input file : source soundfile
output file : destination soundfile (when marked)
or result.wav (for unregistered files)
processing mode : global
Whenever possible old records should be played back using original equipment, namely a phonograph working with an appropriate speed, usually expressed in terms of the RPM (revolutions per minute) rate.
The most frequently encountered rates include 33.33 RPM (modern LP’s), 45 RPM (singles) and 78.26 RPM (most of the old laterals produced up to mid fifties). Occasionally you may come across records that require less typical speeds such as 78.8 RPM (Edison Laterals), 80 RPM (Edison Diamond Disks), 125 RPM (Brown Wax Cylinders) and several other unusual rates.
Since the original equipment may be very difficult to find you may be forced to use another phonograph with a different turntable speed than required. DART XP Pro offers you a special tool for automatic correction of audio data collected under such nonstandard conditions.
Suppose, for example, that you want to restore recordings from an old 78 RPM vinyl record but you don't have a phonograph capable of playing it back with the appropriate speed. Here's what you can do if you have at your disposal a 33.33 RPM phonograph which was in common use prior to the invasion of CD players (check out your attic!):
1. Play the record back with a speed of 33.33 RPM and sample it at a standard rate of 22050 Hz.
2. Use the Adjust RPM rate utility to correct the speed and the sampling rate of the recording obtained at step 1.
If your computer is sufficiently fast you don’t have to store the preliminary results of step 1 on your hard disk - if you use the Adjust RPM rate utility in the real-time mode (after choosing the Real-time command from the Restore menu) DART XP Pro will make all due adjustments ‘on the fly’, i.e. the program will operate directly on the samples collected at the input of your audio card.
The Adjust RPM rate dialog is easy to use. All you have to do is give details (RPM rate) of the recording technique you used to obtain the nonstandard audio data and specify the appropriate sampling parameters (RPM rate, sampling frequency) you would have used had the original equipment been available. Then press the Process button.
NOTICE 1
The choice of an appropriate stylus is another important decision, which affects the record transfer. The trial and error method is perhaps the best one to advice. Elliptical styli usually yield satisfactory results, e.g. you may try a 0.7 mil elliptical stylus to transfer modern LP’s and a 3.0 mil truncated elliptical stylus to transfer 78 RPM laterals.
NOTICE 2
Playing back a record at a lower speed than required is sometimes a good way of avoiding skipping due to the groove tracking problems. The Adjust RPM rate utility will allow you to easily correct all nonstandard recordings obtained in this way.