Reviewer: Steve Marsh
Financial interests: click here
Analogue: Nottingham Analogue Mentor turntable with 10” Ace Anna tonearm, Benz LP-S moving coil cartridge
Digital: Accuphase DP-70 CD player with Tom Evans Audio Design reclocking board
Preamps: Doshi Alaap Purist Mk.II full-function tube preamp, Levinson 26S line stage, Klyne 7PX4 phono stage
Power amp: Tron 211 SET with upgraded exotic-core interstage transformers, General Electric 21, Western Electric 417A, Tung Sol black plate 5U4GB rectifiers
Speakers: Bastanis Sagarmatha with AlNiCo drivers and Gemini Mk.II tweeters, Bastanis 18-inch open baffle powered subwoofers
Interconnects: Audio Magic The Natural (pre to amp), long Radio Shack interconnects from preamp out to Dayton A500 subwoofer plate amps
Power cords: Bastanis Epilog II on Tron amp, industrial power cord on Doshi preamp
Speaker cables: Audio Magic The Natural
Equipment rack: Adona 6-shelf, low profile isolation rack
Power delivery: Triangle Art RA-6 power conditioner, Bastanis Afterburner power conditioner
Sundry accessories: High End Novum PMR Premium Resonator, set of four Stein Harmonizers with Stein Magic Stones, Entreq Silver Tellus grounding box with Atlantis grounding cable, Synergistic Research FEQ, Audio Magic Room Correction Bells, Audio Prism Ground Control, three Bybee Quantum Signal Purifiers, Audio Horizons Fuse in Tron amp, AudioDesk Pro record cleaning machine
Room size: 22' long x 17' wide x 10' high, eaves on front and back walls starting 40 inches up from floor

In the niche of audiophiles who prefer music through high-efficiency speakers mated to low-power single-ended triode amplifiers, most of them probably haven't heard of the Arcturus brand by TubesUSA.com. Of course Arcturus the name has history in tube manufacture dating back to 1927. In addition to making high-quality valves, they gained recognition for their novel use of blue glass. The reborn Arcturus brand is now being affixed to two SET integrateds made on Long Island in the U.S., home to several venerable audio companies of yore like Pilot, Marantz and Lafayette. While I would characterize the current Arcturus brand of amplifiers as boutique, there is standardization of their designs with no customized one-off units. The relative obscurity of the brand is because these are new efforts only recently finalized. My discovery of the Arcturus amps was serendipitous. TubesUSA.com had taken over U.S. distribution of Elrog tubes whilst I was looking into the Elrog 211 for my Tron 211 amp. During conversations with George Lenz, president of the company, I was asked whether I'd be interested in reviewing their SET amp based on the unusual 316A transmitter tube. They were also developing a second SET amp based on the 801A transmitter tube and I opted to hold off for that. The 316A and 801A amps outwardly differ only in their output tubes. Other than a custom one-off from Thomas Mayer, I believe this is the only commercially available SET amp based on the 801A.


The circuitry of the Arcturus amps was designed by the esteemed Roger Modjeski of Music Reference/RAM Tubeworks whom George has known since the late 1980s. Ownership, manufacture and marketing of the amps is controlled by George Lenz and his assistant Raymond Koonce. Raymond has an engineering background and although he lives in Texas and George on Long Island, they put together the amps as a team. George's academic background is in economics and he uses his combined experience in sales and knowledge of the audio industry to help conceptualize the products. He made the two-hour drive from Long Island to hand-deliver their 801-A integrated. Its appearance proved rather conventional with a brushed aluminium chassis attractive in a form-follows-function way without any fanciful frills. That suited me well. I prefer if more development and manufacturing costs go into actual circuit design and parts quality for best sonic results. Weighing in at only 31 pounds, the amp was relatively easy to move around.

Both version rate at 5wpc and retail for $7'995. Other than output tubes, the other bottles are the same: 1 x 6922 or 6DJ8, 1 x 5751, 1 x 7044. Neither uses tube rectification. I queried George Lenz on this. They felt it just wasn't necessary and would just have been another tube to look at and maintain: "We chose diodes for rectification based on size and scale, cost, reliability and efficiency. Could we have used nice rectifier tubes? Certainly but that wouldn't have added anything but more glowing light." I have heard some say that the delayed B+ voltage to the output tube plates provided by a tube rectifier or thyristor can help prevent cathode stripping. However, further reading suggests that cathode stripping only occurs when there are in excess of 1000 volts on the plates. George did tell me that the B+ voltage on the 801A is "north of 500 volts" but I don't spot any concern. Also, 801A tubes are reportedly very rugged and last a very long time. 


The features of both 316A and 801A versions are identical, too. On the back are four pairs of RCA inputs, a pair of pre-out jacks, 5-way speaker bindings posts, three fuses and an IEC power inlet. On the front are a stepped volume control, source selector, two headphone outputs (balanced and single ended) and the mains toggle. On the top plate are three switches: one to select three different levels of gain, one to optimize the output transformer for 8 or 16Ω (the middle position is mute and also chosen for headphones) and one to select and bias each output tube at 30mA. There is a corresponding bias adjustment pot for each output tube in front of the bias meter.