How tape saturation controls transients
I don't have a tape machine, I have a fancy Tascam 122 MKIII cassette deck.
But know this: Reel tape (no pun intended) and cassette tape are not the same. Quality, size and what they can carry is different.
My personal favorite is a tape emulation of Willi Studer's magnetic tape recorder J37 - a fine swiss product just like fine swiss chocolate - it's the Waves J37. I'm not the most esoteric person on the planet but I must admit: I don't know if my preference for the J37 is based on its sound. With tape machine emulations, for some people it's more a feeling that makes the difference, as opposed to the actual sound the emulation has.
The original Studer J37 was an expensive and relatively big four track tape recorder, but of course nowadays we're lucky that we can insert however many tape emulations we want in our projects, if we desire so.
And when I say "however many", I mean however many our CPU* can manage 😛
In this article I want to describe why somebody might actually desire to use a tape emulation (or real tape for that matter) but I will focus almost purely on the relationship of tape and transients.
* Overloud Tapedesk and ToneBoosters ReelBus, both claim that their tape emulation plugins are very CPU efficient. I have only used the Overloud Tapedesk demo on very many channels in one project and it was in fact never clogging the CPU.
Granted, I did a bit of research for this but I'm not a complete expert on how tape recording works, I have only dealt with plugin emulations. But generally speaking, when audio signals are recorded to tape, it is "voltage levels banned onto magnetic tape", via an electromagnet in the recording head. You will know that audio material doesn't travel through analog cable as "music", cables don't know a snare from a guitar or from pure noise. The audio is turned into voltage level.
So the tape itself has a magnetic layer of iron oxide. Yes, it is pure rust powder 😁 The electro magnet in the recording head can then magnetize the particles of that layer.
And here is were this gets a bit dicey but let's see....and I stand to be corrected if necessary.
The recording head will magnetize each particle by the amount that is required to give an accurate* "recording" of said voltage level (the analog equivalent of the source audio material) that is going into the machine.
*As accurate as the particular tape machine allows.
And where is the saturation coming from?
Before the time of digital recording, there was recording to tape. And everybody wanted loud music on tape (sounds familiar?) and everybody wanted as little noise and hiss as possible in their recording. And so the audio had to hit the tape at the right level but in case it was slightly too hot, as we will learn in a bit, tape was a more or less "forgiving" medium in that regard.
If that incoming voltage was "too hot" or outside of what the tape could handle, the recording/playback would show more or less obvious signs of saturation and possibly distortion.
But what does it mean for our precious transients?
Dependent on how hot the signal was recorded, either some transients (peaks in the audio material) would be affected (they'd be softly clipped) or the whole recording could be more or less distorted.
With the right amount, tape saturation tends to "round off" transients (waveform peaks) nicely which can help reduce peaks to gain a little headroom for a bit more level. If the voltage doesn't fit onto the tape, it gets "crammed" onto it no matter what which as a result softens out that transient (waveform peak).
Image you have a drum loop going on and you would like to turn it up a notch but you feel uncomfortable because you read these high peaks in your channel meter already. Okay!
Fear not and try this: Slap that tape emulation on the channel and drive the plugin relatively hard (play with input and output level but don't let it clip//often you'll find a link button to link input and output to adjust with one another) and observe how your your peak meter readings are less high because the "hot tape" takes the sharp edges off those transients.
That can be helpful on a lot of things. I have had a drum bus here and there (both in mixing projects of electronic and acoustic music) that used a tape emulation to tame it, without extra or more standard compression through a compressor. I have had acoustic guitars that sounded great with transient control through tape. Tape emulations can even sound great on a mix but applying the right amount will make all the difference.
!!! If you overdo that saturation you will hear quite audible distortion !!!
As said in the beginning, you can also go beyond than slight peak control and use tape emulations to create overtones through strong saturation or distortion.
Important to know, maybe: Tape distortion, which is on the side of odd harmonics, will be different compared to tube distortion, which is more on the side of even harmonics. The latter is considered to favor musicality because even harmonics are representations of our dear music octaves :) Odd harmonics create overtones in different spots, by some people not considered as "musical" but if you ask me, I say it's a matter of taste.
Questions ? Hit me up at email@example.com or use the contact form.
Until next time.
Author: Robert Hundt // Date: September 2nd, 2019