Automatic limiting or compression is happening to input?


I’m trying to convert a bunch of old cassette tapes to MP3. I’ve just installed a fresh copy of Audacity 2.0.2 on my Win 7.

The only setting I’ve changed is to enable ‘Software Playthrough’ in Recording settings.

My Audio Host is Windows DirectSound, Output Device is Speakers (Realtek High Definition Audio) and Input Device is Microphone (Realtek High Definition Audio).

Listening to the recorded stereo tracks, or just monitoring before recording, it’s apparent that something is happening to the audio input. It’s hard to explain; I’ve attached a few seconds of MP3 to illustrate, but basically, here’s what’s happening:

The tapes are old techno DJ sets. For those who aren’t familiar with the genre :wink: techno can be described as long periods of sustained noise followed by short bursts of relative quiet. After each quiet bit, the noisy bit comes back in and sounds as expected for about two to three seconds. Then it seems to get compressed or limited, or… I don’t know the vocabulary, but it’s all muted. It’s also got that warbly swooshy phaser effect you get with overly-compressed MP3.

In the attached sound clip, the first couple of seconds sound normal (yes, that IS actually meant to sound like that) - the remainder should sound like it but is all… muted.

I’m not seeing any clipping, nor is my input level too high (in fact it’s right down low). I’ve not enabled any effects or plugins, or indeed anything that I’m aware would be doing this.

I’ve also previously made several recordings using the same hardware on the 1.3 beta of Audacity - I never noticed any effect like this.

Any suggestions?

See here:

Yes, that was exactly it. Many thanks - FAQ page bookmarked :blush: