Audacity Forum

I've been recording tracks from records with a Numark. When I export as a WAV it sounds great. If I export as MP3 they have a "wobble" under tone that is quite noticable especially in quieter parts. I have even loaded the WAV file and then exported as MP3 with the same results. What is causing this and is there a way to solve this problem? The WAV file are gigantic.

MP3 is a "lossy" format. To make the file smaller, MP3 encoding throws some data away, then squashes the remaining data together. This makes the file smaller, but the data that is thrown away can never be recovered, so the sound quality deteriorates. If it deteriorates too much, then it will start to sound "wobbly".

If you edit an MP3 then export as MP3, some data has been thrown away in making the original MP3, then more data is thrown away when the edited audio is re-encoded. Each time the data is encoded the sound gets worse.

To reduce the amount of data that is thrown away, use a higher quality encoding setting. The higher the quality, the larger the file size, so it is a trade-off size:quality.
During the Export step, on the Export dialogue screen, click the "Options" button to change the compression settings. Try using "Preset: standard" or "Preset: Extreme".

The other possibilty is that you are getting "wow" from your turntable - small variations in turntable speed. See this Wikipedia article: http://en.wikipedia.org/wiki/Wow_%28recording%29
and: http://en.wikipedia.org/wiki/Phonograph

I used to have an ION iTT-USB turntable - and I junked precisely because of that. The platter was far too lightweight being flimsy plastic, just not good enough for the job.

Instead I resurrected my old Technics TT from the attic and bought a phono pre-amp and an external USB soundcard (You can buy devices with bith packaged in a single unit if required) and I treated it to anew cartridge. It gives MUCH better results - for a start the platter alone on the Technics weighs an awful lot more than the entire ION unit.

WC

Hi guys, thanks for the reply. Yeah, it's definately the MP3 and not the turn table. The WAV files sound great, the MP3's sound like crap. Unfoturnately before I realized it I have recorded 49 song that will all have to be recorder. I have a big hard drive so I think I will do them all in WAV and the experiment with the different MP3 setting. I did record 149 with WAV and those are in good shape. The Numark I have has a cast aluminum turn table and I have been happy with the raw results coming out of the table.

It might be because of the double compression(or otherwise the compression level), as somebody already pointed out.

cSuttle wrote: I have a big hard drive so I think I will do them all in WAV and the experiment with the different MP3 setting.

We generally recommend that people keep an "archive" copy in either WAV or FLAC format and then make MP3's as and when they need them. Some folk keep 2 archive copies on different hard drives to protect their collection against drive failure.

cSuttle wrote:I've been recording tracks from records with a Numark. When I export as a WAV it sounds great. If I export as MP3 they have a "wobble" under tone that is quite noticable especially in quieter parts. I have even loaded the WAV file and then exported as MP3 with the same results. What is causing this and is there a way to solve this problem? The WAV file are gigantic.

Coming in a little late on this but I reported this problem to the powers that be when they redid the Lame.dll a few versions back (and a couple of years ago) and it has not gone away. Anything that I do that has any kind of orchestration in the back ground has this problem. I went to a 3rd party WAV to MP3 converter as a work around, but I would rather be making the MP3 out of Audacity.

FWIW

Tony

TSMusic wrote: Coming in a little late on this but I reported this problem to the powers that be when they redid the Lame.dll a few versions back (and a couple of years ago) and it has not gone away. Anything that I do that has any kind of orchestration in the back ground has this problem. I went to a 3rd party WAV to MP3 converter as a work around, but I would rather be making the MP3 out of Audacity.

The current version of Lame for Audacity is 3.88.3 and is available here: http://audacityteam.org/help/faq?s=install&i=lame-mp3
If you use either "Preset: Extreme" or "Preset: Insane" the sound quality will be excellent.