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December 2013
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World Premiere!
GLOW Audio Two Integrated EL84 Tube Amplifier... Now With DAC!
The Sweetness of the GLOW Audio Two $1508... How do you like your sugar?
Review By A. Colin Flood


Glow Audio Two Integrated EL84 Tube Amplifier  The high gloss white GLOW Audio Amp Two is a charming EL84 integrated tube amplifier. It also comes in gloss black as well. With modern looks, tube cage and the tiny DAC included, it is a very good starting point for building a serious sound system around high efficiency loudspeakers. Have laptop or other digital source already? Just add GLOW Amp Two and you are ready for tweaking audiophile speakers. The village of the GLOW Amp Two is populated with two driver and four EL84 power tubes. The Amp Two requires four power tubes because it is a push-pull design. The signal for each channel splits with each tube handling half the signal. GLOW uses Beijing EL84s because they are the best available in China. The EL84 (also 6BQ5 in North America) tube is popular in amplifiers. It was intended as an inexpensive alternative to larger EL34, 6L6, and KT66 power tubes. In the late 1950s, popular Dynaco, Eico, Mullard and Fisher manufacturers were using them. Popular guitar amplifier maker Vox based incredibly popular stable based around the EL84. A slightly higher power version, the 7189 and 7189A, became the standard power tube in Scott tube audio amplifiers.

In this push/pull configuration, GLOW avoids the graininess that seems common among such amplifiers in this price range, for example, with EL34 tubes. Most of the low-powered, vintage tube integrated and power amplifiers from the 70s are an incredible value for tweaking audiophiles today. Pick them up cheap, get them refurbished with new engines and sidewalls, and then drive any high-efficiency loudspeaker with pride. After drooling over Don Garber’s 1.5 watt X-shaped Fi amplifier, I was also smitten this year by the new Nelson Pass, low-powered SIT-2 with its revolutionary Static Induction Transistors. That solid-state amplifier provided a huge 10 watts, which is easily enough power for mid and upper range horns in my Big Ole Horn loudspeakers.


Tempting Value
The introductory GLOW Amp Two price includes (at least for the time being) the new GLOW Audio DAC 1.3. The Garber costs about a grand, the SIT-2 five times that much. Each amplifier was visually and sonically unique and different. Yet, of the three amplifiers, the GLOW Amp Two with its thumb-size EL84s is rated the most powerful! Wattage ratings sure don’t tell how an amplifier is going to sound though. Not on Big Ole Horn loudspeakers. Not on conventional cones either. I heard the charming little GLOW EL84 integrated amplifier on four different systems. Twice it was up against the incredible new SIT amplifier design from the God of the monster amplifiers, Nelson Pass. The modern white GLOW amplifier - with its sweet sound, thoughtful features and excellent value - really held its own! At over 20 pounds, the amp is quite heavy as a result, despite its compact size.


Tong But Tang Is Okay
I asked questions, dozens of questions, of chief cook and bottle-washer Patrick Tang. I know Tang from several AXPONA trade shows. First, I asked him how to properly pronounce his name. He said due to a historical happenstance beyond his control, his name is spelled "Tang" but it is correctly pronounced "Tong." Seems that when the British became active in China their contacts were primarily in the south, and they developed a Romanization of the language based on the Cantonese dialect. "So the character for my name was Romanized as "TANG," he says, "but it is pronounced "TONG" where my family comes from, which is the Shanghai area.  This is all too complicated for the average non-Chinese, and rather than go through my life explaining to people when they say "Tang" instead of "Tong" that it is really "Tong", I simply pronounce my name "Tang."

Tang heard his first stereo in Hong Kong when his dad bought a German record player that had two detachable speakers. "I was in the second grade. My brother just bought a Beatles album, in stereo. I was blown away by the recreation of the soundstage from this little stereo. That is how it all started. My love for music was reinforced when I went to live with my grandmother in Gulfport, Mississippi, and she took me to hear a New Orleans style jazz band playing by the pool at a nearby hotel. I was 8 years old. I stood there transfixed right in front of the drummer soaking it all in, it was magic. He was working the snare with some brushes, the horns were blowing. Another "a-ha" moment."

"I made money in high school buying trade ins from the local hi-fi store in Nashville TN and putting together systems for friends. I did a lively business buying low and selling high, got to hear and audition all kinds of gear, and learned what people liked and didn't like, and why. Later when I lived in Taiwan teaching English, I worked with a local Chinese audio guy to develop a line of speakers based on small satellites and using subs. There were import restrictions on finished goods in Taiwan at the time, and there was a lively business importing or manufacturing raw drivers and copying the best designs available at the time. This was 1984, and the notion of using a dual voice coil sub to augment the bass for smallish speakers was pretty new. Everything I learned from buying and selling ARs and KLHs and JBLs and Linn and KEF speakers, I put into those designs. We developed a beautiful line of speakers and subs, but this was before the internet, and I had no idea how to market or export them. Being a poor student, I didn't have the money to start a business of that nature, and I picked a business partner who was just as poor as I was. I ended up abandoning the venture and going to law school. I still have one surviving pair of those bookshelf speakers that I developed back in 1984, and even today they still sound excellent!"


Two Better Than One
Glow Audio Two Integrated EL84 Tube AmplifierThe Amp Two is an integrated amplifier. There are only two input sources. A tiny silver toggle on the right side of the amplifier switches them. The silver volume pot on the brushed metal front plate modulates the gain. Tang says they are currently working on new models, including a push-pull offering 30 watts per channel. They hope to introduce the new models next year. Although he says their amplifiers are "designed to provide tight low end bass with most speakers," GLOW makes a Sub One to augment their tube amplifiers. The ideal crossover point he says is more dependent on the speakers chosen and the room acoustics, not the amplifier.

The glossy white of the sample model was a refreshing change to the row of black boxes that adorn the audio rack. Plus, the tubes light up from the bottom with a blue GLOW, while a pale blue ring around the Volume knob lets you know the amplifier is on, even in daylight. Tang says he "didn't want to use a blaring LED," so they went with a subtle blue ring. In addition, there is a glowing red Power toggle on the right side. The blue back-light on the tubes toggles on or off with a rocker switch, also on the right side. With four sides occupied, only the flat bottom and the left side are bare. The visual effect is charming and intentional. It gives the Amp Two an uncluttered and simple Apple look. I love the clean white Apple looks of this amplifier with its tubes glowing. In addition to high gloss white, high gloss black is available. (Tang asked "what other colors would you like to see?")

"About 40% of our customers are non-audiophiles (women, architects, musicians, etc.)," Tang said, "and they have a design aesthetic that favors simplicity. We wanted to avoid the "bristling with buttons" look of so many audio components." Plus, the Amp Two currently ships with a modest DAC, the size of a cigarette pack. It is perfect for the electronic conversion juncture between iPod, iPad and laptop to the Amp Two.


Choosing Charm
Why not use a more unique tube than a fairly common classic like the EL84? Doesn't this put your amp against a lot of other amps with the same tube?

"We wanted a sound signature similar to the Amp One; a family resemblance, if you will. We chose the EL84 power tube because of its inherent sound qualities. This means that at 15 watts per channel, our amplifier is not as powerful as the EL34 driven push-pull amps that are so common today. But the EL34 push-pull amps typically sound quite aggressive and grainy. We chose instead to use the EL84, because of its inherently sweet sound, gorgeous and detailed mid-range, and superior high frequency capabilities."

To improve the bass and treble, Tang said there are a number of decisions that have to be made in designing such an amplifier at this price point, for instance how much negative feedback is sufficient to provide adequate bass response with lower impedance speakers, how much money should be put into the transformers, etc. The Amp Two design is nothing radical or novel. It is a push-pull amp. The art is in selecting the right components for the circuit design that has been chosen, and "tuning" the amp accordingly, based on the characteristics of the particular components chosen. It takes a lot of knowledge and judgment to make those critical decisions.

"There is a huge subjective aspect to this," Tang says, "and we spend a lot of time voicing our gear. In the case of the Amp Two, it took several years to get it the way we wanted it to sound. Typically, we will survey what is out there now, and what has been made before (the classic Eico, Fisher, and Dynaco amplifiers for instance), and settle on the several amps that we find to be the best sounding. Then we figure out what it is that makes them sound the best. We determined early on that performance and price are not that closely correlated. In other words, there are some amplifiers under $2,500 that sound as good or better than amps that cost over $5,000. We then turned it over to our engineers to build prototypes based on the criteria we selected. There is a lot of back and forth at this stage, as the engineers attempt to adjust the sound."


Designing Original Amp One
In determining Tang’s criteria for a new amplifier, Tang establishes the basic parameters before deciding on a design: power, affordability, headphone capable, DAC, easy-to-drive, self-biasing, newbie friendly, etcetera? He then decides what design, based on his experience, best meets those criteria. Once Tang determined the basic design parameters, he worked with his engineers to get the best sound possible given those constraints.

Because it was their first effort, designing the Amp One in 2007 was a much more involved process. Before deciding what to build, Tang took nearly two years listening to all manner of amps. He listened to classic Scott, Dynaco, McIntosh, JoLida, nOrh, Consonance, Spark, and other Asian offerings. Then he decided to get various custom samples from Chinese manufacturers interested in manufacturing amps for him. Tang got all manner of amps; 300b SETS, EL34 push pulls, you name it. Then he took considerable time auditioning them, all the while communicating with the engineers to determine whether they were simply copying another amplifier, or thoughtfully selecting circuit designs and components.

Tang has relatives in China who manufacture electronics, and although they are not involved in audio, they assisted him in making sure he had the right contacts, and were able to get him the best pricing on parts and components. The various amplifier manufacturers Tang contacted were told to give him the best, cost is no object, "kitchen sink" samples. "Some of them were monsters that weighed 50 pounds," he says. "The ones who got it right, were then told to make the amplifiers smaller, with hand wound transformers, quality components, and point-to-point wiring. And hardest of all, the amplifier had to be very affordable, which in 2007 dollars meant a retail price point of around $500. Via this process of elimination, was born the Amp One." Despite this process, there were speed bumps along the way. One manufacturer sold out to another company in the middle of production. "We had to reject all of the amps. The new company made unauthorized changes that were unacceptable. Quality control is our primary focus." According to Tang, the GLOW Amp One has been a huge success, and is now in its 4th version. But the company began looking to expand its amp offerings and in 2010, started focusing on an Amp Two.


Giving Birth To The Amp Two
When Tang turned his attention to the design of the more powerful Amp Two, he knew he needed to go with a push-pull (PP) design. A PP design is more efficient than a single-ended "Class A" amplifier. The output power is higher too. But Tang was not satisfied with most PP amps he tested. He discussed some of the issues with Kara E. Chaffee, Chief Engineer & Manufacturing at deHavilland Electric (Vancouver, Washington). She was of the same mind when it came to evaluating the shortcomings of many PP offerings from China. Tang settled on a particular design from a company who sent him a very nice sample. Build quality was excellent, and their engineers were easy to work with, and knew what they were doing. Yet he said that something was still not right; the pre-production samples still did not match the sound quality of some of the classic American and European PP amps. He needed someone, he said, "who understood what made the classic US and Euro PP amps sound so much tighter and more robust than the modern offerings from Asia.


Bring in American Expertise
"To be perfectly honest," Tang said, "our engineers were not able to get the amplifier sounding like we wanted, despite their best efforts. It still had too much of the graininess and upper-mid aggressiveness that many modern day push-pull amps exhibit. We wanted an amplifier that performed as smoothly and sounded as lovely as our Amp One. This is difficult to do with a push-pull design. That's why we brought in Chaffee as a consultant to assist our engineers in finalizing the design." DeHavilland makes award winning single ended triode amplifiers and preamplifiers, though nothing as economical, low powered, small or as charming as the GLOW Amp Two. (Aries 845-G SE). "We enlisted the assistance of Chaffee to help us perfect the sound.  She worked her magic; the Amp Two has a smoothness that is uncharacteristic for a push-pull amp. And it produces substantially more power than our GLOW Amp One."

Tang met Chaffee when Tang was rolling out the Amp One, through a mutual friend, Randy Bankert, recently deceased founder of Sonist Audio. Chaffee is one of those rare individuals who knows her stuff, and is willing to help a friend in need. She offered several suggestions to improve the Amp One; Tang kept in touch. To improve the pre-production samples, Tang reached out to Chaffee.  "She graciously agreed to consult with me; she made a number of modifications to our pre-production samples that made a huge difference- tighter imaging, improved bass, and a non-fatiguing presentation reminiscent of our acclaimed Amp One."

The Amp Two is thus not a "copy" in the sense that it is not a re-badged or re-branded product; it is completely new from the ground up. A lot of amplifier manufacturers cut corners, using off-the-shelf transformers and printed circuit boards to save money. The transformers are critical of course. Valve (tube) amplifiers usually use an output transformer to match the high load impedance requirement of the tubes (several kOhms) to a low impedance speaker. And printed circuit boards can degrade the sound quality. "This is apparently something Tannoy engineers concluded after considerable testing as early as 1985," Tang said, "when Tannoy quit utilizing PCBs in their speaker components." Tang plans other amplifiers. Another single-ended and another push/pull amplifier are on the drawing boards. They are also discussing the possibility of developing monoblocks and a phono preamp, but that is further down the road. And, he says they have some interesting new speakers to be unveiled before long.


Sizing Transformers
My own personal rule of thumb is the size of the transformer should be as large as the output tubes. Tang agrees this is a good rule of thumb. For these amplifiers, the quality of the transformers is most important. Scrimping on the transformers is common in this price range, but GLOW uses well matched, hand wound transformers. The transformer changes the voltage of an alternating current in one circuit to a different voltage in a second circuit. An ideal transformer would have no energy loss, and would be 100% efficient. In reality, energy is dissipated in the windings, core, and surrounding structures. The transformers are typically the most expensive component in an amplifier. As a general rule, larger and heavier transformers are more efficient and better able to produce sufficient power throughout the audible range. Good bass output requires good transformers. GLOW designed their transformers designed specifically for their amplifiers. "We believe they are the best possible transformers we could build," Tang said, "at the under $2000 price point of the amplifier."

Ultimately, it is the audible performance of the amplifier that reveals whether the transformers are properly designed and matched. "I am aware of a budget push-pull EL84 amplifier that weighs about a third as much as our amp," he said, "and sells for about half the price. Unlike most amps in that range, it is well designed and sounds quite nice, given its price, but it is lacking in the lower bass, and the amplifier's distortion increases considerably at its limits. The budget amplifier might be fine for casual listening, or with unchallenging source material. But the limits resulting from the use of cheaper transformers means it cannot perform as well as an amplifier with more expensive, better matched transformers."

Tube amplifiers are challenged by the impedance of the woofer, what can amplifier designers do to overcome that challenge?

"Judicious use of negative feedback helps to address the flabby bass syndrome common to zero negative feedback designs," he said. "The trick of course is to minimize reliance on negative feedback for this purpose, using just enough to provide sufficient low-end control, without affecting the overall sound."


Glow Audio Two Integrated EL84 Tube AmplifierThe gold RCA connectors on the back are close together, but easy enough to reach. There is a curved, semi-circle white tube cage, with perforated holes, sturdy enough for a cat to walk on, that completely protects, covers and hides the handful of tubes. Plus, the cage snaps in sufficiently tight enough to dissuade child’s fingers. The amplifiers are built in Shenzhen, which is located in Southern China. It is near Guangzhou (Canton), the closest major city. Shenzhen under Deng Xiao-ping was designated a "special economic zone" in order to attract foreign investment. It is a now mega-city with some world-class architecture and five-star hotels, Tang says, "and is not just a smoky manufacturing center."

He recommends 50 hours to break-in the amplifier, though I did not notice any significant difference after warm-up. He says "one might notice an increase in the smoothness in the sound beyond 50 hours." Replacement tubes are not a problem. GLOW has a stock of replacement Beijing EL84/6P14 in matched sets, as well as the driver tubes for the Amp One and Amp Two, and will be posting pricing and availability of the tubes online soon. Although pricing is not yet finally determined, Tang expects tube prices will be competitive with other tube suppliers.

Tang lives in Hercules, California, a sleepy little bayside town 25 miles from San Francisco, 20 miles from Napa and the wine country, and 10 miles from Berkeley. He has a small number of retail dealers. Orders are mailed out within three business days, "but if there are intervening holidays, or if we are simply very busy, then it may take up to five business days." GLOW is at most audio trade shows and will likely be at CES (January). GLOW offers a full, money back 30-day trial period; "so far no customer has sent an Amp Two back!"

GLOW sells amps to customers all over the world. Tang notes, "That is the one of the joys of this business. I get questions from folks in Germany or Finland or Singapore or South Africa, and sometimes we talk about where they are from, and they will send pictures of their part of the world. When they purchase an amp or some of our speakers, it is nice to know that someone so far away is enjoying our products. The world is a big place, and I would never otherwise know about half these places. But the best sale was when we got a customer from Hercules, this little coastal town in California with barely 20,000 residents, a little pin prick on the map, and the same town I live in. And I have no idea who this bloke is. With 7 billion people on the planet, what are the chances of that happening?"



Sub-bass (10Hz - 60Hz)

Mid-bass (80Hz - 200Hz)

Midrange (200Hz - 3,000Hz)

High Frequencies (3,000Hz On Up)



Inner Resolution

Soundscape Width Front

Soundscape Width Rear  
Soundscape Depth Behind Speakers

Soundscape Extension Into Room


Fit And Finish

Self Noise

Value For The Money

On the four different systems I auditioned the charming GLOW EL84 integrated amplifier on, it was always enjoyable listening.

Incredible Beginner Bargain
Glow Audio Two Integrated EL84 Tube AmplifierOn my Big Ole Horn loudspeakers and three other systems, the GLOW Two was a charming sounding and cute looking, lovable little amplifier! Tone was tube-type excellent on above average efficiency loudspeakers. It could not push out the deep sub-bass and certainly did not have the oomph for thick mid-bass either. Midrange and high-frequencies however were tube-type delicate. Attack is swift, but given the paucity of its watts, the Decay did not linger. Tubes excel at the details of inner resolution and this charmer had them on Big Ole Horn loudspeakers, but not on traditional 4 Ohm cone towers. Therefore, soundscape categories were average unless like my Big Ole Horn loudspeakers, the speakers were over 20 feet apart. The tube weakness extends to Imaging also. The GLOW Two images the singer just fine, but other instruments take a back seat. I loved the white color, size, packaging and tube cage of this amplifier, so I bumped up Fit and Finish to four Blue Notes. Self Noise was fine – did not notice any sounds from the amplifier.

Although my Blue Note scores seem harsh, this is an excellent little amplifier for very efficient loud speakers, like single drivers and Big Ole Horns. It is a very good value for the money and a great starter amplifier for beginners. Just add laptop. In my own category, enjoyment, I must award this amplifier four Blue Notes also. It may not be the last word in tube amplifier power for most cone speakers, but this is a sweet, enjoyable amplifier at a very attractive price.

As of this writing, while the Philippines recover from a super-typhoon, GLOW is offering a pair of bookshelf speakers with their Amp Two! Got a source? Simply add their combo and you have yourself a sweet little system with many tweaking audiophile qualities. Hard to beat that value.



Type: Vacuum tube stereo integrated amplifier with USB DAC
Tube Compliment: Two 12AX7 and four EL84
Frequency Response: 10 Hz to 85 kHz (-3dB)
USB Decoder: (with optional GLOW Audio DAC 1.3) 16-bit 2704
Input: Two stereo sets of RCA
Input Sensitivity: 1.1 Volt
Input Impedance: 100 kOhms
Output Power: 15 wpc, two channels
Output Impedance: 4 or 8 Ohms
Output: Two sets of speaker binding posts
T.H.D: <0.3% (5W)
SNR: >85dB
Dimensions: 10.63" X 11.02" X 5.9" (DxWxH)
Weight: 19.8lbs.
Color Options: Gloss black and gloss white
Price: $1508


Company Information
GLOW Audio
P.O. Box 5271
Hercules, CA 94547

E-mail: info@GLOW-audio.com
Website: www.GLOW-Audio.com













































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