In memory of the humble audio cassette tape

TDK MA-X / Type IV / Metal audio cassette

Saturday 7th September was the first International Cassette Store Day. Its organisers described it as “a celebration of a physical product that is accessible, fun, cheap and still going strong in the turbulent current musical climate.” The day saw  a number of limited edition albums released on cassette, and modern classic albums re-released too.

My Tapes

I adored the TDK MA cassette tapes (pictured). I had  a fantastic SONY three head recorder with bias adjustment helper and Dolby-S bought circa 1994. (I still have it actually and it’s as good as new!)

With a fresh metal tape, bias adjusted, dolby S on and using the third head monitoring, you could push the signal really high achieving a wonderful audio signal saturation level that is hard to beat. They just played back with such life on any type of cassette player too, including car radio cassette players!

I used to record a lot of mates’ CDs on to tape for them because they loved the sound quality I could achieve. The tape saturation  brought a life and clarity to music that seems to be missing from a lot of digital music, and even pre-recorded analogue music as well.

Before the ease of hard-disk and digital recording, most of my compositions, MIDI sequences and keyboard improvisation moments were all recorded to the TDK type IV metal cassettes too. I’m slowly revisiting all these and archiving them digitally to share online (see the list under Music).

Sony three head cassette deck with Dobly S.

Tape Saturation in a Digital Age

Those familiar with digital recording of any kind will recognise the life-ending sound that is almost worse than fingers down a black-board: digital clipping. Once a digital signal has clipped, there is rarely anything known to man or gods that can be done to rectify that audio recording.

The analogue audio concept is based on physical electrical voltage current alternations which convey an electrical wave form analogous to the sound pressure wave form, hence being called analogue. In this domain, clipping becomes an electrically relative term that depends on the input and output capabilities of the components of the ‘chain’ or system. There comes a point of overloading, where the power of the electrical signal is too much to handle and the signal, and thus the quality of the audio it is analogous to alters.

The distortion associated with clipping is often unwanted, and is visible on an oscilloscope even if it is inaudible. However there are times when it is wanted for creative reasons, such as with the electric guitar or the distorted vocal effect etc. But there is also another reason, which I mentioned  earlier when talking about recording CDs to tapes.

As the signal level increases, tape approaches a saturation point where no further signal variations can be recorded. This is signal saturation, an inherent flaw in the accuracy of magnetic tape as a recording medium. However, unlike digital recording techniques, where analogue to digital converters in audio interfaces suddenly and aggressively ‘clip’ as the signal exceeds its maximum level, analogue tape breaks down in a less predictable manner. The result is distortion and compression which behaves in a unevenly with regard to signal level, frequency and dynamic range. (Or, in a non-linear way for the techno-bables.)

Ironically, the ‘break down’ and soft-clipping of tape saturation sounds pretty appealing to most people, and recording engineers realised that the pleasant distortion and compression characteristics of saturation could be used as a mix tool, making individual tracks sound more punchy, helping to ‘glue’ elements together and even making entire mixes sound bigger and richer.

Recreating the Warmth of Tape

Most people use Digital Audio Workstation (DAW) software these days, such as Logic and Pro Tools. Many studios, and live engineers, are recording and mixing with digital audio consoles (a few studios have kept the analogue desks of old, but they generally are massive beasts and prone to breaking down with heavy usage.) Introducing”analogue warmth” to your digital sounding mix is the subject of hundreds of articles all over the net, but there are three basic solutions.

  1. Use a DAW plug-in. They range widely in price and quality. Essentially, digital algorithms try to model the effect of signal saturation.
  2. Use a three-head cassette recorder. Just chain an output bus to the input of the tape deck (like the SONY model I have) and route the ‘monitor’ output back in to your DAW. Use a fresh tape, fast forward to about 2 mins in, follow the bias adjust setup, then record your mix via the tape (recording, set to monitor, and volume adjusted as high as sounds pleasing – you may have to manually adjust too) and record the result either live back in to DAW or replay the tape.
  3. Use a Gyraf Audio Gyratec Infundibululm. It will only set you back £3360 and is tested and reviewed in this months Sound on Sound magazine. It is a completely mains-free passive device, so no electrical interference from mains, and is actually rather brilliant. Admittedly, it’s top level pro kit at that price, but there really is nothing like it out there.

What’s it sound like?

Sound on Sound have provided some audio examples of their test with the Gyraterwatsityfidliumthingy, on their website: http://www.soundonsound.com/sos/sep13/articles/gyrafg21-media.htm

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