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Analog Magnetic Tape was the standard for high quality recording between the late 1940s and through until around 1990. It produced a certain distinctive sound due to the magnetic properties (hysteresis, non-linearity, compressive transfer curve, and the encoding and decoding EQ curve). Some people like that sound, although it introduced approximately 1.5% total harmonic distortion onto the audio signal. I spent some time studying the B-H curve of a mid 1950s Ampex recorder which operated at 15 ips and used the NAB recording and playback EQ. I created a multifilter that produced that NAB encoding process, which then fed into the B-H curve created by the polynomial filter. The machine emulated used 100 kHz AC bias (as opposed to DC Bias) which uses both halves of the B-H curve and the hysteresis notching is eliminated. But the sound characteristic is preserved. You must use this three element multifilter via the Forensics Version of the software since the polynomial transfer function of the system had to be created and only the Forensics version includes that capability. Attached, is the preset for the multifilter. The effect is somewhat subtle, not unlike the sort of sound you can get from the Virtual Valve Amplifier (yet different). Comments are welcome.
Craig
Craig
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