Roman Holiday— The Glorious Sound of the Thrax Spartacus Amplifier and Libra Preamplifier

Founder and chief designer Rumen Artarski has one foot in pro, and the other in high performance consumer audio

Maximinus Thrax, a Roman emperor from the third century after Christ, was supposedly eight feet tall and possessed of superhuman strength. It was a bold move for Rumen Artarski, the head of Thrax audio, to name his company after this legendary emperor, but he and it have more than lived up to the challenge. After listening to Artarski’s formidably powerful tubed equipment for several weeks, I half expected to hear it ask through my loudspeakers, “Are you not entertained?”

Located in Bulgaria, Thrax has compiled a reputation for producing sophisticated audio gear that is based around tubes. For Artarski, you could even say, there has never been a question about whether to tube or not to tube. He employs them plentifully in both his preamplifiers and amplifiers—no less than six 300B tubes in the mighty Spartacus amplifier ($97,500) and four 300B tubes in the two-box Libra preamplifier ($67,500).

Both were conveyed to my listening room in March, where a triumvirate--the distributor Ozan Turan, United Home Audio proprietor Greg Beron and Dr. Vinyl, as he is known--gathered to audition them on my Avantgarde Trio G3 loudspeakers. After listening intently for several hours, they pronounced themselves satisfied with the sound, then left me on my lonesome to assess the Libra and Spartacus. With such enticing gear placed at my disposal, I felt a little as though I were going on a Rumen holiday.

The Libra runs in balanced differential pure Class A triode mode and is linked to a hefty and separate power supply. It features what Thrax terms a “post-amplification” volume control and can run two sets of amplifiers separately from its dual outputs. Its natural mate is the Thrax Spartacus 300, which is designed around two stages. One tube is for the input, one for voltage regulation, and four for output for a total of 50 watts. It proved more than ample for the Avantgarde loudspeakers which, it should be noted, are simplicity itself to drive at 109dB efficiency and a 19 ohm load. But the rigidity of the power supply in the Spartacus should ensure that it is able to drive most loudspeakers with ease. It’s also the case that tube watts often seem more powerful than their solid-state equivalents.

What do all those 300B tubes in the Thrax gear deliver? Tube aficionados tend to break down into several camps—there are proponents of the 211, the 845 and the 300B. Some see the 300B as the “purest” of the lot and indeed Western Electric has revived production of this venerable tube in 2017 in Rossville, Georgia, down to the handsome original packaging (I had a full set to play with earlier this year and can confirm that they sound superb). The 300B may not quite have the punch of the 211 or 845 but it does possess a glorious midrange, at least when implemented correctly.

In the case of the Libra and Spartacus, they have. The first and most immediate impression I had was of a beautifully unified and coherent soundstage, from treble to bass. Somehow all that tube power seemed to be a uniter, not a divider. The result was to create a deep and wide soundstage that allowed the speakers to disappear even more fully than with my DartZeel NHB-18NS Mk. 2 preamplifier and NHB-468 Mk 2 monoblock amplifiers.

Take Michael Jackson’s song “Billie Jean” on the Thriller album. There wasn’t a trace of blur or smearing. Instead, the song had a propulsive force, right from the outset as Jackson’s drummer Jonathan “Sugarfoot” Moffett laid down the law. The backing chorus had almost a diaphanous quality to it, floating in its own space, even as the rest of the band played full tilt. The Thrax gear did not lack dynamics, which can sometimes occur with 300B amplifiers. Nor was it overly sweet. If anything, I was impressed by how deep and controlled the bass was as the song progressed. Had there been anything to point fingers at in the nether regions, the Avantgarde Space Horns, coupled with Wilson-Benesch IGX subwoofers, would have disclosed it.

Another album that I’ve had in frequent rotation recently is one that my friend Ali Leeman, an avid record collector and audiophile, bestowed upon me—the Telarc LP of The Firebird. It definitely lit up the room through the Thrax gear, which delivered humongous bass whacks that carried through my listening room. I played it several times, including when Greg Beron visited and I think he was taken aback by the quality of the sound as the LP played on the new Wilson-Benesch direct-drive GMT turntable. He's all about tapes. But I daresay that the GMT, combined with the Thrax, gives tape a good run for its money. Plus you don’t have to deal with the hassle of reel-to-reel, which, frankly, I find to be a real nuisance.

The ultimate convenience of course, is streaming which I did with the Rolling Stones’ tune “Hear Me Knocking.” I have to say that probably nothing renders electric guitars more realistically than tubed gear and the Spartacus amp did not disappoint. Ditto for a jazz album on the Concord label called Great Guitars, featuring Charlie Byrd, Barney Kessel and Herb Ellis. The Thrax gear captured the warmth and tonal richness of their respective guitars better than pretty much anything else that I’ve listened to on my system. On the slower numbers, it had a, to use a ten-dollar word, plangent character.

No question: this tubed gear lacked some of the incisiveness of solid-state. It’s not going to give you that cut jewelry sensation that top-flight solid-state gear has on offer. The Thrax gear reminded me of an impressionist painting. The impressionists didn’t just want to paint a literal scene. Rather, they were after something larger—a sense of how the larger environment shaped the look of the landscape, whether it was the strength of the sun or impending darkness. Something similar could be said about the Thrax gear. For some listeners it will deliver a deeper and more profound sonic truth than a rote, strictly by the numbers duplication of the sound.

This heavenly equipment is also commensurately priced. The exotic nature of this gear means that it is intended for the hardest of the hardcore audiophiles who seek the ultimate window into the music. But for those who are intent on sonic, if not imperial, grandeur, this superb Thrax gear will provide it.

Below bullet points from the Thrax website!

Libra Preamplifier Features

• Two 300B tubes per channel in a true balanced differential pure Class A triode configuration.

• Post-amplification volume control for the lowest noise and maximum signal integrity.

• Dual-mono design with two independent outputs per channel for bi-amplification setups.

• Fully balanced Tape Loop for professional tape recorder integration.

• Home theater bypass and trigger output for seamless system integration.

• External dual-mono power supply with choke input rectifier for noise-free operation.

• Microprocessor-controlled operation with status display and advanced menu system.

• Special filament heating circuit for harmonic richness and tube protection.

• DC-coupled input and output for ultimate transparency.

• Modular construction for easy servicing and upgrades.

Spartacus 300 Features:

Exclusive use of 300B tubes for consistent, captivating sound.

• Two-stage amplification with transformer-coupled input and output for maximum fidelity.

• No capacitors in the signal path—just pure, uncolored sound.

• Parallel push-pull output stage with custom transformer for 50 watts of Class A power.

• Shunt regulator power supply with 300B tube for stable, noise-free operation.

• Auto-bias system and microprocessor control for ease of use and reliability.

• Special filament heating circuit for harmonic richness and tube protection.

• Modular design for easy in-field servicing and upgrades.

• Sealed chassis for safety, reduced microphony, and thermal management.

For more about Mr. Artarski, read this excellent interview with Mono & Stereo's Matej Isak

Below video shows how Spartacus 300b is built