Aural "prognostication" inbetween tracks

When the tape being recorded coils itself around the tape that was recorded a moment before, on the take up spool, some of the magnetic flux from that coil of tape is transferred by its intimacy to the coil before it. It is only on "silent" sections of tape this is noticed. However, it is present all the time, but masked by the loudness of the recording. "Print through" is also known as "Pre-echo".

So why no "echo" or post-"print-through"? This is because pre-echo is a function of decaying magnetism. The tape is "reluctant" in taking up the magnetic signal and more magnetic flux is presented to the tape by the tape head than the tape will retain. The magnetism decays to a settled amount by the time it has been wrapped around the take up spool, giving up some of it to the previous coil, but not back to the next coil, because by then, the decay is minimal.

A reduction in recording level effects a cure to print-through but the tape noise being constant decreases the signal to noise ratio.

To obtain the best signal to noise ratio means recording just below tape saturation and using high quality (high saturation) tape running at high speed such as 30 i.p.s. to get the most extended frequency response. However, such high magnetic saturation means the tape wrapping itself onto the take up spool gives up its magnetism easily to the section of tape just prior to it.

In record mastering a copy at 7.5 i.p.s. is taken of the 30 i.p.s. master. The 7.5 i.p.s. copy is less likely to be responsible for "print through" because its slower speed means the magnetic decay takes place before being reeled onto the take-up spool. You only hear the print through present on the master tape.

If the same master tape is used over and over in getting the "right take", tape stretch can cause a short duration of an earlier "take" to exist after the end of the successful "take". This happens because the pause control is "hit" the moment the "take" finishes rather than letting it it run on. The run on can only take place if the musicians are trained to be quiet at the end of a "take", and hardly happens on orchestral works, but happens often in other genres, where the musicians may get over excited. For example: Genesis "Nursery Crymes" - "The Fountain of Salmacis". On the original pressing you hear "that's it!" from a band member because the tape was run on. On later pressings the master tape is paused prematurely to remove "that's it!" but because there is still some musical decay, this combines with the whiplash effect of hitting the pause button and completely destroys the ending.

This video does not have either ending...




Edited by Graham Slee - 03 Jul 2012 at 5:48am

Yes, thank you Graham for the neat explanation and for sharing your knowledge in this field!