Glow Audio Amp Two

Gigantic

A big, big love
I just picked up a Glow Audio Amp Two, a 15-watt, PTP, hand wired, push pull 12AX7 driven, EL84 driven integrated amp designed by deHavilland Audio's Kara Chaffee, but made in China. Given the mixed reviews on chi-fi products, I was optimistically skeptical, but the price point, reviews, my conversations with Glow Audio's principal and the 30-day, no questions guarantee swayed me. I placed the order weekend before last and 10 days later, it arrived, well packaged and double boxed via UPS. The unboxing was simple enough, it arrived fully assembled but for the separately packaged power cable; it was an easy matter to plug everything in and go.

first impressions:
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it's smol, but handsome! it's a little more half as wide as my rack amp, but at 17#s, it has significant heft for its size.

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I've no idea what iron is beneath the covers, but the chassis seems well laid out and sturdy. It shipped with 2 Shugang 12AX7 tubes and a quartet of Shugang EL84s. I first plugged it in from the pre-outs of my receiver, into a pair of Super Heresy clones and as to be expected, there was a considerable amount of gain mismatch between the Glow and my other power amp, an Emotiva Mini-X 100A diving a pair of Klipsch H700 Heresies, as well as the bookshelf speakers that were driven off of my receiver and my subwoofers, a pair of Velodyne VTX 10B's. With the bookshelf speakers unplugged and the subs and Emotiva attenuated, the sound of the amp was much better, if not a little muddy. putting the receiver in Pure Direct mode disabled the preamp coloration and it really came into focus. Immediately, the soundstage of the Super Heresies expanded. They're just 7 feet apart, but they seemed to fill the entire room. With the subwoofers turned off, the bass response seemed fuller; it almost makes the subs unnecessary when playing Boards of Canada's dub-inspired Aquarius, via a Pro-ject Debut Carbon, equipped with an Ortofon Blue cartridge and stylus. The SQ was a significant increase over my Marantz NR1604 receiver, which previously I had zero qualms with in regard to sound quality.

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Next, I thought I'd see how it sounded on its own, so I plugged in my Oppo BDP 83, spinning Beck's SACD release, Sea Change into the other input. Holy cow! every thing positive I've written about this amp is exponentially increased- while the sound was great with the AVR serving as a pre, on its own, it sounded like a veil had been lifted: high and mid range clarity, dynamics and bass response all seemed better, so much so that I'm entirely rethinking my approach to my system: a second set of Heresies seems superfluous, the Glow Audio Amp Two and the Super Heresy clones are really all I need for two channel listening. I'll likely get rid of the H700's, rotate one of my amps back to my bedroom studio, pick up an amp and speaker switcher and rearrange my subs & SH clones so they play with both the Amp Two for 2-channel and my AVR for home theater. This means I'll also need a DAC to better utilize my digital sources, but I was DAC curious already.



I didn't wait to play with a little tube rolling- I went back to my studio and dug into my stash of tubes- I only had a matched pair of JJ EL84's, so the power stage will have to wait, but I had a couple pair of 12AX7's. First up were a pair from Electro Harmonix: they were extremely mid-forward, a trait which combined with horn loaded speakers, were really too much. in addition to honky, shouty midrange, the bass seemed attenuated and the treble, shrill and thin; I couldn't get them out quickly enough! I put the OEM valve back in to reset my reference and in comparison, they seemed veiled, as if a blanket were laid over the speakers, (but still much better than the transistor AVR). The other pair I had were Groove Tube's 12AX-7 C Selects. I remember not liking them in my Fender Deluxe Reverb, but in the Amp Two, they were well balanced, bright, but not shrill, with ample bass and mama bear, just-right mid range. Next up, I've got a switcher on the way and a matched quad of JJ EL 84's en route. Does anyone have any other tube recs, either UK, USA or European made? (Russian tubes are out, although I'd consider soviet NOS from the former republics) All told, I'm pretty pleased with this purchase so far!
 
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Does anyone have any other tube recs, either UK, USA or European made?

Any major brand US or European tubes should be an improvement, but considering how expensive NOS tubes are these days, and the fact that no tubes are going to turn this amp into a McIntosh, I'd probably leave well enough alone unless you find some pulls. For example, a dilapidated console stereo could set you up with a full set of old stock tubes for this amp for nearly free if you choose the correct model.

If you insist to spend money.... Siemens EL84s, and Mullard, Amperex, or Telefunken ECC83.
 
Nice looking amp. JJ's are always my go to for signal tubes. They have the standard short plates with or without gold pins, long plates and the grid frames. Ive used them all except for the later. I tend to use them in most amps. I'm working on a SE amp that will be wired for a 6EU7, but I bought an adaptor to use 12AX7's too. I'll probably wind up trying another JJ. I haven't tried there EL84's yet though, but peaple.seem to like them. I'm using Sovtek EL84M's in a PP amp and like them.
 
Nice looking amp. JJ's are always my go to for signal tubes. They have the standard short plates with or without gold pins, long plates and the grid frames. Ive used them all except for the later. I tend to use them in most amps. I'm working on a SE amp that will be wired for a 6EU7, but I bought an adaptor to use 12AX7's too. I'll probably wind up trying another JJ. I haven't tried there EL84's yet though, but peaple.seem to like them. I'm using Sovtek EL84M's in a PP amp and like them.

I've got a matched quad of Rubytubes JJ EL34's on the way.
 
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Swapped the power tubes with a matched quad of Ruby Tubes JJ EL84CZ tubes. Imaging is crisp and the sound stage is vast. I’ve been burning it in in my recording studio, using a pair or KRK Rockit unpowered near field monitors and I’ve never heard those speakers sound better. They’re a far cry from my Super Heresy clones in my main listening space, but the sound from a pair of monitors on my recording desk, 3 feet apart and as far away, is remarkable. I’m very pleased with this purchase and I can’t believe how inexpensive it was.
 
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Curious. The Electro Harmonix 12ax7s that I hated with the stock Shugang power tubes, sound incredible with the JJ EL 84s. More midrange clarity and more bass. The GT’s had become a bit shouty in the midrange, lending a “hands around the mouth”
tone after an hour or two of play. None of that with the EH, they sound fantastic. That said, I ordered a matched pair of JJ ECC 803 S Gold Pin valves this morning to roll in.
 
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Without spending big on NOS tubes or resorting to Russian made valves, I may have reached the end of the road with tube rolling for the time being. I’ve installed a matched pair of JJ ECC 803 S Gold Pins.
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They’re an improvement over the Electro-Harmonix 12AX7’s, which were significantly better than the Groove Tubes they replaced, not to mention the stock Shugang tubes. Initial impressions are that the bass is fatter and overall, the sound is warmer, but detail doesn’t seem to be lacking. Imaging is also improved; if I close my eyes, I don’t hear the speakers as much as I hear the music radiating from an 8‘ proscenium in front of me. Overall, I’m beyond pleased with the purchase. I’m into it for quite a bit less than the list price on their website, including tube rolling and I think I’d be pleased if I’d paid twice as much. The sq is really good over a variety of sources, LP‘s Hi-Res streaming, SACDs and DVDs. I was pleased with the sound of my Marantz AVR, but the little Glow Audio Amp Two blows it away by a significant margin. Driving a pair of Super Heresy clones that I built last fall, the Amp Two will play louder than I can tolerate, with no discernible distortion that I can notice. Even with sources muted with the volume knob cranked, the Amp Two is dead silent and build quality is quite good. Looking at other amps in its price range, I find the competition looks pretty cheesy and their issues are well documented. I can’t say at this point, the Hlow Audio Amp Two won’t develop similar trouble, but I’ve had a few brief conversations with long term owners who reported still being pleased after 8-10 years of ownership. I’m tempted to send it to @StepheK and have her give it one of her deep inspections, but right now, I don’t want to part with it and go back to transistors. All I think about at work is getting home and listening to music. I’m very content with this purchase.
 
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I've been a fan of the JJ signal tubes for some time. I haven't used one yet I didn't like. I can't say the same for EH. The one EH signal tube I like is the 6922 though. I tried a few others including JJ's and wound up putting the EH's back into my phono preamp.
 
I bought the EH for one of my guitar amps a few years ago, but I’m pretty sure I replaced them with JJ‘s. They didn’t sound bad, they actually have some positive attributes, but I thing unlike the JJ‘s better, even though I’m only 90 minutes into them.
 
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Curious. The Electro Harmonix 12ax7s that I hated with the stock Shugang power tubes, sound incredible with the JJ EL 84s. .

its funny how many surprises there are around these little turns we take.

do you mean jjecc803s? i never heard of ecc833s., but u mentioned them a coupla times, and im usually a good few steps behind. ive used jj e83cc, 12at7, 12au7 and EL34 and been happy with all of em.

and, hey, if u want old stock, gently used--why not buy some tubes off barter town? @byoungman1 may have some sylvania (baldwin-labeled) 12ax7s left.

seems like u picked up a nice piece a gear there. happy listening!
 
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I've used JJ 5751's and they have been great where I needed a bit less gain than a 12AX7.

@Gigantic - can you take a close up picture of the inside. There may be some opportunities to upgrade a few caps. I can't tell from your previous under hood pic.
 
I've been a fan of the JJ signal tubes for some time. I haven't used one yet I didn't like. I can't say the same for EH. The one EH signal tube I like is the 6922 though. I tried a few others including JJ's and wound up putting the EH's back into my phono preamp.
i had some EH EF86 in my phono. dead quiet and inoffensive.
 
I've used JJ 5751's and they have been great where I needed a bit less gain than a 12AX7.

@Gigantic - can you take a close up picture of the inside. There may be some opportunities to upgrade a few caps. I can't tell from your previous under hood pic.
I'll see what I can do. I pulled those under hood shots from the web and haven't pulled it myself. I've no doubt that there are multiple opportunities for cap upgrades, even if I don't pull a @CohibaJoe and do all Mundorf Supreme...
 
trick with a 5751 in a feedback loop is that its probably not really going to make an obvious difference. Less open loop gain makes for less feedback, and the end result tends to be that the same input signal gives the same output signal. It just tends to measure worse because of the reduced feedback.

I can't quite make out the values from pics but I definitely see a green and a yellow wire coming forward from the speaker jacks to the 12ax7 sockets, and thats what I'd expect to see for a global feedback design. Single 12ax7 per side would probably give me about a 50/50 chance of being right on the driver design but it sure looks like coupling caps on 1 and 3. That would mean split load inverter, and it looks like the feedback comes in on 8. I don't see a third coupling cap in there, and I think I can make out a jumper from 6 to 2 which implies direct coupling from voltage amp to inverter. Output stage looks like wires on 7 and 9 on the EL84 sockets to the transformer, so ultralinear.

Its probably not far off a Dyna ST-35 in design, just with a 12ax7 instead of a 7247 tube. If you're going to be inspired by a design, there are vastly worse choices to pick from. Also honestly you sort of have to work at screwing up an EL84 push-pull amp so badly that it doesn't sound good.

my 2 cents, if I was going to go poking in here for upgrade opportunities, it would probably involve losing what looks like 1960s carbon composition resistors. Especially any in the plate or cathode circuits. They tend to drift and be noisy.
 
If I modded anything on this amp, I'd likely have someone else do the work. While I'm certainly curious about learning and am adept enough with a soldering iron from building passive crossover networks and wiring guitars, I also have to manage my time consuming hobbies... currently, I have four guitars to build, 3 or four more to complete finishes on, another restoration to complete; I have two loudspeaker projects underway; I have a motorcycle to get running; Band practice; I also volunteer doing trail maintenance and trail building in several parks in my city and try to carve out a couple 20 mile mountain bike rides each week, on top of putting in 45-50 hours a week at my 9-5 job. At the moment, I can't afford a new hobby without giving up an old one...
 
I pulled those under hood shots from the web and haven't pulled it myself.

I can't quite make out the values from pics but I definitely see a green and a yellow wire coming forward from the speaker jacks to the 12ax7 sockets, and . . .
??? I've looked through this thread and I don't see any pics of the interior wiring. Could someone please point me to them? Or post them?
 
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