Signal processing for old recordings

[Sashoir]

Hullo all and thank you for this site, which I'm enjoying immensely and from which I'm learning a great deal.
One of the things which has persuaded me from moving to non-physical media is the ability to access all manner of older recordings at a reasonable cost.
Of course, the old tape and acetate recordings sound pretty horrible, quality-wise, even if the performance was marvellous.
I noticed that many DACs have pre-set filters and signal processing settings, and I wondered whether any particular DACs or settings were suited to "cleaning" digitised vintage recordings? I'm pretty ignorant about DSP, but from listening to old recordings, it seems like some of the artefacts are pretty regular/systematic, and it would at least in theory be possible to train something on new vs old recordings of the same piece to generate a sort of cleaning algorithm. Is this something that exists? Or is it just a layman thinking that something which is extremely complex is easy?
Thanks,
Sasha

 

[hyperplanar]

You should look into iZotope RX and good old EQ. DAC filter selection has to do with latency and frequency response/phase linearity tradeoffs at the very top of the audible frequency range.

 

[Sashoir]

Thank you, hyperplanar! Much appreciated.

 

[MRC01]

EQing old recordings can help. For example many of the jazz recordings from the 1950s and 1960s have boosted upper mids / lower treble, making them sound edgy or crisp. EQ is an easy way to take the edge off. I find that RCA Victors from the 1960s also have this, to a lesser extent.

However, EQ has its limitations. For example if you use it to reduce tape hiss, it also attenuates the music at those midrange/treble frequencies which makes it sound dead or dull. I find the tape hiss less objectionable, because after some listening it's easier to tune out.

Another limitation of EQ is that it affects everything which isn't always what you want. Back to the jazz example, the piano in old jazz recordings often sounds terrible, like a toy upright, and dead and muffled with severely attenuated treble. Yet voices are typically the opposite: too bright & edgy, too much treble. If you EQ to reduce treble to fix the voices, it makes the piano even worse.

 

[pacdpm]

Sashoir...Check out TRACERTEK.com...I've been using their products for many, many years..(tried lots of others...none as good)...AMAZING amount of ease removing clicks, pops, scratches, hiss, low frequency noise..etc...Can be somewhat confusing but once you get the hang of it...very easy and the support staff actually ANSWERS THE PHONE!!! Their DIAMOND CUT 10.6 is latest edition...they also have 'auto' choices for the technically challenged (like me!) but the programs can get very sophisticated...years of cleaning up Callas pirates,,Grateful Dead...old old opera reels...tv shows etc no other program I've used even come close to TracerTek...and...I have NO financial interest or any relatives or any stockholdings in the company...I just have a HUGE collection of old..old..OLD recordings that this program has salvaged...need any more info? contact them (or me!)...best of luck....

 

[Sashoir]

Thanks for the tips, MRC01! It's interesting you mentioned jazz and tuning out the noise; I guess it reinforces that listening is itself a discipline. Funnily enough, I don't have anywhere near the difficulty being distracted by recording artefacts listening to Fats Waller or Parker, Tatum or whomever: I guess it's because they don't sound like anyone else, and I'm acculturated to the fact that old bebop & cetera records "just sound like that". Whereas listening to, say, a Hans Knappertsbusch recording from the 40s of a classical work I'm familiar with from modern recordings, I'm much more aware/distracted by the recording noise. Practice makes perfect, I suppose. Thanks again, S.

 

[Sashoir]

Dear pacdpm, thank you for the tip! I'll check it out over the week-end.

 

[vavan]

See also stereo tool

 

[MRC01]

... removing clicks, pops, scratches, hiss, low frequency noise..etc...

That's a good point -if the recording is from LP then a subsonic filter can be useful. It may actually improve sonics in the midrange by "unloading" the signal. By this I mean, since the extreme low frequencies usually have big amplitudes, the mids & treble can be imagined as ripples riding on the bigger amplitude low bass wave. That big amplitude low frequency wave forces the mids & treble toward full scale amplitudes which can have less linear response (more distortion) in speakers, and to a lesser extent in amplifiers. More info on that here.

 

[kevinh]

So 35 years ago there was a component called the Cello Palette. It was designed by Dick Burwen and sold by Cello a Mark Levinson company. IT was pretty expensive. LAter about 15 years ago Dick Burwen sought to make a software version of the Audio Palette.

Dick is almost 90 now and doesn't want to sup[port users anymore. Levinson has another company at this time Daniel Hertz, it appear he has is selling the Burwen software. It requires a Mac Computer to run the software. It costs $595. Here is a link at the bottom og the page there are a few tracks. some older tracks where you can listen the the original track and one using the eq software witht he same track. I find the effect very impressive.

I am trying to get some questions answered and will likely by this software.

https://danielhertz.com/daniel-hertz-products/daniel-hertz-products-master-class-software

 

[digitalfrost]

You should look into iZotope RX and good old EQ. DAC filter selection has to do with latency and frequency response/phase linearity tradeoffs at the very top of the audible frequency range.

I second iZotope RX. Expensive, but probably most advanced tool for cleaning up audio.

Besides that I'd like to recommend:

https://clickrepair.net/software_info/clickrepair.html

https://www.har-bal.com/

If you have a modern good recording of the same song, you can use Har-Bal to EQ your old recording same (or closer to) the known good one.