At 12:46 PM 2010-04-29, Mike Gray wrote:
>What a simple and elegant idea - use the bias signal as a clock; 
>wow+flutter=jitter; heterodyne - same as recovering audio modulation 
>from an RF signal.  Congratulations to all involved.
>
>One criticism I heard when I mentioned this technique to someone in 
>the restoration community - is the bias signal sufficiently stable 
>to ensure that the derived signal is accurate?

Hi, Mike,

There are many different "windows" of perturbations in tape systems. 
Bias would generally be stable enough to correct for wow and flutter. 
Where it might fail us is in certain circumstances over the length of 
a recording. As you may have noted, David mentioned that Jamie 
suggested transferring on a song-by-song basis, recalibrating the 
Plangent bias recovery for each song.

Once we have the wow and flutter filtered out via Plangent, we can 
apply long-term speed drift compensation using a variety of tools 
(although some of the "autotune" tools might have too much of an 
acoustic signature).

Cheers,

Richard


Richard L. Hess                   email: [log in to unmask]
Aurora, Ontario, Canada       (905) 713 6733     1-877-TAPE-FIX
Detailed contact information: http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.