3rd generation Variable inductance (frequency) Pleiades filters

An inductors connected in parallel to the signal source which has a variable inductance with respect to frequency.


This can be done by using a core material which gives has an inductance index which varies with frequency. Mumetal for example [Babani].


It reminds a mass which has a different mass with respect to velocity. See special theory of relativity - Ainstein. Approaching the speed of light any mass with non 0 rest mass tends to infinity so there is no way that the speed of light be exceeded. For a mass at least that was already traveling at less than c?



It was inevitable that it would have led to metallurgy.


How about connecting a microphone in parallel to an inductor which has an inductance of 140mH at 97Hz and 40mH at 1028Hz?


This would create a very gentle low cut, high pass slope aiming for flat frequency response from producer's brain to listener's brain.


One transformer made by Freed was found whose primary has this behaviour. It sounds great on Senheiser MD211, MD441 U3 (the version with no LF shaping) without doing anything else than connecting to its secondary an electrometer CV2269 electron tube as a head amplifier powered by 1.2V for both heaters and anode [Pleiadss 1 - euroelectron].


A variable load impedance with respect to frequency changes the output of a mic as the latter has a non 0 output impedance, usually 200Ω. This can be taken to advantage. Such filters can be seen in all major mic Datasheets, eg RCA 77DX, AKG 1000E, Electro-Voice RE15, Sennheiser MD441?


Nanoperm for example seems to have a constant inductance index core so the slope is 6dB/oct.


The second generation Pleiades filters have a resistor in series with the coil inductor for producing less than 6dB per octave high pass slopes.


There is also the listening observation while clipping inductors (attention for hearing protection) that Nanoperm creates high harmonics whereas older type of transformers (Mumetal?) produced less high order overtones. See an older post.


More investigation is needed in such areas.


Later addition. How would ordinary power transformer core sound? Or winding simultaniously on 2 rings of different material? Or using E, I laminations of different materials sandwiched? Eg. Silicon steel, Mumetal, iron etc. It sounds more and more like cooking. The art of electronics.


References:


Coil design and construction manual - B. B. Babani


The use of microphone transformers for flat frequency response from producer's brain to listener's brain - euroelectron
http://euroelectron.blogspot.com/2018/07/the-use-of-microphone-transformers-for.html