TOKYO DAWN Kotelnikov User Manual

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TOKYO DAWN LABS

Kotelnikov – Manual

Product version: 1.6.0
Revision 10, last update: January 5, 2020
Editor: Fabien Schivre, Dax Linière, Mario “Susiwong”, Ady Connor and Shane Johnson

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CONTENT S

The concept ............................................................................................................................................................. 5

Precision, aliasing and the solution ......................................................................................................................... 6

Audio dynamics control .......................................................................................................................................... 7

Controls and displays .............................................................................................................................................. 9

Detection pre-processing ...................................................................................................................................... 10

Low frequency relaxation .................................................................................................................................. 10

Stereo sensitivity ............................................................................................................................................... 10

Gain control ........................................................................................................................................................... 11

Threshold .......................................................................................................................................................... 11

Peak Crest.......................................................................................................................................................... 11

Soft knee ........................................................................................................................................................... 11

Ratio .................................................................................................................................................................. 11

Timing section ....................................................................................................................................................... 12

Attack ................................................................................................................................................................ 12

Release LEDs ...................................................................................................................................................... 12

Release peak ..................................................................................................................................................... 12

Release RMS ...................................................................................................................................................... 12

More on the timing section ............................................................................................................................... 13

Output section ...................................................................................................................................................... 13

Makeup ............................................................................................................................................................. 13

Dry mix .............................................................................................................................................................. 13

Output gain ....................................................................................................................................................... 13

Monitoring section ................................................................................................................................................ 14

Delta .................................................................................................................................................................. 14

Equal loudness bypass....................................................................................................................................... 14

Gain control metering ........................................................................................................................................... 14

Generic settings (toolbar) ..................................................................................................................................... 15

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Preset Management .......................................................................................................................................... 15

Undo/Redo ........................................................................................................................................................ 15

A/B Control ........................................................................................................................................................ 15

Process-Quality ................................................................................................................................................. 16

Process-Target ................................................................................................................................................... 16

Help Mode ......................................................................................................................................................... 16

Settings .............................................................................................................................................................. 16

Sliders ............................................................................................................................................................ 17

Processing ..................................................................................................................................................... 17

Registration ................................................................................................................................................... 17

Local Data ...................................................................................................................................................... 17

Updates ......................................................................................................................................................... 17

Help ............................................................................................................................................................... 17

About ............................................................................................................................................................. 17

Mouse control behavior .................................................................................................................................... 18

Appendix A: Getting started with Kotelnikov ........................................................................................................ 19

Appendix B: Vladimir Aleksandrovich Kotelnikov ................................................................................................. 23

Installation ............................................................................................................................................................ 24

Technical Specifications ........................................................................................................................................ 24

Get in touch! ......................................................................................................................................................... 24

Credits ................................................................................................................................................................... 25

Disclaimer and License .......................................................................................................................................... 25

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Thank you for choosing a Tokyo Dawn Labs product!

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THE CON CEPT

TDR Kotelnikov is a wideband dynamics processor combining high fidelity dynamic range control with deep
musical flexibility. As a descendant of the venerable TDR Feedback Compressor product family, Kotelnikov has
directly inherited several unique features such as a proven control scheme, individual release control for peak
and RMS content, an intuitive user interface, and powerful, state of the art, high-precision algorithms.

With a sonic signature best described as “stealthy”, Kotelnikov has the ability to manipulate the dynamic range
by dramatic amounts, while carefully preserving the original tone, timbre and punch of a musical signal. As
such, it is perfectly suited to stereo bus compression as well as other critical applications.

Kotelnikov does not try to emulate any previously available device. The concept is a proud digital processor, it
is the original!

Notable features

• 64bit floating point precision for all relevant calculations

• Multi-rate processing structure for highest accuracy

• “Delta” oversampled signal path (bit transparent at 0dB gain reduction)

• Super fast, yet natural sounding compression

• Control scheme based on “Crest factor”, offering independent release controls for peak and RMS

events

• Flexible sidechain highpass filter

• Advanced stereo linking options optimized for the stereo bus

• Delta preview mode to preview the difference between compressed and original signal

• Latency compensated parallel bypass (i.e. processing not interrupted)

• Extensive documentation

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PRECISI ON, ALIASING AND THE SOLU TION

Controlling the dynamic range of an audio signal in the digital domain is not as easy as it looks. A whole array of
problems makes it very difficult to build a truly effective and musically attractive compressor in the digital
domain.

The most significant restrictions are due to the discrete (i.e. “stepped”) nature of digital signal storage. Without

delving too deep into the mathematics, it is essential to understand that the data stored in audio-files is not the
actual analogue audio signal. It is a very economic, intermediate format. The true analogue signal is only
reconstructed by the anti-alias filter inside the D/A converter. However, if one wants to control the amplitude
of music accurately, it is absolutely essential to know the actual waveform (i.e. it needs to know about the
values between samples as well).

Another huge problem in digital dynamics control is a phenomenon called aliasing or Moiré images. Aliasing
appears in all discrete (i.e. “digital”) systems as soon the frequency of a signal exceeds the Nyquist rate (half
the sample-rate). The evil detail here is that contrary to analogue systems, signals exceeding the bandwidth
aren’t gradually “faded out”, instead, they mirror at the Nyquist frequency and overlap into the audible range
at full energy, and in this process, lose any harmonic relation to the original signal.

Compressors are non-linear systems. All non-linear systems add harmonic (or non-harmonic) content to the
processed signal and thus have the potential to extend the bandwidth significantly. The more aggressive the
non-linearity, the stronger and higher the newly generated partials (harmonics). If the sample-rate is too low to
handle the extended bandwidth, these harmonics will alias and lose their harmonic relation to the

fundamental, resulting in inaccurate, “unwanted” behavior, which in turn directly produces an unpleasant

sound.

Kotelnikov’s algorithm was carefully designed to avoid these issues. To achieve this in an efficient manner, the
algorithm is split in two parts, both typically running at higher rates than the original signal (given a standard
rate such as 44.1kHz or 48kHz).

• Sidechain

The sidechain is responsible for generating a control signal for the gain cell. It consists of several non­linear elements such as the threshold, RMS detection and timing filters. To avoid aliasing in the control
signal (which would severely limit the accuracy of the compression), the sidechain uses a bandwidth
up to 20x wider than the audible bandwidth.

• Gain cell

The gain cell is a central part of the compressor where the audio signal’s level is adjusted by the
control signal delivered by the sidechain. This operation is a non-linear process and potentially
doubles the bandwidth. To handle this bandwidth, this multiplication always runs at a minimum of
double the audio sample rate (i.e. at least 88.2kHz). One interesting design feature of Kotelnikov is

that only the compressed portion of the signal (listen via “Delta” switch) is oversampled. This leaves

the original signal completely untouched - as long as no gain reduction is occurring, the plugin is 100%
bit transparent.

In both cases, the resampling is done with very high quality linear-phase time-domain convolution.

Please note that these quality improvements come at a price - CPU cycles - but from a sonic point of view, and
in the context of the fast growth of computer power, we think they are well worth the compromise.

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AUDIO D YNAM ICS CONT R OL

Beside the more or less obvious technical issues illustrated in the previous chapter, generations of audio
engineers suffered from the fact that the dynamic behavior of music signals can be very complex. Controlling
these dynamics, be it overload protection, loudness balancing or creative shaping is hard to achieve without
introducing negative side-effects (audible collateral damage). The central problem being the processor’s
unawareness of musical criteria, which in turn enforces its own sound (and intellectual restrictions) onto the
signal.

In the best case, this common phenomenon is referred to as a compressor’s “color” and sometimes can be of
great creative use. However, it also means that the processor alters the original fidelity in one way or another.
There are times when the audio engineer faces a dynamic challenge, an error that needs correction, but

doesn’t want to accept any additional color being brushed all over the entire signal. This is particularly

important to the mastering engineer, especially in the case of high quality mixes, but also during creative
shaping of natural instruments in a mix.

Most offers on the market are based on rather crude attack/release timing concepts, sometimes combined
with more or less intelligent automatisms. In fact, they aren’t much more elaborate than simple thermostats.
However, dynamics in music usually do not only consist of attack and decay phases, they are far more
complicated. In order to control dynamics in a both effective and transparent manner, it is essential that the
processor has the ability to analyze the signal in a musically sensible manner. It’s no wonder that dynamics
control systems purely based on A/R models are much better suited to relatively simple signals such as
monophonic instruments or other sources already having predictable dynamics, and typically do more harm
than good once they face more complex material and/or processing tasks.

Kotelnikov uses an elaborate control system based on two specialized parallel paths, each handling specific
signal phases independently with high technical effectivity and musical grace. The compressor runs two distinct
and separate detection and compression algorithms in parallel:

A. Peak Path

The peak detection/compression path primarily follows the rectified version of the (true!) audio
waveform with great precision. The peak path’s release phase can be tuned via the PEAK RELEASE
control, but also automatically accelerates the release time in certain, high dynamic range situations.
This avoids over-compression of small, “crispy” transient events. This form of over-compression is
highly audible, as it dulls the original signal substantially and can creates a “nervous” pumping side­effect.

B. RMS Path

The RMS path reacts to overall energy levels (similar to human hearing) and ignores short transients. It
can be seen as a very slow and smooth compressor that handles the constant or ‘steady-state’ parts of
the signal. To be honest, Kotelnikov’s RMS path doesn’t use a true RMS detection in the “text-book”
sense. Instead, it relies on a highly advanced derivate of the regular RMS detector based on a precise
Hilbert Transform detector. The result is a frequency-independent RMS detector, practically free of
any harmonic distortion. Contrary to conventional RMS detectors which handle low frequencies much
like peak detectors and only higher frequencies as true RMS, Kotelnikov’s RMS stage automatically
uses the optimal RMS window size for every frequency. Additionally, Kotelnikov’s RMS path features
an advanced release gating (“freezing”) mechanism preventing noise floor build-ups during
programme pauses as well as other forms of pumping. It activates as soon the RMS section detects a
sudden pause in the input signal.

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To summarize, in contrast to the peak stage, the RMS stage’s own dynamic behavior has the ability to
lengthen the RMS release time as required by given audio content. Kotelnikov can even increase RMS
release to (almost) infinity during certain situations.

The section generating the highest reduction at a specific point in time takes control of the whole compression
action. Technically speaking, we have 2 cross-linked side-chains running in parallel, whereby the peak section

mostly controls short, high amplitude events and the RMS section takes control over sections having “steady
state dynamics”. This contradiction is perhaps better explained as “Sections without substantial dynamics”.

This unique approach offers all of the advantages of peak compression combined with all of the advantages of
RMS compression. Furthermore, the RMS path negates the disadvantages of the peak path and vice versa. This
design guarantees a very stable stereo image and low compression artifacts over a wide range of material and
settings.

The image below roughly illustrates the general idea: