Number of tubes in Pure Class A amps

Allen

This has always been something of a mystery to me the exact difference within tubes, and I have never seen it written about in such a straight forward fashion. Really insightful in the best possible way!

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?

I see no reference to Class A operation. Zero NFB does NOT imply Class A operation, they are two very different things.

And if it was pure ClassA, then the power consuption would need to be MUCH higher than 145 watts. As I said, 4 times as much as the triode output power - which would then need to be 40 x 2 x 4=360 watts. But it only uses 145 watts.

Regards, Allen (Vacuum State)