Pleiades Phantom Powered inline Microphone Booster Low Noise Pre Preamplifier Schematic, Photos and Specifications

Pleiades Phantom Microphone inline Booster pre preamplifier.


Designed while waiting for the metro and listening to Tell me Lies - Fleetwood Mac.


This should act as a microscope getting the subtlest nuances of voice.


The Pleiades input transformer passively steps up the microphone signal and then the high impedance feeds the high input impedance gate of a low noise JFET as on condenser circuits.


So the JFET receives an already highly magnified signal with the least possible noise on our planet.


Proximity bass compensation can be adjusted by reducing the number of turns in the primary winding of the input transformer.


All components of the circuit fit inside Neutrik Modules..


The in line booster pre preamplifier passes phantom to it's input.


A switch is added to switch off phantom power at the input when a ribbon mic is connected.


You act at your own risk.





 Pleiades Phantom in line Booster Microphone Pre Preamplifier



 Pleiades Phantom  in line microphone Booster pre preamplifier (3) schematics



Pleiades Phantom in line microphone booster pre preamplifier showing Magnetec 073 input transformer core and Neutrik Modules
 

Pleiades Phantom in line Microphone Booster Pre Pre amplifier showing output transformer 073 Magnetec Nanocrystalinne core and Neutrik Modules


Architect's Specifications:


The Pleiades Phantom Microphone in line Booster pre preamplifier:


1. Shall be contained inside an XLR module adapter of the highest quality,  Neutrik or equivalent.


2. Shall provide enough gain boost while keeping noise the lowest possible comparable or less than the best condenser mics while giving an output comparable or higher.


3. Shall have transformer balanced input for highest common mode noise rejection and being able to pass phantom power.


4. The input transformer shall be made of state of the art Magnetec 073 nanocrystalinne core or equivalent. The primary and secondary windings shall  be physically (geoimetricaly balanced).


5. The number of primary turns shall dictate the amount of bass cut for effective bass proximity effect compensation.


6. The step up ratio shall be made as large as possible to extract maximum information from the microphone with the least possible noise before driving the high input impedance of a quietest JFET stage.


7. The JFET stage shall contain the least possible components for extremely natural amplification and high integrity.


8. The JFET stage shall be single ended or long tailed pair etc., class A (electrons flowing all the time) having therefore extreme linearity at small signals and objective compression with subjective intact dynamics at high levels due to ear-brain analogous gentle overload characteristics. It shall therefore provide instantaneous peak limiting.


9. Power shall be supplied from a phantom source derived from the center tap of the secondary of the output transformer.


10. The output transformer made in a similar way to the input transformer, shall be contained inside the XLR adapter, shall step down the output impedance of the JFET and provide balanced output and isolation to feed ordinary mic input stages.


The Pleiades Phantom booster inline microphone pre preamplifier is specified.


(A similar but even simpler implementation of the Pleiades microphone pre preamplifier for devices such as iPad, iPhone, m Audio microtrack, Zoom etc is described in earlier euroelectron blog entries).


Public Domain