(Using Audacity version 1.2.6)Sometimes when I’m trying to record an album, I get a low volume of the song about a half second before a louder volume of the same song. It sounds like a pre-echo running thru the whole recording. I’m running Windows XP and using the line-in on a Soundblaster sound card from a turntable with a pre-amp. It doesn’t seem to always happen and may be because I’m setting my input volume too high,but if I crank the input down to record,the recording volume is REALLY low and then I’ve used the amplify effect to raise it,but then the recording sounds kind of distorted. (P.S.-Is this clipping? What IS clipping?)
last question first (via wikipedia):
http://en.wikipedia.org/wiki/Clipping_(signal_processing)
The problem you’re getting from boosting a weak signal is due to a low Signal-to-Noise ratio. The noise floor in a soundcard (while using an analog input) is constant and the signal you’re inputting is lower than it should be. Therefore the difference is volume between the signal you want and the noise floor is smaller than it should be, so when you boost the file after recording it you are also boosting the noise floor. Look up the terms “SNR” and “noise floor” in wikipedia for a few good articles.
Also, while this is technically distortion, it’s not what people usually mean when they use the word “distortion”. “Noisy” is a better word. The language barrier is one of the audio world’s most common problems so don’t worry about it.
On to the real question:
It’s odd that this problem only happens occasionally. Which source are you using to record from (the Edit → Preferences menu should tell you)?
You really should be recording at the highest possible volume (without clipping, see above, avoiding clipping takes precedence over a high recording volume).
I suspect that you may be getting bleed-through from the neighbouring tracks - sometimes happens when the recording engineer cutting the master applies a little too much “welly” and puts down a strong signal in the grooves - or when the LP is longer (playing-time) in which case the greooves are closer together and the walls are thinner.
BTW: you can get a similar effect with tape where the neighbouring layers print through when they have a trong signal. Especially happens if the tape is stored for a long time. Professional studios wind/rewind master tapes occasionally to mitigate this.
WC
(1) Audacity preference are: Audio I/O = SB X-Fi Audio [DCEO], Everything else left at Defaults. (2)As far as “welly”, it’s a new term to me, but I HAVE heard this same pre-echo listening to vinyl records playing on a stereo just briefly before the first cut, but not once the song started. (It may have been there, but inaudible.) It is audible throughout (WHEN it happens) on the Audacity file. I’ve got hundreds of albums I’m hoping to transfer to my computer and copy to CDs and since it has to be done in REAL time (to the best of my knowledge), it sure would be nice to set up an album to get recorded on the first attempt. I’m brand new at this, not very computer savvy and still need to learn a LOT more about editing these files…things like breaking up an album into individual songs on the CD, so once burned I can skip songs when playing the CD in my car. Also, I STILL don’t understand exactly what ‘clipping’ is. Any advice is greatly appreciated. Thank you.
Oops…finally noticed the wikipedia link about clipping, so I don’t need that answered now. Someone at a different site said the problem was vinyl manufacturers that didn’t give a crap. I know I’ve heard this trouble faintly on my stereo systems, but it seems more noticeable using Audacity (both 1.2.6 and 1.3.3).I also changed the stylus on my turntable…that didn’t help.
[quote=“bfl6h6m”] (2)As far as “welly”, it’s a new term to me …quote]
Sorry it’s a modern English colloquialism - it relates to heavy-footedness on the accelerator or “gas pedal” - often used as “give it a bit more welly” i.e. go faster. The “welly” referred to is a Wellington boot, a rubber mid-high calf-length boot.
WC
We don’t speak Brit here, Waxy.
Just kidding 
Seriously, the UK is great.
I can give some advice about how to split tracks up so they burn nicely to a CD.
In the Edit menu, set Snap To on. Then, in the View menu, click “Set Selection Format” → “CDDA min:sec:frames”. Add a flag to the audacity project in between each track on the album and then you can use Export Multiple to get each track as a separate file that you can burn. Check the wiki for more info if you need it:
http://audacityteam.org/wiki/index.php?title=Main_Page
Is this the same turntable you are recording from as using with the stereo? It’s possible (I think) for a poor quality or badly adjusted turntable to cause more pre-echo than a good one.
Anyone who has done a significant amount of transcribing will have come across pre-echo. It has nothing to do with the software (Audacity or otherwise) and nothing to do with the soundcard. On magnetic tape it is caused by print-through and on vinyl it is caused either by print-through on a master tape or by spill-over from the next groove in. Other posters have already explained both of these mechanisms. Post-echo can occur for similar reasons, but the nature of music generally makes it less noticeable.
In the case of print-through, the lead time depends on the circumstances under which this has occurred. In the case of spill-over the lead time is 1.8 seconds for LP (the time taken for one rotation of the record). Print-through is independent of the entire transcribing process. Spill-over can be stylus-dependent.
The simplest way to remove pre-echo at the start of a track is just to mute the lead-in before the first sound, but that may not always be appropriate, especially in the context of classical music or live concert recording where there can be a very low level of genuine ambient sound before the music begins. In that case, and in the case of a noticeable pre-echo within a track when a loud passage follows a quiet one, it ought, at least in principle (I haven’t tried it!) to be possible to copy the track, or a suitable section of it, shift it forward, reduce the amplitude, and subtract it from the original.