Physiological sound control: some essentials and demo schematics
Video about the so called “physiological sound control”. Please read the textbox first. Based on a 1951 book, translated into 2020.
On 1.33 the 1951 book tells about “acoustic power” to give enough sound in a living room. Necessary level to do that is 70 MilliWatt acoustic (say: “sound waves out of the loudspeaker cone”). But to reach that “acoustic” goal, approx. 9 (electrical) Watts must be (had to be, 1950’s) generated.
Has of course also to do with tube-loss and specific properties of 1950’s electronic cicuits, say with audio end transformers, hooked up to “end-tubes”. In Europe: tubes with “L” in their names, like the EL 80 family or so.
But: get an idea that only 70 Milliwatt acoustic energy is good enough to fill a living room with sound.
On 3.06 I say: “decouple the DC”, that has everything to do with the coupling capacitor that blocks DC current but lets AC (say: sound) pass.
On 4.22 I say “bleak sound” but I mean “bald” sound (lacking, say, a certain warmth).
On 5.37 it is of course not a 470 uF (!) (Micro-Farad) capacitor but a 470 N (Nano Farad, so 0,47 uF) capacitor that always has to be non-polar (bipolar means the same).
The video gives many idea’s to realize a “warm” sound on verly low audio levels in your living room.
The audio filter (R-C) circuits are showed with tubes, but you can easily “translate” them to circuits with transistors, the showed circuit with 2 x BC547 b transistors is a very good basic circuit to test this all out. Also a 1 transistor stage (of the 2 showed) can be enough to get success.
Keep in mind: transistors have a low input and output impedance (“resistance”). That, in general, means you need higher value capacitors compared to tube circuits to get the same sound effects.
Good experimental values for sound effects with transistor circuits are: 4N7,10N,100N (=0,1 uF),470N (0,47 uF) and 1 uF (absolutely non-polar).
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Regarding all my video’s: I constantly keep them actual, so the original video’s with the most recent information are always on YouTube. That is the source, and search there. When my video’s are reproduced or re-edited on other websites/channels you can not (!) be sure about the original content (=really working electronics with real properties for a purpose) and important adaptations to the circuits.
Be aware of that, I saw on the internet my circuits reproduced in a poor or not proper way.
I also found that people probably republish my circuits under phantasy names and/or with phantasy properties, attributing electronic properties to them that they were never made for, so phantasy properties. Sometimes they want to find gold with them. I take distance from all these fake claims; I cannot help that it happens, sorry. Upload 13 June 2020.