More on the Pleiades single ended class A power amplifiers

If an ordinary 2x5mW headphone Walkman CD amplifier can sound driving loudspeakers beautiful even at 14 meters outdoors in quiet night surroundings...(see a recent previous euroelectron post titled The Best Compressor).


Then a 200mW amplifier would be paradise.


A point is how beautiful, loud and full electron tube amplifiers sound near their signsl overload area.


A very nice sounding EF183 triode connected power amplifier could be made fed with an anode voltage of 12V or above. A resistor or the order of Megohm from anode to grid would increase the anode current and thus lower the output impedance to properly drive the big? output transformers matching to 4 or 8 ohms.


With big transformers designed with air gap it should be possible to go down to 20Hz without the need of negative feedback.


The point is also using just one electron tube per channel (no preamp tube for a pure signal path).


A battery if 12V can supply both heaters of the 2 EF183 in series.


These 12V can supply the anode circuits too.


So there would be no need of bulky and heavy power transformer, tube rectifier, heavy and expensive choke, paper in oil capacitors etc.


If more power than a few great sounding milliwatts is needed then...


Bulgin battery holders (drawer action) can be used for many 9V rechargeable batteries in series. Using batteries seems much simpler than using all the above components.


And there would be absolutely no hum and noise. Just pure silence.


So much silence that the output of the amplifier with nothing connected to its input could be connected to a microphone input and the only sound heard would be the random thermal motion of electrons, ie hiss.


Every time the supply anode voltage is doubled the power should increase four times since Power=(Voltage x Voltage) : Resistance. If by then more voltage signal input is needed to drive the grid of the EF183 then input transformers with say a 1:4 to 1:7 step up ratio could be used. It may be possible to use standard Sowter or Jensen microphone transformers.


Just 5 9V batteries would give 45V. And they can be charged on those Imedion bulk battery chargers. If anode current is 10mA for example and 300mAh batteries are used, they should last less than 30 hours.


This amplifier should be ideal for listening at night. It should sound loud as the tubes would be near their clipping point but the neibours won't mind or notice.


See also the next post on having single ended amplifiers sound loud at any volume.


It is great that so many engineers in Asia know since a long time how great 1 or 2 Watt single ended amplifiers can sound, especially on efficient speakers.