On the Pleiades 2N3053 single ended class A (electrons flowing all the time) power amplifier the RCA/GE 2N3053 transistor is normally driven by a relative high output impedance and it sounds great.
Is it because the transistor is a current controlled current output device? An electron tube is a voltage controlled current output device. (The output current is converted to voltage by the load resistor, in many Pleiades amplifiers the output current of the device goes directly to the voice coil as for example on the electron tube Pleiades Electra II). But on this this post we are concerned with what happens at the input. There is a nonlinear relation of input voltage to input current in transistors as we are effectively driving a diode kind of curve? So by driving with a high impedance are we making this much better by going towards a constant current condition?
On the mono notblock Pleiades 2N3053 driving the Philips AD5046N 800Ω loudspeaker the 300Ω line output of the Sony CD Walkman is increased by a variable series resistor which is then connected to base. It acts as a volume control. The potentimeter used as a series variable resistor (rheostat) is a 4K7 pot. Only 2 of its pins are used. So at the moments the max series resistor is 4.7K. Sound is still heard but at a lower volume.
On the 2 channel 2N3053 driving the Sennheiser HD580 (on breadboard, first test with a 1.3V battery) the input potentiometer is 50K. It sounds fantastic too. A very big and natural sound at all the frequency spectrum, smooth, with just 1 transistor per channel, the series resistor mentioned and a collector to base biasing resistor to class A. It is easy to bias just by turning the bias trimmer resistor for best and louder sound.
Attention, even with 1.3V the sound may be quite loud. If you do any such experiments protect your precious hearing with all known means.
Reference:
http://euroelectron.blogspot.gr/2018/03/madonnas-voice-coming-from-point-source.html
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