Open base transistors

A common emitter Pleiades Siemens AC151 germanium one transistor microphone front end preamplifier was made on S-DeC projects breadboard. Signal path: male singing voice in reverberent room - Revox M3500 - German 500 ohm to 600 ohm low inductance input transformer for isolation and low cut - phase inversion adaptor - 56nf to base - Pleiades amp with Siemens AC151 with Rc=5K6, R(Vb to base)=1Mohm, Cc=220nF, Vb=9.3V, emmiter to ground +, Realistic 32-1101A disco mixer line in or mic in = Sennheiser HD580 - Singer (listener) brain. At such conditions Vc drops to 3.5V. It is noisy, hissy. When the bias resistor was removed ie base floating, gain was reduced, but noise improved, input impedance must had increased and fat nice sounding distortion took place making vocals sound airy and big. At such open base conditions Vc=8.2V, so drop across load resistor is ish 1V and from Ohm's law Ic is ish 1V/5.6Kohm ish 1V/5Kohm ish 200 microampreres.