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Transfer engineers who use digital processing (such as CEDAR) for removing noise on 78-rpm recordings sometimes find that a flat initial playback allows the digital noise removal to work better, before the recording curve is applied. The flat position can be extremely useful here. The disc is played without equalization, then fed to the digital processor. The EQS MK12 also has a line input, just ahead of the equalization circuitry, which allows you to apply the recording curve at line level, after the digital pro- cessing has been done. Some engineers will tell you that you can apply the play- back curve in the digital domain, and the equalization capabilities of many computer-based digital processors and editors will allow you to do this.
There's a flaw in this approach, however. Among the virtues of digital equalization is the lack of nasty phase shifts inherent in analog filters. In the case of playback curves, the lack of frequency-dependent phase shifts presents a problem. Most readers know that the playback curves provide proper frequency equalization for the record. What is generally ignored-probably because it happens automatically-is the fact that the play- back curves also provide correct phase equalization. The filters used to pro- duce the recording curves in the first place caused phase shifts. When complementary analog play- back equalization takes place, the phase response of the record is also corrected. Ideally, a properly equalized record will have flat frequency and phase response (the fact that we can geta credible square wave off an LP test record is proof that we can come pretty close when everything is working properly). To achieve this, old-fashioned analog playback equalization is the only way to go; digital filtering won't accomplish this task.
It should certainly be possible to design digital filters to mimic both the phase and frequency characteristics of analog filters, but no one has yet done this commercially for playback equalization of disc records, as far as I know.
Kilde.
Stemmer dette?
Edit: Lagt inn korrekt lenke.
Transfer engineers who use digital processing (such as CEDAR) for removing noise on 78-rpm recordings sometimes find that a flat initial playback allows the digital noise removal to work better, before the recording curve is applied. The flat position can be extremely useful here. The disc is played without equalization, then fed to the digital processor. The EQS MK12 also has a line input, just ahead of the equalization circuitry, which allows you to apply the recording curve at line level, after the digital pro- cessing has been done. Some engineers will tell you that you can apply the play- back curve in the digital domain, and the equalization capabilities of many computer-based digital processors and editors will allow you to do this.
There's a flaw in this approach, however. Among the virtues of digital equalization is the lack of nasty phase shifts inherent in analog filters. In the case of playback curves, the lack of frequency-dependent phase shifts presents a problem. Most readers know that the playback curves provide proper frequency equalization for the record. What is generally ignored-probably because it happens automatically-is the fact that the play- back curves also provide correct phase equalization. The filters used to pro- duce the recording curves in the first place caused phase shifts. When complementary analog play- back equalization takes place, the phase response of the record is also corrected. Ideally, a properly equalized record will have flat frequency and phase response (the fact that we can geta credible square wave off an LP test record is proof that we can come pretty close when everything is working properly). To achieve this, old-fashioned analog playback equalization is the only way to go; digital filtering won't accomplish this task.
It should certainly be possible to design digital filters to mimic both the phase and frequency characteristics of analog filters, but no one has yet done this commercially for playback equalization of disc records, as far as I know.
Kilde.
Stemmer dette?
Edit: Lagt inn korrekt lenke.
