I shamelessly copied this from http://faq.waldorfian.info/faq-browse.php?product=mq and am leaving it here. The tl;dr is that clicks are a feature; not a bug.
Why do some synths produce clicks?
Chapter 1: The click in theory
A click is produced when a very fast level change in the audio signal occurs. You can easily check that on your home stereo when you play back a CD and switch the Source Selector back and forth between CD and a source that doesn’t play anything.
The brightness of the click depends on the speed of the level change. The faster the level changes, the brighter is the click. So, the level change speed can be compared with the cutoff of a lowpass filter. There is an easy formula for it:
Let’s consider a level change from full to zero (or from zero to full) output from one sample to another on a machine that uses 44.1kHz sample rate. So, we first transfer the sample to milliseconds:
1 sample equals 1/44100 second, which is = 0.02267573696ms.
To calculate the cutoff frequency of the click, just use this formula:
Cutoff (Hz) = 1000 / Level Change Time (ms)
which in the example results in:
44100Hz = 1000 / 0.02267573696ms
Whoops? This the sampling frequency and, err, very bright.
Chapter 2: The click in the real world
Now, how could this knowledge help you and what has it to do with Waldorf synthesizers? Easy:
When you play a sine wave sound, only the base frequency (the fundamental or the 1st harmonic) is present. That means, when you play note A=110Hz, no other frequencies are involved except this 110Hz oscillation.
Now, what happens when you abruptly cut the sine wave to zero when it just is at its maximum level? You get the same effect as with your home stereo.
From one sample to the next, the waveform is brought from maximum to zero, resulting in the aforementioned bright click.
The same applies when the opposite happens. On Waldorf synthesizers, you can setup the oscillators so that their phases start randomly when a new note is played. So, you never know at which level the sine wave is when you hit a note.
Consider it would be at the maximum level, you would get an immediate change from zero to maximum when the amp envelope’s attack rate is set to 0.
BTW: the effect is the same, when you have a bright waveform but filter it so that it is very hollow.
Chapter 3: In which situations does the click occur on my Waldorf synth?
There are several situations when you can get a click and when you know where they happen, you can try to prevent them:
Amp Envelope Attack
On digital Waldorf synthesizers like the MWII and the Q, the Attack rate can be as short as 1 sample. This means that the amp volume of a note can change from zero to maximum in one sample, or in ms: 0.02267573696ms. This results in a very bright click.
On the Pulse, we chose a minimum attack rate of 1.9ms, resulting in a click with a maximum cutoff of around 526Hz. When you own a Pulse, you probably know of the 1.9ms number from the user’s manual, because that’s the update speed of all CVs that are used in it.
So, when you hear a click on note start every now and then, just increase the Amp Envelope Attack rate until you don’t hear a click anymore.
1. Amp Envelope Release
Here, the same as with the Attack rate applies. When you hear a click when you release a note, increase the Amp Envelope’s Release rate.
If the click still persists, you should also check the Release rate of the Filter Envelope. Maybe the filter closes very fast, which can result in a click, too.
2. Voice Stealing
We know that this is the most annoying situation. But, the click helps you: When you hear a click at a certain position in your song, you know that a voice stealing happened and you can easily shorten or delete notes in the editors of your sequencer.
When you count the notes and say that they don’t exceed the maximum number of voices of your synthesizer, just keep in mind that other notes might still be in their release phases and therefore have to be added, too.
3. Mono mode
In Mono mode, a click might occur when any envelopes (Amp or maybe Filter, too) are set to retrigger on new notes. When the Attack rate of a sound is greater than 0, they are brought to zero so that they can go up to their full level again. This rapid
change to zero results in a click.
4. Unisono sounds
Here, a click might occur even heavier. Unisono sounds easily exceed the maximum number of voices and because they steal not only one but several notes at once, a click can be a lot more present. It is louder and happens more often. You should check several points on unisono sounds to lower clicks as much as possible: are the envelope rates set to reasonable values, are the oscillator phases set to free, is filter keytrack set to 0% (because this can also be a rapid change) and so on.
Chapter 4: Why does my synth xy (insert product name here) produce no clicks
Should I really answer that? Because it is slooooow.
Some japanese manufacturers (I don’t say names here) prevent voice stealing clicks by fading out voices slowly before they start new notes. Hey, brillant idea, why doesn’t Waldorf do that? Because it ends up in a very bad MIDI timing (and those japanese synths are well-known for that).
Furthermore, most of these synths are sample-based, which means that their attack behaviour is stored in the sample that they should play. So, a click on note start is also not possible because the sample somehow gradually fades from zero to maximum.
If those synths allow you to change the sample start position, they hopefully produce clicks, too (if not, they also have slow envelopes which we don’t hope).
A couple of days ago, someone mentioned the Matrix 12 producing no clicks on retriggering envelopes. Yes, that’s correct, because the Matrix 12’s minimum attack rate is around 20ms. Or in other words: its envelopes are among the slowest you can find in a synthesizer.
The same applies to all synthesizers of the Matrix series, because they all used Curtis chips that had an automatic smoothing filter to prevent steppiness. The older Oberheim synths like the 4-Voice were better here.
Also, the Waldorf Microwave and the Waldorf Wave used those Curtis chips, but when the Attack rates of the envelopes were set to 0, this smoothing filter was temporarily switched off, resulting in an abrupt change. Attack 1 there is the same as minimum attack on a Matrix
synthesizer.
Chapter 5: Conclusion
You know that we at Waldorf could prevent clicks by increasing the minimum envelope rates or allowing bad MIDI timing. We could also prevent that the filter resonance can destroy your hearing ability or that you could play a C major chord. But who are we that we could decide what you want from a synthesizer.
Clicks can even be musically useful and add a kind of randomness to a song that brings it to live. A very good example is the bad, ugly, annoying, but famous and beloved keyclick on Hammond organs. Recently I bought the latest Art Of Noise album “the seduction of Claude Debussy” produced by Trevor Horn and played by the creme de la creme (even including Lol Creme of 10CC and Godley&Creme) of musicians and I heard a lot of clicks during a couple of tracks. I am even quite sure that they came from Waldorf synths but I don’t know if. You can easily imagine that I had a smile on my face.
I hope you now have even more fun with your “clicking” Waldorf synth.
