Windows 10 Home.
I’m trying to increase the volume of a CD-R of a local band which was originally a reel to reel tape from 1973. It was put onto a CD by a friend, but the volume is low. I’m trying to use Audacity to bring up the volume and re-burn the CD. When I use Amplify, it, of course, brings everything up, but the distortion is pretty bad. Is there another way to increase the volume without all the distortion?
If you amplify to 0 dB, no distortion will be added, but the wanted sound and the unwanted noise will be amplified equally.
How does de original CD sound if you just increase the playback volume on any player?
It is necessary to establish if it sounds different from amplifying it in Audacity.
You “win” the [u]Loudness War[/u] with compression and limiting. These both of these compress (reduce) the dynamic contrast which can be undesirable to some listeners but it is 'the modern sound". And you may not be able to get the loudness (with as little damage) as a professional mastering engineer can get.
Try the Limiting effect first, set to Hard or Soft Limiting and with Make-up Gain (or you can re-amplify after limiting). The Audacity limiter is very good… It uses look-ahead so it doesn’t distort the waveform. Maybe start with -6dB and then repeat it if it’s not enough, or start over if it’s too much. (You’ll have to use make-up gain or amplify before repeating or it won’t have any affect the 2nd time.)
You can also experiment with the compressor but there are more settings to mess with and more chance of getting undesired side-effects.
which was originally a reel to reel tape from 1973.
Off topic - When you push analog tape “into the red” it starts to soft-clip… A kind of limiting. It is distortion but it’s not as bad as digital hard clipping. Then the NAB tape equalization (which boosts the highs during record and cuts them during playback) further “softens” the distortion components.
But of course, digital has no tape hiss so there’s no problem recording lower, leaving plenty of headroom. You can amplify later.
I recommend the ToneBooster’s “broadcast” plugin (V3 is free)
It’s a multi*  band compressor, & limiter combo. It looks complicated but it has presets …
[ * Audacity’s native compressor is only single band ].
Thank you all. I need to try all these. I appreciate the help I get here.