VAC Renaissance 70/70 - Manual (Page 5)

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INTRODUCTION
The Renaissance Seventy/Seventy is a completely unique power amplifier. It allies purist amplifying devices
with the power and solidity required to control modern audiophile loudspeakers.
The most noticeable feature of this amplifier is the 300B filamentary triode output tube. Originally designed
by Western Electric in 1935 (Footnote 1), it has several extremely desirable features that have kept it in
continuous production since that time. An examination of its dynamic curves (Figure 1) reveals it to be a
naturally linear device, more so than triode connected pentodes or beam power tubes (ex: KT88, EL34), let
alone any transistor device. It gives this superb performance with voltages on the order of 450 VDC, not the
1000-1500 VDC required by other output triodes like the 211 or 845. This lower voltage and lower output
impedance allows superior output transformer design, control of the loudspeaker, and safety.
Each 300B tube has its own separate heater power supply and independent cathode self-bias network. This has
several major advantages. No user adjustment of any kind is necessary to maintain proper balance of the
amplifier. The stabilizing action of this technique upon the idle current (bias point) of each tube is exceptionally
strong, and self corrects for large mismatches among tubes or drift with age. This circuit also results in real-
world output capability much greater than the test-bench rating would indicate (Footnotes 2,3,4).
A total of four 300B are used in each channel to reach 70 watts per channel in Class A.
The input circuitry of the Renaissance Seventy/Seventy is derivative of the unique Williamson circuit, which
provides pure, direct coupled, inherently balanced input amplification and phase splitting. Type 6SN7/5692
octal twin triodes do the honors.
The superb VAC output transformer provides superb voltage/current translation, allowing impedances from
eight ohms to as low as one ohm to be driven.
The 35 pound chassis is machined from quarter inch thick aluminum plate. This strong, resonance-resistent
structure houses two electrically independent channels of amplification. Each channel is separate, down to two
dedicated shielded power cords. A total of eight transformers are used, providing sixteen power supplies.
The units is completely hand wired in three dimensional space for the shortest possible lead lengths, allowing
passive components to perform much nearer to the theoretical ideal.
The Renaissance Seventy/Seventy is designed not to the latest fad but to substance, for the highest possible
sound quality. Time spent familiarizing yourself with this manual will be well rewarded.