That can still mean a high harmonic distortion of several percent, well above a typical HiFi standard of <<1%, but may be tolerable for listening to AM radio.
That can still mean a high harmonic distortion of several percent, well above a typical HiFi standard of <<1%, but may be tolerable for listening to AM radio.I meant I did not see any _visual_ distortions on the scope screen.
Totally down with that, cpt.Wally, I am just wondering what it has to do with a bold statement "There's still a LOT wrong with that circuit" of our esteemed pointy-haired boss?That can still mean a high harmonic distortion of several percent, well above a typical HiFi standard of <<1%, but may be tolerable for listening to AM radio.
Your simulation is a bit disconnected from reality.You did not see distortion because C3 was cutting all the high frequency distortion harmonics. C3 also cut high frequency audio making the amplifier muffled like an old AM radio.
I fixed it and got an output power 5 times more than before. The output power is still very low because the power supply voltage is very low.
Bootstrapping is when the output reaches down with C7 ands pulls up the bootstrap voltage on R8 and R14 allowing a higher output signal swing.
section 9.2.1.2.1 only mentions limitations related to the presence of bass boost RC, which is not the case here.My simulation of the "horrible" circuit shows that its maximum positive output is only to +2.9V but with the output emitter resistors value reduced and with bootstrapping the positive output is much higher at +4.5V.
Instability when the LM386 is properly on a pcb and with gain less than 9 is in the datasheet section 9.2.1.2.1 Gain Control. A gain of 20 is close to a gain of 9 so the problems caused by a Mickey Mouse solderless breadboard adds to the instability.
Instability is also caused by a missing supply bypass capacitor that the designers of the LM386 assume that you have, but is not shown in the circuits on the datasheet.
1) As I said, Bass boost is not the case here. Stop wondering about it, IT IS NOT HERE1) The "bass boost" for an LM386 amplifier IC does not boost low frequencies. instead it cuts the gain of high frequencies which can result in instability if the reduced gain is less than 9 times.
2) Most amplifiers produce low distortion at low output levels My simulation of the original "horrible" circuit at maximum output level shows the top of the waveform is squashed which is horrible distortion.
3) Look at many of the amplifiers at Elliot Sound Products to see 0.22 ohm emitter resistors.
4) Yes, C3 was in the wrong location in my simulation. In the original location where it cuts high frequencies it causes much more distortion.
Forgive me my little knowledge of electronics...what is 'bootstrapping R8'? Were you trying to say in this highly professional way 'I'd connect a capacitor in parallel with R8'? Please use simple words, if possible, I'd appreciate that. Why do we need this capacitor? Something related to thermal stability?
Can you give a link to ' four transistors (and less passive components) ... used in commercial radios ' schematics _without transformers_ that would have sensitivity of 10mV, output to 8 ohm speaker and satisfy you in regards to the scale from 1 to 10?
Please point out an example of the 'negative feedback from the output' in 4 transistors push-pull amplifier (no transformers)?
How I can see 'high distortions' you've mentioned? I applied up to 10 kHz 20 mV sine input, did not notice anything distorted on 8 ohms speaker output.
How I can see the mentioned 'unstability'? It works every time I turn it on, no self-generation, no spontaneous output change.
So my next question is - can you please explain the purpose of R9&R10?
Most example diagrams of this type show direct connection of emitters.
Do they have anything with limiting output current and power consumption or is there something more sophisticated to it?
3) Sorry, Australia (or is it Austria) is a bit too far. Amp for radio amateurs must have easily available parts only. Preferably from a standard IEC series. We have standards on resistors, you know. Lowest starts with 1 ohm. If your circuit uses 0.22 ohm resistors then it is waaay more horrible. This is the basics of circuits design.
Thank you!
Tell me the truth please, do you seriously deep in your heart believe that this blurry tiny fragment of some exotic radio interception from 50 years ago - does it match you brave words '... Using four transistors (and less passive components) you can make a 'proper' push pull amplifier, as used in commercial radios etc. for decades'??? really?
This is just hilarious. I appreciate you efforts, though, it took you a whole day to dig out this piece of Roswell blueprints.
BTW, one of your local 'guru' here (he really calls himself a guru) gave me a great advice to get rid of R8&R9 and I barely managed to turn it off before the magical blue smoke showed up. I so love theorists!
I am sorry for tons of sarcasm...it is definitely not your fault.
I was just trying to find a group of people who has actual practical knowledge of analogue electronics.
I am aware of IEC standard where the minimal value starts with 1 ohm. Do you have in mind some Australian standards? I was looking at all kind of resistors for 50 years and never heard of '0.22'.0.22 ohm is a standard value and easily available resistor, and is commonly used in high power amplifiers as the emitter resistors.
You've already got that, but aren't prepared to listen.
I am aware of IEC standard where the minimal value starts with 1 ohm. Do you have in mind some Australian standards? I was looking at all kind of resistors for 50 years and never heard of '0.22'.
I am obviously too low for your shining wisdom, or great gurus of magical blue smoke!)
Don't flatter yourself.
BTW, your self-proclaimed 'guru' said literally -' For an old AM radio then they are not needed '. Please keep doubting, you will be more comfortable this way.
I am a simple man, I ask simple questions and I see a wise man when I am getting concise and simple answers. Not a chain of excuses or some mumbo-jumbo only produced to make you feel insignificant.
You are correct but... the MINIMAL design was set at 20 but that does not mean additional components cannot be added to get lower. The datasheet explicitly says the device is only internally compensated for gains down to 9.AFAIK the minimal, built-in gain of LM386 is 20.
actually they are used a lot in audio amplifiers for output emitter resistors, and they're more common these days than back in the 1970s and 1980s when most amplifiers used 0.47 ohm or even 1 ohm emitter resistors.You know, resistors 0.22 Ohm are not kind of realistic.
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