Audio amplifier class introduction - Part 1: Class A

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JohnAudioTech

JohnAudioTech

Күн бұрын

Пікірлер: 49
@Abihef
@Abihef 2 жыл бұрын
Nice, definitely gonna follow this one. Gonna start after finishing the living room today
@henrypsosa5220
@henrypsosa5220 2 жыл бұрын
After I watched this video, I was looking for the complete series on your channel... hahaha. I didn't realize it was a new video. I'm looking forward to the sequel.
@teechui2401
@teechui2401 2 жыл бұрын
Note that a single-ended Class A stage designed to drive a low impedance load (like a speaker) would be more likely to be configured as an emitter follower with current sink as the emitter load, and the output AC coupled to the load. What is shown here is a common emitter stage with current source at the collector, which would not have as low an output impedance.
@SANJAY-ArtnStuff
@SANJAY-ArtnStuff 2 жыл бұрын
cool looking forward to the next post.
@SH-vv7zq
@SH-vv7zq 2 жыл бұрын
Fantastic John - thanks for a great start to the series
@goosgitaar
@goosgitaar 2 жыл бұрын
Like the "sound" of class A It has more depth and quality Nelson Pass is the Guru in my opinion,he has some great article s and circuits 😎🎶👍
@xyzconceptsYT
@xyzconceptsYT 2 жыл бұрын
Thanks John, looking forward to the rest of the series! Love your work.
@keithblume5159
@keithblume5159 2 жыл бұрын
It is wintertime. Think of it as a 100 percent efficient heater that also makes music. Let your ears be the judge. Class A wins every time
@Dazzwidd
@Dazzwidd 2 жыл бұрын
especially if it's a 500W amplifier and it never produces any more than a few watts output 😂
@keithblume5159
@keithblume5159 2 жыл бұрын
JLH1969 is my favorite of all time. Recently I built a pair using aluminum lawn tractor heads for sinks
@leiferickson3183
@leiferickson3183 2 жыл бұрын
Looking forward to this series. Your videos are always very good.
@KunalVaidya
@KunalVaidya 2 жыл бұрын
I have following along videos of cheapaudioman, michael beeny, PS Audio, and yours to get better understanding of various amp options and getting the itch to go for it and make amp, and also assemble speakers for them. i heard that the class D has good efficiency but the PWM concept in it may cause fatigue for listener after some time. So class AB appear to be next option, Which are great chip / DIY boards for this to get decent audio for home setting
@EngineeringEssentials
@EngineeringEssentials 2 жыл бұрын
Great to see you back!
@vinxybee6824
@vinxybee6824 2 жыл бұрын
thank you sir for this series, also it would be great if you also include transistor differential amplifier and various stages for signal before output stage... from Kenya 🇰🇪
@isoguy.
@isoguy. 2 жыл бұрын
Great vid, as always. You explain things so clearly. Thank you for sharing.
@davidahmad6090
@davidahmad6090 2 жыл бұрын
excelent as usual sir, thanks John, very interesting.
@narayanbandodker5482
@narayanbandodker5482 2 жыл бұрын
This will be a good series. I would also like to learn more about other amplifier circuits using OpAmps such as transimpedance amplifiers and instrumentation amplifiers. Perhaps you can cover in this series?
@euroshopperbier1337
@euroshopperbier1337 2 жыл бұрын
Very interesting John
@gkdresden
@gkdresden 2 жыл бұрын
In fact there are 2 versions of class A output stages. The first version is to operate the output transistor against a current source. In this case, the current source must provide the maximum current of the load. The maximum efficiency for this version is 25%. The other version is to operate two output transistors in push-pull configuration. In this case, the idle current is only half of the maximum current drawn by the load. Depending on the signal direction one transistor carries more and the other one less current until one transistor carries the full current and the other transistor carries almost no current. The maximum efficiency of this version is 50% and not so much worser than class AB operation.
@CalebePriester
@CalebePriester 2 жыл бұрын
Awesome! I really enjoy your content.
@cuongnguyenquoc6356
@cuongnguyenquoc6356 2 жыл бұрын
Hope you make a video analyzing and evaluating ACA AMP.
@andymouse
@andymouse 2 жыл бұрын
Love it already !...cheers.
@MrHeatification
@MrHeatification 2 жыл бұрын
Great content Sir thank you
@omsingharjit
@omsingharjit 2 жыл бұрын
How Class A ( Signal Transistor based ) produce AC output as drawn ?
@CraftAero
@CraftAero 2 жыл бұрын
AC input = AC output
@omsingharjit
@omsingharjit 2 жыл бұрын
@@CraftAero Bjt is dc device not ac
@CraftAero
@CraftAero 2 жыл бұрын
@@omsingharjit The audio input is AC.
@omsingharjit
@omsingharjit 2 жыл бұрын
@@CraftAero how can you get ac from BJT connected with vcc and Gnd ? You can get sine wave but how ac ?
@CraftAero
@CraftAero 2 жыл бұрын
@@omsingharjit "You can get sine wave but how ac ?" 🤣🤣
@jimdavis5230
@jimdavis5230 2 жыл бұрын
Also as class A output transistors run hot it's worth noting that for every 10 degree Centigrade increase in the transistor junction temperature, the life expectancy halves.
@Blowncaraudio
@Blowncaraudio 2 жыл бұрын
Awesome! Cant wait for the next one!!!
@kamleshchavan7451
@kamleshchavan7451 2 жыл бұрын
When part 2 is coming
@johnsonlam
@johnsonlam 2 жыл бұрын
Thanks John.
@McTroyd
@McTroyd 2 жыл бұрын
I've got a couple old Crown D-series amplifiers (the ones built like tanks that can be used as DC bench power supplies). In their manuals, they describe their operation as Class AB+B. My understanding from the manual is that the core of the amp is class AB, but there's an additional Class B power stage that kicks in for high-power use. Pretty neat solution, but doesn't help with the "letter soup" problem of amplifier classes.
@michaelspiering7585
@michaelspiering7585 2 жыл бұрын
My best sounding tube guitar amp is single ended class A.
@jamesw5584
@jamesw5584 2 жыл бұрын
The ideal solution is to run class A at low power then class AB at higher power. One problem with class A is having to have a big capacitor to block the DC since they usual sit at 50% supply voltage. But in some A+AB amps with complimentary transistors there is no cap so I suspect they sit the dc offset at around 1v on speaker terminals and dump current into each pair? Or you would melt your speakers sending DC into them so Ive always wondered how that's achieved.
@paulb4661
@paulb4661 2 жыл бұрын
With a complementary stage, you either simply set the DC offset to 0mV, if adjustable, or match long tail pair transistors until you achieve the desired result. And since you have both the positive and negative supply rail, the midpoint is naturally zero. Negative or positive DC offset does to a speaker ... what the name actually implies - offsets the cone from its rest position by keeping it inwards, or outwards correspondingly. DC voltage drop across the coil resistance produces heat, just like music signal, but with no sound output the entire 100% turns to heat, not the usual 99%.
@jamesw5584
@jamesw5584 2 жыл бұрын
@@paulb4661 my question is really how do u achieve class a operation without the need of either a capacitor or transformer for dc isolation since class a normally sits mid voltage. I get that if u have a split power supply the center point is 0v but there needs to be some voltage at the emitter for the current to flow. That voltage would normally drop across the emitter resistor but that's a lot of current in class a.
@paulb4661
@paulb4661 2 жыл бұрын
@@jamesw5584 It runs from the positive rail, if you take the conventional current flow, to the negative rail through both transistors and source/emitter resistors. Imagine one transistor as supplying and the other as absorbing current instead. Majority of voltage drop takes place across the actual devices, not the resistors, with usual 0.15-0.33ohms they do not drop much voltage. Take 1A bias; 1x1x0.22 = 0.22W power loss at each resistor.
@jamesw5584
@jamesw5584 2 жыл бұрын
@@paulb4661 I see what you're saying but take for example the hood amp I built that idles at 2.5 amp at 12v midpoint. To achieve a similar bias on a split power supply of +12 -12 instead of 24v presumably ud still be burning 30 Watts in heat and that won't be effected? assuming ud want the same output power and to remain in class a operation? Just don't need a cap or transformer because the dc is sunk into the p or n transistor depending on +/- biasing. I have seen it done with mosfets in marantz and Hitachi amps this way and they pull the bias into class ab from class a when the output reaches a certain threshold.
@teechui2401
@teechui2401 2 жыл бұрын
Sounds like you're conflating amplifier class with bipolar / unipolar supply. Any amp can be on one or split rails, with no relationship to amplifier class. The classic JLH amp is single supply with an output coupling cap, but there have been versions with split supply and bias servos to achieve near zero dc on the output.
@janakapriyadarshana5835
@janakapriyadarshana5835 2 жыл бұрын
Great.......
@RixtronixLAB
@RixtronixLAB Жыл бұрын
Nice video, thanks :)
@dexterperucho90
@dexterperucho90 2 жыл бұрын
1st sir🔥🇵🇭
@1pcfred
@1pcfred 2 жыл бұрын
In this video John takes a big giant dump on Class A amplifiers. 🤣
@antoniojoseandreomartinez9710
@antoniojoseandreomartinez9710 2 жыл бұрын
Like
@samppazzz
@samppazzz Жыл бұрын
Here is one build class a mono amplifier. kzbin.info/www/bejne/sIbLZ4Rmd7yNn9U
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