The meter was a simple bar graph calibrated in volts per microsecond. There were level meters below the slew meters.
Remember that was in the late 1970's. 8 bit A to D was SOTA. And processors were slow. I had been working on computers that were discrete transistor and tunnel diode logic and just moved to the first gen MSI computers at the time. I had to make a "processor" for that amp since the Z80 was too much to consider building into an amp to control it.
However someone with the skills could import audio tracks into Matlab and extract that info pretty easily I think today. Scaling for actual output should be trivial once you have the raw data. It would also highlight any significant differences between redbook CD and the high rez formats.
Remember that was in the late 1970's. 8 bit A to D was SOTA. And processors were slow. I had been working on computers that were discrete transistor and tunnel diode logic and just moved to the first gen MSI computers at the time. I had to make a "processor" for that amp since the Z80 was too much to consider building into an amp to control it.
However someone with the skills could import audio tracks into Matlab and extract that info pretty easily I think today. Scaling for actual output should be trivial once you have the raw data. It would also highlight any significant differences between redbook CD and the high rez formats.
The highest power compression driver I use can handle 70 volts at 20,000 hertz. So that would give a simplified maximum rate of rise of 140 volts in 1/40,000 of a second.
140V/25uS = 5.6 V/uS if my arithmetic is correct. (Oops RMS to peak would put that at 8V/uS)
140V/25uS = 5.6 V/uS if my arithmetic is correct. (Oops RMS to peak would put that at 8V/uS)
Same with a Python script, maybe 10 lines. The recordings we made in Austin were completely unprocessed 24/96 with applause that went to just below full scale, might be an interesting data point. You are correct, today a complete Raspberry Pi would hardly effect the BOM on a top end PA.
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However it is alleged that all-analog phono playback reproducing ticks and pops and other vinyl whoopsie daisies, is more strenuous than CDs or high rez digital. Your gizmo could possibly verify or refute that claim.
The ADC input will be band-limited at a low frequency though, unless it's done with a non-audio ADC. Certain people here would just argue that you're unable to sample it correctly.
More complicated than streamers and such? That really depends on one's level of engagement with computers. Many older audiophiles much prefer something physical and easy to understand even if its complicated. But I don't listen to music because it's convenient either... I find vinyl much more pleasurable with all its "woes" that make it fun, where as digital feels more like a headache and the results is something that robs the fun.
Missed his point: the ticks and pops of vinyl playback are going to be able to generate signals with slew rate greater than a (theoretical, since you're long into the lowpass at this point) 22.05 kHz full-range sinusoid.
One could ask why accurate reproduction of defects is important other than that they might drive the electronics into pathological behavior. My experience is a big don't care, the folklore is amusing but lacking any substance.
It's about recovering the rather high (>60dB) amplifier from the overload that matters, not accurately reproducing the ticks and pops. Ideally, it should never get into overload, which requires some unusual (for audio) dynamic range.
The mechanical system's vinyl compliance - effective tip mass resonance gives a two pole high frequency rolloff. Pretty steep if the additional two poles of a high impedance (MM) cartridge are added.
All good fortune,
Chris
All good fortune,
Chris
I tend to think the ticks and pops create significant issue for RIAA preamps. Not to mention the annoyance of it all.
On the amp SR issue -- 100v/usec seems like a better new minimum 'standard' for HiEnd. Even higher wont hurt anything too much. Kinda reminds me of noise -- lower is better even if you cant hear it as lower than X, Y or Z amp. Same with distortion... maybe .05% is min spec but lower doesnt hurt, either.
---- the freq response of what I am listening to (Damir) is band limited at the input to 250KHz. What makes a difference is a constantly low output Z vs freq. Unchanging distortion with dynamic load Z changes, channel separation vs OP level, vs freq., clipping behaviour including recovery speed, low distortion at high peak current required,
RIAA has its own host of requirements and with high gain needed, overload margin is often a real issue..... and distortion near that max., behavor from overload. As well as low noise etc. Ive forgotten too much about LP systems, so What else....?
THx-RNMarsh
On the amp SR issue -- 100v/usec seems like a better new minimum 'standard' for HiEnd. Even higher wont hurt anything too much. Kinda reminds me of noise -- lower is better even if you cant hear it as lower than X, Y or Z amp. Same with distortion... maybe .05% is min spec but lower doesnt hurt, either.
---- the freq response of what I am listening to (Damir) is band limited at the input to 250KHz. What makes a difference is a constantly low output Z vs freq. Unchanging distortion with dynamic load Z changes, channel separation vs OP level, vs freq., clipping behaviour including recovery speed, low distortion at high peak current required,
RIAA has its own host of requirements and with high gain needed, overload margin is often a real issue..... and distortion near that max., behavor from overload. As well as low noise etc. Ive forgotten too much about LP systems, so What else....?
THx-RNMarsh
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How about speculations on how FM Acoustics LP noise reduction option (for clicks and pops) works without really affecting the music in a discernible way? That's all I can think about when it comes to clicks and pops.
That article doesn't seem to cover real time reduction for vinyl. But perhaps the concept is in use.
How big of a worry is SR during a moment of non-music, anyway?
How big of a worry is SR during a moment of non-music, anyway?
The "click and pop" issue with LPs has been solved long ago. The two main contenders for solving the problem were SAE 5000 and there was a similar unit from the UK; can't remember who was it from. Both promised to ELIMINATE such problems, the UK unit wasn't too good at it, but the SAE delivered in spades.
I had the SAE 5000 for some 15 years or so and sold it when I crossed over ito the CD camp. I had two pretty badly damaged LPs with many probles, and it was interesting to observe the RIAA equalized signal after the SAE did its thing. It wasn't quite perfect, of course, but it was damn good at it, less that 1% of truly cruel scratches was liquidated with truly no trace. If memory serves the SAE did it by almost instantaneously blocking the problem part of the signal and replacing it with a corresponding part of the other channel signal. Their theory was that most problem signals were very assymetrical and typically happened on one channel only. They had about a zillion shots of this happening to prove the claim.
The really big deal was the Inverse button. This let you hear only what it was eliminating without the rest of the signal. On many occasions, this did make me smile.
If memory serves, I bought it in 1975, give or take a year.
I had the SAE 5000 for some 15 years or so and sold it when I crossed over ito the CD camp. I had two pretty badly damaged LPs with many probles, and it was interesting to observe the RIAA equalized signal after the SAE did its thing. It wasn't quite perfect, of course, but it was damn good at it, less that 1% of truly cruel scratches was liquidated with truly no trace. If memory serves the SAE did it by almost instantaneously blocking the problem part of the signal and replacing it with a corresponding part of the other channel signal. Their theory was that most problem signals were very assymetrical and typically happened on one channel only. They had about a zillion shots of this happening to prove the claim.
The really big deal was the Inverse button. This let you hear only what it was eliminating without the rest of the signal. On many occasions, this did make me smile.
If memory serves, I bought it in 1975, give or take a year.
One of the standards - CEDAR Audio Ltd: Audio Restoration and Forensic Audio Systems
You can get some very nice solutions that don't work in real time even for free, I personally don't see trying to do this in analog anymore. Off hand I can only think of one LP (that I actually scratched by accident) where it is so annoying I had to digitize it and clean it up.
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