What is Digital Audio Restoration?

Put simply: It's the preservation of audio recordings combined with the removal of unwanted artefacts. But of course it isn't simple... there are several key issues - please read this page carefully.

If you are a musician making new recordings, no rules apply and you 'produce' whatever you like (almost!). Pre-recorded sounds that we know and love fall into a very different category.
It is the job of an audio restorer to maintain what the original producers and artists had in mind and to avoid introducing ideas of their own. Flaws that previous media have added, eg. clicks, hiss, glitches etc., form a layer of audio that might be best removed... but with great care. A working knowledge of what artists and producers originally intended is key. Restoring audio has striking similarities to the 'Restoration' of a painting; if you try to clean too much, or change things to what you prefer, you might be re-writing musical history.

Noise is good... sometimes.
The late John Peel, when asked to defend his love of 'noisy' vinyl over CD, famously replied 'Life has surface noise'. Amen to that, sir.
It is possible to remove all noise from a recording. I've heard it done (yuck!). And it's not always necessary. Tape hiss that is constant, that forms an inseparable part of the original sound, is acceptable to the ear; you can 'tune it out'. Groove noise often overlaps this tape hiss so you need to be careful when reducing it.
Clicks and pops, however, are far more disturbing; a big click can swamp a listeners attention depending on what the background sound is. A really loud scratch can even physically cause your ears to shut down momentarily. Luckily, clicks are easy to treat because they occupy so little space in time. However, If you forcibly remove steady state 'broadband' noise such as tape hiss from a music recording, you run the risk of removing some of the music as well because low level musical information sits inside the hiss and you never know it's gone until you lose it. Circumstances often arise where leaving noise in results in a more musical sound.

What is the best source of audio for restoration?

The best source for any recording remains the original studio master tape in good condition, analogue or digital. It isn't easy to find these tapes... good luck!
Tapes don't last forever and music recorded on tape has a good chance of being damaged through misuse, poor storage, cosmic bombardment (!) or just plain loss.
If no suitable tape is available, your next obvious source is... vinyl. And if the vinyl is good enough it may even be better than the master tape.
Yes, vinyl really could be your best source for an affordable, good quality restoration/reissue. A well kept vinyl record should have the same sound in its grooves as it did the day it was made. Most vinyl was made by highly skilled people. Their hard work lives on in the humble groove of a vinyl record. Modern restoration techniques used on vinyl-sourced audio can yield very high quality results - indistinguishable to the ear from the originals.
Analogue Vs. Digital.
It should be noted that for the purposes of 'Audio Restoration' it's a given that it all takes place in the digital realm. This is basically because there are no tools in the analogue world sensitive enough to remove clicks and pops.
See Why Audio always uses high resolution (96Khz/24bit) digital recording technology and keeps it that way throughout the work-chain. You really don't need to worry about any loss of quality because of digitization. Honest!

What about CEDAR and similar?
Ah yes
, vinyl sources will always have noises that you want to remove but be careful - it's a one-way process. Remove too much of the bad and you risk losing some music along with the junk. It's important to get your decisions right.
There are two main approaches to digital audio restoration and you must choose the one that best suits your needs.
One way is to use specially written software such as CEDAR. It employs fiendishly clever algorithms written by genius software engineers to remove the unwanted junk from the music signal. It's one approach and may be suitable for you, however there is another way: the manual human approach and arguably only humans can decide if something should remain. I've worked on material ranging from flawless mint Japanese pressings, all the way down to battle-scarred Jamaican 45's. Each project is different. A machine can never know all this. A skilled manual restorer can save little things such as the switch clicks of a King Tubby dub-mix, or Eric Clapton plugging in a guitar on-stage, for example. You'd want to keep those clicks and these are choices only a human can make. If your material includes many such elements, you probably should choose a manual approach.

What are the costs?
No two projects are alike and you really need to get in touch if you want to discuss costs. As a basic average, a well-kept LP record that contains mostly average level musical content and is in pretty good condition, roughly 38 mins long, would take between 3-5 hours work to restore and cost GBP 150-250 plus transport costs. It's almost never that simple!

Preserve the original recording. Use good equipment..
Preservation is most important. In order to preserve, you need to have the original information. You should use good equipment to transfer the vinyl signal to digital. Clean your records before transfer. Ensure it's all working properly!
Seewhyaudio's current primary system comprises a Vpi HW-27 Typhoon Record Cleaning Machine, a special power-supply modified Technics 1210 turntable (bypassing the speed slider and adding extra solidity to the already rock-solid rotational stability), the Origin Live! Silver MK2 tonearm (and armboard for the Technics) Ortofon Cadenza Black moving coil cartridge. The A/D is the flagship Benchmark ADC1. This stuff is not cheap but you must get the best information possible from your grooves in order to make the restoration worthwhile.

Preserve the Dynamic Range. When someone asks me to 'make it louder' I just point to the volume control. If you want compression that's your decision, especially if you are competing with your average commercial pop CD, etc, but let it be known that such compression is damaging the original recording and that the damage is irreversible. If your project is destined to go back on to vinyl, keep it unchanged. Making it louder is not always good and often quite the reverse.
There are three negative aspects to loudness compression;
1) you get less dynamic 'peaks' in the music, causing listener fatigue and monotony.
2) A louder groove cut with hard compression will be more difficult for the stylus to track and
3) It actually raises the noise floor. Whatever noise came with the original recording will be raised while the top volume of the material will be reduced.
NB: it is often pointed out that vinyl has a poor dynamic range. That's only true in the context of a comparison with digital. The comparison is driven by the total noise-floor difference. Vinyl's noise-floor is a lot higher than digital.
This does NOT mean that digital is louder, it means that digital can go quieter. In practise this issue only concerns music which contains near-silence or actual silence (except tape hiss). So, if your music is anything above a whisper all the way through, it shouldn't be a problem.

These are the basics of Audio Restoration - According to See Why Audio. :-)

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