Buzz Audio 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. WELLINGTON, 6141 NEW ZEALAND. PH. [phone]

www.buzzaudio.com email [e-mail]

Welcome…

Thank you for choosing the Buzz Audio DBC-20 Diode Bridge Compressor. In
this manual you will find important information regarding the use of the DBC
and we suggest you do read it before using the unit to become familiar with 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 what to do.

We also suggest you retain the original packaging at least during the warranty
period in case you need to return the unit for servicing, however we are
confident this will 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

②

1] Installation Precautions

Normally the DBC can be mounted into a rack without any special ventilation
requirements as it runs pretty cool. If there are other units in the rack above
and below the DBC that run hot, it may be necessary to allow for ventilation
gaps between 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 will find a circular voltage selector switch to set this up. Generally the
DBC mains voltage is set for the country to which it has been initially sent, but
before powering 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. Below the IEC inlet you will see
the fuse draw. Using a small flat blade screwdriver, you can flick open the
draw and change the fuse if required. The fuse draw also has a place to hold
a spare fuse (the square tube). The correct fuses are;

110V = 2 amp slow blow
230V = 1 amp slow blow

These fuses will either be fitted in the fuse draw, and/or supplied in an
accessory bag with the DBC.

3] Audio Connections

On the rear panel of the DBC you will find the XLR input and output connectors.
These connectors are wired as follows;

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 with 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 whereby one of the
output “legs” will be short circuited to ground. This will cause the output to be
6dB low and operation of the BYPASS function will be adversely affected. The
input of the DBC-20 can accept balanced or unbalanced input signals with no
change in operation.

③

4] Controls and Indicators

The DBC-20 has two channels with 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. Clockwise 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 will 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. Clockwise rotation increases gain from 0dB to approx.
+15dB of gain.

ATTACK

This switch has 6 positions and adjusts the time taken for the DBC to respond to
signals that exceed the threshold (as set with 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 switch 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 will be slower on more
constant signals (bass guitar for example). Using fast release times may cause
audible distortion with some signals, especially low 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 how much compression is
being applied.

④

HARD-SOFT

This control selects between two modes of operation. In HARD mode the self­adjusting ratio control is in normal operation. When switched to SOFT the
automatic ratio is modified and a measured amount of dynamic is retained. It’s
easier to try it and hear how it works rather than describe it here, but it is useful
when lighter compression effects are desired.

FLAT-BASS

When switched to BASS, a high pass filter in the DBC side chain is introduced
which reduces the sensitivity of the compressor at low frequencies. This is
useful in maintaining the low end of a full mix or perhaps only controlling the
high end of a bass track.

BYPASS-ENGAGE

In the up position, this switch provides a hard relay bypass of audio input to
audio output with no electronics in the signal path. This is useful in comparing
the compressed to un-compressed signal. When using the DBC with stereo
signals, both A and B channels’ bypass switches would be operated together
for a meaningful result.

SEPARATE-LINK A/B

In SEPARATE mode, the DBC-20 operates as two completely individual mono
channels. When switched 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 with 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 switches the mains power to the DBC-20 on and off. An aqua colored led
tells you when you have successfully achieved this operation. The DBC bypass
relays are engaged for a few seconds at power up to prevent thumps.

⑤

5] Specifications

Maximum Input Level = +27dBu

Maximum Output Level = +27dBu

Frequency Response = 6Hz to 400kHz

Noise = -80dBu A weighted (measured with 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 with 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 Information

We are confident that you will receive many years of trouble free operation from
your unit. If however you experience any technical problem with your DBC-20,
contact your dealer or Buzz Audio for recommendations on what to do.

The DBC is constructed with non-surface mount serviceable parts, this means
most electronic faults can be easily repaired. Pots and switches do eventually
wear 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 without the alignment instructions and
correct test equipment is not recommended.

For on line support visit our web site www.buzzaudio.com
Buzz Audio Ltd, PO Box 6677, Wellington 6141, New Zealand.
Phone [phone]. Email; [e-mail]

⑥

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 workmanship for a period of 1 year (12 months) from
the date of sale, and will replace defective parts and repair malfunctioning
products under this warranty when the defect occurs under normal installation
and use – provided the unit is returned to our factory (or duly authorised service
centre) via prepaid transportation with a copy of the proof of purchase, ie, sales
receipt. This warranty provides that examination of the returned product must
indicate, in our judgment, a manufacturing defect. This warranty does not
extend to any product that has been subjected to misuse, neglect, accident,
improper installation, or where the date code has been removed or defaced.
The standard warranty 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 within 4 weeks (28 days) from purchase
date. Alternatively, you may Register your purchase on-line at our web-site
www.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. WELLINGTON, 6141 NEW ZEALAND. PH. [phone]

www.buzzaudio.com email [e-mail]

⑦

⑧