EMI - pioneers.
We must not forget Decca's arch rivals, EMI and their pioneering work on stereo recording. It's probably true to say that EMI were the pioneers (in the UK) but for some reason, I never really warmed to their recordings. Perhaps warmed is really the word. Maybe it's all a romantic memory now.
What is unarguably a fact is that what is recorded onto analogue magnetic tape - no matter how fine - is significantly corrupted by the tape from the very instant that the tape passes the record head. That's because recording tape stores audio as magnetism - in other words, we have transformed the electrical voltage that represents the audio into magnetic flux. And there is no such thing as a perfect electrical > magnetic > electrical transformer.
Every Christmas holiday I promise myself that I'll service even one of my studio analogue tape recorders - my Telefunken M21A or Studers. But I never get around to it, despite the recollections they connote for an era long passed. The reason is that it's so easy to demonstrate that if you record an absolutely pure tone you will replay from the tape that reference tone plus other harmonically related tones that you never recorded. Perhaps worse, if you simultaneously record two pure tones, you will certainly replay those two tones plus numerous mathematically related tones that were never there at the input. That's the real problem with analogue: the process generates frequency components never there in the recording which, for most listeners most of the time, are masked. But when you know what to listen for, just reduce the resolution and overall fidelity. Those intermodulation products remove the crispness from the original source. I guess some folk prefer the less analytical, warm analogue sound because the 'spaces between the notes' (a very crude analogy) have been filled-in with the intermodulation products. Overall, analogue can sounds 'nicer' and less effort to listen to, just like those lovely old 50s recordings. But that's just another audio illusion.
And then there is the ghastly business of tape (or groove) print-through. Have you ever noticed the 'pre-echo' of a loud passage in the silence just before the music starts? That's usually because the recording tape's magnetic field doesn't stop dead on the layer of tape .... it bleeds onto the next layer, the next layer, the layer beyond that with decreasing strength. Some record companies occasionally unwound and re-wound the stored tapes. All that did was to move the problem around on the tape, randomising the audibility of the print-through. In other words, adding a general magnetic print-through mush to the entire tape.
Maybe I'll run one machine up over the break just to give it some exercise and demonstrate these limitations of analogue tape.
Alan A. Shaw
Harbeth Audio UK