pop and click filters

At one point or other I tried all of the above with the exception of the Packburn, and found they all simply did more harm than good. I would think that now something much better would be possible in purely digital foremat, but have no idea if anything is.

There were many noise reduction units marketed several decades ago, aimed at rumble, surface noise, pops, clicks, and dynamic range expansion and peak unlimiting. Some, like Bob Carver's Autocorrelator, were very "clever". All worked reasonably well, but none were perfect. Today's vinyl fans prefer to say that all these LP problems either don't exist or can be eliminated by some rather exotic and expensive turntables, pickups, and arms. Whatever...

The only really good way to restore old LPs is to play them back as well as you can, and digitize the signal. Once that is done many techniques can be used that are quite impossible if you try to do the cleanup in real time (while the LP is playing). An example is playing the music backwards. Music has leading edge transients that are similar to clicks and pops, but music has no trailing edge transient...the sound dies away over some time. If you analyse the digital signal forwards and backwards, the clicks and pops, which are transients both ways, can be distinguished from musical transients which only occur with forward playback. I have not actually used this type of LP cleanup software, but the results I have heard far exceed those of the old boxes of electronics.

Eld, music is filled with trailing AND leading edge transients. For example, an acoustic piano has not only a sustain pedal but a mute one too. Likewise, string players use their palms to mute vibrating strings and resonating wood. These mutes create trailing edge transients, a necessary ingredient in the production and reproduction of music.

Rockvirgo...The Mute function performed by a musician, although it may sound abrupt, is too slow to be called a "transient". The fact is that the "play it backwards" approach to click elimination does work.

I suppose that some sort of electronic mute could be used that would chop the waveform off as sharply as a scratch in the LP.

And...the electronic mute would have to be something done by the recording engineer, at his console, not by the musician. Even if an electronic instrument's output were chopped off, the sound would linger on in the hall.