Yes that's my point even though studies of music show the max slewrate is more like .6V/us. Yes, an amp that barely goes max to min in 1/2 cycle of 20k will measure very poorly, probably enough to actually matter.
Wow, talk about learning about slew rate from scratch! Get over it Scott, records often generate slew rates approximating TIM 30. I proved it myself in 1978, and it is in my IEEE paper, and included in Otala's, Jung's, Leach's and my 16 page 'critique' of Cordell in 1980. Just because many here are using CD and below for their general listening, does not remove the need for reasonably high slew rate in power amps, for better sources. Of course, PIM distortion, that goes along with TIM, might be the major problem, but you don't believe in that either. Oh well.
I also was wondering about a good reference for analog low frequency spectrum analyzers. That HP was about the best I remember, a 3Hz IF BW was achieved with a complex crystal filter. I don't see getting it much better. The mixers and log amps sort of limited the dynamic range. It would be hard to better 100dB. Both of these are easily bested by FFT's. And SY is right there is essentially no computational bottleneck anymore continuous 4M point FFT's are trivial. That HP took forever to average sweeps at max resolution. Of course it did cover up to 40MHz, but for audio...
I was simply quoting Peter Baxendall, please take this up with your new buddy Soundminded he certainly has an opinion about Otala I'm sure. Frankly I'm tired of being in the middle of these discussions.
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Take that wikipedia article with a pinch of salt - for example it says that the IPS is where the large OL gain of the amp is generated. Guess that knowledgeable amp designers have better things to do (build amps) than try to edit wikipedia pages (and then watch them reverted minutes later).
Then, if cables do not matter for you why do you make and sell them?
Am I correct in assuming that English is your second language?
se
Continuous 4M FFTs (by that meaning a new FFT for every fresh input sample) ain't happening any time soon. Way too slow in software as FFT complexity is NlogN. Not even desirable - who wants to wait hundreds of seconds for the acquisition of 4M points only to see they forgot to connect the input correctly
I think SY uses 131k FFTs and averages them. So 4M points might contribute to the overall average.
MIGHT be time to split the thread off again??
Sorry to drop in out of the sky... been a bit busy with personal stuff for a number of months... But it occurred to me that at >9000 posts that it maybe just might be time for the moderators to split this thread off again??
I mean it is a great discussion overall, but it's gotten to the size where it will take a normal human a long time to get through it, much less start at the original thread... and while we're at it, it is likely worthy of a title change, although I'd say that is optional...
Regards from Bearlandia,
_-_-bear
Sorry to drop in out of the sky... been a bit busy with personal stuff for a number of months... But it occurred to me that at >9000 posts that it maybe just might be time for the moderators to split this thread off again??
I mean it is a great discussion overall, but it's gotten to the size where it will take a normal human a long time to get through it, much less start at the original thread... and while we're at it, it is likely worthy of a title change, although I'd say that is optional...
Regards from Bearlandia,
_-_-bear
While I have some respect for Peter Baxendall, I found him more conservative than many of his contemporaries, such as Bob Stuart, whom I met while attending a Baxendall lecture in London in 1972. I would be very surprised if he ever even bothered with a moving coil phono cartridge, much like Lipshitz et al..
Mr. Curl, when you say the largest CM choke, does it mean the largest inductance value, current rating or both?
That depends on what's being measured. There's a reason for the drop down window in software which allows choosing number of averages, sample rate, and FFT points (up to 1048576 in the software I use most often).
No. Fourier simply says that to reproduce a particular waveform you need certain frequency components. That says nothing about audibility. Fourier does not stop you from designing a system which can 'hear' some frequencies above 20kHz when certain frequencies below 20kHz are also present (for example).
We think in terms of waveforms because waveforms are what our amplifiers work on. My understanding is that our ears work like a big filter bank, sensing the amplitudes within a huge set of narrow bands. Our ears do not directly respond to the waveform, so Fourier is useful for thinking about amplifiers and transducers, but less useful for thinking about hearing. In addition, acoustic musical instruments do not produce a waveform but a set of frequencies with different amplitudes in different directions. The waveform only arises when you sample the air pressure (or velocity) at a particular point e.g. with a microphone.
Thanks Jan, I seriously tried to look up Baxandall's spelling while I was writing a response, because the one that was initially used didn't look 'right' but I had one heck of a time finding it in any convenient audio book, so I went with Scott's spelling. I found examples of his tone control in various texts, but no reference to him. Sad really. Good tone control circuit, used it myself in one design, 25 years ago. However, he was one of the 'conservatives' in his later years, and he would not be looking for worst case slew-rate from the fastest sources. I did, and found the limit, 32 years ago, to recommend about 50V/us for a 100W power amp. 5V/us for a preamp stage. Tube designs might be significantly less, because their gain structure would probably let you work closer to the actual limit, without compromise.
This has been published by Walt Jung, with most of the audio researchers, concurring, over 30 years ago. Of course, your slew rate may be much less, just like I don't think that the 160 mph point on my Porsche will be seen ever, in my case, but someone, somewhere, with a somewhat modified engine 'might' get close with a similar vehicle.
This has been published by Walt Jung, with most of the audio researchers, concurring, over 30 years ago. Of course, your slew rate may be much less, just like I don't think that the 160 mph point on my Porsche will be seen ever, in my case, but someone, somewhere, with a somewhat modified engine 'might' get close with a similar vehicle.
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