Number of tubes in Pure Class A amps


Can someone explain, as simply as possible:), how, eg a Jadis DA S88 (60 WPC) needs 8 KT 88 output tubes, whereas an Ayon Spirit II, also advertised as pure Class A (60 WPC in pentode mode, 40 in triode) only has 4 KT 88 output tubes? Is the power output ability in pure Class A not a linear function of number of tubes?
springbok10

Showing 4 responses by springbok10

That answered all my questions. That's why I love Audiogon. Instant experts on tap. Thanks, Allen!

So Ayon may indeed be accurate in saying that it is Pure Class A, both in Triode and Pentode? But the 4 tubes only seems a stretch?
Furthermore, does Triode mode mean Class A by definition, and, conversely, does Pentode mode mean AB? Is Ultralinear the same as Pentode? (eg Manley Stingray and TAD 1000 have Ultralinear/Triode modes.
SPIRIT II - SPECIFICATIONS

Amplifier Ayon Spirit II
Class of Operation Triode or Pentode mode
Tube Complement 4 x KT88, 4 x 12AU7
Load Impedance 4 & 8 Ohms
Bandwidth 15Hz-60kHz
Output Power / Pentode mode 2 x 60 Watt
Output Power / Triode mode 2 x 40 Watt
Peak Output Power / Pentode mode 2 x 75 Watt
Nominal voltage gain 40dB
Damping factor 1.02
Frequency Response 27 Hz – 42 kHz/ +/- 0.5 dB
Input sensitivity for full power 1V
Input Impedance at 1 kHz 100K Ohm
S/N ratio at full power 80 dB (2mV)
Hum 0,003 V
NFB 0dB
Volume Control Potentiometer
Remote Control Yes
Inputs - Output 4x Line, 1 x Direct IN, 1 x Pre out
Polarity invert +
THD at 1 Watt <1%
Power Consumption 145 Watt
Dimensions (WxDxH) cm 46x34x26 cm
Dimensions (WxDxH) cm (shipping) 57x47x35 cm
Weight 75 lb
Shipping weight 85 lb
Specifications subject to change without notice
This is where they allude to Class A operation:
Pure Class A, Zero Feedback

Is this enough, Allen?