I've seen one of these amplifiers - printed-circuit board but on a metal baseplate the same size as the previous 606 amplifier's chassis.
I'm rather interested if a circuit diagram comes to light, how the sound exciter lamp is powered. B & H were fond of using a 6V6 as an oscillator and driving the lamp from HF AC (the light source needs to be steady and ripple-free, so 50/60Hz AC is no good). Whether with the extra space, as a result of the miniature valves, allowed use of a metal rectifier and smoothing cap, to run the lamp from DC, I'm curious to see!
I'm rather interested if a circuit diagram comes to light, how the sound exciter lamp is powered. B & H were fond of using a 6V6 as an oscillator and driving the lamp from HF AC (the light source needs to be steady and ripple-free, so 50/60Hz AC is no good). Whether with the extra space, as a result of the miniature valves, allowed use of a metal rectifier and smoothing cap, to run the lamp from DC, I'm curious to see!
