using notch filter produces clipping

Hello all,

I am a little new here, but my end goal here is to digitize some vinyl records. I am really low budget on my equipment, and audacity looks like a great tool to use for recording software. I have an old turntable (mid late 1980’s, I’m guessing, it’s not grounded and has no grounding wire). this turntable is introducing some noise (at 60 hz and several multiples of 60, but oddly enough not at 420 hz, it just skips over that looking at the frequency spectrum. anyways, I am attempting to use the notch filter effect to remove this nuisance, however, when I do I have two issues I’m still trying to work out:

  1. I immediately see clipping. I didn’t have any before, and the original recording fills up a large portion of the dynamic range, but there’s a constant gap to start out. following the notch filter application, lots of red lines on the screen. this makes me sad. anything I can do? I’ve tried changing the turntable’s volume output, but it’s pretty fragile and if I adjust it any other direction it comes out either too loud and produces a lot of clipping, or i lose the signal (interestingly, I seem to lose it in one channel before the other, not sure why)

  2. the notch removed seems to large. should I just reduce the Q level further to alleviate this?

here’s my signal path:
Montgomery Ward JSA 631957 (whatever stock components come with that, just an ancient machine my dad had)
rca cables
Sherwood RX-1010 (from sketchy ebay guy, he thought the screen was broken but everything seems functional to me)
rca to trrs cable
dell inspiron 17r 5737 with windows 8.1
audacity 2.0.6

if you don’t know how to help in any way, thanks anyways for reading!


  1. Your original audio is not clipped,
  2. The track is in the default “32 bit float” format,
    then there is nothing to worry about. All you need to do is to apply the Amplify effect (or Normalize) to bring the level back down below 0 dB.

Unlike your sound card (which is probably 16 bit or perhaps 24 bit integer), 32 bit float format can handle signals over 0 dB.

No. Increase the Q. Higher Q levels produce a narrower notch. If the Q is too high it will tend to cause ringing close to the filter frequency, so don’t go too extreme.

“Q” is the Quality Factor of the filter. Broad, gentle, sloppy filters have a low Q. Tight, precise, accurate filters have a high Q.


Natural sounds are made up of bunches of different tones at different sizes and times. These are the overtones and harmonics that let you pay a lot of money for a good instrument.

But all the tones don’t just add up. Some of them, in the natural order of things, subtract. If you manage to delete one or more tones that were intended to subtract, then you could be removing sound from the show and the show will not only change, but increase.

This is one of the things that plagues MP3 generators. MP3 also removes some overtones and harmonics and it can create a show that suddenly overloads for no apparent reason.

See Fourier Analysis etc. Throwing filters around can give you magic results.


So, does this mean I should amplify before, or after I apply the notch filter, or does it make a difference?

If the track is 16 bit o 24 bit, then to avoid permanent damage due to clipping, you must ensure that the track remains below 0 dB at all times.
If the track is 32 bit (float) format, then you can use the Amplify (or Normalize) effects either before or after.