De-clipping, best time to use?

[Menchi]

My source files show "sheared off" plateaus, so I assume I need to de-clip.

If de-clipping introduces distortion, what the best time to run the de-clipper, in relation to other filters? Can other filters have any effect on the distortion that might be introduced?

In case the answer is project specific, here is what I have been doing:

Souce material: Cassette tape, recorded from radio
Recorded to computer, at a peak of about -2 dB.
( Using DC6 )
Reducing gain to about -6.
Running multifilter as follows:
- Hi pass
- Low pass
- Impluse
- Dynamic Noise
- Median
- Continous Noise auto spectrum CNF
Continuous Noise CNF ( several times, taking different sound samples )
Normalize to 0dB

Thanks, Mechi.

[Craig Maier]

I would think that the best time to run the de-clipper would be right after decreasing the gain about - 6 dB. Running the de-clipper should decrease the distortion, not increase it.

[Menchi]

Thanks for the reply - now putting it into use ...

Menchi

[DougMac]

At the source creation

To me the best time to de-clip is at the recording stage by creating an unclipped file.

It's hard to tell from your post, but have you stepped through the recording chain to make sure the clipping exists in the original file and is not being introduced in the digital transfer? Can you hear the same distortion from headphones plugged into the deck? Also, analog distortion from overdriving should have a different looking waveform than digital clipping.

I learned the hard way that in some sound cards you can overdrive the front end sound card pre-amp in an attempt to get a good gain out of the back.

Forgive me if you've already checked this out. I just got to thinking why you'd need to de-clip at all.

Doug

[Craig Maier]

DougMac -

Good point. It is best never to have to use the de-clipper.

[gfpeek26]

noise

A related "yeah verily" I've often heard -

It is almost always more efficient to eliminate noise at the source!

best,

George Peek
Safford, Arizona

[quartet87]

Coincidentally, just last night I tried de-clipper on a file from a commercially-duped cassette with Dolby-B. The dupe was very hot and fairly well clipped. I assume the cassette was mastered intentionally that way to hold hiss level to as low as possible. I recorded the file at near peak, so I reduced it by 3dB then experimented with De-Clipper. I ended up settling on the "operational amp" preset which restored the dynamics nicely, putting a little punch back into the music.

[Menchi]

[QUOTE=DougMac]To me the best time to de-clip is at the recording stage by creating an unclipped file.

It's hard to tell from your post, but have you stepped through the recording chain to make sure the clipping exists in the original file and is not being introduced in the digital transfer? Can you hear the same distortion from headphones plugged into the deck? Also, analog distortion from overdriving should have a different looking waveform than digital clipping.

I learned the hard way that in some sound cards you can overdrive the front end sound card pre-amp in an attempt to get a good gain out of the back.

Forgive me if you've already checked this out. I just got to thinking why you'd need to de-clip at all.

Doug[/QUO

The source material is on cassette, recorded from FM radio. It covers vocal and music segments from many different decades. The individual segements all vary widely in quality as the original broadcast material is from the 1930's to current.

It is too time intensive to try to restore each individual segment on a tape, so I usually concentrate on background noise elimination over the whole file. I haven't applied any de-clipping up to now.

I record the cassettes to PC, at about -4db. I don't know if my soundcard is introducing more distortion or not - I am guessing that it doesn't. Its a good card, an Audigy 2 Platinum, and this is the first time in 13 CDs of finished restoration I have encounted this issue.

CD 13 while clean in the background, had slighly distorted vocals for the station announcers, and a muddy, "out of focus" sound that I wasn't able to filter out. The poor quality was in the original tape as well.

I looked at the wave, found the "flat tops" and thought I would see if de-clipping would help.