking other things in my chain like full copper interconnects, and a warm/slightly laid-back DAC.




LCD-3: TBD – My LCD-3 are out right now, only had a few days (few hours really) with it before they were sent out, but will update this post when I get them back.


Alpha Dog: TBD – Waiting patiently on the upgrade list!




Mad Dog: The MD pairing was not to my liking. This was the only headphone that I’ve tried so far with the M9 that I feel sounded better with other amps, even from my DAP (Sony NW-ZX1). After sometime with the MD, I appreciate how good the headphone sounds for the money – but after you hear headphones like the HE-6 etc. the pairing just didn’t jive. Mids were too upfront resulting in shouty vocals, too much mid-bass emphasis clouding lower-end definition and detail, and treble was not crisp and clean. This could very well be the headphone alone, but I just didn’t enjoy the glossy sound between the M9+MD.  



LCD-X: This pairing was extremely enjoyable, second only to the HE-6 pairing. Sound was very musical and toe-tapping with excellent tightness in the bass and crystal clear treble. Mids were accurate and silky smooth. Soundstage did deepen and separation did become more distinguishable. Overall very nice, non-fatiguing sound.


Sidebar - Really liked the LCD-X headphone as a whole. I feel the this next gen Audeze line is truly on to something, and I look forward to what the LCD-4 brings. The difference in sound wasn’t enough to justify owning it, or selling my precious LCD-3 off  but I can appreciate good engineering and this is definitely one of the best headphones I’ve heard.


TH-600/900: These two headphones need bass control. I don’t feel these headphones sounded their best with the M9 but good enough to still recommend the pairing. The GS-X mk2 is still my reference amp with the TH-900, but this amp doesn’t fall too far behind. Nothing sounded out of place, but the bass could be better controlled and tighter. One of the reasons I have no sold both of these headphones is because the bass can be somewhat overpowering with certain genres. Still feel the treble on the TH-900 is one of best I’ve ever heard, and that wasn’t any different on the M9.






While I find the M9 to be warmer than the GS-X mk2, it still remains quite precise and accurate with great detail and resolution. In comparison the M9 is more full-bodied to the “thinner” sounding GS-X mk2. Depending on the person, these qualities can be seen as coloration and in result a duller sound, but I don’t find that to be the case. The GS-X mk2 is brutally honest, almost to the point of being “raw”. Your audio chain better be up to snuff, from source material to interconnects/power cables. Between the two – I find the overall differences in sound to be more natural and live performance like versus deadly accurate, monitor like sound.  (Natural vs. Neutral?)


I don’t want to fill this review with a bunch of superlatives and hype because I’m very much against such writing. What I want to do is convey as accurate as I can what I hear and why I feel this amp is very good in its own way compared to what I’ve heard and specifically the GS-X mk2. The short answer is the Audio GD M9 is the complete package - a very versatile, well rounded headphone amp that can power any and every headphone on the market. The volume control and preamp both are above par, and well implemented.  It has tons of functionality including multiple outs, ins, ACSS, gain settings, and of course a preamp for people wanting their headphone amp to pull down double-duty.


Note: Stratus thoughts coming soon, as well as more pictures and more thoughts.


Thanks for reading!


Great stuff, good review. I'm more curious on your Paul Hynes PSU for your CAP's music server pc though. hehe
Also, what tube amp would you consider to pair extremely well with the HD800's? One that is still in production...
Nice review. I have to say, though, I'll never understand this idea of an "audiophile" as some glorified, uber-rich person with golden ears who is so OCD that they must have *perfectly* accurate sound, which is basically a unicorn...especially when it comes to headphones.
The literal definition of an audiophile is someone who loves sound; I will never understand why some people feel that budget limitations or differences in opinion or taste contradict the core concept of being a "sound lover." I would say that anyone who takes the time to create an account or lurk regularly on a place like Head-Fi is probably an audiophile in the strict sense, and I don't understand why it has come to be such an exclusive term rather than an inclusive one.
Thank you both for the kind comments. 
@DefQon - The Paul Hynes linear PS is very special and mates with the CAPS extremely well. It has three different isolated rails each with its own PSB. The CAPS server takes three different voltages, so each rail is set to mate with each individual component. Honestly I haven't heard the CAPS without the PSU, but from what I've read, most people upgrade the PSU to an external linear unit of some kind. Blacker background, great sense of depth in the sound, etc. as a result of the upgraded PSU. I believe this unit costs around $2200. You can now get a SR3 from Paul for quite a very reasonable price. 
The two best tube amps I've heard with the HD800 thus far are the DNA Stratus and the EC BA. I had a very short time with the EC 2A3x4 which was also very nice. Not enough time to get a handle on its sound, but it seemed like it could have been the best of all three. The Stratus I have in house right now and it is quite impressive. More organic than Craig's stuff and maybe a tad less clarity and detail, but a very pleasing, non-offensive sound that you could listen to for hours. 
@Gilly - I agree that an Audiophile must love music (sound) in order to keep going, but I've found that throughout my time here and on other forums the word Audiophile is used more as a title to flaunt their ultra expensive gear. I don't know how I feel about this definition - but you always hear about that Audiophiles analyze, Enthusiasts enjoy or Audiophiles listen to their gear, not the music. Not sure how much truth there is to those statements, but I for one don't want to be a part of a group that feels they need to be critical. I guess the word is highly subjective, but no one can argue that audio gear is extremely expensive past a certain threshold. Most people will never be able to afford them and therefore don't title themselves as Audiophiles because they are limited and can't experience the "best" the market has to offer. 
Either way, I totally understand your point of view and agree I wish the word would be defined as by their love for music, other than their love for music/gear. 
If you think the GS-X has a weird treble have you gone down the line in the Dynalo range?  The Gilmore Lite has a harder more etched treble in my experience but gives up that bass control you mention.  These amps are overall great for many headphones but like you I did not like the HD800 match and prefer more warm/tube combos, I really like the Zana Deux and would venture to guess it may be a better call than the ECBA!
And on power, I wish I could hear some HE-6 myself but back in the k1k days I found great sound out of an "underpowered" EC2a3 amp while really not caring for a First Watt F1 in comparison; sometimes sounding great can trump the technical merits of having tons of power on hand.  The difficult part is getting over that psychological barrier of enough is enough.
@Ricky - I've briefly heard the Gilmore Lite but it was paired with a NOS Tube DAC so no immediate piercing daggers were present. I'm sure with more time I would have picked up on it. Generally, I'm not against any Dynalo, but I do understand that they all exhibit some sort etch or hardness to their treble. 
In regards to the HE-6, I can understand and respect that for sure. I feel like synergy is much more important than going by how powerful an amp is. I guess it really comes down to personal preference. I found the F5 to be a superb match. Haven't heard the F1 though, so I may feel differently with that one. 
@Greed, great review.  I love your disclaimer.  :)
Great review.
Way to go Eric, good review.   I think the Technical Specifications:  are for the GS-X mk1.  I may be wrong though
@Darryl - It is possible, I grabbed them from the website. I'll double check and edit if so. Thanks for the heads up.
Thank you for the kind words guys. 
Phenominal review with fantastic photos to match. Kudos.
Loved reading your review, beautifully written.
You added the color to the  painted the picture in my head of what the M9 can do.
Very interesting comparison with another great amp the GSX-2.
I only wish I could explain things like you did....You did it the KISS version.
(keep it simple stupid)
Simple maybe, yet effective. Well done....
I just listened to this amplifier with the HE-6 last Sunday. I sounds very very nice. It has plenty of power to drive the HE-6 perfectly fine. I personally liked it better than when I listen to the GSX-2/HE-6 combo.
The sound was very transparent but in the warm side a the same time. the bass was deep and controlled. It has also a very nice soundstage presentation. I may venture to say that I liked it better than when i had the DS/HE-6 combination.
Lovely read, with all the gears u have..u are closer to being named an "audiophile" than most...and that ability to express in words..hmmm..
I have given up on what is musically accurate...transparent...should-be/s;
but more like picking my favorite spot from the orchestra to listen to my music.
Sometimes parking myself infront of the times sitting with the conductor, or distancing my listening to 20 feet away from the maestro. :P
That way my cans dun get sold ...that fast ! lolz
Thanks Eric!   Didn't know why I haven't catch this review earlier.  Alas I'm still kicking myself for not picking up your earlier gsx2.......