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Thursday, February 28, 2013

Q. What settings should I use when backing up vinyl?

I’ve just started putting my vinyl collection onto my hard drive for the purposes of backing up and preserving it. I’m currently using Audacity to record the WAVs but I don’t know what settings I should be using. Someone mentioned that I should record at 32-bit — is this correct?

Via SOS web site

SOS Technical Editor Hugh Robjohns replies: 

To answer the last question first: not really! The longest word length you can get from any converter or interface is 24 bits, so that’s the format you should record and archive your files in, and if you plan to make ‘safety copies’ in the CD audio format you’ll need 16/44.1kHz files.
However, the 32‑bit format does exist. Most DAWs process signals internally using a ’32‑bit floating-point’ format and some allow you to choose whether to save ongoing projects in this native form to avoid multiple format changes as a project proceeds. In general, the 32‑bit floating‑point format still works with 24‑bit audio samples, but adds a scaling factor using the other eight bits to allow it to accommodate very loud or very quiet signals following processing. The problem is that not all DAWs share the same 32‑bit float format, so, for maximum compatibility, it’s not the best idea to long‑term archive audio files in this format.

As the longest word length any converter can record in is 24 bits, that’s the setting you should use when backing up your vinyl. If you’re likely to want to run de-clicking software, it’s worth making your original recordings at 96kHz

If your records are in bad shape, it might be worth using de‑clicking software on your recordings before doing anything else.

As for the other settings, it depends on the condition of the records you are transferring and how much processing you are planning to do to them. For starters, though, if your records suffer from clicks, these can have a huge dynamic range that can easily overload the A‑D converter (which doesn’t sound nice!). The sensible way around this is to leave masses of headroom when digitising, and that means using a 24‑bit analogue-to-digital converter and leaving at least 20‑30dB of headroom — more if the noise floor of the disc and converter allow it.

If you are planning to run de‑click software, then I would also recommend using a higher sample rate during the digitisation. That makes things much easier for the software, so digitising at 24/96 would be a good starting point.

If you are going to use de‑clicking software, run that first. There are various packages that do this, from the superb (but expensive) CEDAR tools, down to various low‑cost plug‑ins. I often use Izotope RX, which is a very cost‑effective solution. Alternatively, you can manually edit out the clicks or, in some DAWs, redraw the waveform to erase them.

With the clicks taken out, you can then remove the (now empty) headroom margin by bringing up the level of the music signal to peak close to 0dBFS (I generally aim to normalise to ‑1dBFS).

You may, at this stage, want to deal with the surface noise — again, there are various tools for that — or adjust the overall tonal balance, but my advice would be to tread lightly if you do go down these routes.
Finally, sample‑rate convert the files down to 44.1kHz, reduce the word length (with dither) to 16 bits, and burn to CD.

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