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EGS 10-22-2020 09:45 AM

fix distortion in audio restoration project?
 
Hey all,

I've got an audio restoration gig, consisting of cleaning up several precious old out-of-print classical records. One in particular has brief moments of distortion at loud peaks. It is clean except for these peaks. This is not digital clipping, but rather an analog distortion present on the source. We've even been able to examined more than one (identical) LP pressings, and the distortion is present in the same spots on all.

How to fix?

My best solution - so far - is to use Izotope RX to manually select and lower the gain of the tiny bits of distortion, often working the frequencies in-between the music when possible. Sometimes this kinda sorta works...

Help!

albee1952 10-22-2020 09:52 AM

Re: fix distortion in audio restoration project?
 
That would have been my suggestion too. Maybe check their website and look for some tutorial videos on that function? Then there are some other plugins that are worth a demo:

https://accusonus.com/products/audio...era-de-clipper

http://www.perfectdeclipper.com/

EGS 10-22-2020 12:40 PM

Re: fix distortion in audio restoration project?
 
Thnx I'll check those out

daeron80 10-22-2020 02:28 PM

Re: fix distortion in audio restoration project?
 
First, congrats! That's a cool gig.

Second, if the distortion was electronic, that's a tough problem, especially if it was transistor breakup. Almost intractable in some cases. Zoom in to the detailed waveform level and see where the discontinuities lie. If they're restricted to the high amplitude portion of the waveform, that's easier to deal with. If they lie along the ramp up or down, several dB below the peaks, then digging out between the overtones may be the best strategy.

If it was mechanical distortion during pressing, which is more similar to clipping, that can sometimes be moderated with the De-clip module of RX. Zoom in and adjust the threshold until it's catching most of the discontinuities. You'll lose some high end detail, but it can be an overall improvement.

Don't forget to try Interpolate and the various Spectral Repair modes. Sometimes they'll surprise you.

musicman691 10-23-2020 05:55 AM

Re: fix distortion in audio restoration project?
 
Quote:

Originally Posted by daeron80 (Post 2580889)
First, congrats! That's a cool gig.

Second, if the distortion was electronic, that's a tough problem, especially if it was transistor breakup. Almost intractable in some cases. Zoom in to the detailed waveform level and see where the discontinuities lie. If they're restricted to the high amplitude portion of the waveform, that's easier to deal with. If they lie along the ramp up or down, several dB below the peaks, then digging out between the overtones may be the best strategy.

If it was mechanical distortion during pressing, which is more similar to clipping, that can sometimes be moderated with the De-clip module of RX. Zoom in and adjust the threshold until it's catching most of the discontinuities. You'll lose some high end detail, but it can be an overall improvement.

Don't forget to try Interpolate and the various Spectral Repair modes. Sometimes they'll surprise you.

I've done vinyl restoration on and off for over a decade using various tools and RX is pure genius with the modules it has. Well worth the money & time spent with it. Is the distortion in one or both channels? If only one channel try bringing audio from the non-distorted channel (if the vinyl is stereo).

Something to think about is it might just be an instrument or instruments played a bit too forcefully and they just got blatty. Or a mic just got overdriven (thinking ribbon mic here).

itsjustmeee123 10-23-2020 10:52 AM

Re: fix distortion in audio restoration project?
 
Question... how does RX do with clipped vocals? I have a project where the singer is recording remotely from her home and sometimes the vocal files she sends me are squared off at the top and there’s various degrees of distortion in the louder parts.

originalscottyg 10-23-2020 01:52 PM

Re: fix distortion in audio restoration project?
 
Quote:

Originally Posted by itsjustmeee123 (Post 2580935)
Question... how does RX do with clipped vocals? I have a project where the singer is recording remotely from her home and sometimes the vocal files she sends me are squared off at the top and there’s various degrees of distortion in the louder parts.

RX De-clip module pretty hit or miss for me. Sometimes I am amazed with the results, and sometimes no matter what I do it only sounds the same or worse. It really depends on the source material, and it definitely requires a lot of trial and error with adjusting settings and re-rendering (from the raw audio). Anything that is severely distorted will never sound pristine, but De-Clip can improve things, sometimes significantly, many times marginally.

musicman691 10-23-2020 02:12 PM

Re: fix distortion in audio restoration project?
 
Quote:

Originally Posted by originalscottyg (Post 2580944)
RX De-clip module pretty hit or miss for me. Sometimes I am amazed with the results, and sometimes no matter what I do it only sounds the same or worse. It really depends on the source material, and it definitely requires a lot of trial and error with adjusting settings and re-rendering (from the raw audio). Anything that is severely distorted will never sound pristine, but De-Clip can improve things, sometimes significantly, many times marginally.

The secret with a lot of rescue work in RX is to do things a little at a time; don't try and fix it in one pass.

seanmccoy 10-23-2020 04:03 PM

Re: fix distortion in audio restoration project?
 
Quote:

Originally Posted by originalscottyg (Post 2580944)
RX De-clip module pretty hit or miss for me. Sometimes I am amazed with the results, and sometimes no matter what I do it only sounds the same or worse. It really depends on the source material, and it definitely requires a lot of trial and error with adjusting settings and re-rendering (from the raw audio). Anything that is severely distorted will never sound pristine, but De-Clip can improve things, sometimes significantly, many times marginally.

My experience exactly. It's occasionally jaw-dropping, usually an improvement, and a total fail only once in a while. Clearly it depends on the nature and severity of the distortion. But overall I've definitely had more successes than disappointments.

daeron80 10-26-2020 08:35 AM

Re: fix distortion in audio restoration project?
 
Quote:

Originally Posted by musicman691 (Post 2580946)
The secret with a lot of rescue work in RX is to do things a little at a time; don't try and fix it in one pass.

Bingo. :cool:


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