( Photos at End )
Kouzelna Productions Presents
In Conjunction with Head-Fi Entertainment
*-* The Glow Audio Amp One *-*
Tube Headphone & Speaker Amp
With Onboard USB DAC
Starring Venerable Players:
Denon “MD”AH-D2000, modified by Lawton Audio
Etymotic ER-4P with “S” conversion cable
Sennheiser HD650 with Cardas Headphone Cable
and making their Kouzelna Productions debut…
AKG K701 with 100 hours of burn-in
Audio Technica AD2000 brand new
New: Beyerdynamic DT880/600
During our presentation, various references may be made to classic staring roles of the past years, performed by the following supporting actors:
Grace 901 Headphone Amp and DAC
Wheatfield HA-2 Tube Headphone & Speaker Amp, by Peter Millet
Whiplash Audio’s Mini Millet Starving Student Tube Headphone Amp
NuForce Icon Mobile, portable headphone amp w/ USB DAC
Headroom Total Airhead, portable headphone amp
All year I’ve gone through a slew of headphone amps until I stumbled onto my new Glow Audio Amp One, and am very pleased to put it through the paces a little for the Head-Fi gang. (No burn-in, it’s brand new, sorry). I recently sold my MD2000 for strange and tragic reasons, but before I did I spent quite a bit of time with it on the Glow gathering notes for this review.
In addition, I’ve been listening to the Glow lately with my ER-4S both straight with a normal source, (Creative Zen and an iPod Nano), and via the Glow’s onboard USB DAC using my iMac and iTunes 9.2 as the source. Of course I would greatly prefer a more stable, high res source like a quality CD transport! But the bulk of the music I listen to with headphones is Vocal Trance, which kind of pins me to the world of MP3, AAC and MPEG Audio files. Can’t fund the idea of buying 16,000,000 CDs for the purpose of one song each, y’know. As much as I’d love to! Trust me!
So let’s start the review.
The Story So Far…
I guess the best way to describe the sound and quality of the Glow is to compare it to previous setups I owned.
Using the Grace 901, the ultimate headphone amp for professionals and solid state fanatics in my mind, with the much admired Sennheiser HD650 was an icy if perfect experience. The music was so well produced, including each and every flaw in the recording, that sadly I was never able to actually get into the music which kinda killed the whole experience for me. I grew to have a humongous respect for both pieces, and the super-awesome top of the line Yamaha CD transport with optical out that I used as a source. But I sold it after half a year, and missed my original setup that included the Wheatfield HA-2 (prototype) tube headphone amp, HD600 and a Sony ER CD player with high end RCA cable.
Both the Wheatfield HA-2 and the Mini Millet Starving Student (iPod Nano, source) shared in common a lush, full and honey-like warmth. Music didn’t play so much through these amps, but oozed out in luxurious, rich tones and sweet vocals that licked your ear as you listened. (Sorry, don’t know how else to describe it!).
The best way to describe the quality of sound through these amps, is to say the music flowed out like soft water, glinting and shimmering in the forest sunlight under a shady canopy of leafy green trees, while your girlfriend in form-fitting cutoff jeans and a faded Iron Maiden t-shirt and Tevas smiles and hands you your favorite, ice cold beverage. Ok perhaps I’ve said too much now. But you get the drift. Throw in a couple of inner-tubes and some Class 4 rapids and…
Point: it was definitely a tube sound, and definitely a coloration of the amp. You either liked it, or hated it. Personally… I loved it! I had this tendency to stay up listening all night listening to the HA-2, and drag my sorry butt into work the next day. (Luckily, I owned the shop I worked in at the time I owned the HA-2, and we had a full-sized original Defender machine in the back next to a fully stocked mini-fridge. So needless to say, I didn’t have to feel my best to show up…)
Present Day: We Join Our Hero
The Glow takes music reproduction a bold step forward from its kin, providing clean, smooth, accurate sound without the honey-like “warm” coloration that make tube amps a “love ‘em or hate ‘em” proposition for serious audiophiles. Instead the full, mature, lush sound and pinpoint accuracy doesn’t so much emanate from an electronic device, but rather appears out of the ether of outer space, or an all but imperceptible breeze that stirs the hairs on your skin, without making the tiniest rustle or sound in the in the trees.
Quality-wise I feel this amp will hold its own to the flawless Grace 901 SS, but it’s so much more forgiving. Rather than fish out every flaw for all to see as does the Grace, it covers them with, well, grace and allows every song to shine in its own way. It's presentation is revealing and detailed to be sure, but kind. Nothing actually sounds "bad" played through the Glow, even with less-than-perfect source material like most of my Vocal Trance collection (256k MP4). Pretty awesome! The songs lilt and flow like water. It seems there is no limit to the amp's range and power, or the heights and lows it can drive your cans to reach for. The Glow leaves literally nothing in the way of your falling in love with what you're hearing. I just can’t say enough about how GOOD and MUSICAL all of my music sounds through the Glow.
MD2000 (Mark Lawton Audio Modified Denon D-2000)
My Glow Audio Amp One powers the MD2000 (150+ hours burn-in) with total ease, of course, not that I’m saying that is a can that is hard to drive. Of course it’s not. But it brings out it’s full potential so easily, naturally, that it’s almost like the headphone is not even plugged into anything, but simply operating under it’s own inimitable power. Like a ghost has inhabited the cans to communicate with you glorious sound and vision from beyond time.
Bass is full, thick and precise. No bleed over into other frequencies. Mids are taken to the very limit, as far as the Denon can provide, (which is not enough for my tastes, but enough not to worry about what you’re missing). Highs, well, you know the MD2000 highs and the Glow leaves nothing wanting, providing a completely natural sound. No artificial roll off, and definitely no shrills to interrupt your groovy experience. The MD2000 is taken to its utter limit of performance. In a word, the sound is just FAT.
Etymotic ER-4S (using “S” cable)
The same goes for the ER-4S, which has about 10 Kazillion hours of burn-in. Maybe a little more. Those of you who have spent time with this gem of usefulness will know it’s classic near-perfect frequency curve, and totally balanced, completely natural sound reproduction. The only thing always missing, of course, is the bass. Generally, it has none. Right?
But not so when matched with the Glow. This is the only amp I’ve ever played my Etymotics through that pulls the bass out of this notoriously bass-shy IEM. Finally, you get the full and total potential of the ER-4S produced by the power of the Glow tube amp. And how sweet it is, indeed!
The Glow produces awesome soundstage in the ER-4S, another elusive quality of the IEMs that only a decent amp can bring out. And the effects are crystal clear. With my Vocal Trance collection the layering appears enforce, in sustain... air... echo... soft decay. It really kicks butt! I just love these IEMs when they get the opportunity to shine at their full potential, and the Glow makes it happen!
Episode Two: Germany & Austria Makes a Play
As it did with the previous two headphones, I believe the Glow takes both the HD650 and the K701 to their outermost limit. OK, bold statement. So maybe I’ll say, the limit it can possibly be with the Glow Audio One! Point being, it doesn’t sound like anything is missing or straining. Both cans appear to be operating at full capacity, with that same effortlessly driven sound as the Glow had with the previous cans listed above (D2000 & ER-4S).
Sennheiser HD650 w/ Cardas Cable Upgrade
My HD650 included the Cardas Cable upgrade, and had about, uh, 5 hours of burn-in. With the Glow it produced a tight, deep and snappy bass. Well controlled, dramatic, but not overpowering in any way, even with Trance. The sound itself is filled with awesome, precise detail, and the 650s really show off that Glow-style “liquid music from outer space” (I’ll call it: LMOS). The music is just effortless, like a soft breath.
One thing I loved about the HD650 was the very warm and intimate midrange. The female vocals sounded so sweet and full, and really drew you in. It radiated with that tube-like smoothness, and in this case the warmth as well, but I think that was more the HD650 sound signature than anything produced by the Glow, because it doesn’t have that warmth with any of the other 3 cans I listed here in this review. Using Vocal Trance, the 650 with the Glow produced a beautiful and balanced soundstage with near perfect effects panning.
The limitations of the HD650 however, were a downer for me, and I don’t know if this is the headphone design or how it sounds with my amp. But for example, during circular pans (sound going around and around your head 360 style, like a satellite goes around the earth), some areas got kinda lost and the effect wasn’t so great. Worse, many of the effect sounds that were easily perceivable on the K701 were basically lost on the 650 during more complex and layered passages. However, dramatic bass drum / cymbal hits sounded awesome and carried the necessary power on the 650, while they just kind of thudded out of the K701.
These babies had 100 hours of burn-in when I tested them, which means they were in their infancy stages, so I’m thinking they would have improved. (Update: yes, with longer burn-in, they did improve; either that, or I got more used to them, you decide!). Anyway, I loved them! Apart from some bummer flaws, when matched with the Glow’s effortless ability to express the music, they made Vocal Trance come alive!
Finally, I reached the outer limits of what I had previously only dreamed about in Soundstage. Wow! Sound was all around me, just all over the place! Effects zoomed by… circle panning looped around my head… all the mysterious layers present in these remixes suddenly separated, with each individual flavor and sequence loop suddenly totally audible and separated. It blended together in rather a perfectly made Tequila Sunrise or Black & Tan, rather than a cacophony of Long Island Iced Tea. Just amazing.
Besides the perfect separation, detail and soundstage that makes the K701 legendary, I can tell (being my first time hearing them) that these are some cold, analytical cans. (Note: they got a lot smoother with more burn-in; my opinion; see UPDATE below).
I think the Glow did a lot to add body and emotion to the sound, for example the highs I guess these cans are noted for did not have any fatiguing brightness to me, which made me sell the DT880 after ten minutes of testing it. They sounded super great, no roll off, no flat response, just perfect and lovely. Every detail of the music was perfectly audible, every instrument well separated, and the complete sound was airy and spacious to an almost absurd degree.
But without that characteristic tube warmth the Glow could only do so much. I really appreciated the total sound package produced by this combo. I would be happy with it. But I didn’t “love” it, I only loved parts of it. Technically, I can’t say enough about it. But in warmth and musicality, in lushness of midrange, and most especially in dramatic bass power, well, it wasn’t there as you know. The cans sounded almost “cheap,” especially compared to the lush, professional quality sound of the HD650. People have said the K701 will improve with burn-in, and I’m hoping that may solve some of these issues. (They did get better: see UPDATE below).
Back on the good side, there was little mid bass, which is exactly what I needed for my ears, but there is plenty of lower end on the K701, and with the Glow it was dramatic, deep and tightly controlled. So, the lower end rumblings and gut is there, but just don’t look for slam ‘cause there ain’t none.
I’m looking forward to seeing how these improve with time and burn-in, because they have the most potential for me personally of any can I’ve heard this year. Even my reigning king, the MD2000, had great but somewhat limited mids and soundstage, and I think the K701 might solve this situation while also eliminating the awesome fat bass slam of the MD2000 that I can no longer handle, health wise.
The K701 did burn-in, I’m happy to say, and the “cheap plasticky” sound is totally gone, leaving a very professional, beautiful and artistic sound. Still light compared to the Senns for example, but I like the sound sig much better, in fact I love it. I can’t get enough of listening to the K701 with the Glow, they seem to be made for each other. This is hands down my favorite match-up of the whole review. The only single thing I would change on the AKGs is that I would bring the mids more to the forefront, like the Beyer 880/300.
I recently switched MP3 players with my K701/Glow rig. I dropped the Zen and hooked up my old Nano with a SendStation line out dongle. WOW! Huge difference.
Hard to believe, but it immediately and noticeably did three things:
1. Tightened up the bass dramatically.
2. Increased the already amazing soundstage and panning effects.
3. Best of all, brought out even more detail, making things very clear that were very muddy off the Zen through headphone out setup.
Got a new SendStation from the company and it eliminated all previous problems with the old one, for the most part. It seems to be intermittent. Finally tracked problem to the iPod Nano itself. Am getting a new one to solve issue.
Rising Sun: Japan Makes it's Debut
OK, the Audio Technica AD2000 showed up, and I ran it through some tests against the K701. Of course, this can was brand new out of the box, so take that with a grain of salt.
The first thing I noticed about the AD2000 was the awesome intimacy of the midrange! Very similar to the M50; that sweet, sexy vocal presentation that just draw you right into the music. Obviously with the Glow the result was a full, realistically human sound and I loved it. I had missed that with the K701.
In addition, I think this was the only headphone that actually had even greater detail retrieval than the K701! Although that is such a big statement, I'm going to say I'm not quite sure as I didn't listen enough: but it was awesome! Panning effect (my term for stereo sounds wrapping around your head properly as recorded) also was on par with the mighty K701, a champion in this regard. I was very impressed!
Finally, hands down the bass was probably the best I'd heard since the MD2000. Big and bold like the M50, the champion in this regard, however far tighter and controlled than it's younger sibling. It was, in a word, awesome! Even for a closed can, let alone an open one! If you love the open sound, but miss deep, full and tight bass, this may be your headphone!
However, the AD2000 places it fell short, to me, against the K701 were soundstage (of course - who can keep up with the K701 in that area?) and worse, warmth of sound.
The soundstage of the AD2000 was mightily accurate, to my ears, and reminiscent of the M50's style, only much better. Along the lines of the HD650 I think. Beautiful, present and real, but so far shy of the K701 which I have grown very used to and enjoy. In addition, the "airiness" was not there, it had a much tighter and more intimate presentation, which to be honest I think a lot of people would like better than the K701's separation, which is like listening to a band play in an empty gym hall or desert!
As for warmth of sound, that's hard to explain. I once had an extended listen to the AT 950 LTD, and it had much the same sound signature. Awesome separation and soundstage, detail retrieval, bass accuracy and intimate midrange. Just breathtaking in these areas. But overall, the sound was a little flat, cold, and lifeless when compared to, for example, the M50, MD2000 and K701. Those of you who have heard many high-end AT cans, I hear that they are all very similar in this regard, and you either love it or hate it.
Personally, I've never heard a better sounding headphone than the M50, and if it's weaknesses could be improved, (slightly bloated bass, slightly tinny highs, and compressed soundstage), it would be the one for me. It just has an intimate, warm, musical sound that I've never heard in anything else to that degree, save perhaps the MD2000. However, the higher end AT cans I've heard seem to leave this overall musicality out, and the presentation is a bit colder, more clinical.
In direct comparison to the K701, and I suppose the MD2000 as well, the music simply doesn't get up and live in the AD2000 like it does in those cans. This, of course, could be because the can was just out of the box. I could seriously believe that with use it would warm up, just like the M50 did after about 100 hours.
And Back to Europe...
Germany, to be precise. The DT880/600 sounds so totally different than the 880/32, they should definitely be different models. I can't even believe these are the same headphones? They sound absolutely NOTHING alike, at all. (I hated the treble of the 32 model; way, way too harsh IMHO).
From first impression on the Glow, the DT880/600 is beautiful! Everything on them is near-perfect. The bass is awesome and precise, just beautiful. The midranges are so intimate and I really, totally miss that so much coming from the K701. And the treble is perfectly fine, exactly what it's supposed to be. What stands out the most, is the awesome and stunning detail. Just amazing. Every single detail of the music is so accurately presented. And layered perfectly, without getting muddy. It's like I realize that you miss nothing at all. Incredible.
I picked up some slight muddiness somewhere, perhaps where the midbass is. I don't know, I'm not that technically astute. But my theory is this: the only place where the 880 fails against the K701 is in spatial presentation. The K701 simply has much more space between the instruments, which avoids the muddiness at that frequency. I think this is called congestion, meaning that some detail gets squashed together. But it's rare, and only in that particular frequency. However, this may not actually be a failure.
The 880 presents a very tight, intimate sound, but does not sacrifice accuracy at all! (Except for that slight congestion). It's like listening in a good club. And with the Glow, it's like being in a club that uses tube amps! :D Just to compare, the K701 is like the musicians having more room, like on a theater stage. There's more air between the instruments. That's the best way I can describe it. The 880 also performs perfectly at a lower volume on the Glow, which the K701 doesn't.
I used mainly Vocal Trance for my listening tests, of course, as that's my primary music for headphone use. The whole point of Vocal Trance, among other things, is that sweet female midrange, which presents such intimacy when its reproduced right; it literally tickles your ears, as though she's breathing right into your ear. Which, hey, I like! The K701 is more like sitting a few rows back, and seeing the singer on the stage somewhat far away from you, not noticing you, like you're a big geek.
The Secret Plans: Glow Build Quality & Drawbacks
(Patrick at Glow responds to the two problems I listed below, and how they've been solved. I've printed his letter on the second page of this thread).
The design and look of the Glow, to me, is top notch. The unit is 9.5” long (not counting volume knob), 5.25” wide, and 6” tall (feet to top of power supply / transformer thingy). It weighs a whopping 15 pounds, which doesn’t seem like much but is a big surprise considering it’s size! It gets pretty hot when running, but not nearly as hot as my old Mini Millet, for example.
It has four tubes, don’t ask me what they do because I don’t know, on the top which are bordered by two chrome tube rails, and which sit under a mesh metal guard that connects (tightly!) by magnets. Headphone port is on the left side (looking at the volume knob), and the on/off toggle is on the right. All ports are in back, which include standard AC Power Supply (not wall wart connector), USB IN, 2 RCA IN jacks and 2 sets of speaker jacks. It works on both 110/220 via a switch somewhere out of sight, and has no gain switch to my knowledge.
One cool thing about the Glow, which is neither here nor there, is the LED that encircles the volume knob is completely lit, and changes color every few seconds, softly fading in and out of about 5 or 6 different colors. Pretty neat. But pretty bright at night, hence I usually stick a sock over it if I’m listening in bed, which is a pretty funny sight. Heh heh.
As for drawbacks to the Glow, I have found only two, one minor and one I’m not sure.
First off, some of the headphone plugs I’ve used fit correctly into the Glow’s headphone IN port, and some do. Patrick at Glow gave me a reason for this, that the Glow was specifically designed using a certain style of headphones, and therefore not every plug is going to fit exactly right. However, there is an easy fix: a simple .5 O-Ring from Home Depot which costs 30 cents takes care of it. I fit these over the ¼” plugs of my headphone jacks, and then they seat at exactly the right place in the headphone port. Nice!
Patrick at Glow said this issue was solved in the '09 model; I have the '08 model. Also, I tried a brand new Audio Technica AD2000 today, and the plug fit perfectly with no problems, as is, without the o-ring. As does my 235-ohm resistance cable plug.
The second issue is a little more problematic, and that is a persistent very low hum I can’t get rid of. Patrick said this is normal with low impedance headphones, as the Glow being a SET tube amp is designed for higher impedance cans. However, I’ve had the same problems with the 300-Ohm HD650, and the low Ohm by high sensitivity K701 as well. The hum isn’t terrible, but I’d sure rather not have it! I talked to the guys at HeadRoom and they think it might be as simple as a loose ground, so I’m working on that.
In any case, Patrick specifically said that the Glow can be modified for different Ohm cans, depending on what I settle for, and there is a guy who does the work right here in Los Angeles, so no biggie. Since it’s a repairable flaw, that’s no big whoop. Other than that, I’ve found no flaw with the Glow.
First, I tried moving the Glow off of a Surge Protector strip I had it plugged into and onto a dedicated socket that had nothing else running. Well, duh, a lot of the noise went away. Then, I hooked up a +235 resistance cable to my K701, bumping it up to 295-ohm total, which completely eliminated the hum entirely, at any volume level.
(Patrick at Glow responds to the two problems I listed above, and how they've been solved. I've printed his letter on the second page of this thread).
Last but not least… the Glow is of course designed to work with speakers!
Patrick at Glow went out of his way to recommend me trying it with quality speakers, as the sound is known to be out of this world. But… and here’s the thing… I don’t have any! At least none that I think would show off the Glow. So, it’s headphones only for me, until someone, ah, well, sends me a free pair of great speakers that’ll work well with the Glow! Yeah! Good idea. I’ll wait by my mailbox. Patrick said, of course, that the Glow speakers are designed to work with their amp, and are extraordinary for a great price. Someday...
Well, that’s that for now. Any questions, please send them over by posting to this thread so everyone can benefit. Hope you guys are enjoying this and it’s providing some usefulness to the Head-Fi community. Ciao. Or as we say in the Czech Republic, Cau.
Edited by Kouzelna - 4/7/11 at 1:26pm