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Maximum slew rate typically found in music/voice
Karel:
Please read this article:
A Method for Measuring Transient Intermodulation Distortion TIM
https://www.ka-electronics.com/images/pdf/Leinonen_Otala_Curl_TIM_Measurement.pdf
newbrain:
--- Quote from: Nominal Animal on September 16, 2023, 09:12:36 pm ---This means that at that frequency, the phase resolution of CD audio is 360°/12 = 30°. If we produce two sinusoidal signals at 3675 Hz (each full wave taking about 272 µs), one for each ear, both starting at zero phase, but one minutely delayed, humans can generally discriminate at down to 10 µs difference. That corresponds to a 360° × 10µs / 272µs ≃ 13° phase difference at 3675 Hz. Thus, CD stereo audio does not have sufficient phase resolution at 3675 Hz to match human hearing.
--- End quote ---
Nope. Sampling and reconstruction simply do not work that way.
The theory says that any band limited signal can be reconstructed perfectly, and that include its phase; any reasonably implemented sampling system (CD) is able to reproduce the phase shift with inaudible accuracy.
Please check this very old but still extremely valid video, it's absolutely worth watching the whole thing, but the relevant part starts at 20.56.
https://youtu.be/UqiBJbREUgU?feature=shared&t=1256
Zero999:
Wow, there's a lot of interesting, yet irrelevant information in this thread.
It's true, the original question isn't very well phrased, but it does have merit. An amplifier does not have to have its full power bandwidth extend all the way up to 20kHz. Look at a loudspeaker cabinet and note, the tweeter has around a tenth of the power rating, of the woofer. That should be enough to give you a clue. Most of the energy in music, can be found at lower frequencies. An LM741 run at +15/-15V will have more than sufficient slew rate to output an audio waveform with an amplitude of 20V peak-to-peak. There are other reasons not to use the 741.
TimFox:
--- Quote from: Zero999 on September 19, 2023, 02:42:12 pm ---Wow, there's a lot of interesting, yet irrelevant information in this thread.
It's true, the original question isn't very well phrased, but it does have merit. An amplifier does not have to have its full power bandwidth extend all the way up to 20kHz. Look at a loudspeaker cabinet and note, the tweeter has around a tenth of the power rating, of the woofer. That should be enough to give you a clue. Most of the energy in music, can be found at lower frequencies. An LM741 run at +15/-15V will have more than sufficient slew rate to output an audio waveform with an amplitude of 20V peak-to-peak. There are other reasons not to use the 741.
--- End quote ---
The 741 putting out 20 V pk-pk will push its slew rate limit. Minimum 0.3 V/us rating corresponds to only 4.8 kHz at 20 V pk-pk.
The actual slew rate limit is like clipping: you don't want to hit it, since the feedback around the circuit will fail and no good will come of it, and stuff happens as you approach it.
As I pointed out above, the input differential stage in a typical op amp is reasonably linear at small amplitudes, but at larger current outputs (the maximum current into the compensation capacitor defines the slew rate) it is less linear and distortion increases.
Zero999:
--- Quote from: TimFox on September 19, 2023, 03:27:02 pm ---
--- Quote from: Zero999 on September 19, 2023, 02:42:12 pm ---Wow, there's a lot of interesting, yet irrelevant information in this thread.
It's true, the original question isn't very well phrased, but it does have merit. An amplifier does not have to have its full power bandwidth extend all the way up to 20kHz. Look at a loudspeaker cabinet and note, the tweeter has around a tenth of the power rating, of the woofer. That should be enough to give you a clue. Most of the energy in music, can be found at lower frequencies. An LM741 run at +15/-15V will have more than sufficient slew rate to output an audio waveform with an amplitude of 20V peak-to-peak. There are other reasons not to use the 741.
--- End quote ---
The 741 putting out 20 V pk-pk will push its slew rate limit. Minimum 0.3 V/us rating corresponds to only 4.8 kHz at 20 V pk-pk.
The actual slew rate limit is like clipping: you don't want to hit it, since the feedback around the circuit will fail and no good will come of it, and stuff happens as you approach it.
--- End quote ---
That's more than good enough, considering the bandwidth of music. You'll only get 20V peak to peak, at low frequencies, up to a few hundreds of Hz, not at 4.8kHz.
As far as not hitting the slew rate vs clipping is concerned. The distortion from limited slew rate doesn't sound as bad as clipping. The effect is more similar to when the sound has travelled through a wall, or ceiling than clipping.
Having a wider bandwidth op-amp is good, but primarily because negative feedback is maintained at higher frequencies, which minimises the distortion due to the non-linearities in the output stage, rather than the slew rate.
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