One of the best presents of my student was how she got disapointed when I told her that the control grid is usually biased negatively. She said, no it should be positive to free electrons.
So it was tried and a 4MOhms resistor from plate or Vb to grid made an EF183 operate as an excellent low noise, small signal microphone amplifier at Vb of only 4.5V. Heaters were also supplied with 4,5V, (less than specs rating), Georg Neumann style.
It sounds amazing.
Preliminary tests show that the input impedance of this configuration is around 100KOhms.
So it was tried and a 4MOhms resistor from plate or Vb to grid made an EF183 operate as an excellent low noise, small signal microphone amplifier at Vb of only 4.5V. Heaters were also supplied with 4,5V, (less than specs rating), Georg Neumann style.
It sounds amazing.
Preliminary tests show that the input impedance of this configuration is around 100KOhms.
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