Please read the description first before you comment. Much more info there.

Final propery working 15 Watt audio amp & def. schematic of this BD 743 - BD 744 is here (21 sept 2022) [ Ссылка ]

This first vid is/was made for experienced hobby electronics and “makers”.Thus showing fails (!) and developments, by changing capacitor/resistor values etc.

Second video in this series talking about class B amplifiers (upload 17 september 2022) is here [ Ссылка ]

THIRD Video (with a really working & tested audio amp for 10-15 Watt, 18 september 2022) is here
[ Ссылка ]

This first video is/was only a first VLOG.

Talking about principles of class B: an audio signal of say 0.4-0.8 Volts AC must cause an enormous current into a loudspeaker that is connected to the end-transistors, say to a 12-40 V DC source.

Of course Ohms Law is valid always.

And that sound must also be reproduced “pure” via that LS box. With low distortion, that is what I mean, distortion of whatever kind.

CORRECTION: on 13.01 I talk about the capacitor between the base and the collector or the base of the driver transistor in the order of 50 pF-1000 pF.
On 13.09 I talk about “resistors in the order of 4000 Ohms”, but that is of course not OK, of course I mean capacitors in the order of 4000 pF (say 4N or 4N7). They can damp out parasitic oscillations in such a circuit.

When you want to do experiments? Try these “damping” capacitors between the electrodes of the used transistors (E-C-B) to get to a stable circuit. Range: 500 pF-1000 pF.

Please note: this is only a VLOG that tells something about this/the development. The circuit (thus) does NOT work, it is a demo circuit with flaws, flaws that are explained by the way.

When you want direct success in audio amplifiers? YES, here are the circuits:

There are many succesfull audio amplifiers/schematics on my YT Channel, very easy to make, in this order (max 10 Watt).

Let me mention them & examples, more on my YT Channel (Radiofun232 on You Tube).

Say go to the "looking glass", type there "741" or "2N3055" or "audio" or "audio amplifier" or "watt" or "5 Watt" or "TL 071" or "071" etc.

A) Nice sounding audio amplifier with the 2N3055 (NPN) and the 2955 (PNP). Can be made for mono or stereo, always works good is here:
[ Ссылка ]

B) Audio amplifier with the TDA 2003 CHIP for say 12 -15 Volt (say mono 5 Watt). Two of these Chip amplifiers mean: stereo. Usable in automotive/car audio. Circuit is here:
[ Ссылка ]

C) Audio amplifier with a few transistors, e.g. the BD 139 NPN and the BD 140 PNP for say max 18 Volt (mono say 1-2 Watt) is here:
[ Ссылка ]

D) Audio amplifier with the TDA2615, it is the best and cheapest stereo 5 Watt Hi-FI Chip audio stereo amplifier that you can get now, 2022, the sound is extremely pure:
[ Ссылка ]

Best value for money with the TDA 2615 !! (this video shows it).

E) Update & VLOG about that TDA 2615 Chip audio amplifier (3 stage...) say stereo or triplo audio amp. made with the TDA 2615: [ Ссылка ]

F) Stereo audio tube amplifier with the ECL 80 is here [ Ссылка ]

So don’t get distracted by this video. It is made for hardliners that want to develop themselves a Class B audio amplifier from scratch.

The pins in the schematic showed in this video (15 sep. 2022) refer to very old 1970's pins of the 741, they were sometimes sold as doubled (??). For experimenters now, in 2022, the NORMAL values of the 741 Chip and the TL 071 Chip are: pin 6=out, pin 4=ground minus, pin 7 = + positive, pin 2 = min (-) INPUT in and pin 3 = positive (+) INPUT, that regards the 741 Opamp and also the TL 071 Opamp. TL 071 has a FET input stage with an extremely high input impedance/resistance, sometimes usable, and a somewhat higher freq. range. Study the datasheets on the www.

My You Tube channel trailer is here: [ Ссылка ] When you search, search always “NEWEST FIRST” to get the right overview.

You can also search via the “looking glass” on my Channel trailer via keywords like ”audio”, “radio”, “amplifier”, “filter”, “Shortwave”, “transistor”, “FET”, “oscillator”, “generator”, “switch”, “schmitt trigger” etc; so the electronic subject you are interested in.

My books about electronics & analog radio technology are available via the website of "LULU”, search for author “Ko Tilman” there.

[ Ссылка ] I keep all my YT videos constant actual, so the original video’s with the most recent information are always on YouTube. Search there, and avoid my circuits that are republished, re-arranged, re-edited on other websites, giving not probable re-wiring, etc.

Some persons try to find gold via my circuits. I take distance from all these fake claims. I cannot help that these things happen. Upload 14 September 2022.

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