by Derek » Mon Jul 31, 2006 1:53 pm
Surface noise from 78's (crackle) is the most difficult type of noise to remove. It is too spiky to be susceptible to a hiss filter, but too continuous for click removal to be fully effective. There is a good article on this at that you might find interesting.
Using Wave Corrector for this, the best advice is to make multiple passes of the click filter. Use the Superscan command on the Waveform menu and set the number of passes to at least 3. You will need to experiment to find the optimum values for number of passes versus click detection threshold.
Having removed most of the crackle, you could then apply the hiss filter although I'd advise against over-filtering as the effect willl be detrimental to the music.
As Stan says, you can also apply some treble cut.
Some other factors worth considering:
1. Use the speed conversion option in Wave Corrector to record your 78's at 45rpn. This has the advantage that the tracking velocity is lower and therefore there should be less tracking distortion.
2. Experiment with different styluses. You find one othat tracks a portion of the groove that is less worn.
3. At the end of the de-noise process, convert your stereo recording to mono. Unfortunately, you cannot use Wave Corrector for this but it will theoretically gain you an extra 3db of S/N ratio.
Finally you may find this thread interestiing: . Although I haven't yet implemented this suggestion, I may do so if there is sufficient demand.