Pleiades SM57 mic filters (dampers) on Drums

Mark Baykian is the first worldwide to apply Pleiades filters on SM57s for bass drum, toms.


He used the term dampers as the low impedance of the filter at very low frequencies damps the microphone's membrane.

Shure SM57 SM58 proximity effect compensation using Pleiades Filters

A great way to low cut on an SM58 is to connect a Pleiades Filter in parallel to the voice coil.


The mic output transformer can be kept in place.


For very intimate and crystal clear vocals.

Box of Pleiades

Using 3 Pleiades filters of 100Hz, 50Hz, 25Hz, with a switch each (in or out of the parallel bus) the combinations are:

000              flat

001            25Hz

010            50Hz

011            75Hz

100          100Hz

101          125Hz

110          150Hz

111          175Hz

The push buttons could change color when they are pressed so that the binary code would indicate the cutoff frequency.

Interested users may  to buy or wind 1 at a time. Then they could insert them as XLR adaptor plug ins or use them combined on their own without a box.

Pleiades Filters Operate at Line Livel Too

A pair of Pleiades filters was used after a binaural recording at the line out of  M-audio microtrack recorder to compensate for proximity effect, difference in reproduced to original level, bad bass acoustics etc.

Pleiades 3D microphone

The Pleiades binaural microphone consists of 2 in ear electrets.


It therefore uses the original information influenced by our skin, hair etc to recreate the exact sound field on headphones. Up down and behind our head can be faithfully reproduced.


Can a hologram of sound be made?

Cascading Pleades filters with switches to create any cutoff Frequency

If 14 Pleiades are connected with switches in parallel any frequency can be selected from 1Hz to 16,384Hz at steps of just 1Hz.


Frequency can be selected using binary code.

Non linearity of Pleiades High Pass Filter

There may be an interaction of the Pleiades filter with the sgnal itself.


At high input signals the inductance may drop decreasing bandwidth like magnetic tape recording.


At mid frequencies our hearing mechanism is sensitive for survival.

Feedback on Pleiades Merope Mic Highpass Filters

Mark Baykian (Magnetic Recording  Studios) is the 1st to buy the Pleiades filter worldwide.


One comment from his top US studio:


"The Pleiades filter works  so well I will use a dozen at different values."

The Pleiades input transformer passes phantom power

Pleiades mic input transformer and Pleiades electra amplifier combined and phantom powered

The Pleiades input transformer can be connected to just an active device (e.g. F.E.T.) and powered by the standard mini jack mic input for Electret condenser mics.


Alternatively 1 or 2 active devices can be connected all inside an XLR adaptor that can be phantom powered.


The above will fully exploit the very high input impedance of the active devices (electron tubes e.t.c.) and the great step up ratio capability of the Pleiades input transformer.

pleiades low cut high pass microphone filter schematic

The Pleiades Filter is an inductor in parallel with signal

One implementation is a nanoperm toroid coil inside an XLR adapter for microphones.


Compensates the proximity effect at 6dB per octave and electromagnetically damps moving coil membrane.


It therefore presents a low distortion sparkling high pass signal to the mic preamp.

Another Neumann Secret

The beauty of a tube front end is that gain reduction takes place at high levels.


This is similar to what happens in our outer ear 3 tiny bone variable gain compressor.


This is due to grid leak bias as Armstrong explained and Neumann beautifuly used on the U47.

pleiades sun battery charger

Uses a nice 6 volt solar panel, a Schottky diode from + to battery +, and interchangeable battery holders for 2, 3 or 4 rechargeable batteries.

on pleiades filters

A useful property of Pleiades filters is that if 2 are connected one after the other the new cut off frequency is the sum of their cut off frequencies.


( Using the known relation for 2 inductors in parallel:  1/L=1/L1 + 1/L2 )


f = R / ( 2 x PI x L )   ==>


f = R / (2 x PI) x 1/L ==>


f = R / (2 x PI ) x (1/L1 + 1/L2) ==>


f = R  / (2 x PI x L1) + R / (2 x PI x L2) ==>


f = f1 + f2

pleiades preamplifier schematic

Please note tube is drawn upside down!


The grid needs  to be biased  positive hence the order of 4 Megohm resistor.


Input impedance is around 100KOhms.

Pleiades Microphone Preamplifier

Possibly the best way on our planet to amplify the tiniest signal with less noise is to use a battery powered electron tube.


This is done by using a high transconductance variable mu tube such as an EF183 at very low voltages.


The heater and plate can be supplied with 3.7V only and a few Megs resistor is needed between 3.7+ and control grid to free electrons and have an anode (plate) current of  >100 micro amperes.


This can make a nice portable single battery electron tube pre pre amplifier. Pleiades filters can be used as input and output transformers. It's a beauty to "hear" the absence of noise from battery clean dc supplies.


Could this be used to detect a most distant object in universe by being the front end of a radio telescope helping to unveil borders of the past?


Georg Neumann used lower than specified heater voltage and small plate voltage on the VF14 tube on the legendary U47 Telefunken Neumann microphone and changed our planet musically.

At 0Hz the Pleiades Filter acts as a short circuit

This damps the microphone membrane and dissipates pop noise without needing a pop screen.


It should be great for live vocals with dynamic mics protecting the first stage of the mixing console from the low frequency crowd PA and stage noise.


Great with ribbon microphones at any distance.

The most beautiful addiction is being under the sun

οταν δεν οικειοποιούμαστε τίποτα έχουμε πρόσβαση παντού

The Pleiades Electra Amplifier can also be made with Junction Field Effect Transistors JFETS

Pleiades Microphone Filters

It would be great to have a wirewound Pleiades nanoperm toroidal  low cut mic filter that uses same technology as variable wirewound resistor potentiometers.


This may act simillarly to a focusing lens for any microphone singer-actor distance.


The Pleiades filter sounds so natural possibly because its gentle 6dB per octave attenuation inversly matches the unwanted proximity bass boost effect giving an overall flat response.


Can a variable multiturn wire wound Pleiades filter be made?

Pleiades Voice Filters Received Excellent Comments from top US Q ADR Studio