Dual Compressor/De-Esser/Limiter



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Our experience of the audio engineer’s

situation on the road and in the studio

has shown us that compressor / limiters

and de-esser combinations frequently

prove so inflexible that they create as

many problems as they solve. We have

applied our audio design skills to solve

these problems, and the result - the BSS

DPR-402 - is much more than an

ordinary compressor / limiter.


A quick look at the front panel shows

that as a result each of the two channels

combines a full range of signal level

control facilities a dedicated and

tuneable de-esser section; a compressor

section with comprehensive control of

all main parameters and an AUTO mode

option for general use; a fully informative

LED metering section that never

leaves the engineer ‘in the dark’; and

finally a calibrated and variable peak

limiter section.


Unlimited Uses


The double side-chain and subtractor

architecture of the DPR-402 makes it

predictable enough for conventional

programs, and flexible enough for

unlimited effects. Among the facilities, it

offer are: loudness control for

recording, mixdown, live sound

reinforcement and clubs; peak

amplitude control in disc cutting; split

band and peak amplitude control for

broadcast feeds; dynamic sibilance

control on individual mikes or even on

post-mix production, where remarkable

results are obtained from narrow-band



But the DPR-402 really shows its

colours when its internal filters are

configured to dynamically compress OR

expand individual parts of the audio

band- leaving the rest of the spectrum

unmodified. The endless possibilities

range from low frequency expansion

and narrow band resonance control to

general dynamic equalisation to create

enhancement effect. Further

possibilities include dynamically

controlled mixing, gating and ducking

for new and novel sounds.


The Double Side Chain


The circuit design secret that makes the

DPR-402 so successful is the use of an

extra side-chain. Because of this, only

the subtractor circuit and the gain

control lie in the signal path. The

sophisticated control circuitry -

including a voltage control amplifier -

lies parallel to the signal path, controlling

the subtractor while its components

have no adverse effect on the signal.

This not only ensures a cleaner, purer

signal, but forms the basis of entirely

new possibilities in signal processing.


# It gives hard or soft knee compression

for general purpose loudness

control during recording, mixdown or

live-sound reinforcement.


# It adds a peak-limiting stage to

normal compression to provide the

protection needed for disc cutting and

broadcast feeds.


# In reverse mode, it expands

previously compressed recorded

material, and is also used for producing



Music often suffers when compressed

over its full range. To overcome this,

the innovative technology of the DPR-

402 introduces a new flexibility in signal

compression, not only giving control of

threshold levels but making it frequency



Compressing selected levels and

frequencies can reduce noise and

distortion problems while leaving other

significant signal elements at full

strength to maximise artistic effects.


Sophisticated De-Essing


The DPR-402 provides two main deessing

options to suit different program

material and means of reproduction.


Broadband de-essing adds to normal

compressor performance the ability to

compress the whole signal when HF

signals exceed the preset de-ess

threshold level, or for greater precision

in demanding applications it can be set

by the main compressor controls.


HF - only de-essing, the other main

option, uses all the compressor control

circuitry to create a dedicated,

frequency-selective de-esser channel

compressing high frequency signals

while leaving low frequency content



Develop new skills to do what other

compressors cannot do


# Combine selective de-essing

sibilance control with compression or



# Control loudness in a way suited to

AM/FM broadcast processing.


# Use the frequency-selective

loudness control to enhance a frequency

spectrum without additional



# Preset LF loudness to maintain club

safety limits.


# Obtain automatic level-controlled

mixing of program sources for special









Input Section

IMPEDANCE 10KOhm, electronically balanced.


INPUT CMRR > -50dB 30Hz-20Hz.

INPUT XLR3-31 or equivalent. Wired as

CONNECTOR pin 1 o/c, pin 2 cold, pin 3 hot.


Output Section

IMPEDANCE Less than 1 Ohm unbalanced, 

current limited.

MAX OUTPUT LEVEL +20dBv into 600 ohms.

OUTPUT GAIN +20dB continuously variable.

OUTPUT XLR3-32 or equivalent. Wired as

CONNECTOR pin 1 earth, pin 2 earth, pin 3 hot.


System Performance

FREQUENCY +1dB 25Hz-20kHz. Ultrasonic

RESPONSE filter -3dB@ 30kHz.

NOISE Equiv. input noise -86dBv 22Hz -

22kHz, -82dBv CCIR weighted.

DISTORTION Unity gain, + 10 dBm output, below threshold: THD 0.03%


IMD 0.01%SMPTE, 10 dB compression. Threshold 0dB. 1kHz, 5 sec rel. time setting: 2ND


HARMONIC 0.05%.IMD 0.25%


Harmonic distortion in this type of

equipment will increase with reduced

frequency and shorter time constants.


CROSSTALK < -85dB 20Hz -20kHz.



THRESHOLD -30 to +20 dBv cont. variable.

RATIO 1:1 continuously variable to infinity:1.


ATTACK TIME 11 steps 50μsec-80msec.

RELEASE TIME 10 steps 5ms to 5 sec and AUTO.


Attack times are measured at 63% of final gain reduction with step

signal 8dB above threshold. Release times are measured at 63% of

open gain or removing a signal 8dB above threshold.




A two part program-dependent time constant. Typical attack

time is 200 μsec on fast transients, release time 10msec for 63%

recovery from a 10dB 4msec

response, and 1 sec for a 10dB 40 msec response.



THRESHOLD RANGE -30 to +20 dBv continuously variable.


RATIO Infinite, at and above twice the set frequency.


FREQUENCY RANGE 800Hz to 15kHz continuously variable.


Frequency is that at which 3dB of gain

reduction occurs for 10dB of signal overdrive above threshold.

10dB of gain reduction will occur at and above twice this



Peak Limiter


THRESHOLD RANGE +4dBv to +20dBv continuously



RATIO 20:1.


ATTACK TIME Fast setting 150μsec, Slow setting 750μsec.


RELEASE TIME Fast setting 100msec, Slow setting 500msec.


Dimensions and Power

SIZE 482 x 44 x 228mm 19in x 13/4in x 9in overall.

WEIGHT 4.5kg (10lbs) packed.

ELECTRICAL SUPPLY 120-220V +105-20% 50/60Hz 15VA.




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