allencmcbride wrote:I read (on the Audacity wiki, I think) that if you're recording in 32 bits, you don't need to worry too much about keeping the recording levels as hot as possible. I'm wondering just how far that goes, because the tapes I'm recording have widely varying signal levels.
As a very rough guide, aim for a peak level that reaches around 0.5 on the vertical scale.
When recording in 32 bit, you can be a very long way below that without any loss in sound quality. If the maximum peak of the loudest sound that your tape player is capable of producing goes somewhere near to 0.5 mark, then the background hiss on the tapes (as close as you can get to silence) will still be reproduced with perfect clarity (subject to the limitations of your sound card).
0.5 on the vertical scale equates to -6 dB.
0.25 on the vertical scale equates to -12 dB.
The maximum dynamic range of your tape player will be worse than 75 dB (unless you are the lucky owner of a professional Revox mastering tape recorder), which means that the noise floor of the tape recorder will be at around -85 dB. Even 16 bit recording, with a dynamic range of around 90dB) will cope with this.
If your sound card works at 16 bit, there is arguably no benefit in recording at greater than 16 bit, however in terms of sound quality it will do no harm. When it comes to processing your audio (Equalizing, Normalizing, and so on) 32 bit recordings have the advantage of virtually zero rounding off errors. Whether or not you can hear the difference between a 16 bit recording and a 32 bit recording is another question, but if the highest achievable quality is your main aim, then you can be satisfied that 32 bit recording is up to the job.
In practice, the main reason that you want a reasonable recording level, is not a question of the bit depth in Audacity, but the fact that your sound card will have its own noise floor and limited dynamic range. Giving your sound card a reasonably strong signal will allow it to perform to its best.
One thing that makes it easier to get the right recording level when recording tapes is the fact that there is an absolute limit to how loud a tape can go before it reaches "saturation". If you set your recording levels with a very loud tape, then you can be assured that any other tape that you record will not go much higher. 6dB should be enough "headroom" for any exceptional peaks, while still offering enough dynamic range to reproduce the quietest parts of any tapes.