At your risk. Take all safety precautions. There may be smoke or fire in case of short circuit until a suitable fuse is used in series with a battery.
Va is 1.3V. A 100mA safety fuse is now used.
Vb is 48V.
1st stage operates with grid at space potential, ie with just a coupling capacitor connected to control grid. 2nd and 3rd stages would not turn on in this way due to the initial transient voltage at turn on from the previous stages. S0 a 10Mohm resistor was connected between grid and ground.
It works and the preamplifier sounds very nice. It is directly feeding the Sennheiser HD580 headphones through the output transformer at a low volume.
It makes sense to use an input transformer even for MM cartridges and and additional input transformer for MC cartridges. So thing to having one transformer inside a ribbon microphone, and then the input transformer of the preamplifier.
Promising results.
There is hiss from the second stage, due possibly from bad electron tube contacts or RF pickup.
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