Posted on 13. Mar, 2016 by Daniel Duskin (Record Producer, Mixing & Mastering Engineer) in Mastering, Mixing, Saturation
Mixing & Mastering “Rules”
Clipping is not professional, right? Sometimes. Can clipping be good? Sometimes.
Running the tape recorder into the red is good, but digital clipping is bad, right? Yes… Sometimes.
This article will look into these questions, find answers, and explain them.
The History Of Clipping
For every decade audio recording has been around, their has been a new idea about what kind of clipping is good, and what kind of clipping is bad.
From the beginning, a primary goal in recording audio has been to get a low-noise recording without audible clipping. Harmonic distortion was most definitely never considered a good thing in the early days.
By the time rock music was all over the radio, clipping was being used as part of “the sound.” The preferred method of clipping at that time was tube saturation, primarily applied to the electric guitar signal. For the first time, clipping wasn’t always bad, sometimes it was good.
It wasn’t long before experimenting with hard and intentional tape clipping became relatively common. Eventually over-driving the tape input into the red became a common occurrence for skinned drums (kick, snare, toms), and bass guitar as well.
When I was first getting interested in recording, the last two taboo’s were transformer clipping, and digital clipping.
Not before long, engineers spoke of riding transformer inputs close to—or just into—clipping to get a certain sound. Not too long after that, the final taboo was crossed, and digital clipping was used for both artistic purposes, and to get some more level in the loudness wars.
One thing remains true. Clipping can sound really bad. But now, another thing can be equally true. Clipping can sound really good!
Different Types Of Clipping
When you increase the input level into a vacuum tube, clipping happens gradually—this is sometimes referred to as soft clipping. Additionally, the harmonic overtones produced by tube saturation tend to be even-order harmonics. Even order harmonics are often described as more musical, because the overtones are generally—or mostly—at intervals that fall within key of the music produced. Even order harmonic distortion also produces a smoother and more even fuzziness at extreme levels. Because of the soft and gradual onset, harmonically musical overtones, and smooth fuzziness at high levels, it can be more difficult to hear tube distortion as audible distortion until the input is really pushed hard and those tubes really start glowing.
If you increase the input level on a tape recording, you’ll notice some similarities to tube saturation, such as the gradual onset. The slow onset of audible distortion is similar to that of vacuum tubes, only slightly less gradual. The harmonic distortion produced when tape is clipping is a bit different than tubes. While much of the mid and high frequencies will produce even order harmonic distortion like tubes do, the low-frequencies start to produce 3rd order harmonic distortion.
Another interesting character of tape clipping is the reduction of high frequencies when bright sounds are clipped hard. This has to do with the physical limitations of high frequency detail that can be produced with a limited number of metallic particles on the tape.
As we increase the input signal into a transformer, clipping happens more suddenly—there is a gradual soft harmonic onset before the serious clipping occurs, but that serious clipping happens rather suddenly. The harmonic distortion is mostly of the 3rd order, and very little even order distortion. The sound of transformer clipping sounds like clicks and pops for short bursts above the clip threshold, and a nasty crackly and scratchy crusty buzz for sounds that sustain for longer periods over the clip threshold. Low frequencies can much more easily clip a transformer than high frequencies. Really well designed—and often very large—transformers produce harmonics that are more even order in the mids to highs, and 3rd order in the low end, very much like tape.
Clipping is never soft or gradual when done digitally. Once the signal hits 0dB, nothing can exceed that level. This results in hard squaring of the waveform as the the level continues to rise, until the signal finally represents a square wave.
The harmonic order produced by digital clipping is odd, and not generally described as “musical” as it is described with vacuum tubes.
Because of the sudden squaring of the signal, digital clipping can be extremely transparent on extremely fast transient material, until the input level rises to dip below the short transient point.
Different Reasons To Clip
Clipping certainly isn’t the most common process that you will want—or need—to apply to every channel in your multi-track recording. If you did, you’d end up with a very noisy mix—if that’s you’re thing, go for it, but it’s certainly not what most people will want to do, or hear for that matter.
With that said…
When clipping is warranted, it can be your secret weapon!
And with all of the analog modeling plugins we have available today, anyone with access to these plugins can mix and match the different types of clipping for different parts of their mix. Guess what? It just so happens that different types of clipping work better for different instruments and for different tasks. Let’s get into it!
If your goal is to get some fuzz, even order tube saturation is probably what you’re after. Tube saturation sounds great on guitars, vocals, and is even tolerable on cymbals and shaker (though maybe not recommended).
A really cool trick for vocals is to mult the output of the vocal and apply some tube saturation to the mult, turn that fader down, and start bringing it up for a beautiful fuzz from underneath.
If you’re after a thick bottom, tape and/or high quality transformer saturation is what you’re after. That added third order harmonic in the bottom can add a lot of weight.
If you want to warm up a track, tape will not only provide hefty bottom with that added lower third order harmonic. Tape can also soften those harsh high frequency bursts as well.
So you’re on the edge, and you want some harsh and noisy crunch? Transformers can transform that pleasant sound into a nasty mess for you. If you want that nasty mess to sound thin and brittle as well, then digital clipping is what you’re after.
But what if you’re after transparency? You’d assume the best bet would be to steer clear of clipping, right? Well, what if you need something loud, and you don’t want the audible pumping that comes from limiting? This is where pure even order harmonic clipping, and hard digital clipping can both come in handy.
Rich chordal material can be pushed further into the red without audible destruction with even order harmonic distortion. Alternatively, transient material can be pushed the furthest without audible destruction with digital clipping.
Summary — Overview
- Tube: Smooth, Fuzzy, Tolerant
- Tape: Warm, Thick
- Transformer: Hard, Crunchy, Thick
- Digital: Crackly
- Kick Drum, Snare, Toms: Tape, Transformer
- Bass Guitar or Synth: Tape, Transformer, Tube
- Room (any instrument): Tape
- Guitar, Organ, other Chordal: Tube
- Vocals: Tube
- Make It Fat: Tape, Transformer
- Smooth & Fuzzy: Tube
- Warm It Up: Tape
- Crunchy & Nasty: Transformer, Digital
- Make It LOUD: Digital, Tube
In a future article, I’ll break the safe on the most unknown and taboo clipping technique used by the biggest and best mastering engineers in the industry. That one is gonna hurt!