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Reviewer: Srajan Ebaen
Financial Interests: click here
Source: APL HiFi NWO 3.0-GO; Ancient Audio Lektor Prime; Raysonic Audio CD-168; Yamamoto YDA-01
Preamp/Integrated: ModWright LS-36.5 with PS 36.5; Hegel P-10 [on review]

Amp: Yamamoto A-09S; FirstWatt F5; Trafomatic Audio Experience Reference monos [on loan]
Speakers: Acoustic System Tango R, Neeper Acoustics Perfection One [on review]; WLM La Scala [on review]
Cables: Acoustic System Liveline interconnects; Crystal Cable Ultra loom; Crystal Cable Reference power cords

Stands: 2 x Ikea Molger with Ikea butcher block platforms and Acoustic System footers
Powerline conditioning: 2 x Walker Audio Velocitor S
Sundry accessories: Furutech RD-2 CD demagnetizer; Nanotech Nespa Pro; full-house installation of Acoustic System resonators, noise filters and phase inverters
Room size: Sound platform 3 x 4.5m with 2-story slanted ceiling; four steps below continues into 8m long open kitchen, dining room and office which widen to 5.2m with 2.8m ceiling; sound platform space is open to 2nd story landing and 3rd-floor studio; concrete floor, concrete and brick walls, converted barn with no parallel walls nor perfect right angles; short-wall setup with speaker backs facing the 8-meter expanse
Review Component Retail: €10,000/pr

Ancient Audio's Jaromir 'Jarek' Waszczyszyn is one of the best-known high-end designers of Poland. His signature style is the granite slab component. Think top-loading single or triple chassis players or his flagship 4-box 300B monos. My one-box Lektor Prime disc spinner was conceived to bundle most the performance of the Lektor Grand statement mono DACs + transport triptych (lower left) while easing the price of admission. Jarek's new Single Six monos with integral power supplies promise the same relative to the Silver Grand monos (lower right).

First popularized by BAT and Lamm, later Almarro and others, the Russian 6C33C now also appears on the Single Six in 18-watt SET mode. The amp uses "a special 3-stage circuit to protect itself and the tube. This circuit switches on the high-tension power. Switch-off is indicated by a red LED. This supply powers down during the 3-minute warm-up cycle as well as during overload conditions. The latter could be from too high an input signal or tube failure. With the 6C33S, tube failure is no joke. This tube can deliver 2-3 amperes of plate current, lethal for both the tube and amplifier. Should the red LED come on during play, decrease volume or hit 'pause'. If it occurs under no signal, it's time to replace the tube."

"The Single Six incorporates many solutions originally developed for our flagship Silver Grand. One of them is DC tube control. The Single Six runs a fully regulated HT power supply to deliver 240 volts of plate voltage. This voltage is stable on mains voltages from 215 and 250V. A second circuit stabilizes bias current to 200mA regardless of tube, parameter shifts during warm-up or aging. Tube replacement is plug 'n' play. All parameters will set automatically to 90-watt power dissipation, 48-watt plate and 42-
watt cathode heating. So the plate voltage is fully regulated and stabilized with a current monitor. My current regulator for the ideal auto bias is a DC servo whose current sensor feeds DC current prior to the HT regulator to have no influence on the audio circuit. This is probably the only 6C33S amplifier on the market with these particular features."

"The speaker terminals are not sensitive to a short or being open for a few minutes so it is possible to switch speaker cables under signal. Input sensitivity is 900mV RMS and the input impedance a very high 1Mohm. Despite the true power topology, these monos can thus be driven directly from a CD player without a preamplifier*. The amplifiers were tested over a wide range of speakers, including difficult-to-drive 4-ohm Dynaudios. We evaluated a few different speaker cables and the best were by Tara Labs and Cardas."

This feature is highly relevant because Ancient Audio's CD players sport tube-buffered analog-domain-variable outputs capable of swinging up to 7 volts; and feature an analog input to double as a 'two-source' preamp. Ancient Audio premiered the Single Six at the Warsaw Hifi Show 2008 with the Lektor Prime and their own speakers.

While Ancient Audio has always championed the black/gold two-tone aesthetic -- black granite, floating panels and transformer covers; gold decals and adjustable point footers -- the Single Six is optionally available with silver accents as shown below.

Instead of multiple output transformer tabs, Jarek has decided on a single pair of speaker terminals. "Our transformers are optimized for loads between 4 and 8 ohms as they are in all my amplifiers. It is a good solution because in reality, speaker impedance varies with frequency already. My flagship Silver Grand Mono (also with one pair of terminals) was reviewed with the Avalon Eidolon, a low impedance speaker. Their owner Adam Mokrzycki, founder of the Warsaw Audio Show, still remembers them as the best sound in his life. A problem with multiple terminals is that only parts of the secondaries are active, leaving the unused windings inactive to reduce magnetic coupling."

Circuit gain of the Single Six is 23dB. As most triode cognoscenti are aware of, the 6C33C was originally deployed as a voltage regulator in Russian MIG fighter jets. It sports a far lower plate resistance than the famous 300B, 2A3, 45, 211 and related triodes we usually see in audio. As a result, the double C-core output transformer can use a ration lower than 10 to create smaller capacitance and inductance. Here it rewards with bandwidth to 80kHz.

In the Single Six, power supply capacitance approaches a whopping kilo joule to perhaps clone a virtual battery. There are Teflon/tin-foil V-Cap coupling caps and silver ribbon hook-up wiring. The latter is kept deliberately short for the filament supply connections which carry 7 amps. As the lead-in image shows, the power and output transformers are spaced as wide as possible to support "very low levels of noise and hum". I/o socketry can be either WBT or Furutech. Input and driver tubes are NOS E88CC/6922, higher-spec long-life versions of the ECC88/6DJ8 and here by Philips SQ and Tesla respectively.

Considering that Jarek's reference monos use the direct-heated 300B in parallel single-ended mode, I was curious what had led him to the 6C33C now.