It may be possible to have a self contained world class moving coil microphone with its tube preamplifier and battery inside the same mic housing structure. Advantages high output, unheard sensitivity and low noise, amazing sound quality.
The constituent elements would be as follows compared to a Neumann U47 for example:
Neumann U47 simplified:
Condencer capsule - High Megohm resistor - VF14 tube - output trasformer
External power supply
Pleiades microphone:
Moving coil capsule (removable) - step up transformer - capacitor coupling - EF183 tube with 4ΜΩ from plate to grid - 3.7 volt li ion battery - output transformer directly to anode (plate)
The 4MΩ resistor neutralises the self assumed negative grid voltage as explained in reference 3. This frees electrons from the cathode cloud and makes possible the operation of the electron tube at 3 volts. A typical value of input impedance is 100KΩ.
An advantage is extremely low noise.
Another advantage is that no high voltage is needed for magnetic moving coil capsules. The magnetic filed is supplied by the permanent magnet.
Therefore there is no need for a DC to DC oscillator for stepping up, or other source of high voltage.
The EF183 electron tube operates at a phenomenal signal to noise ratio using 3.7 volts (practically no secondary emission effects) as on the Pleiades V4 preamplifier.
The heaters are underheated as on the VF14 amplifier of the U47 to extract maximum information with least of noise. So they are supplied from the same 3.7 volts battery source.
Electronic cigarette type li-ion batteries of 5000mAh for example would give plenty of hours of operation.
Of course this amplifier could be used for any other dynamic microphone or capsule.
Moving coils mics are usually 200Ω or 500Ω so cables can be of any length unlike condencer capsules which have to be next to the electron tube of JFET.
A variation of the Pleiades microphone can be with a JFET amplifier such as the K117 as on the Pleiades K117 preamplifier.
The Pleiades microphone may have the posibility of interchangeable moving coil capsules.
A useful protocol may be that the female input on the microphone for any capsule being a standard XLR female connector.
The capsules would have a male termination as on talk back microphones.
So the Pleiades microphone system would be compatible to connecting any microphone even ribbon
ones to its input using a cable of any length or directly.
Other options include phantom powering. Or USB powering as the electron tube operates only with 3.7 volts at about 220mA.
There can be possibility of digital out, making it a digital microphone.
It may be advantageous to have everything in modules so any configuration may be possible. For example: Various moving coil capsules of any polar diagram - input transformer modules with Pleiades proximity degree of compensation for any distance - electron tube or JFET preamp module - analog go digital converter module - iPad lightning connector module etc.
Modules can be made inside Neutrik XLR modules or otherwise.
Suitable cores for the Pleiades transformers are the superb Magnetec Nanocrystalinne Nanoperm tape would cores of extreme inductance index requiring relatively very few turns.
The extreme high signal to noise ratio, the quietness of the battery and the dynamic and smooth sound of the electron tube will make the system suitable to be connected to any other microphone preamplifier as we would connect a Neumann U47 with its high voltage output, low noise and pristine sound quality.
The development of this and any Pleiades concept is open source, public domain, free.
References:
Neumann U47 schematic
Pleiades V4 schematic
On preserving transconductance of electron tubes at anode potential as low as 3 volts
http://euroelectron.blogspot.gr/2017/03/on-preserving-transconductance-of.html
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