Pre-Amplify vs Post-Amplify

[AnonGuy]

I noticed that when I record sound from my laptop's speakers on Ubuntu, the volume slider goes from "mute" to "unamplified" to various amounts of amplification. This amplifocation is applied at the time of recording. There is also an "amplify" effect in audacity, where all the effects and filters are. I was wondering if applying the amplify effect does essentially the same thing as setting the amplification under recording sounds settings. Of if there two types of amplification are different. I noticed both of them produce clipping when set to high. Is recording on "unamplified" and then applying amplification with audacity the same as recording with the volume(gain?amplification?) turned up?

[kozikowski]

Some computers route the digital sound signal from the playback system to the record system and on to Audacity. Those puppies have no control at all because none is needed. If the signal is damaged, there's nothing you can do with a volume control to fix it. Most of the time it just sails through with no adjustments.

However, there's another way to self-record that involves turning around the analog portions of the soundcard. That's a lot more of a problem because the show can go through both the playback volume and the record volume portions of the card. Either of those can cause very serious damage or noise and you can have problems with both.

They're cousins of Effect > Amplify (and Effect > Normalize) in how they work, but neither of those Audacity controls will be useful if the show arrives so low that it's noisy (FFFFFFFFFFFF) or so loud that it overloads and clips. In both cases you have no show and it doesn't matter what Audacity effect you apply. So you have to get that right at the capture system — before Audacity.

http://manual.audacityteam.org/o/man/tu ... linux.html

Koz

[AnonGuy]

What about if I record from an external usb microphone? Is the amplification at time of recording still different than using the amplification effect in audacity post recording?

[Gale Andrews]

I noticed that when I record sound from my laptop's speakers on Ubuntu

How exactly are you doing that? Exactly what version of Ubuntu?

the volume slider goes from "mute" to "unamplified" to various amounts of amplification.

Exactly which slider does that? That sounds like an output slider. Mute it and you hear no playback.

A volume meter would move up and down live with playback while the volume slider was at the same level.

Have you looked at http://manual.audacityteam.org/o/man/tu ... linux.html ?


Gale

[Gale Andrews]

What about if I record from an external usb microphone? Is the amplification at time of recording still different than using the amplification effect in audacity post recording?

What amplification at time of recording? If you record something playing on the computer, the recorded level you achieve in the recording will be affected by the output level of what you are recording and by the input level you choose.

If you record from a USB microphone, only the input level affects the recorded level you achieve.

If you choose to record at a low input level and then amplify it in Audacity so you can hear it, you will hear noise as well as what you wanted to record.

Click in the Audacity recording meter to monitor the level before you record, then adjust the input level (and the output level for recordings of computer playback), so that the red bars on the recording meter don't exceed about -6 dB. Then you will have a good level of recording that will not distort by being too loud.

If you then use Effect > Amplify without changing its settings this will make the peak of the recorded audio as loud as it can be without clipping. It should not make the recording too noisy unless the noise level was already too high. Amplify will not clip unless you deliberately enable clipping.


Gale