Audacity Forum

I am copying some old analog recordings from tape and vinyl and would find it useful if there were an automatic record level setting utility which can pre-scan a few minutes and seek optimum record level using an RMS / averaging technique so as to help ignore the odd transient click.

My present method is to deliberately guestimate a low record level with an over generous headroom and, after 10 mins or so of recording, stop, and visually look for optimal level and apply the visual dB correction to my initially guessed record levels (I use a tone source for this). Then I do the full record run. I'd like to think that this task could so easily be automated.

TimUK wrote:I'd like to think that this task could so easily be automated.

Yes it would be nice, but I doubt if it is possible.

If, like me, you come from a background of analogue recording, there are some important differences that need to be remembered:

With analogue, you can get away with the odd peak being excessively high, in fact it can often be beneficial by compressing the dynamics of transient peaks. With digital this is not the case - exceeding 0dB is bad and is always bad. In the digital domain it does not cause dynamic compression but digital clipping which invariably sounds nasty and can be difficult (or in bad cases, impossible) to correct.

Optimising the recording level is very important with analogue recording as the recording medium (tape) has a very limited dynamic range, so you need to be able to use every available dB. With digital recording, the recording level is still important to some extent, but if it is a bit low it does not really matter. Although the dynamic range of the analogue components is still limited, the recording format has a huge dynamic range, so if the recording level is a bit low then it does not matter. This is particularly true if you are working with large bit depths such as 32 bit recording. The really important thing is that you do not exceed 0dB.

An easy way to set your recording level for transfering from tape is to make yourself a short test recording on tape that is recorded extremely loud so that it distorts and saturates the tape. (Dance music is good for this as it is already heavily compressed). Set your levels using this (leave a couple of dB headroom) and you are all set. Record in 32 bit, and apply the Amplify effect when the recording is complete if you want it a bit louder. If you want to be obsessive about sound quality, set the maximum level in the Amplify effect to a little under 0.0db (say -0.2dB) to allow the curve of the waveform on the highest peak to go beyond the highest sample value without clipping.

You are likely to find that there is very little noticeable quality loss when recording in 32 bit even if your peak level is as little as -20dB, though this will depend on the quality of the analogue components.