General > General Technical Chat
Maximum slew rate typically found in music/voice
magic:
--- Quote from: Zero999 on September 19, 2023, 05:47:40 pm ---
--- Quote from: TimFox on September 19, 2023, 03:27:02 pm ---Minimum 0.3 V/us rating corresponds to only 4.8 kHz at 20 V pk-pk.
--- End quote ---
That's more than good enough, considering the bandwidth of music.
--- End quote ---
--- Quote from: mzzj on September 17, 2023, 07:06:08 am ---See my link above earlier.. " The prize for greatest slew rate found goes to a single peak from 'Year 3000' by Busted, which hit 150mV, equivalent to the slew rate of a full level sine wave about 10kHz, i.e. five times greater than Baxandall's figure, and equivalent to a level of 2.5V/µsec for a 100W power level."
https://www.renardson-audio.com/slew-tid.html
--- End quote ---
100W into 8Ω being 40Vpp. Not so good for the old 741.
--- Quote from: Zero999 on September 19, 2023, 05:47:40 pm ---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.
--- End quote ---
Correction of output stage distortion has nothing to do with slew rate, it only depends on loop gain at given frequency.
Zero999:
--- Quote from: magic on September 19, 2023, 06:11:10 pm ---
--- Quote from: Zero999 on September 19, 2023, 05:47:40 pm ---
--- Quote from: TimFox on September 19, 2023, 03:27:02 pm ---Minimum 0.3 V/us rating corresponds to only 4.8 kHz at 20 V pk-pk.
--- End quote ---
That's more than good enough, considering the bandwidth of music.
--- End quote ---
--- Quote from: mzzj on September 17, 2023, 07:06:08 am ---See my link above earlier.. " The prize for greatest slew rate found goes to a single peak from 'Year 3000' by Busted, which hit 150mV, equivalent to the slew rate of a full level sine wave about 10kHz, i.e. five times greater than Baxandall's figure, and equivalent to a level of 2.5V/µsec for a 100W power level."
https://www.renardson-audio.com/slew-tid.html
--- End quote ---
100W into 8Ω being 40Vpp. Not so good for the old 741.
--- End quote ---
That's a moot point because the 741 is not a power amplifier and can't handle the current either.
--- Quote ---
--- Quote from: Zero999 on September 19, 2023, 05:47:40 pm ---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.
--- End quote ---
Correction of output stage distortion has nothing to do with slew rate, it only depends on loop gain at given frequency.
--- End quote ---
That's true.
magic:
But it can handle the voltage swing. Or at least a quarter of it (sorry, 100W is 80Vpp, not 40Vpp).
Which means that over 0.6V/μs is needed to reproduce some real world CDs at 20Vpp full scale.
Which also means that 741 likely wasn't used to produced these CDs, maybe for good reason ;)
Zero999:
--- Quote from: magic on September 20, 2023, 05:46:18 am ---But it can handle the voltage swing. Or at least a quarter of it (sorry, 100W is 80Vpp, not 40Vpp).
Which means that over 0.6V/μs is needed to reproduce some real world CDs at 20Vpp full scale.
Which also means that 741 likely wasn't used to produced these CDs, maybe for good reason ;)
--- End quote ---
I don't know where the figure of 0.3V/µs taken from, but the datasheet says 0.5µ/s.
https://www.ti.com/lit/ds/symlink/ua741.pdf
Alright I take the point, if can't quite be able to produce all real world CDs, just most of them. There are a couple of outliers.
I'm not advocating the 741 audio, just point out that an audio amplifier doesn't have to have sufficient slew rate to output a 20kHz sine wave at the maximum output voltage.
TimFox:
0.5 V/us is typical
The only minimum value I could find is 0.3 V/us, which I used and noted as minimum
National LM741A datasheet https://www.mit.edu/~6.301/LM741.pdf
Of course, no one seriously recommends the 741 for modern audio, since there are reasonably-priced devices with roughly 10x the slew rate.
TL071/2/4: 8 V/us min, 16 V/us typ
NE5532: 9 V/us typ
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