Dreaming today the song with working title No Comment

Suddenly while dreaming of Marina singing a song and while trying to rememer it, she sung another one which sounded very nice while I was flying quite high above ground. There were lyrics but they could be any lyrics. Trying to remember the verse and chorus, waking up, rushing to record on a small portable cassette recorder, could remember some of it. It is bossa nova in Dminor. Similar temo to The Girl from Ipanema - Jobim. Intro:F-EB/----/F-EB/----/G--FD/etc. Verse goes in melody (Dminor)--D-/F-E-/B---(Gminor7)/----,--E-(A7)/G-F-/D---(Dminor),repeat with improvisation,Chorus:--D-/E-F-/G---(Gminor7)/---/--GG(A7)/GAAB/B--A(Dminor)/----/--F-/E-D-/F---(Gmin7)/----/--E-(A7)/D-C-/D---(Dminor)

God may be a great record producer

How are gentle slope passive EQ (equalizers) created?

At your risk. Using patent US3624298? ie bridged T constant K with varying resistors on each of the inverse circuits, one being inductor, the other capacitor? For example by using equations from Elements on Sound recording - frayne, Wolfe... for a Shure SM58 microphone impedance of 314 ohms, left and right resistor of the T network, 314 Ohms each, lower shunt inductor 100mH, upper series capacitor approx. 1uF. Equations are L/C=R times R, l=R/(PIxfc), C=1/(PIxfcxR). For Fc=1KHz. Or using a simpler passive EQ described in Audio Cyclopedia - Tremain, where inductor circuit is connected to tap of variable resistor, capacitor circuit connected to tap of other variable resistor, each potentiometer for LF, HF bass, treble (attenuate or boost) respectively. If memory is correct potentiometers are in parallel with signal out. Or using just an inductor in series with variable resistor and total in parallel with mic, ie Pleiades (R,L) filter but with component valkues recalculated for a lower cutoff like the Cinema Eng EQ? By the way what is the variable filter, EQ inside the so nice Sennheiser MD421 microphone? By the way the AKG D 330 microphone used by ABBA at live shows? has 2 very nice EQs: bass correct, high increase. The Shure SM7 has a nice bass correction or low cut? filter and a broad band? reject, apparently to make the high frequency peak flat, schematic can be found on www.coutant.org. The AKG D1000 microphone has a nice bass correction passive filter too. Other non insertion loss way could be an inductor with core magnetic permeability that varies with frequency. This would create an inductance that varies in frequency in a different way to 6dB per octave. Some audio transformers (with silicon steel? mumetal?) such as Hammond transformers seem to have this property by measuring the primary inductance. If a low primary inductace transformer is choosen or the mic impedance is steped up by another transformer then the cutoff frequency could be moved to 1KHz which is close to a frequency in the Cinema Enguineering low frequency correcting side of the 4031-B program equalizer. Such inductance is to be connected in parallel with the microphone output.

It seems the Cinema Engineering Program Equalizer low cut is a shelving filter?

At your risk. Basic, quick frequency responce tests at bass -12dB showed (towards low frequency) slow decrease below say 5KHz, then more abrupt below 2KHz, finally shelving at about 150Hz. At a setting of -4dB, simmilar but gentler slope, shelvibg at around 300Hz. The Pleiades (130Ohm,20mH) gave a somehow similar responce but starting dropping at a much higher frequency. (signal generator by by Lode output impedance, aprox. 400 Ohms, readings taken on Rohde & Schwarz Psophometer).

Many thanks to Mikes Psalidas for giving me so much information on Cinema equalizers

Mikes Psalidas was an electronic Engineer. He designed the mixing cosole used by Finos Films, and gave the same mixing console for electronic music composer and producer Vangelis (Vangelis Papathanasiou). I admired the sound quality of the Finos Films songs by Aliki Vougouklaki et Al, made very very insisting phonecalls to the late Finos Films headquarters, after Finos death and they inventually let on the name of the man who designed them, Mikes psalidas at that later time engineering director at Pitsos factory. A phonecall to the factory made me speak to the man. asking, "are you the man responsible for the fantastic Finos Film sound?" He laughingly said "yes" and immediately invited me to his place later on, same day. The first thing he did was handing me a full pack of Altec original schematics, including engineering notes. From a paper by John Eargle - Altec, on monitoring equalisation, the US patent 3624298 was found on passive equalizers used by Altec, see today's posts. Mikes Psalidas generously immediately said that flat electronic frequency responce leads to non flat listeners's brain frequency response (not in his words), because flat electronically in simple terms sounds very bass heavy (not in his words). And he proceeded to donate me one of the gretest books, by Hollywood engineers, Elements of Sound Recording - Frayne, Wolfe. Saying i know, i also have this book. (First time seeing it was at the great Warwick University library). After thanking him again and taking the book we continued the interesting conversation. We hit off very well with Mikes Psalidas, and his wife was very kind too. I miss him. P.S. He could not find the schematic of the mixing desks, neither did he know what had happened to the mixing desks themselves. The coils for the inductors were wound by his friend Fousekis (both were at some time at Hellenic Radio and television) in the basement of an international Airline offices at Syntagma square. His daugther later, generous as him donated most of his books.

Understanding how the Motown, Altec9062A attenuation part of Equalizer operates with possible schematic, on patent US3624298, assignee LTV Ling Altec, Inc. Anaheim, Calif.

At your risk. The patent explains in detail 1/3 octave band attenuation equalizers, ie an EQ with greater resolution, but the principle and components used seem to be the same. A very recent light giving paper is Graphic Equalizers Based on Limited Action Networks, by Kurt James Werner. Inside the paper are actual measurments, equations given too.

Design equations, schematic link for the Motown graphic EQ, Altec 9062A graphic EQ

At your risk. This very informative and very recent paper was found with great bibliographic and journal references: Graphic Equalizers Based on Limited Action Netqworks - Kurt James Werner - Proc. 27th International Conference on Digital Audio Effects. If i am not mistaken by reading this paper, the Altec 9062A, Motown EQ are not constant B (constant bandwidth designs), and they are based on simpler constant K, bridged T networks where the varying 2 resistors are part of the LCR (inductor, capacitor, resistor) upper and lower inverse circuits. Also the paper Professional Audio Controls - Artur C. Davis, Don Davis was found by web search and it was realised that Davis are the inventors. Then in the Pleiades lab schematic library a printed patent was found by inventors Artur C. Davis, Donald B. Davis, James J. Noble, (Altec). It is US3624298, Sound Improving Means and Method. It shows in fig. 3 a bridged T constant K network with 2 varying resistors each in the LCR top and bottom inverse circuit. This EQ is an only attenuation version as it is meant for room sound system EQ correction. The inventors describe in detail how it works and the varying Resistors are linear and decrease in oposite directions. Left and right arm resistors are said each to be equal to system impedance. A simpler circuit on this patent, fig 2, is just a variable resistor in parallel with (an inductor in series with a resistor), in parallel with a capacitor. Signal is fed in series with such network. This is very similar to the recently described on euroelectron, fullrange speaker correction crossover network. The inductor in series reduces mid high heaviness, the varying resistor puts back some high frequencies, the capacitor passes higher frequencies if the speaker cannot go very high by itself. Back to the patent, the varying resistor controls increase attenuation bandwidth.