Buzzaudio DBC-20 User manual

DBC-20
Diode Bridge Compressor
Users Manual
DBC-20 USERS MANUAL VERSION-1, NOVEMBER 2014. CONTENTS COPYRIGHT BUZZ AUDIO LTD 2014.
PO BOX 6677, TE ARO. ELLINGTON, 6141 NE ZEALAND. PH. [phone]
www.buzzaudio.com email [email protected]

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Welcome…
Thank you for choosing the Buzz Audio DBC-20 Diode Bridge Compressor. In
this manual you ill find important information regarding the use of the DBC
and e suggest you do read it before using the unit to become familiar ith all
the controls and their function.
If after unpacking the DBC you find any damage to the unit you should contact
your dealer or supplier immediately for advice on hat to do.
We also suggest you retain the original packaging at least during the arranty
period in case you need to return the unit for servicing, ho ever e are
confident this ill not be necessary!
Contents
1] Installation Precautions ............................................................ 3
2] The Mains Input ............................................................................ 3
3] Audio Connections ..................................................................... 3
4] Controls and Indicators ............................................................ 4
5] Specifications ................................................................................. 6
6] Service Information ..................................................................... 6
7] Warranty Information ................................................................. 7
8] Recall Sheet ..................................................................................... 8

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1] Installation Precautions
Normally the DBC can be mounted into a rack ithout any special ventilation
requirements as it runs pretty cool. If there are other units in the rack above
and belo the DBC that run hot, it may be necessary to allo for ventilation
gaps bet een the units to avoid over heating. Excessive heat for long periods
can shorten the life of all electronic devices.
2] The Mains Input
The DBC-20 mains input can be set to run from 110V or 230V. On the rear
panel you ill find a circular voltage selector s itch to set this up. Generally the
DBC mains voltage is set for the country to hich it has been initially sent, but
before po ering up the unit, please check the voltage selector.
POWERING UP THE UNIT WITH THE WRONG VOLTAGE SETTING MAY CAUSE
BURN OUT OF THE POWER TRANSFORMER!
It is also important to fit the correct mains fuse. Belo the IEC inlet you ill see
the fuse dra . Using a small flat blade scre driver, you can flick open the
dra and change the fuse if required. The fuse dra also has a place to hold
a spare fuse (the square tube). The correct fuses are;
110V = 2 amp slo blo
230V = 1 amp slo blo
These fuses ill either be fitted in the fuse dra , and/or supplied in an
accessory bag ith the DBC.
3] Audio Connections
On the rear panel of the DBC you ill find the XLR input and output connectors.
These connectors are ired as follo s;
Pin 1 = Signal Ground
Pin 2 = Signal + (hot)
Pin 3 = Signal – (cold)
Note that the pin1 connection of these connectors is not part of the audio path,
and is provided to shield the interconnecting cable. Leaving pin 1 free at one
end of the cable can help reduce earth loops ith other equipment as only the
signal hot and signal cold connections are required.
IMPORTANT; The output of the DBC is balanced using direct drive amplifiers, this
means it should NOT be connected to an unbalanced input hereby one of the
output “legs” ill be short circuited to ground. This ill cause the output to be
6dB lo and operation of the BYPASS function ill be adversely affected. The
input of the DBC-20 can accept balanced or unbalanced input signals ith no
change in operation.

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4] Controls and Indicators
The DBC-20 has t o channels ith identical controls. The DBC utilizes silicon
diodes in a transformer coupled balanced arrangement as the gain reduction
element and has a unique self-adjusting ratio control.
COMPRESSION
This control adjusts the amount of signal sent to the side chain circuit and
therefore the amount of gain reduction (or compression) applied to the input
signal. Clock ise rotation increases the amount of gain reduction. Note that as
the amount or depth of the compression is increased, so does the compression
ratio and it ill vary from about 2:1 up to 10:1 from threshold to about 15dB of
gain reduction.
GAIN
Adjusts the post compression make up gain to bring the output level back up to
the desired volume. Clock ise rotation increases gain from 0dB to approx.
+15dB of gain.
ATTACK
This s itch has 6 positions and adjusts the time taken for the DBC to respond to
signals that exceed the threshold (as set ith the Compression control). This is
the time taken (in milliseconds) to achieve about 15dB of gain reduction. The
FAST position has an attack time of less than 0.5 milliseconds and is slightly
dependent on the input signal.
RELEASE
This 6 position s itch sets the time taken (in 100’s of mS) for the DBC to release
from 15dB gain reduction. The AUTO position has a clever circuit that releases
from short transients (like percussive sounds) quickly but ill be slo er on more
constant signals (bass guitar for example). Using fast release times may cause
audible distortion ith some signals, especially lo frequency sounds.
GR METER
The 15 led bar graph display is used to indicate the amount of gain reduction
and it has a fast response so you can clearly see ho much compression is
being applied.

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HARD-SOFT
This control selects bet een t o modes of operation. In HARD mode the self-
adjusting ratio control is in normal operation. When s itched to SOFT the
automatic ratio is modified and a measured amount of dynamic is retained. It’s
easier to try it and hear ho it orks rather than describe it here, but it is useful
hen lighter compression effects are desired.
FLAT-BASS
When s itched to BASS, a high pass filter in the DBC side chain is introduced
hich reduces the sensitivity of the compressor at lo frequencies. This is
useful in maintaining the lo end of a full mix or perhaps only controlling the
high end of a bass track.
BYPASS-ENGAGE
In the up position, this s itch provides a hard relay bypass of audio input to
audio output ith no electronics in the signal path. This is useful in comparing
the compressed to un-compressed signal. When using the DBC ith stereo
signals, both A and B channels’ bypass s itches ould be operated together
for a meaningful result.
SEPARATE-LINK A/B
In SEPARATE mode, the DBC-20 operates as t o completely individual mono
channels. When s itched to LINK A/B, the compressor side chains are linked to
provide stereo tracking. This mode is used to prevent the stereo “image”
shifting if a loud sound appears only in one channel of a stereo mix.
Note that unlike some VCA based compressors, all controls remain operational
in LINK A/B mode. You MUST still set up both A and B channel’s controls
usually ith identical settings for stereo program. Note the COMPRESSION
controls of each channel are interactive, so reducing the compression on one
channel results in a measured amount of reduction in the other channel.
POWER ON
This s itches the mains po er to the DBC-20 on and off. An aqua colored led
tells you hen you have successfully achieved this operation. The DBC bypass
relays are engaged for a fe seconds at po er up to prevent thumps.

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5] Speci ications
Maximum Input Level = +27dBu
Maximum Output Level = +27dBu
Frequency Response = 6Hz to 400kHz
Noise = -80dBu A eighted (measured ith 10dB make up gain applied)
Harmonic Distortion at +10dBu input level and no gain reduction =
0.28%@100Hz, 0.25%@1kHz, 0.15%@10kHz
Harmonic Distortion ith 10dB gain reduction (release 400mS)
1.5%@100Hz, 0.5%@1kHz, 0.5%@10kHz
Gain variable from 0 to +15dB
Dimensions = 1U rack mount case (482W x 44H x 250D)
Weight = 2.9kg
Mains voltage = 110 to 240Vac selectable
6] Service In ormation
We are confident that you ill receive many years of trouble free operation from
your unit. If ho ever you experience any technical problem ith your DBC-20,
contact your dealer or Buzz Audio for recommendations on hat to do.
The DBC is constructed ith non-surface mount serviceable parts, this means
most electronic faults can be easily repaired. Pots and s itches do eventually
ear out but you should receive many years of use before replacement might
be necessary.
Please note there are no user serviceable parts inside the DBC-20 and
attempting any internal adjustments ithout the alignment instructions and
correct test equipment is not recommended.
For on line support visit our eb site .buzzaudio.com
Buzz Audio Ltd, PO Box 6677, Wellington 6141, Ne Zealand.
Phone [phone]. Email; [email protected]

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7] Product Warranty
• Disclaimer
Buzz Audio Ltd is not liable for any damage to microphones, amplifiers,
consoles, speakers or any other equipment and/or electric shock to humans
that is caused by negligence or improper installation and/or use of the DBC-20
Diode Bridge Compressor.
• Standard Product Warranty
Buzz Audio Ltd guarantees the DBC-20 Stereo Optical Compressor to be free of
defective materials and/or orkmanship for a period of 1 year (12 months) from
the date of sale, and ill replace defective parts and repair malfunctioning
products under this arranty hen the defect occurs under normal installation
and use – provided the unit is returned to our factory (or duly authorised service
centre) via prepaid transportation ith a copy of the proof of purchase, ie, sales
receipt. This arranty provides that examination of the returned product must
indicate, in our judgment, a manufacturing defect. This arranty does not
extend to any product that has been subjected to misuse, neglect, accident,
improper installation, or here the date code has been removed or defaced.
The standard arranty is NOT transferable.
• Product Warranty Extension
The above Warranty may be extended to a period of 2 years (24 months) from
date of sale provided the enclosed Warranty Registration card is completed and
returned to the office of Buzz Audio Ltd ithin 4 eeks (28 days) from purchase
date. Alternatively, you may Register your purchase on-line at our eb-site
.buzzaudio.com. The Extended Warranty is transferable.
DBC-20 USERS MANUAL VERSION-1, NOVEMBER 2014. CONTENTS COPYRIGHT BUZZ AUDIO LTD 2014.
PO BOX 6677, TE ARO. ELLINGTON, 6141 NE ZEALAND. PH. [phone]
www.buzzaudio.com email [email protected]

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