Really difficult de-click problem

[ike]

I'm trying to restore a vinyl LP from the 1960s(?). Woodwind Octets ... a lot of high frequencies. While the LP appears clean and unscratched it is full of pops, clicks and ticks. The ticks and clicks audibly appear to be of the magnitude of the actual signal S/N=1(!).

No matter what I do with the impulse filter it audibly distorts the high frequencies. I have tracking set at 100 and it still distorts the high frequencies. I've tried to reversing the file trick and ... it works but I still end up with high frequency distortion no matter how gentle I am with the impulse filter. I've also tried the median filter with limited success ..... it needs 15~20 samples to impact the noise with significant high frequency loss.

Another thing I have noticed is that the noise "breathes" with the signal...I think this in an artifact of a primitive tape recording technology of the master.

Any ideas??

[Craig Maier]

If you are getting distortion with the tracking at 100, that sure does mean that these clicks are huge! I would try to use the gain change feature first to knock the overall signal down by maybe 6 dB and then re-try the declicking process. That should help.

[Craig Maier]

Another thing just occurred to me. You said that the recording is "breathing." That is indicative of a dbx encoded record. If that is the case, the dbx decoding process MUST be applied before attempting to declick such a record. Please check the record jacket to see if some form of noise reduction technique like dbx was used. That concept was popular for a period of time in the 1970's.

[ike]

More to this after some really intense listening

Thanks for the suggestions...I suspected dbx encoding when I heard the "breathing". The album jacket refers to new recording technology but isn't specific (Stereolab Vanguard album with no pressed or copyright date).

Anyway, this is what I've discovered. I went back to the record and played it with headphones and there is a buzzing noise breathing with the basoons at ~3200Hz. I'm unsure of it's origin. I suspected cartridge mistracking but after checking alignment, this is a remote possibility. I guess I'm stuck with it in the recording.

This "buzz" sends the impulse filter wild... on preview it jumps to 300 clicks/second..... and even with tracking set at 100 it amplifies this "buzz" making it worse.

So I tried this with some degree of success ....using the notch filter (I used this to isolate the buzz) I set it at 3200Hz and 1.9 octaves to remove the buzz..... this worked with a noticable loss of music along with the buzz..... but the impulse filter is now ineffective at removing the clicks through the remaining recording... as expected from warnings in the help screens.

So this is what I'm going to try and do.....I'm still learning the software but I'm going to try and remove the buzz just from the left channel (where it seems to be isolated) and then re-run the impulse filter(s).

Any better suggestions???

[Craig Maier]

I think that I would try the Harmonic Reject filter set to 3200 Hz and several harmonics instead of the Notch Filter, especially if the buzz is constant in tonality. That way you will, in a very selective manner, remove the harmonics of the fundamental as well as the fundamental. I would try both Odds and Evens since I do not have the signal here to view. I hope this helps. Please advise.

[ike]

Making Progress

Thanks for the advice Craig ...I'll work on this some more and let you know how I go. I'm leaving town for a couple of weeks and will get back to this later.

[ike]

Damaged Vinyl

I'm back on this problem again and have come to the conclusion that I'm dealing with a damaged record. My conclusion is based on doing several restorations now and noting some characteristics of well played/worn & poorly cared for vinyl.

Well cared for vinyl, infrequently played is a snap to de-click and de-noise and the results are difficult to hear from CDs. On the other hand I've found that when the vinyl is damaged to the point the music is audibly distored in some manner (as it is on the recording mentioned above) the de-click filter seems to amplify the distortion. I'd like your comments on this.

The poor way I've dealt with this is to raise the size parameter on the de-click filter so that the distortion is not effected by it..... but, of course, it is still there and (of course) it does a poor job of de-clicking the rest of the recording. I'd like your comments on this and whether there is a better approach.

I have applied the virtual valve amplifier in harmonic enhancer mode to clean up the distortion with some success but those pesky clicks are still there. Is there a better tool to clean up distortion?

[Craig Maier]

I am going to have to shoot from the hip here, because I can only imagine what this recording sounds like. In general, there are a number of different types of distortion including:

Harmonic
Amplitude
Intermodulation
Transient Intermodulation
Clipping

Most likely, with a worn record, you are dealing with Harmonic Distortion or Amplitude Distortion.

If the record is also "clicky" those distortion products could present a problem for the detector algorithm in the Impulse filter. Theoretically, the harmonic products could extend beyond the top of the audio spectrum (over 20 KHz).

So, here is where I am shooting from the hip - - - maybe try a pre-processing step before de-clicking with the impulse filter. Just a guess, but try applying the lowpass filter set to 6 dB/Octave and 4 to 5 KHz. Run that first and then try the impulse filter. Try variations on that theme and let us know what you discover. Maybe even try raising the order of the filter to 12 dB / Octave at various frequencies.

Sorry if this does not work, but I am shooting in the dark. Theoretically, this has the possibility of working for you. You will loose some of the top end of the recording by doing this, but by the sounds of things, the top end of the recording is nothing but distortion anyway. You can always rejuvinate it later with the VVA.

[kent]

worn vinyl

One thing that should be considered when trying to restore a vinyl record that is worn, is to use a different size stylus. I use a 1 mil elliptical stylus on my old 45's and in most, but not all cases, they sound much better with fewer clicks and less distortion. You might have to buy a different cartridge in order to use a 1 mil stylus, but I found it to be well worth the money.

Kent

[Craig Maier]

Kent,

I have a 1 mil stylus for my 45 rpm record player. But, where do I get one for my regular turntable?

BTW - the 45's sound better on that old 45 rpm record player than they do on my modern turntable with a 0.7 mil eliptical stylus.

[ike]

Low pass filter did the trick

Bingo! Took your advice. I need to experiment more for an optimal restoration but the low pass filter seems to help a great deal.

This is how I proceeded. I declicked the whole side using reasonable de-click settings with the triple filter preset. Listening to the destination file I found the distortion was only in a contiguos section of the recording .... only about 20% of the side. I went back to the source file and applied the low pass only to the troublesome section and then de-clicked (using the multifilter). I really didn't have to be a harsh as you indicated I might need to be with the corner point or the slope (still experimenting). The de-click on this section is still not as effective as the rest of the side but it is acceptable. In sync mode the declick pasted over the distored section of the destination file. Result was superior to all my previous attempts.

Thanks a lot Craig ...I agree with Jonathen... you guys have great support.... and a great product!