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Glow Audio Amp One (Headphone & Speaker Amp) - Pretty Cool New Redesign and Improvements!

post #1 of 13
Thread Starter 

Hey all,


I'm thrilled to announce a totally new redesign of my all-time favorite headphone amp, the Glow Audio Amp One!


I still haven't had the pleasure of directly comparing it to a Woo Audio WA-6, but unless that were to radically change things, this is my absolute reigning champion desert island amp (assuming that island has an electrical outlet) for any and all headphones I use, especially my regulars an AKG K702 and Etymotic ER-4S.


You can read both my review of this amp with multiple headphones, (Denon 'Mark Lawton' D2000, K701, HD650, ER-4S, Audio Tech AD2000 and DT880/600), plus some workarounds for issues with previous older designs, at my thread here:





"But wait, there's more!" :eek:


Patrick at Glow Audio has also assured me that his team went way further than to just correct previous annoying little glitches for the 2013 - 2014 Amp One.  (Which, it must be added, did not affect sound quality).


Instead, they've taken the opportunity to make the most of recent improvements in technology, and created some real boosts in the quality of the amp's reproduction as well. In addition, they made a radical departure with previous designs by removing the DAC features of the Amp One, which made it such a great value, and instead repackaging it as a separate unit.


This redesign allowed them to really focus on insuring the best sound quality from each product, without issues of space in side the amp's chassis. And better still, the stand-alone DAC which normally runs at $125 is being offered F-R-E-E with purchase of either their Amp One or Amp Two. And "free" is one of my all-time favorite words, (especially when it precedes the word "mojitos!")



So what you have, indeed, isn't merely a "revamp" but a completely redesigned headphone amp. And right now's a good time to give it a listen, if you haven't heard this awesome little guy yet.


Patrick says they are so proud of their new amp redesign, that they really want everyone to hear for themselves.  So in addition to the free standalone DAC, Glow Audio is also for a limited time offering a free set of AKG M80 Mk II (list price $179), or Pioneer SE-A1000 (list price $159) with any Glow Amp purchase.  Pretty cool, indeed.


And remember that the Glow Audio Amp One wasn't created only for headphones, but to run small high-end speakers, including some from Glow Audio created especially to be matched with this amplifier, which have gotten some great reviews over the last few years. This doubles your investment, in a sense, allowing you to run a pretty decent high quality system for small to medium sized areas that won't melt your wallet. (Though the Glow plus their matching speakers are loud enough I read to melt your face off in small areas).


I haven't had the chance to audition the speakers, but they are on my list of "things to buy when I have the cash," and when I do I'll post a review here to be sure.


So, on with the improvements!



1. The Dreaded Headphone Jack o' Doom


As a lot of people have written about, including yours truly, the original 2007 - 2008 amp design was a great sounding amp. Patrick at Glow Audio says most are still running strong and trouble free. But he and his team had to make some compromises to keep the price point they were shooting for, and about the most troublesome was the headphone jack.


The jack had to fit it into a pretty tight space inside the amp's chassis to incorporate their point-to-point design (I'm guessing here), and were unable to design a special jack because it would've bumped up the price substantially. Long story short, for some of us with that amp the jack had a tendency to come loose over time. (I didn't have this problem).  For others, like me, some headphones tended to seat imperfectly in the jack, forcing the "rubber o-ring" workaround. (30 cents for a rubber plumber's o-ring, which when placed around the headphone plug at its base, created the perfect fit for the jack).


So, how did they solve it?


Patrick's assured me recently that all subsequent models of the amp use a much sturdier jack, able to provide a secure connection with any headphone, (and unlikely to ever come loose, of course). Simple enough, and a very welcome improvement.



2. Headphone Hum


The headphone signal in the Amp One is tapped directly from the output transformer, so the guys at Glow Audio have to step it down. In the original designs, the amp was calibrated to match with higher impedance headphones. The recommendation was 300 Ohm and above.  For some of us with lower Ohm designs, like me, this created a humming problem.  I solve it by simply adding a quality resistance cable to my cans, as designed for me by Armaegis.  With the additional cable, the Amp One was deadly silent, and the music "appeared" to my ears as if out of the vacuum of space.  Amazing, amazing sound, and I've never heard a tube amp that sounded that good.


In the 2013 design, however, a Hi/Lo impedance switch has been added so the amp's output can be tailored to match the impedance of whichever headphones you normally use.  This isn't available on all headphone amps, but is certainly welcome when it is, and I'm glad the guys at Glow Audio decided to do this.



3. The DAC


As I mentioned, the DAC is now offered as a standalone unit for $125, but it is also included free of charge with the purchase of either the Amp One or the Amp Two.


The reason the Glow Audio team decided to do this, is that the DAC previously incorporated into the Amp One was based on technology available in 2007, when the amp's design was being planned. In order to fit the DAC circuitry into the tight space inside the chassis, this DAC was somewhat of a compromise. Compared with modern DACs, it wasn't the best sound quality. However, it was an easy plug n' play unit, allowing the amp to be used easily with digital sources such as your MacBook or whatever. They did upgrade the internal DAC over time, managing to incorporate a Burr-Brown unit and Glow's own gain stage design into the 2011 - 2012 model, but given the tight space there was a limit to what they could do.


For 2013 - 2014 the DAC is now being offered as a separate unit. Instead, an additional RCA input has been added to the amp (making a total of 2), and the new Glow Audio DAC is based on their own design. About the size of a deck of cards, it's USB powered and uses a Burr-Brown 2704 chip. Patrick says it's so popular they've begun offering it as a stand-alone purchase for $125, and it's very hard to keep in stock due to the quality circuit design and associated components, which make for a really awesome sound. They use KOA precision resistors, ELNA electrolytic capacitors, and a Simons MKT non-polar capacitor.


Patrick said their goal was to make it sound at least as good as any DAC in the $250 and up range, so they didn't scrimp on anything. He also mentioned that if you're already familiar with the $250 Dragonfly, they were shooting for this quality range or better in designing the DAC, according to their own specs, and feel they have really succeeded.



4. Tube Madness and Misconception


Finally, one of the main issues we all complained about with the Amp One's previous designs was its tube limitations. The original design could only use Russian or Chinese tubes. However, this was a misconception.  This limitation was true only for one of the older Amp One versions, and even it could be addressed with minor modifications.


Patrick has corrected me that there up to now (Sept. 2013) there have been four production versions of the Amp One.  Of these four, only the 2009/2010 units (series II) had the limitation requiring the use of Chinese or Russian power tubes.  All other units including the 2007/2008 (series I), 2011/2012 (series III) and 2013/2014 (Ver. 1.3) all can use ANY EL84 power tube available on the market currently.



In Summary


The new Amp One continues to keep the same cosmetic design, which I thought was pretty cool and retro, the way a tube amp should be IMO. It's also still hand-built, using point-to-point wiring. And Glow Audio claims there have been little improvements all along the way over the past 6 years besides the ones Patrick talked to me about, and I've tried my best to give justice to above.


I remarked on the new higher cost, and he reminded me that the cost of labor and parts has nearly tripled in China, as we in the US already know because so many of our businesses are "coming home..." to Mexico. (Thank you very much). However, he said sales are going well, and they're thrilled to keep serving the audio community with great products and personal service, and feel that in this design they are offering a product of superior quality. Patrick said he feels very strongly that this is their best amp yet, and thus they've made the DAC available free with purchase, and are currently offering the free headphones as well to get people off the fence and into enjoying their new Glow amp.


Based on my own experience with an older design, I would certainly agree, and am glad to present these improvements to you all of us here at Head-Fi.  I am looking forward to buying a new 2013 - 2014 amp myself, and have scotched my up-til-now current plans to save money and get a hybrid instead.  With all these improvements, I think the Amp One is going to be well worth the months of Top Ramen for dinner to come up with the cash.


If you haven't had the privilege of checking out the Glow Audio Amp One, do yourself and favor and arrange to do so.  I know this amp doesn't get a lot of mileage here on Head-Fi, and personally I think that is a shame.  It's an awesome product, offered at a pretty fair price-point considering it's sound quality.


In addition, the fact that it serves as a dedicated headphone amp, AND a high quality stereo amp for speakers, just takes its value that much further, and that's further indeed.  All you need is a good source and some quality speakers, and you've got a full blown audio setup for well under 2k all told.  (The Amp One itself is currently running $840 plus $40 CONUS, and that includes the standalone DAC and even a pair of AKG M80 Mk II or Pioneer SE-A1000 headphones they are throwing in as well).


To get more info, you can start with my review, linked above, and feel free to write Patrick as he's really great about responding to questions and concerns fairly quickly and comprehensively.



Some Photos


As I still haven't gotten the new model yet, here are just some photos of my original model.  The new model keeps basically the same look, with an additional RCA input as mentioned and a Hi/Lo Gain switch.  (I believe the "glowing light" around the volume knob which softly changes colors, and is pretty cool, now has an on/off switch).


Sorry I suck so bad at taking photos.  The DAC picture is from the Glow site, as I don't own it (yet).  I'll post new photos as soon as I get my new Amp One.













Edited by Kouzelna - 9/23/13 at 2:37am
post #2 of 13

OK, what am I missing here?  No one else is interested in this amp?  Anyone else have one or heard one at a meet or show of some type?


It still seems quite intriguing to me, especially with some issues addressed and an external USB DAC.  Is this a very high value option for those of us who would like to add a tube amp for a different sound signature once in a while?  Anyone compare this to a Panam or Crack?...or any other fairly well known tube amp in the entry to middle range?


Just thought I would ping the Head-Fi community and see if anyone besides Kouzelna here has given this thing a try.

post #3 of 13
Thread Starter 

Hey Greggo, I'm sure hoping others will get some experience and this amp will start getting the traction it deserves.  Glow Audio's done a lot to offer an alternative to Woo and match their quality in this price range.  I've heard quite a few entry and mid-level tube amps and SS amps, and though by no means any kind of exhaustive number, I can say that the Glow is a whole different world from those.  I had issues with all the other amps I'd heard; they were good, but flawed in major ways.  The Glow is the first and so far only amp I've heard in any kind of affordable price range that truly sounds flawless to my ears, and doesn't leave me wanting something more.


I would very much like to have the opportunity to compare it to a Woo, or something else in the sub 1k and preferably $400 - 600 price range in the future.  But so far, it's the best and I keep hoping more and more people will have a chance to hear it and comment on it, post comparisons, etc.

post #4 of 13

Hey, I'm new here and I've spent most of the last few days reading and learning from you guys at Head-Fi. Thanks, lots of collective knowledge and information!


And, browsing through Head-Fi I came across the two threads on the Amp Glow One, an amp that I've owned for several years. It powers my Rogers LS/35A speakers in my bedroom. I love the sound! I never used the Glow Amp One for headphones, but having recently decided to set up a headphone system—after many years of being away from them—I plugged in my new Sennheiser Momentums and was disappointed by the hum and poor fit of the ¼-inch headphone jack. It's only through reading the threads on this forum that I learned that I need an O-ring and a cable that increases the impedance of my phones. Thanks, good information!


I am writing Len at HRS Records to ask about modifying my Glow Amp One headphone jack. Hopefully, he is still there and they still perform the work. I will keep you posted.

post #5 of 13
Thread Starter 

Hey Visualista,


Sorry for the late reply.  Sounds like you own the original '08 / '09 model, which had some issues with the headphone jack.  I also owned that unit.  (I have the brand new one now).


Here are my suggestions:


1.  Yes, make sure you have the proper resistance cable to help match the headphones to the amp.  As I recall, that amp was designed to work best with 300-ohm headphones.  I had many pair at the time of various headphones, but the only one that had issues was (of course) my AKG K702s.  A simple 225-ohm resistance cable made for me by one of the Headphoneus Maximums guys solved my issue.


2.  Other cans had issues with the connection, and yes a simple 3 cent o-ring from Home Depot solved that issue.


3.  I had a hum issue for a while, but simply moved my amp to another location in my house to use a different socket, and problem was solved.


Finally, I'd suggest you write Patrick over at Glow and run the issue by him.  You can tell him what I said (David), and then just double check with him to identify your exact model and hear any suggestions he might recommend.


Good luck, and continue to have a blast with your amp.  It's no secret that I really love this amp.  I've been meaning to do a grand review of the latest model myself, but have just been swamped at work for months.  But keep your eyes peeled on my profile page, it will be coming in the next two weeks tops.




post #6 of 13

Hey Kouzelna,


Thank you for your reply. I spoke with Len at History of Recorded Sound and he confirmed that they service the Glow amps. He said replacing the headphone socket would cost $120 and it would remove most hum but not necessarily eliminate it because of the way it was wired. Since a dead silent background is important with headphones I decided that I would pursue a dedicated tube headphone amp (in the future) and be happy with the Glow as a speaker amp.


I am interested in your review of the current Glow Amp One and, specially, whether it sounds as good through headphones as it does through speakers. As a long-time tube amp enthusiast, I think EL84-based amps have a midrange to die for, and even more so in a single-ended pentode topology.

post #7 of 13
Thread Starter 

Well, what I can tell you right now, is that the new Glow sounds every bit as great with headphones as the old one, and even better.  And it has zero of the old problems, which is great.  Plus, they added the following common-sense features:


a.  A simple toggle switch for high/low gain headphones


b.  toggle switch for the volume light on/off


c.  a second set of inputs, so you can run two sources, with A/B toggle switch


d.  a bottom switch to choose between 120 / 220 voltages


e.  screws instead of magnets to hold down the tube cage, to keep it more secure.  (This annoyingly requires a special screwdriver from them, however, and is a real pain to use so I just keep it on).


Pretty nice!  


My review would've gone up much sooner, though as I said I was busy, and worse I've had a lot of problems getting my headphones to break-in and match up with the amp.  In the end, I realize my headphones aren't great.  I switched from the  K702 to the Q701 just to check it out.  In the end, I'm unhappy with it and will sell the Q next month and repurchase the K.  Then I'll update the review, which I'll do with the Q in a few days.


So stay tuned....

post #8 of 13

Hi Kouzelna


I just picked up a Glow One on audiogon and was thinking it was "broken" on account of the hum and static from the headphone output to AKG K240mkII. Totally newbius maximus here. I can see that these cans are spec'd at 55ohms definitely in need of "a proper resistance cable to help match the headphones to the amp.  ...that amp was designed to work best with 300-ohm headphones. "


Can you please explain in detail how and where you got the new cable? A quick google search and I could not readily find a vendor that sold something like this for the K240. Can you please detail a bit the steps for some of us completely new to the community here how to get "A simple 225-ohm resistance cable made for me by one of the Headphoneus Maximums" or "adding a quality resistance cable to my cans, as designed for me by Armaegis"?

post #9 of 13

It would still be cool to define how and where you got your adapters from, especially if they are higher quality. I was able to find this thread http://www.head-fi.org/t/601669/impedance-adapters-cables-explained-listed and just ordered one of these at 300ohm (starting out with the least expensive of options and will look at more expensive options if I'm not happy with the sound) http://www.ebay.com/itm/Etymotic-ER4P-to-ER4S-6-35-to-3-5mm-resistor-adaptor-/271644098644?pt=US_MP3_Player_Cables_Adapters&hash=item3f3f400054

post #10 of 13
Thread Starter 

It was from a member, Armaegis.  Here's his profile:




You can also head over to the Glow Audio site and write their support.  Patrick will probably answer you, and he's great for follow up and information about getting the best out of your Glow.  Good luck, and don't worry you'll get it sorted out.

post #11 of 13
I wrote to glow support three or four days ago but I hadn't heard back yet. Thankfully I referred to this thread and the advice. I've never encountered impedance issues with headphones previously specially I would've thought the EKG were pretty universal. Looking forward to receiving the impedance adapter asI was really looking forward to the headphone section of the glow, having heard that it was pretty amazing.

I have to agree with your assessment of the glow amp, the value being significantly high. More happy customers like yourself should spread the gospel. I had been looking to get into a quality SET and luckily stumbled onto some discussion comments on Amazon while shopping for a GemTune. Then I found the 'glowing' review at 6moons. I would echo the same comments that I read on Amazon, if you can find one of these used (matching the original under $500 price from a few years ago) it is an outrageously great value bargain. Great single ended triode amp and hopefully will soon be able to confirm a great headphone section.
post #12 of 13
I got a 300ohm resistor adapter but I see now you used a 225ohm cable for your AKG 702. Do you think I got too much resistance for AKG 240?
Also very curious, what speakers have you previously successfully paired with the Glow One?

For myself, I was thinking something from Zu hoping the Glow would satisfactorily drive the bass on larger albeit very efficient speakers. I am currently pairing with Pioneer SP-BS22-LR. Despite the 85db rating of those I have been pleasantly surprised by the sweet sound even if they cannot play super loud
post #13 of 13
Thread Starter 

Hey Crispin,


Glow sometimes takes a while to get back to you, because the replies will usually come from the one of the partners, Patrick, and he's constantly traveling to promote the amp, check on quality control, etc.  But he will get back to you I'm sure.  I'm sorry for the late reply myself, as I'm on holiday right now.


Impedance questions are above my pay grade, but there are a million guys here who can answer that.  Patrick can too, of course.  My best advice would be to try it and see.  I believe the older Glow that you're using was set for 300-ohm, so you'd want to bring the headphones up to around that.  But again, I really have no idea what I'm talking about, sorry.  I know that snapping the 225-ohm onto my K702 solved the problem for me.  The new Glow I have now doesn't have that problem anymore, and it includes a gain switch as well.  (Either setting is fine for my headphones so far). 


As for speakers, I'm in a quandary.  I live in Europe now, where everything is overpriced compared to the US.  It's really hard to shell out $400 ea. for some basic speakers that I know I could pick up used in the US for 25% of that.  However, transporting speakers would take an entire suitcase, and thus far on my trips home I've had other priorities.  One of these days...


I'd shoot for Glow's own speakers myself, or at least start there and then compare on this site, considering you have the budget for it.  Otherwise, I've been looking at Amazon's offerings, and found a lot of bookshelf speakers from Polk and Paradigm that seem to be pretty great.  I like the sound both of those companies aim for (emphasis on neutrality + extra treble, typically), so that's where I'd look first personally.  And you can pick up a used pair for $100 - 200 pretty easily there.


The best bet, again, would be to ask Patrick's recommendations, and then present those to the group here.  He always tells me the Glow is mainly meant for speakers, and from the reviews I've read I believe him, and am looking forward to having that opportunity one of these days.

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