Not very long ago I received an e-mail from a 20 year old company called Audio Mirror. They manufacture some stunning tube powered audio amplifiers. They apparently had one of my business cards from the AXPONA 2018 show in Chicago. Ever curious I set out to familiarize myself with this company. A search of some of the popular audio chat rooms revealed a very interesting thread generated by some very committed audiophiles. They were talking about Audio Mirror amplifiers and comparing them to some very well-known and very expensive tube based competition.
This convinced me that something seriously significant was afoot. And in part the conversation was about a pair of SET (Single Ended Triodes) Monoblocks powered by 6C33 Russian Triodes. OK, I'm hooked, curiosity won the day as have always been curious about those 6C33 tubes. There is a very interesting story to be told about the origin of these tubes.
The 6C33 Triode was a Russian secret until 1976. The West only discovered this tube when a defecting Soviet pilot Viktor Belenko landed his MiG-25 in Hokkaido, Japan. Lieutenant Belenko was a pilot with the Soviet Air Defense Forces and his defection provided the West with its first close examination of a MiG-25. The Japanese invited the USA to dismantle and study the fighter jet piece by piece. In fact Lieutenant Belenko had brought along with him the airplanes operations manual. After a few weeks the Japanese were courteous enough to offer the return of the jet plane to the USSR in 30 crates filled with MiG 25 parts! Apparently they also invoiced the Soviets $40,000 for the packing expenses. Some people have called the Soviet 6C33 a super tube. It was designed to be super rugged to withstand high G-forces and to resist the effects of (atomic) radiation.
Hollow State Audio Mirror
These are SET (single ended tube) Class A all triode mono blocks, rated at 45 Watts into 8 Ohms. The font end is based on 6SN7 driver and 6SL7 input tubes. The two 6C33C output tubes are connected in parallel mode. There is a unique proprietary biasing circuit but the details remain copyrighted. "I can only say I use MOSFETs to keep the tubes working at there most linear point. This allows very high dynamic and transient response coupled with a fast and tight well controlled low end. I also use proprietary protection, these 6C33C tubes are famous with their tendency to run away. After many years fighting with this I finally tamed the beasts. Circuit protection monitors the output tubes for over biasing, over voltage, arcing, and over driving. If any of this occurs it will shut down the HT (B+) and will indicate which tube is malfunctioning. The output transformers are custom made and hand wired. The first two amplifier stages are DC coupled. They are using Clarity XMR series high-end caps for the driver / power tubes connection. And additionally, I use a Choke regulated power supply." -- Vladimir Bazelkov of Audio Mirror.
The switch closer to the speaker terminal side on both monoblocks is a high voltage cut off. More precisely, it disables the one minute timed delay relay that switches on the B+ (high voltage) power to the 6C33 tubes. So if you have brand new 6C33-C power tubes, you will indeed need to burn them in. They need a burn in period between 15 and 24 hrs. So if you flip that switch you won’t have high voltage, you will only have the filaments powered on. That’s how you burn in your power tubes. Flip the switch, leave the power tubes in the sockets, and you’re good to go there. The other two driver tubes you can leave in place or remove them it doesn’t matter.
Turn on the amps and leave them in this condition. You won’t hear a click from the delay relay after one minute. After you finished the 15 to 24 hour burn in, flip the switch back. If you flip the switch while the amps are working you will lose the high voltage and they’ll stop producing sound. Nothing else will happen. You won’t damage anything. Both amplifiers are mirrored so are the two switches positions. When both switches are pointing toward the speaker connection side of the amplifiers, that is for normal operational. What about the other switch placed right next to that B + cutoff? That switch is a Ground Lift switch only to be used if you experience a ground hum problem.
Using the Acoustic Signature Double X Turntable sample I just finished reviewing. It came with the Acoustic Signature TA 2000 tone arm and a Dynavector XX-2 moving coil cartridge. I played the Basia track, "Until You Come Back To Me", which was wonderfully Dynamic with a great flowing presence and with image depth you could throw a rock into. What a very complex multi-layered vocal and instrumental score this is. It seems to me tubes and vinyl recordings have a certain very logical affinity to each other. I seriously considered stopping right here and not describing anything more about sound. Most recordings just will not be of a high enough quality to challenge the performance of this SET amplifier. Then I remembered that great Nils Lofgren's SACD album, Acoustic Live. The body of Nils acoustic guitar strings is the something that hollow state tubes do better than stiff state amplifiers. It’s all about that halo afterglow of wooden overtones that gradually fades from the guitars resonant body. If there is anything lacking it would be down below 120 Hz. Razor sharp bass transients tubes cannot due what some solid state muscle amplifiers can do. About these low frequencies I do not give a hoot about them. My reference is the sound of human voice.
Remember to enjoy the music, and from me, Semper Hi-Fi.