I subscribe to audio engineer Mark Waldrep's
"Real HD Audio" tech blog (and highly recommend it). Recently he described a project by a certain company that has the potential to remove wow and flutter from any tape-sourced analog recording.
Excerpt:
From the Plangent Processes website:
“The Plangent Processes software, developed with researchers at Cambridge University in England, is proprietary UNIX-based, and is non-realtime. It runs at 768 kHz with 32-bit double precision internally, ensuring scrupulous audio fidelity with little or no artifacts. The basic function of the software is to identify a steady-state ultrasonic reference tone (such as tape bias or logic control) embedded within the original analog signal and then perform continuous high-resolution pitch correction in order to keep the reference tone at a fixed frequency. For transfer, we maintain a fleet of analog ATR102 tape machines rebuilt by ATR Services, along with custom headstacks and preamps, as well as ancillary electronics and most popular A/D converters. Conversion resolution is minimum 96 kHz / 24-bit, though 192/24 is preferred. A 44.1 kHz version of the process is also available with slightly diminished performance.”
In simple terms, what Jamie and the brainiacs at Cambridge University have done is remove or reduce the macro and micro speed fluctuations that invariably occur during analog tape recording and playback. Everything from “wow & flutter” to “scrap flutter” is diminished resulting in “near perfect” playback. This is the ideal way to do a tape transfer. The use of ATR 102 tape machines and custom electronics doesn’t hurt but the essence is in the proper alignment of timing…something that a very well clocked PCM digital system has going for it as well.
Although Waldrep goes on to chastise Plangent for compressing the same recording, the technique, should they choose to license it for instance, sounds promising. Can you imagine (say) your favorite vintage piano recordings with all wow and flutter gone?
