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Q: "How can I combine the special sound of analog with digital recording?

"What do I have to attend to when recording with an analog tape recorder (Revox B77)? I want this special sound but it seems that it gets lost when I go into the computer. How can I combine analog and digital recording?"


Question from a Audio Masterclass visitor...

"What do I have to attend to when recording with an analog tape recorder (Revox B77)? I want this special sound but it seems that it gets lost when I go into the computer. How can I combine analog and digital recording?"

My first inclination is to say that I think we should put analog in the past where it belongs and use the wonderful digital equipment that is now available, often at very low cost.

But the problem is that we long for the analog sounds of a bygone era. and digital emulations don't quite work as well as we would like them to.

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In many cases, we don't need to plug-ins to emulate aspects of the 'classic' analog sound. We can buy tube microphones, tube preamps, tube and optical compressors and there is even a device (the Portico 5042 “True Tape” Emulation and Line Driver) that incorporates the magnetic effect of the tape and tape head.

But you can't go out and buy a genuine tape recorder, new off the shelf, from your local pro audio dealer. They are history, and probably never to be repeated.

You can however easily source a used analog tape recorder from eBay. They are currently dirt cheap, and you might get a few reels of tape thrown in.

And since it's the raw 'analog sound' that you want, does it really matter if the heads are not in tip top condition?

But the person who asked the question already has a Revox B77 analog tape recorder, which should give him all the analog sound he wants. But he is having difficulty transferring the analog magic into his computer.

This then raises the further question of what the analog sound actually is.

My opinion is that although the special kind of distortion produced by the tape and tape head is a factor, and of course the inevitable noise of analog tape is a factor, it is the instability of analog tape that is the main mechanism in generating the analog sound.

There is no such thing as the perfect tape transport and the speed will inevitably vary a little. This is called wow.

But also, the tape scrapes against the heads and guides producing a variation in speed that is much faster, and highly irregular. This is called flutter, sometimes 'scrape flutter'.

This instability leads to the generation of additional frequencies that were not present in the original signal. These are called sidebands, and there are masses of them.

Any kind of distortion produces sidebands, but a tube amplifier, for instance, produces only a few that are widely separated and mostly whole-number multiples of the original input frequencies.

But analog tape produces much more richly textured sidebands, some of which are simply related to the original signal, but many that are much more complex.

Now, getting this to transfer into a computer should not be a problem. The complex sound of analog tape is just a signal like any other and the audio interface should have no trouble.

My guess would be that there is something about the look, feel and perhaps even smell of the tape recorder that enhances the analog experience subjectively. And when you only have the sound, it doesn't seem quite the same.

However it is worth considering that the frequency response of an analog tape recorder is much wider than digital audio sampled at 44.1 or 48 kHz, where the frequency response tops out at around 20 kHz..

An analog recorder can have a frequency response up to 25 kHz or even 30 kHz if the heads are in good condition and clean.

Although we are told to believe that the range of human hearing only extends to 20 kHz, and then only in a few people, it is often thought that we appreciate these higher frequencies subliminally and they do make a difference.

So, to capture the analog sound at its truest, the best advice would be to sample at 96 kHz, and of course 24 bits to ensure that the rich texture of the analog noise floor is transferred in detail.

Let us know how you get on.

P.S. The tape recorder in the photo is a Boosey & Hawkes Reporter. If you have one like this, let us know!

By David Mellor Thursday November 30, 2006