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| AB-class amplifier schematic analysis & optimization |
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| ratatax:
Any audio-related discussion inevitably ends like that ;D |
| Zero999:
--- Quote from: ratatax on May 24, 2019, 01:27:07 pm ---Any audio-related discussion inevitably ends like that ;D --- End quote --- Yes it does get on my nerves how audio threads invariably turn to audiophoolery and trolling. I apologise for my part in it and am no longer responding to it. --- Quote from: ratatax on May 24, 2019, 12:54:03 pm ---I know your suggestions here may be using higher quality parts, but what about this one : http://www.ti.com/lit/ds/symlink/rc4580.pdf It's cheap, has some oomph to be used as a headphones amplifier, has low enough THD/noise... and the implementation seems dead easy. I'm a musician but I like when choices are made with measurable, scientific proofs, since audio as it is perceived by our ears is way too much subjective. Some opamps with thousand of V/uS slew rate and hundred of Mhz bandwidth may sound very good but I feel it's just unneeded complications (unneeded costs too), like you can buy a race car to drive at 30mph in a city...but WHY ? ;D --- End quote --- That's a good idea. I'll add that to my list of decent op-amps. How about the MC33078 or use two channels of the MC33079 in parallel? The NJM2060 also looks good. |
| Alex Nikitin:
Same, I am sorry for this off-topic, stops here. Cheers Alex |
| David Hess:
--- Quote from: Alex Nikitin on May 24, 2019, 07:51:09 am ---driving a speaker coil is not equivalent of driving a resistive load, that is one of reasons why amplifiers with similar traditional measurements could sound different in real life --- End quote --- The reactive part of the load changes the phase relationship between the current and voltage which can be seen in a class-b design where the crossover distortion will move away from zero volts. But in a well designed amplifier, it makes no practical difference assuming that the reactive load characteristics were designed for. A more important effect is that the reactive load shifts the current to voltage across the output devices which can result in violation of their breakdown rating. The protection circuits and output device derating need to take this into account. --- Quote from: magic on May 24, 2019, 08:53:03 am ---True that, but after all those years of hearing about it I would like to finally see a demonstration of two amplifiers which both show no perceptible noise, 0.1dB gain flatness from 10Hz to 50kHz and some low THD figure, all measured into the actual demo speaker, and yet sound different enough that somebody (bonus: everybody) can tell them apart. I'm not aware of any instances of such demonstration actually being done. I suppose it would be all over the Internet if it happened, given the amount of controversy. --- End quote --- I have seen differences in amplifiers with otherwise similar characteristics in two areas: 1. Harmonic and intermodulation distortion tests will not reveal low full power bandwidth which will create additional distortion in real content. Production designs should never have this problem. 2. Overload recovery after clipping can be significantly different. This is especially a problem with naive designs which use frequency compensation to control noise and bandwidth and I suspect this is where negative feedback in audio amplifiers gets a bad image. As far as the like of rigorous scientific tests, maybe they are allergic? |
| Alex Nikitin:
--- Quote from: David Hess on May 24, 2019, 07:45:10 pm --- --- Quote from: Alex Nikitin on May 24, 2019, 07:51:09 am ---driving a speaker coil is not equivalent of driving a resistive load, that is one of reasons why amplifiers with similar traditional measurements could sound different in real life --- End quote --- The reactive part of the load changes the phase relationship between the current and voltage which can be seen in a class-b design where the crossover distortion will move away from zero volts. But in a well designed amplifier, it makes no practical difference assuming that the reactive load characteristics were designed for. A more important effect is that the reactive load shifts the current to voltage across the output devices which can result in violation of their breakdown rating. The protection circuits and output device derating need to take this into account. --- End quote --- The main problem is not that loudspeaker is a reactive load (at least that is a reasonably measurable and easy to deal with effect) , but that it is a very non-linear load, and not only load but a source as it acts as a microphone picking up vibrations and sounds. All this rubbish gets back to the amplifier and enters the feedback loop, as well as other drivers in a multi-way speaker. Cheers Alex |
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