Thrax Enyo Integrated Amplifier Mk 1

George Sallit


One of the great benefits of the internet has been access to a huge amount of data, a lot that is useful for audiophiles. In addition, the internet is a great gateway for audio products that come from less well-known paths. Of course, there is a lot that is less good but that is not what I have been following over the last month or so.

I had heard of Thrax amplifiers with people mentioning them in hushed tones with tales of fantastic build quality, audio to die for, but at a price. So, when Richard Morris of Lotus Hifi, the exclusive seller of Thrax products, mentioned the was amenable to a review of their integrated amplifiers I said yes, of course.

I have to admit the profile of Thrax has been very, very low in the UK but knowing that Lotus Hifi are the sole seller of these products will change that. Vitus were in a similar position some years ago before Lotus started selling them. Within a few years, Richard has helped establish Vitus as a significant quality product within the UK. This was done the hard way, by demonstration and installation in people’s homes. Not only that he chose a tough target audience, Naim owners. Convincing those guys to try something different is bad enough but with a different sound phew.

And to make life interesting Thrax makes two integrated amplifiers the Enyo and the Ares. The Enyo is a valve amplifier and the Ares is a solid-state amplifier. Richard thought it would be great to listen to the Enyo and then the Ares. He also knew I owned a Vitus RI101 Mk 2 which would be an ideal foil for these two amplifiers. Both (all three) are the least expensive amplifiers from companies that produce some really exotic products and produce integrated amplifiers with great pretensions for high sound quality.

But before getting into details of the Enyo, who are Thrax and who is behind the company?

The man behind Thrax is Rumen Artarski. He is the founder and chief designer at Thrax. Thrax is based in Bulgaria, not a country most people will associate with high-end audio, but I am told there is vigorous interest in Bulgaria for high-quality audio. Something that Rumen had a hand in creating.

Rumen started his audio journey by getting vinyl albums and cassettes into Bulgaria and selling them. When he subsequently moved to Denmark to study at the Denmark Technical University, he found Denmark was a noted centre for high-quality audio. He, therefore, saw his chance to move equipment from Denmark to Sofia in Bulgaria and start what became a profitable business. The audio bug had bit and deep. As a result, he became determined to move to London, to study audio and become a recording engineer/producer. So, he moved to London.

Now at that time Paul Messenger was writing for Studio Sound and Rumen, through that magazine, saw his future at the London School of Audio Engineering in London, so he applied to join them.

However, as happens in life, he found it was not as he hoped it would be. Most of the people at that time were not that interested in high-quality sound. So, surprise, surprise. he became disillusioned. And then he saw a new course being run in advanced audio production at Alcheama. He joined them and what a difference. Under the guidance of John Lundstem, Rumen was at home and started to have a hand in all aspects of the recording process with a keen interest in high-quality audio. More importantly, he was really enjoying it.

He was then invited to help with constructing some new recording and post-production facilities and got heavily involved in setting up mixing desks, audio monitoring equipment and designing the acoustics of a studio. In one instance, John Lundstem wanted to use Tannoy speakers, but Rumen suggested using Dynaudio speakers, which was a brave move as they were not that well known outside of Denmark. Rumen went ahead, bought their drivers and constructed the monitoring speakers as Dynaudio was only available as kits. He soon noticed he was doing the main equipment work. One of their suppliers offered him a job as a system specialist and they could take care of his audio equipment imports.

Rumen set up a company in the UK and a joint one in Bulgaria, travelling between the two countries and running two growing companies. And then the main TV company in Bulgaria contacted him and asked him to design and build their new TV studios. Rumen decided to move back to Bulgaria to build the TV company’s studios. After doing that he was asked to build more and more studios and this growing business helped finance his growing interest in high-end audio and then super high-end audio.

He bought some fantastic equipment (Kondo and Wavac.) He then got a great idea to learn from the masters about super audio design and add his own considerable skills and make something better. After some time, he designed and built a new preamplifier. It was put into the best system in his shop and at the demo, he got three orders. And now the real problem. He had to build them to his high standards, repeatably and in a reasonable time. An issue most single-person companies face early in their careers and have to overcome.

He started making serious audio products inspired by Kondo and Wavac. They were single-ended triodes and were made to the same build standards as the Japanese masters. These products helped establish Thrax as a serious audio manufacturer. As the company developed Rumen decided he wanted to make his own cases and decided to buy some very advanced machines. This left him with the problem of becoming an expert in using these machines, something he achieved, but it was initially a bit daunting. He now has the capability to make advanced cases for audio and makes them for other companies.

Having established a great reputation for high-quality audio at the super end of the market Rumen saw the recent trend for high-quality integrateds with digital and phono amplifiers added into the case. So, he joined in this trend with the Thrax Enyo which I picked up from Richard Morris at Lotus Hifi. When I say, picked up, please do not take it literally. The two of us assisted the beastie into the boot of my car. This amp is heavy and comes in a heavy-duty flight case and a substantial box. It needs two people to lift the complete package into a car. Once indoors I put the amplifier on a board and could slide it around on the carpet as it only weighs 30kgs (66lbs)!


The amp is a fine-looking tall box with the front panel showing off the benefits of Thrax’s precision lathes. The Enyo is a push-pull pentode design using a valve I have not come across before, the Russian Gu50, based on the Telefunken LS50. It is made by Russia for radio comms in MiG aircraft. The valve is encased within a sprung-loaded metal case to stop the valves from falling out due to flight vibrations, which should help any microphony. The whole front end of the amplifier is passive, and all input-switching and attenuation are handled by a resistor matrix using relays. The power output is 50w/channel for both 8 and 4 ohms and should be sufficient for any reasonably sensitive speakers (>88dB).

The design of the amplifier is based on their research over the last 10 years. It is a 3 stage fully differential architecture. The output stage uses the rare arrangement of cathode feedback while retaining the usual ultra-linear connection of the pentodes. This required the design of a special output transformer wound on double C core GOSS. Driving this output stage called for the development of a special front-end circuit accommodating positive grid swing. DC coupled tubes are rare but Enyo uses a single capacitor in the signal path. The amplifier has auto-bias so there is no need for users to carry out any biasing.


Russia has made a lot of GU50 valves and it is available worldwide. The power supply for the amplifier uses choke filtering to guarantee black backgrounds and freedom from power supply modulation.

The quality of construction is first class and whilst near the amplifier shine a torch through the black metal grille and see the superb way these amplifiers are made.

The front panel has a large screen that displays the controls of the amplifier. The remote for the amplifier is the ubiquitous Apple remote. I did most of the set-up at the amplifier and controlled volume and input switching using the Apple remote. Set-up is not entirely intuitive but you should not need to do this more than once. I found the screen easily visible from my seated position 4m away, so that is a plus for me.

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The amplifier has the ability to have two additional boards added that provide a phono stage and a DAC board. And as you expect they are not the usual add-ons. The DAC is an R2R board that can deal with DSD and has a reasonable streamer included as well as Bluetooth. The MM/MC phono stage has variable loading and is included in the £11K base price, the DAC board adds £2,900.

The amplifier had been run-in but I still let it bed in for a day or two before serious listening. The amplifier was providing good sound after 30 mins but gave all it could after 45-60 mins. It was straightforward to put into my system of a Melco/PlixR digital front end and a pair of Audionote E/HE (Silver Signatures) loudspeakers. I used Audioquest, Cut Loose and Audionote cables and Richard loaned me a lovely USB cable from Shunyata Research. I also had a Vitus RI101/MkII amplifier for comparisons and a Denafrips T+ and Gaia for digital comparisons. I also added a pair of Avalon PM1 speakers to the mix.

I only had one oddity, as I changed the volume there was a clicking sound coming from the speakers. Provided I changed volume slowly then it was not too much of an issue. I suspect this is a firmware issue as the follow-on Ares amplifier had no such problems.

OK, how about the sound quality? I started out using my Denafrips digital front end to reduce the variables. The first thing I noticed was a very large soundstage. It was huge, but only when on the recording, and all the instruments were the correct size. The music and the soundstage were well integrated and each instrument in studio recordings had its own space. This made it easy to separate instruments, even in dense recordings, and hear each instrument’s contribution to the musical whole. There was nothing artificial about this large soundstage.

Playing Hans Zimmer’s 2049, the music starts with powerful deep bass and there was NO valve bass softness here but big powerful deep bass adding to the statement that this is a big film track. I find some SS amplifiers can have very tight bass but it sounds less powerful than the great bass from high-quality valves. Not soft plummy bass, but controlled bass. The orchestration is on a big soundstage with the instruments clearly spaced out with great depth. It was easy to hear the details of the instruments being played. A great start.

And for something different, some Beatles, Strawberry Fields, the stereo on this track is unusual and very 60s, but it was easy to hear a young John Lennon in a simple stereo soundstage. The track is not the best audio quality but because no DAWs were used it has a simple and easy sound. The cymbals had a nice metallic ring to them with no accentuation of the cymbals in the track. The Cello was realistic taking account of the recording era. And keeping with that era I played David Bowie’s Space Oddity which was also a simple recording with a very realistic early Bowie voice. Staying with voices, I tried Tom Jones’s version of Dimming of the Day from his Spirit in the Room album produced by Ethan Johns. This Richard Thompson song was sung superbly well with a huge amount of emotion. The track is a cut-back version (no smaltz) and although simple was a great and moving rendition.

This was getting interesting so time for the big music tests. On goes the Reference Recordings of Beethoven 9th. This was a ‘Professor’ Johnson recording that really captures the forces unleashed by the Pittsburgh Symphony Orchestra and Mendelssohn Choir of Pittsburgh. I, of course, had to play the finale which the conductor Honeck said was at the limit of playability. The Enyo was really pushed with this track and did so without any complaint and kept everything under tight control. The power of this track was immense and could frighten with the dynamics.

OK, how about some great bass from James Blake’s Limit to Your Love? This has some very low electronic bass and really got the Avalon PM1s now added, to pressurise the room. This bass is in complete contrast to the piano which though closely miked was controlled. And as I was playing good bass recordings on goes the deep bass organ pipes from Stravinsky’s Pictures at an Exhibition played by I Guillou. It had the same effect on the room and provided a wonderful 3D backdrop for this great organ. Finally, Michel Jonsz’s Le Temps Passe with a big powerful bass that sounds like it is rolling out into the room. It was superbly played and has a jazzy feel with some great sound quality as well as the bass histrionics. Ok and for the last taste of deep bass how about Chameleon from Denmark’s Anders Trentemoller’s The Last Resort? No problem. This big slab of electronic music has a really interesting feel with deep synthesised bass adding to the mix. This platinum seller debut album established Ander as a force to be reckoned with.

So, this integrated was acquitting itself.

How about the added digital board? I fed the Enyo’s USB from my Melco and it was seen easily by the Melco’s control APP and we were off. One of the easiest connections I have had from digital. And using the above tracks I listened to the digital board. Putting aside that my Denafrips Terminator + and Denafrips DDC Gaia are much more expensive than the added board, the Enyo got mighty close. In fact, I can imagine that if you are not chasing the tiniest details that this digital board would give you all that you want, with the convenience of being built-in, no need for digital DAC cables with a very good sound as well. In fact, the money saved would be better put into improving what is feeding the Enyo and the Melco seemed to work really well with this integrated.

I was unable to test the phono stage so can’t comment on it due to not having a good quality very long cables.

So, given this is a really good integrated amplifier how does it fit into the market? Well, I had the ideal comparison, the Vitus RI 101 Mk2, which I reviewed here:

Now I was really impressed with the Vitus (yes, I bought it) and it costs £14,500 vs the Enyo priced at £11,000 with a phono stage. So, I connected my digital front end of Melco, Denafrips T+ and Gaia through an Audioquest Diamond AES cable and Gothic Audio silver balanced cables to the integrated amplifiers.

And the winner in this competition of serious integrated amplifiers was……a DRAW.

Boring, I know in these click-bait days of the internet with every one proclaiming the BEST, the WORLD’s BEST etc. Life is not like that or as simple as these guys make out. In my system, the Vitus was neutral, natural and had quietly stated dynamics with string quartets not having the dynamics of a German Oompah Band. The sound was highly detailed with a well-integrated image and it was easy to hear the great musicianship. The Vitus quietly gets under your skin and is an easy amplifier to listen to and relax with. However, with big orchestra music like Beethoven's 9th, it plays without restraint. The Vitus can play loud, with high impact and keep it all under total control without dampening the dynamics. 600w/channel into my Avalon PM1s gave great and easy control.

And the Enyo? Well, its sound is more demonstrative and it has a slightly livelier presentation. This made it sound more upfront but not to the point of making it less easy to listen to. It does not have the relaxed sound of the Vitus but then it only has 50 w/channel, which is more than enough with the PM1s to play loud. You would need to be more circumspect in your choice of speakers with the Enyo as 50w/channel will only stretch so far, especially with some modern inefficient speakers. So, to decide which one to buy would require you to ensure the matching parameters between the amplifier and your speakers are well suited and then dare I say it, really listen to the amplifier in your system.

Given that, if you like the Enyo’s sound (and why not) then I would advise you to get the digital board unless you have a very good digital front end. With the complete Enyo you can forget about worrying about the digital front end and its connecting cables and just enjoy the music.

The Enyo is a very good integrated amplifier that is already competing with the established references.

Now, what could be better? How about for the valve nervous a solid-state amplifier, using Class A, with more power that will not need valve replacement in the future? Well, guess what, Thrax also makes the Ares amplifier. It is an integrated solid-state amplifier that delivers 120w/channel 8 ohms and 200w/4ohms. The cost? The same as the Enyo. Yes, I am reviewing that integrated as well. Review coming to the Wam soon.

I have been informed that there is now a Mk II Enyo with a different and new digital board and the clicking has been removed. The amplification is the same.

Lotus Hifi:

Thrax Audio: