Hephaestus Audio

HMA-1000 Monoblock Amplifiers

List Price $4,900 per pair


William Schuchard

Hephaestus Audio dives into the audio marketplace with it's first product, the HMA-1000, a 1000 watt class D monoblock amplifier. When asked to review these amplifiers I asked; “Who?”. I had to look them up. That' s not that unusual around Stereomojo headquarters since, like this, we do so many world's first reviews. I don't know how our publisher achieves that, but it sure is exciting. Bill, a large part of the credt goes to our readers who write to us from all around the world telling us about promising new products and companies that we should contact. We actually do read and respond to our loyal readers. As you know, we consider them a part of our team - publisher

Joey White, the designer, is no newcomer to the audio scene and completely designed the amplifier and power supply to his exact wishes. I asked Joey about his background;
“I have been designing audio amplifiers, both successfully and unsuccessfully, ever since I was a kid. I have a formal education in physics and electrical engineering, but when it comes down to it, pretty much everything I know about amplifier design I have learned on my own. A love for music has certainly motivated me, but also a love for simple and elegant circuitry. I have known for quite some time that I would design amplifiers for a living and ultimately build a company around it.”

He also said he did a stint at Ashley Audio, a name that would be familiar to musicians and audio engineers. In business now for 35 years, they make amplifiers and signal processors used in commercial sound reinforcement as well as recording studios.

I followed up by asking him how he got from there to Hephaestus Audio;

“Prior to entering the audio industry, I had the great fortune of spending some time with terawatt pulsed power. This taught me a great deal about effective means to deal with EMI. My crash course began when one of my systems suddenly failed after a two-terawatt Z-pinch was fired”.

He went on to say his design philosophy is to be simple, both electronically and aesthetically with every element complimentary. He believes that simple designs just “sound better” with the added qualities of robustness, even when being abused, resistant to aging and environmental changes.

I had to ask him about the company name “Hephaestus”;

“I love Greek, Norse and Arthurian mythology and enjoy telling the stories to my oldest son. As an engineer, I was naturally drawn to the Olympian, Hephaestus, because of his fantastic creations for gods and heroes, such as Zeus' thunderbolts, Hades' cap of invisibility, Poseidon's trident, Achilles' shield, and some of the first robots: golden handmaidens, bronze bulls, and the giant Talos - the list goes on. I knew well before I formed Hephaestus Audio that I just had to name my future audio company in honor of this legendary craftsman. Plus, he married Aphrodite, despite being quite homely, and sometimes I feel lucky like that with my wife.”

Yes Joey, I know the feeling!

In keeping with his stated design philosophy, this is not another shiny, expensive wrapper of an existing OEM class D amplifier. The utilitarian chassis with simple black matte finish and anvil logo encase carefully crafted custom high tech internals.


A note, Class D’s are exceptionally good at bass. Many find them excellent for powering the low end of bi-ampable speakers. These would certainly fill that role admirably. It’s the treble region that causes problems with extension adding a dry, flinty character.

Stereomojo has been a leader in exploring and evaluating Class D amplification. Several years ago we did the first blind test of the burgeoning technology with our “Great Digital Amp Shootout” that was hailed internationally. We assembled eleven different amplifiers and compared them to each other in front of a five member panel who could not see and did not know which amps were being played.

We have also reviewed several class D amps from Halcro, Dolan, Kingrex (Tripath) and just recently the Spectron Musician II SE Mk 2 to name a few. We have even reviewed speakers with built in switching amps from AV123, Salagar and others as well.

As a reminder, Class D amplifiers are essentially switching amplifiers in which the switching mode of transistors is used to regulate the power creating a much more efficient way to amplify. They are not really “digital”, though that description is widely used. There has been a lot of interest in class D amplification lately and many seem to have already made up their minds.

Having heard a few class D amplifiers, I was biased to expect heightened detail and focus, lean treble, and a lack of refinement from the Hephas. I was wrong.
One should be aware that just like class A or any other methodology, everything matters including implementation, materials, and execution. Just as not all class A amps sound the same, neither do all of the class D amps.

Continuing the simplicity theme, the circuit was intentionally kept simple and the layout was painstakingly configured for the most direct path. There are no LEDs or even a power switch. They are meant to be left on at all times. Good thing they are efficient. They only draw XXX watts at idle and produce almost no heat, something our publisher would appreciate since he lives in Florida. It may be an important factor for you if you have a very small room that can heat up quickly.

Joey mentions that the added efforts and complexity used to take amplifiers to the n'th degree can cause more harm than good. As an amateur speaker designer, I found that there is some truth to that. One needs to know where to draw the line.


Each monoblock amplifier is the same size as a Harry Potter hardcover book. They are smaller than my modified Lite Audio DAC AM from Pacific Valve. They don't come with feet or power cords as it is assumed that the customer would want to use their own. One thing we have learned in our extensive experience with D class amps is that they benefit greatly from better power cables and isolation from vibration and resonance.

I used four pieces of 1” x 3/4” x 1/4” sorbothane for each amplifier's feet. Without them, you could feel vibrations in the chassis from the rack. Joey mentioned that the isolation cones from PartsExpress work surprisingly well with the Hephas but I did not try them. I used a Volex 17604 power cord for each monoblock and never felt the need to tweak or change them out.


Hephaestus Audio boasts the following differentiators from their competitors;

Lowest component count for switching amplifier plus switching supply
Highest total system efficiency (85% from ac inlet to speaker output)
Highest power density for switching amplifier plus switching supply (0.5W/cm^3)
Noise floor comparable to that of the best linear amplifiers (119dB SNR unweighted)

Hephaestus also boasts the following that some of their competitors also have although none have this complete set of commonalities;

Load independent frequency response (+0.0dB/-0.5dB 20Hz-20kHz)
Valve-like distortion characteristic (monotonic rise with level)
Excellent clipping behavior (no overhang, or "sticking", following clipping)

The Hephas come in several different connector options

Neutrik gold plated XLR or gold plated RCA inputs
Neutrik gold plated binding posts or Speakon connectors
Neutrik PowerCon or IEC AC power inle

The Hephas were nicely presented with a wrap of fine blue cloth. Inside one of the boxes was a CD he sends out with each pair of monoblocks. In my case it was “It Could Be Verse” by the Red Blumeneau Trio. It's a decent recording of some great music that should span musical tastes. I will be sending a copy to our publisher for a full music review.


My review sample came with RCA inputs, binding posts, and an IEC power inlet. Unpacking the boxes and installing the amplifiers was simple; the boxes were small, the amplifiers were light, and there was plenty of space to work in the wide open cavern left by my reference Forte Model 5 amplifier. When installed, the Hephas looked like two little engines that could. Combined with the simple no frills utilitarian logo, I found the only downside to these amplifiers before I even turned them on. Ego. I like to look at big hefty shiny amplifiers. Over the years, they have typically but not always been synonymous with big smooth effortless sound. They are also nice to look at while listening. I was humbled to realize this about myself and flipped on the music. I quickly left the room and let an entire CD play for a quick break in. I started listening after only an hour of play.





The Hepha monoblocks sound decidedly like the Goldmund JOB circuit amplifiers in terms of delicacy and openness but with a big fat bottom end and loads of brute force power when required. The closest thing I have in house is a Xindak XA6950 class A integrated amplifier. Joey wasn't surprised at how close the HMA-1000 sounded to a class A amplifier and quoted; “The comparison between a linear class-A amplifier and my amplifier is more appropriate than you may think. If you measure THD+N versus amplitude, there is a gradual rise with level. Also, an FFT reveals primarily low-order harmonics. These are characteristics shared with some of the better class-A amplifiers and the resulting sound is smooth and natural.” I still don't get it Joey but you can't argue with the sound.

The Hephas sound effortless, powerful, and transparent. There is a sense of ease and subtle detail. The details don't jump out at you yet you just hear more of what's going on. I was consistently hearing things I had never noticed and popping in headphones to verify. The highs are delicate and airy with a huge sense of space. The soundstage is taller and wider and surprisingly deeper than I am used to. Music in the foreground was not only a little closer than I expected but simultaneously the music in the background seemed further away than usual. Typically, I have found amplifiers to sound either forward or recessed but having both shows the delicate balance it struck. I attribute this to the amplifier's ability to delineate the subtle lower level detail that sets up the space. String instruments not only had an added sense of air about them but some midrange bloom. Getting midrange bloom from a class D amplifier just goes to show that they are not all the same. One main striking aspect of the Hephas is it's ability to attack transients. It is lightning fast and makes listening to energetic and uncompressed music so much more enjoyable. Lastly, the bass is interesting in that it's a tad less controlled than the Bryston 2B SST and slightly richer; almost tube like. When pushed loudly, the bass stayed powerful and controlled all the way up until my woofers started to bottom. At the risk of shredding my GR Research M165X woofers, I had to be a little judicious with the volume knob.

After my first listening session one weekend morning, I was out raking the front yard near the sidewalk. As I toiled, I couldn't help notice a man walking by wincing out of the corner of his eye at me and hastening his gait. Only then did I realize what was going on. I was so moved by the music I had been unknowingly belting out the song; “We Are In Love” by Harry Connick, Jr. I wanted to say; “It wasn't ME, it was the HEPHAS!” but I sheepishly shut my mouth and kept raking. The first few notes of that song hint at it's dynamic capabilities. A loud burst of notes from the bass, drums, horns, etc, spanning many frequency ranges comes all at once several times. It should sound powerful and effortless across the board. Many amplifiers and speakers don't do this justice. In my case, the amplifiers sounded powerful, clean, and effortless with the only compression happening from my DIY reference speakers.

Another similar test is Tricycle from Flim and the BB's which James Darby uses from time to time.


I was lucky enough to go see John McLaughlin, Chick Corea, and Christian McBride in “Five Peace Band” play live at Berkeley in Boston. It was truly a stunning performance so I picked up an earlier recording of the same play list at another venue; “Five Peace Band Live”. One often reads references to “live music” but folks seem to forget that live, unplugged, acoustical music can be a very different experience from live amplified music. In this case, we're dealing with the latter. The performance was wrought with sheer energy and excitement as well as subtle quick intricate details. The day after the performance, I poured through the aforementioned CD. The Hephaestus HMA-1000 monoblocks got me closer to live amplified music in my home than ever before.

The drum performance in “New Blues Old Bruise” was really stellar and the Hephas were able to reproduce the initial attack with amazing speed. The drum hits are hard, fast, and dynamic with amazing power and clarity. Christian McBride's bass was also powerful without being overwhelming or boomy. The song “Hymn to Andromeda” is a vast exercise in creativity. It begins with some clever piano fingering and some other sounds generated by Chick Corea poking at the strings inside the piano with a padded drum stick. The details come through super clear and believable through the Hephas. At the performance, Christian McBride was looking on in disbelief while watching Chick Corea pull off this feat. I can almost see him doing that when listening to the recording. I'm almost there. About 5 minutes into that song, he pulls out an acoustic bass and takes the stage for a while. The details and the weight of the instrument are quite believable. It just works. The detail of the bow moving on the strings and the resonant overtones of the acoustic instrument were fantastic. At this point I am really enjoying the amplifier and start rethinking the price tag. I'm a frugal guy and I initially scoffed at a $5,000 amplifier set but the more I heard music through the Hephas, the more it made sense. I've had some $5,000 amplifiers in my home before and they were no better than the $3,500 Bryston B100 SST; just different.

The Hephas are the first amps to actually improve upon the Bryston. I have no complaints from a sonic standpoint. I thought that I had found something odd in that the lower treble was getting a little congested and compressed when the amplifiers were pushed to disgustingly loud levels. I then placed some gorgeous monitors from Acoustic Preference using Morel's high end drivers known for their power handling and dynamic capabilities. They handled the same very loud listening levels better in a clean and uncompressed manner. The problem was not in the Hephas, but the B&G ribbon tweeter crossed over at 2.2Khz with a third order crossover. I was hitting the limits of what it could do and the tweeter was compressing distorting a bit at those insanely loud levels. One needs to remember that with 600 watts into 8 ohms, one could easily shred their speakers just by overdriving them.

I was enjoying the Hephas so much that they really got a lot of play time. They did very well with both late night low level listening as well as ear splitting wall pounding music. One CD that came to mind was the Hans Zimmer soundtrack to Pirates of the Caribbean; “Dead Man's Chest”. It's filled with detailed layers of subtle nuance and has considerable amounts of low end information that can be real demanding on an amplifier. Through the Hephas and the Bryston preamp, the sound was nothing short of astonishing. It was effortless, transparent, powerful, and detailed without being in your face. Some close mic'd cellos sound even better than Christian McBride's acoustic bass references with the aforementioned Five Peace Band. The sound of the strings is incredibly detailed and the textures of the wooden enclosure are so realistic that one feels they could reach out and touch them.


Melody Gardot's, “Worrisome Heart” sounded impressive. The air and sense of space from the recording was rendered beautifully. The vibrato in her voice was more noticeable than I have noticed as well as the breaths she took in between the verses. In “All That I Need Is Love” on the same album, the notes in her voice rise up and down with lots of emotion. Through the Hephas, the speedy rise in her voice is captured perfectly preserving the feeling of the recording. One could easily make out the drums being hit with brushes and the cymbals sounded just right. Melody Gardot was placed up front and center with the instruments and drums clearly giving her the stage. When I came back to listen and double check my notes, I found myself just sitting and listening through half the album when I should have been joining my family for dinner. It took a three foot tall person with a big smile to come in and pull me away from it. A link to our review is found and the end of this review and we will soon have a review of her second just released effort.

The affect was similarly striking listening to Eva Cassidey “Live at Blues Alley”. My friend John McDonald always throws this one in when he stops in for a chat and a listen. He quoted; “I liked those amplifiers. It was extremely clear without being in your face or annoying.” For fun I popped the input on the preamp from the outboard DAC to the analog outputs of the transport. He and another visiting listener both screamed “Hey!” because the difference was clear and obvious through these monoblocks.

The Hephas Rock. I played all sorts of music from Nirvana, Led Zeppelin, Bare Naked Ladies (do they count?), the Beatles, Queen, Aerosmith... you get the idea. I even played some techno-pop like Madonna. Some of the older recordings from Led Zeppelin like “Over the Hills and Far Away” really took on a new flavor with some midrange bloom from the guitars not to mention more airy guitar harmonics. There was also an added sense of power and weight when the music got churning. That was until I nearly shredded the woofers with music from Nirvana and Madonna. The Hephas put 1000 watts each into 4 ohms. With great power comes great responsibility. In this case you are responsible for not pounding your woofers into a torn mess or melting your voice coils solid. I never blew any speakers but when I bottomed a woofer I the pop of the suspension running out was a not so subtle reminder. These were at crazy loud levels however.


Four sets of reference speakers used here. Some Maggie MMG MC1 speakers with a subwoofer, a set of relatively small three way open baffle speakers using GR Research drivers and B&G planar ribbon tweeters, and a pair of minimonitors using the SEAS L15RLYP and SEAS 27TDFC drivers and some rather monitors from Acoustic Preference that I am currently reviewing. The Hephas mated fine with each set of speakers with the only problem being bountiful power and no giant speakers around to really put it to use. The largest woofers were the GR M165X with 8mm of travel but I could have used three more of them per speaker or much larger woofers as the Hephaestus amplifiers would likely shed any of these speakers in the wrong hands. I started getting used to hearing the woofers bottom out. They sounded so good, I just kept turning it up. The Acoustic Preference speakers use some of Morel's finest drivers and sounded the cleanest when really pushed. The review will be published mid summer.

Most of my listening was using the preamp section of a Bryston B100 SST. This is essentially the Bryston BP16 preamp. It runs in class A and is all about the measurements and robustness. I think it is the strongest part of the B100. I tried several other preamps but the Bryston and the Hephas were a match made in heaven. The bass was just right and the level of transparency, air, power, and soundstage were the best with the Bryston. There was a sense that you could “reach out and touch it”. The next preamp was the Xindak XA3200 MK2 tube preamp using 12AX7 and 12AT7 tubes. This was also a very enjoyable combination but differences were easy to hear. The Xindak is currently under review and will be published mid summer. Next was a passive attenuator from Niles. The Hephas easily and clearly showed the differences.

The Niles was slightly grainy; likely a function of it being a mediocre rheostat. The bass was less authoritative and it sounded as if the frequency response shifted a bit over different volume levels. The final preamp was the Jaton RC7000P which is basically mass market quality. It’s a $500 preamp that you can get for $450 and it uses average parts. I like that it has a DAC, tuner, and bass management in it. It’s not gritty like the Adcom and it’s only sins were of omission; The overall presentation is a little more laid back and less focused. Striking details and layers within the sounds disappear and so does some of the magic. There’s a whole bunch going on, or supposed to be going on, that you just don’t hear with the Jaton. It’s not bad but it masks the potential of the Hephaestus monoblocks. The point to take home here is that the amp is amazing and will live up to the potential of whatever else you mix it with. The limiting factor here may very well be the preamp itself. Both the Bryston and the Xindak preamps were my top choices with the Hephas.



The Hephaestus Audio HMA-1000 is a great monoblock amplifier. It sounds fast, clean, transparent, open, and airy with powerful but neutral bass and massive headroom. It worked well with a variety of speakers and sources, takes up very little shelf space, and produces quite a bit amount of power efficiently. Those looking for a big shiny bauble with a fancy name to show off may be perturbed by the utilitarian look and understated size and miss out on some amazing sound. The $4900 list price per pair is a tough pill to swallow from a relatively unknown company; especially for those who are frugal like myself. The spoonful of sugar that makes the pill slip down is the sound. I am very pleased to announce my new reference amplifier; the Hephaestus Audio HMA-1000 monoblocks or Hephas as we've started calling them.

Based on their high level of performance and their more than reasonable price, we bestow upon the Hephaestus Audio HMA-1000 our Stereomojo Maxium Mojo Award.

Money speaks larger than words. I purchased the amps and couldn't be happier with them. If you can't stomach the price, take a listen and think again. If you can't afford them, listening is just a tease. The 7 year parts and workmanship warranty and 90 full day “no questions asked” return policy make it easy for one to take the chance on them.


Website: http://hephaestusaudio.com/


Power: 1.0kWrms into 4 / 0.6kWrms into 8
2.5kWpeak transient capability into 4
20Hz to 20kHz +0.0dB/-0.5dB frequency response
119dB SNR/ 70uVrms (20Hz-20kHz unweighted)
26dB gain / 10k input impedance
9.0” x 6.75” x 2.25” / 3.5 pounds
7 Year Parts and Workmanship Warranty
90 Day “no questions asked” return policy

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