Dinky little 2-valve Chinese pre-amp

[Yorkie]

HT is 12 volts.
Rob T

Yes indeed - the 12V AC is no problem with the 18V AC input Rob - it was just that the component count was so low that I wondered how the upped it for the HT, rated at 300V for that valve though no doubt the valve will work with lower HT than that. I can see how they could uses a 'diode pump' to up the voltage, and to rectify it to DC for the HT, but given its compact size and low component count, it's an impressive little thing. I can only see one diode - a 1N4007, four transistors (presumably?), nine electrolytic and three little brown square jobbies which are 1uF. Can see any transformers/inductors at all.

If I'd have had the time - not that it's mine to play with, I might have taken the Perspex base off and taken a few Voltage readings, if only out of curiosity.

Time will tell as to how it performs and if it proves to be reliable.