Figured Bass Orchestra

Could an orchestra be made where all musicians have perfect pitch and play without reading notes, by understanding figured bass?


It would be like  the most beautiful instrument playing on its own.


They could hear something and play it or compose themselves in real time thinking fighter bass.

Pleiades Magnetec Neutrik iPad microphone setup

It would be great to make a Pleiades microphone pre preamplifier as follows:


Everything inside Neutrik XLR modules:


Inside a Magnetec 073 nanocrystalinne core,  few primary turns for bass proximity compensation.


Capacitor coupling of secondary to a K177 JFET.


Everything inside the Neutrik modules and power and drain resistor supplied by the iPad headphone mic connector.


This would provide at the same time: proximity compensation for next to mouth mic work, make up gain, extremely low noise, ie great signal to noise ratio, portability, crystal clear sound.

Maximum Information Extraction

If a Pleiades microphone transformer with Magnetec 073 core, capacitor couples the grid of a positive biased EF183 at 5V anode voltage and less than 3V? Heater voltage, a microscope equivalent is created as at such small electron speeds the electron tube is extremely quiet.


Maximum information extraction.


Makes wonders on dynamic and ribbon microphones.

10k to 600 ohm audio transformer microphone step-up step-down impedance hi-z

Just tried this step up transformer bought from TechnoFix on eBay, TL019-R 1438.


Sounded amazing connected to the Pleiades V4 pre preamplifier.


The coupling capacitor to grid on V4 is 220nF. It is very important to capacitor couple to an electron tube grid so that the valve's grid is free. (Not made by force to assume a potential).


The primary inductance of the transformer is 100mH at 1028Hz and 165mH at 97Hz making wonders at compensating the proximity effect of the MD421HL and SM58 (made in Mexico) used. Mic mouth distance approximately 1 in.


Connecting the transformer to the grid of the EF183 made the high frequency response high but not high enough to sound over detailed and unnatural. It seems therefore to compensate the high frequency proximity effect due to the obstacle effect too.


Secondary inductance is 7H making a 1:8.5 step up.


Bravo to the designers, a giant killer!

Who said that microphones should have a flat frequency response?

Perhaps nobody did.


Truth is that what counts is not flat response from mic to loudspeaker but...


Flat frequency response from the vocal cords of the singer to the brain of the listener (explained on the Hollywood paper referred to in older posts).


Apart from this are proximity boost effects at low and high frequencies which must be compensated.


All these effects may explain why a "lesser" mic or input transformer can be a giant killer.


The record industry uses Pultec filters to this end but why not producing a mic where the sound is already there?


Be prepared that frequencies below 1KHz for example must be reduced if a directional microphone is used at next to mouth distance. Similar apparently crazy things must be done at the high end of the spectrum
More on the following posts....

How does a Pleiades filter work?

A Pleiades filter is just an inductor in parallel with the signal.


By reducing the winding turns the cutoff frequency is increased and even closer mic source distances are possible. The same principle can be applied to a Pleiades transformer ie reducing primary turns thereby reducing primary inductance and increasing cuttoff frequency therefore making the mic focus at a smaller distance. Decreasing primary turns has the added advantage of automatically increasing the transformer turn ratio. So this iautomaticaly makes up gain. The core used to make the Pleiades inductor or transformer is an extremely high inductance index nanocrystalinne cores made by Magnetec. This makes possible Pleiades filters with very few number of turns. Example of a core is Magnetec Nanoperm 073.


A Pleiades filter can compensate for proximity effect even at a next to mouth mic distance minimising feedback at PA systems and virtualy eliminating pop and wind noise although its a good idea not to remove the microphone grill as it does much wind noise reducing work. After filtering the signal is so clear that one can hear the greyest detail from a voice. If high frequency cutoff is needed for reasons explained on other posts this can be done by a Pleiades high cut finger which consist of just one capacitor in parallel with signal.


A Pleiades transformer with its high impedance can drive the gate of a JFET or the grid of a vacuum tube trough a calling capacitor. On following posts Pleiades pre preamplifier are  described including an extremely low noise electron tube one powered by 5V only at the the anode (plate). This is achieved by large Megohm resistor from Anode to grid to free electrons.


Such Pleiades pre preamplifiers next to the output of the microphone transformer make dynamic or ribbon microphones so sensitive that play condenser microphones in their own game.


How does a Pleiades filter work?


The microphone output impedance is in series with the inductor and together form a potential divider.
The inductor impedance as usual increases with frequency and makes the microphone output increasing with frequency at 6dB per octave compensating the proximity effect. After the cutof frequency the impedance of the inductor becomes so high that there is no voltage drop at the mic and response contineous to be flat.


How does damping work?


At low frequencies the droping impedance of the inductor (which becomes just it's winding resistance at zero frequency) makes a large current flow through the coil (shorts circuits the coil at LF). This makes the coil behave like a loudspeker but moving in the oposite direction to the cause (sound wave, blast, pop etc) this is Lens  law in action being a represantation of concervatiin of energy for if this force were of the same direction as the cause we would have amplification for free, imposible.




This is the same principle as a brake in electric cars by short circuiting  the output of the motor when the car is running.



Another way to put it, it's kunitic energy converted to heat.



This creates a very effective pop and wind filter.
Wanted sound is  unaffected as at voice frequencies the impedance of the inductor (which increases with frequency) has become large as to no longer be a load on the voice coil, letting it free to move at the pristine quality of your voice.

Compensating for the 2 proximity effects on a Shure SM58

There are 2 proximity effects (when mic is close to mouth), one the increases bass  and the other that increases treble called the obstacle effect


Natural sound from vocal cords to brain of listener for a Mexico made  SM58 next to mouth were obtained as follows:


SM58 was shunt with 19.5mH !  i.e. low cut at 1.6KHz and 15nF shunt to the Pleiades V4 (EF183 pre preamp with 4 AA batteries) output to reduce treble boost, sibilants, saliva noise (sometimes desirable). Added advantage is the reduction of any hiss left and rounding waveform curves should instantaneous peak limiting  occurs at the electron tube, thereby preserving subjective volume due to natural harmonics produced while objectively limiting the signal.


Signal path used:


Voice - SM58 - Pleiades 1:7 input transformer, 19.5mH primary L - V4 (+ve bias from plate to grid) - 15nF across output - Realistic Disco mixer mic in - pad before headphones - Sennheiser HD560 - ears - brain

Pleiades Ribbon mic transformers

A great ribbon microphone transformer can be wound on an extremely high inductance index nanoperm tape wound core by Magnetec.


The very few turns needed would result in an excellent step up transformer with least noise figure.


Silver wire could be used for the 2 windings.

Pleiades Mixing Console

It would be great to make a passive mixing console with just summing transformers (hybrid transformers) made with Magnetec's nanocrystalinne tape wound toroidal cores.


The best way to add signals with minimum loss is with spliter transformers connected the other way round.


Signal 1 is connected to upper side of primary winding. Signal 2 is connected to lower side of primary, Center tap of primary is connected through canceling resistor to ground. Signal (1+2) is received from secondary in all its pristine glory.


This is how Hollywood did it and more information can be found in earlier euroelectron posts. Many signals can be combined to one.

Pleiades 2 stage EF183 battery microphone preamplifier with positive biasing resistor from anode to grid and Magnetec core Pleiades bass proximity compensating input transformer, (under construction)

2 li-ion 3.7V batteries will be used in series for series heaters (each tube heater deliberately at 3.7V, see older posts) and anode supply 7.4V.


Schematic and completed prototype of 1 stage EF183 battery pre preamplifier is given on following posts.


Pleiades public domain dedication

Pleiades 4 focus points, microphone proximity compensating and pop filter schematic with Magnetec cores and Neutrik modules

4 focus points. (optimum bass proximity compensated distances from sound source to microphone)


For 16 points use 4 cascaded Pleiades filters.


Pop blast filtering due to electromagnetic damping.


Passes phantom power as inductors are in parallel with signal.


Gentle 6dB per octave low cut filtering (1st order slope as filter consists of the mic's output impedance in series with the Pleiades filter's  inductance) for overall flat frequency response compensating for the increase of bass content when directional mics at used at close distance.


Relatively few turns needed due to the extremely high inductance index of nanocrystalinne Magnetec cores, Magnetec 073 tape wound nanoperm core or equivalent. Typical number of turns is 40 - 100.


Ease of construction due to the amazing Neutrik modules with switch.


Other variations can include impedance matching transformers. Step up transformers with switched primary in order to low cut and at the same time make up gain.(decreasing primary turns increases cutoff while increases step up ratio).



Impedance matching transformers with deliberate low primary inductance to compensate for excessive bass boost of vocals at close mic distance due to proximity effect. Ambient low frequency noise noise is canceled.


Pop filtering due to electromagnetic damping. (the lower the frequency the lower the impedance of the inductor in parallel thereby converting voice coil movement to heat.


Neutrik connectors and Magnetec cores are the most beautiful worldwide.


Pleiades public domain dedication.


More details:


Directional (unidirectional cardioid) microphones boost bass frequencies progressively below 1 KHz when a singer is closer than an inch to a microphone, the usual case.


The amount of boost can easily be heard experimentally (in practice) or seen in any directional microphone data sheet Shure for example. This can prove an advantage as we shall later see.


The low cut filter of most consoles is at 100Hz giving erroneous results and we are all familiar with the unnatural bass heavy voice when a singer is close to the microphone for  avoiding acoustic feedback. The amount of bass boost as seen on curves is inversely proportional to the mic source distance and can as high as +15dB at 200Hz.


The Pleiades filters intends to give a flat overall response at the usual different close preferred microphone  mouth distances. It may be thought to act analogous to a macro camera focusing lens for very near objects.


Added advantage is a very high signal to noise ratio capturing the detail of the faintest voice even in high ambient noise environments. (Bass environment content is dramatically reduced while voice remains natural).


The Pleiades filter consists of just an inductor in parallel with the mic output signal. This gives the added advantage of electromagnetically damping the mic membrane and dramatically reducing pop and wind noise.


Magnetec makes possibly the best noncrystalline magnetic cores and Neutrik the best modular connectors. It seems natural to combine these elements to make a state of the art variable Pleiades filter.

Using Neutrik adapters, modules for Pleiades microphone filters and transformers

The Neutrik modules would be excellent for assembling a variable proximity compensating filter, cascading many Pleiades filters and switching with binary code combinations. Similarly for variable primary Pleiades microphone transformers.


The D shape adaptors would be great to accommodate large Nanocrystalinne tape wound cores for microphone matching transformers and moving coil cartridge matching transformers (passive pre preamplifier).


Neutrik connectors are the most beautiful worldwide.

Can a Pleiades Electra headphones tube amp be made with just one PCC88 or ECC88?

Preferably PCC88.


It may be possible if positive grid bias is used to increase anode current and gm.


The higher battery voltage source will supply and under heat if needed heaters and also supply anodes directly through the high impedance headphone windings.


Oops, the heater is 7V which is not very high. Perhaps 2 PCC88 can be used heaters in series. This will allow under heated operation (which seems desirable) at 12V supply. 12V for anodes should be great as a doubling of voltage quadruples power, P=(V squared) / 2.


The 2 paralleled triodes for each channel will also reduce output impedance to half .

Can a tube mic pre pre amp be made that operates on 1.3 Volts?

An electrometer tube can be used as shown in an earlier entry.


But can a PCxxx or PFxxx type be used?


Since their heaters operate at 4V, 1.3 Volts may provide the right under heating needed for low anode voltage operation.


Positive grid bias may do the trick as well as output transformer use so that the plate (anode) can be supplied  with 1.3V which is already too low.


The trick is to find a tube that is high gm and vary gm (variable tranconductance) as they have uneven grid spacing. Pentodes are very suitable since when triode connected the 2nd grid (screen grid) acts as an anode and is very close to the cathode to attract electrons.