TK Audio 500 series, BC501 User Manual

TK AUDIO BC501

500 series Stereo Bus Compressor

Congratulations on buying one of the most transparent stereo bus compressors ever made,
it’s manufactured and assembled by hand in Sweden and thoroughly tested before leaving
the factory .
The BC501 provides smooth bus compression associated with one of the most famous bus

compressors from the mid 80’s. Mixing engineers call it the ”magic glue” when transparent

compression strengthens mixes without compromising clarity . The BC501 provides just that
kind of compression bringing cohesion and punch; equally useful for drum bus and instrument
compression.
The built-in blend control makes it easy to apply parallel compression by adjusting the mix of
dry and compressed signal.
A switchable side chain filter can be applied at 80Hz, 150Hz or 220Hz which makes the
BC501 less responsive to low frequency energy .
The external side chain input makes it possible to have the BC501 pump to an external
source.
The BC501 will add the ”magic glue” and make your mixes sound punchy and coherent.
All controls are stepped for 100% repeatability .

THE PARAMETERS:
THRESHOLD: -20dB to +20dB in 41 steps. The threshold adjusts the level above where the

signal is reduced. A lower threshold means a larger portion of the signal will be treated. For
optimal results make sure that the input level is high enough.

RATIO: 1.25:1 / 1.5:1 / 2:1 / 4:1 / 6:1 / 10:1. The ratio determines the input/output ratio for
signals above the threshold. For example, a 4:1 ratio means that a signal overshooting the
threshold by 4 dB will leave the compressor 1 dB above the threshold. At the 1.5:1 and 2:1
setting a relatively subtle soft knee compression is applied. At 4:1, the compression becomes
more obvious, and at 10:1, the BC1-S is basically a peak limiter.

HPF: When engaged a gentle 6dB/octave high pass filter at 80Hz, 150Hz or 220Hz is
applied to the internal or external side chain signal, making the compression less responsive
to low frequency energy . Both 80Hz and 150Hz engaged gives 220Hz.

EXT SC: Engages the external side chain input through the 1/8” stereo jack. By using the
external side chain another signal can control the behavior of the compressor; most
commonly used by DJs for ducking / lowering the music volume automatically when speaking.
It’s also effectively used for ducking the bass track or background whenever the kick drum hits
by sending the kick track to the external sidechain input. For more information please read
the section about side chain compression.

ATTACK: UF (ultrafast) / 0.1 / 0.3 / 0.6 / 1 / 3 / 10 / 30 / 60 / 120mS. The attack setting
defines the time it takes for the compressor to decrease the gain and reach the level
determined by the ratio. Faster attack settings means better control of the transient part of the
sound, but if set too fast the compressor might cut away more transients than wanted. A good
starting point is 10ms.

RELEASE: 50 / 100 / 300 / 600ms / 1.2S / Auto. The release setting defines the time it takes
for the compressor to increase the gain to the level determined by the ratio, once the level has
fallen below the threshold. Higher release settings will result in a less intrusive compression
with lower distortion, but if set too high the compression might not be effective enough. A
good starting point is 100ms or Auto.

AUTO RELEASE: Makes the release function time dependent on the duration of the signal
peak. In practise it’s a fire-and-forget setting that behaves the same way as a classic British
bus compressor used by many since the 80’s.

GAIN REDUCTION METER: The metering shows the average level (RMS) of the gain
reduction which differs from the peak level meters of most plug-ins - comparatively it’s slower
and in practise it means that a little goes a long way . The proper amount of compression on a
mix is usually done when the needle moves in the middle of 0 and 4. Higher ratio and faster
release settings will result in a more obvious compression/limiting that sometimes is too fast
for the needle to show. Always use your ears first and just use the metering as a quick
reference.

MAKE-UP: 0 to+20dB of gain in 41 steps to balance the compressed signal level against the
input signal level.

IN: Engages and disengages the compressor. Should be used a lot to control how the
compressor is affecting the sound.

BLEND: Straight to compressed sound in 21 steps. Turning the knob clock wise will mix the
original signal with the compressed signal. For more information please read the section
about parallel compression.

STARTING PRESETS
MIX BUS

The main purpose of the BC501 is to act as a bus compressor and it does it very well.

AUTO RELEASE MAGIC

One of the true unique features of the BC501 is the auto release setting and it’s ability to glue
the mix together. The auto release is a good starting point when setting up the compressor for
2 bus duty . Adjust the Threshold until 2 to 3 dB of compression is shown by the meter . It’s all it
takes to glue the mix together .

Threshold: ±0 dB
Ratio: 1.25:1, 1.5:1, 2:1 or 4:1
HFP: ON
Attack: 10 ms
Release: Auto
Make-up: 8 o’clock
Blend: Comp

POP MIX COMPRESSION

For more obvious compression a fast release should be used. Adjust the Threshold until it
shows about 3 to 4 dB of compression on the loudest parts of the song.

Threshold: ±0 dB
Ratio: 4:1
HFP: ON
Attack: 10 ms
Release: 100 or 300 ms
Make-up: 9 o’clock
Blend: Comp

SLAMMING 2 BUS COMPRESSION

Depending on the source material sometimes the compression can effectively slam the mix. It
usually works for electronic music with fast transients that need to be tamed. The result can be
a bit fatiguing but it sure can inject energy when needed rendering a super processed mix.

Threshold: 5 dB
Ratio: 10:1
HFP: ON
Attack: 3 ms
Release: 50 ms
Make-up: 9 to 10 o’clock
Blend: Comp