Tweet
Lateral cuts records (78s and early LPs) rely on a stereo cartridge stylus moving in one direction to represent the absolute displacement of the cut in the groove via an electrical signal. Thus, when the stylus moves towards the outer edge of the record, a positive signal is produced by both channels of the stereo cartridge. When the stylus moves towards the center of the record, a negative signal is produced by both channels of the stereo cartridge. So, when these two signals are summed together, they produce a net increase in the overall signal level compared to just one channel's signal level, and the signal is in the proper phase with respect to the recorded information on the disc.
If a needle drop had occurred in the past history of the record during the performance on the record, it can cause a 'divett' on the recording surface. For example, old acoustical phonographs had very heavy tone arms. Usually the 'needle drop' occurred at the lead - in portion of the record. But, sometimes, the tone arm could have been dropped elsewhere on the record. This would put gouge out a small crater or divett where the drop occurred. That divett would be picked up by a stereo cartridge with the two signals being out of phase with respect to one another. (The same thing could have occurred with early mono LP records). Thus, summing to mono would have the effect of partially canceling out these types of out-of-phase impulse noises on your transfer. You can often see these on the vector x-y display as deviations, almost orthogonal to the normal up and to the right straight line slope of the recorded signal. Bottom line - - - some impulse noise reduction can be had on poorly treated monophonic lateral cut recordings by simply summing to mono (L+R). But, it will never remove all of the impulse noise filter. That job is best left for the EZ Impulse Filter and/or the manual interpolation "I" key.
Craig
If a needle drop had occurred in the past history of the record during the performance on the record, it can cause a 'divett' on the recording surface. For example, old acoustical phonographs had very heavy tone arms. Usually the 'needle drop' occurred at the lead - in portion of the record. But, sometimes, the tone arm could have been dropped elsewhere on the record. This would put gouge out a small crater or divett where the drop occurred. That divett would be picked up by a stereo cartridge with the two signals being out of phase with respect to one another. (The same thing could have occurred with early mono LP records). Thus, summing to mono would have the effect of partially canceling out these types of out-of-phase impulse noises on your transfer. You can often see these on the vector x-y display as deviations, almost orthogonal to the normal up and to the right straight line slope of the recorded signal. Bottom line - - - some impulse noise reduction can be had on poorly treated monophonic lateral cut recordings by simply summing to mono (L+R). But, it will never remove all of the impulse noise filter. That job is best left for the EZ Impulse Filter and/or the manual interpolation "I" key.
Craig
Comment