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COMP-554
INTRODUCTION
Congratulations on choosing the Golden Age Project COMP-554 compressor!
The COMP-554 is a one-channel vintage style compressor for the 500-format. The signal path uses only discrete components like resistors, capacitors and transistors. The input and output are transformer balanced
and the unit also uses a third interstage transformer.
This is the way audio components were built before integrated circuits became available. IC´s are small and
cheap and they are widely used in most modern designs. It is clear though that audio components built with
modern technology doesn´t always provide the best perceived sound quality or character that the modern user
desires.
On the contrary, the subjective sound quality delivered by vintage equipment is often prefered over the one delivered by modern units. This is the reason why so many vintage audio components are cloned and produced
again and also why the vintage originals are often very expensive on the second hand market.
The class-A circuit used in the COMP-554 is similar to the one in the classic 2254 compressor that was designed in 1969. It quickly became a legend due to it´s totally unique sound character that is warm, smooth,
sweet and musical.
These characteristics have been heard on countless recordings through the years and it is a versatile sound
that works very well on many sound sources and in many genres. The essence of this sound is now available
at a surprisingly low cost, making it available to nearly everyone.
FEATURES
- Vintage style electronics. No integrated circuits in the signal path.
- Based on a classic diode bridge design.
- Transformer balanced input and output.
- Prepared for a Carnhill transformer upgrade (standard in the Plus version).
- Flexible control range for threshold, ratio, attack and recovery.
- All controls except the gain make-up one are stepped.
- Three selectable sidechain fi lter frequencies.
- Three fl exibel sidechain options; Internal, Insert and External.
- The external sidechain I/O is electronically balanced @ 4dBu and appears on the right slot rack connections.
- Separate switches for hardwire bypass and compression out.
- Two insert connectors for inserting the EQ-573 in the main audio and/or sidechain signal path.
- Meter selectable for output (two reference levels, +4 and +12 dBu) and gain reduction.
- Possibility to link two units for stereo operation.
- Three position Air EQ switch, Flat, +3 or +6 dB @ 30 kHz.
- Two position output termination switch for different tones.
- A soft start circuit that ramps up the supply voltage slowly (about 10 sec.) to avoid a power-on current surge.
- A great sound that suits most sound sources and genres.
OUT: Pressing this switch removes the compression action, the signal still
passes through the circuitry though so you can compare the sound with and
without compression.
METER SWITCH: Select the meter to show output level at two different reference levels or gain reduction.
BYPASS: This is a hardwire bypass, meaning that the signal is fed from the
input jack directly to the output jack when this switch is pressed. You can
then easily compare the sound with and without the COMP-554 in the signal
chain.
TERM: The output transformer is made for having an ideal load of 600 ohms.
Most modern equipment have an input impedance of 10 kohm or more.
When the COMP-554 drives a modern unit, the output level will increase and
the higher frequencies will be slightly accentuated.
If you connect the COMP-554 to a modern unit, the switch should usually
be set in the 600 or 2k position. You can always let your ears decide which
position you prefer, the switch can be used as a three position subtle high
frequency eq.
AIR EQ SWITCH: There are two position for adding a boost centered around
30 kHz, AIR1 adds 3 dB, AIR2 adds 6 dB.
SIDECHAIN SOURCE SWITCH: There are three selectable positions.
- INTERNAL: The sidechain signal is sourced from the main signal path with
nothing in between.
- INSERT: The sidechain signal passes the CZ13 Insert jack located on the
top of the small right hand circuit board at the back of the unit. The jack is
made for connecting one of our EQ-573 units, allowing you to equalize the
sidechain signal and thereby the compression action.
- EXTERNAL: The sidechain signal passes through the 500 rack connectors
corresponding to the right hand slot of the two slots used by the COMP-554,
allowing you to insert an external equalizer in the sidechain signal path. You
can also feed an external signal to the sidechain input to do ducking. The
operating level is + 4dBu.
PLEASE NOTE: The external sidechain connections can only be used with
external units that have balanced connections, they do not work with unbalanced connections.
MAIN AUDIO PATH INSERT JACK: There is an unbalanced insert jack (CZ7)
located on the top of the left hand circuit board at the back of the unit. Connecting our EQ-573 module will give you a great comp + eq combination
where the eq will be located after the compressor. Please note that you must
remove the black plastic jumper above the Insert jack to activate it.
LEVELS AND METER CARE
Care must be taken to protect the meter from physical overload when it
is set to show output level. If the needle is hitting the end of it´s travel for
prolonged periods, there is a risk that the meter will be damaged. This is not
covered by warranty.
The meter is calibrated from factory to show 0 VU when the output level is
about +4 dBu (or 1,23 volts) with the meter switch in the +4dB position. Set
the meter switch to the +12dB position if the meter is hitting the end of scale.
WARRANTY
The COMP-554 come with a limited parts and labor warranty. It is built to last,
but components can break down.
If your unit need repair, please contact the reseller where you bought the
unit, they will direct you to the distributor for your area that handle repairs.
The warranty period and terms are decided by the Distributor for your country. The Distributor will support Golden Age Project resellers and end users
with spare parts and repairs.
REGISTRATION
You are welcome to register your unit at our website:
www.goldenagemusic.se
WWW.GOLDENAGEPROJECT.COM
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CIRCUIT DESCRIPTION
The signal fi rst enters the input transformer,
a damping network and is then passed on
to the diode bridge where the actual gain
reduction is taking place. It is followed by a
balanced FET-transistor stage. Then follows
an interstage step-up transformer that feeds
the sidechain circuitry and a three transistor
gain stage followed by the gain potentiometer
and the insert jack.
The signal then goes to the output stage. This stage again uses only three
transistors, the last one in the chain is a hefty 2N3055 power transistor running in class-A mode, driving the output transformer.
So, all in all, the complete signal chain only contains a maximum of ten active
elements. Compare that to the big number of transistors that are usually used
in one single integrated circuit!
MODERN VERSUS OLD
It is true that there are some great IC´s available today that achieves very low
levels of static and dynamic distortion.The simple circuits that the COMP-554
uses, and even more so the transformers, cannot match the low distortion
specifi cations of modern IC´s.
It is the distortion components that imparts a sound character to the audio
signal and, if the distortion components are of the right sort, this is a good
thing since it makes the recorded voice or instrument sound “better”, more
musical, more pleasing to the ear. This is one reason why vintage style units
are so popular today.
Sometimes, transparent units are prefered over colored ones. It´s all about
taste and it depends on the genre. For most modern music styles though,
color and character is defi nitely a good thing.
USING THE COMP-554
The best way to learn using a compressor is by experimentation. A compressor can be set to do its job, which is to lower the dynamic range of a signal,
more or less invisible or it can be used as a creative tool, affecting the sound
in a big way. You will fi nd a lot of information about how to use and adjust
compressors on the internet.
- As a start, you need to mount the COMP-554 in a 500 series rack unit. There
are a number of alternatives available from different manufacturers, the
COMP-554 should work fi ne in most of them. Make sure that the rack unit
power supply is turned off when you mount or remove the COMP-554.
CONNECTING THE COMP-554
The Line in- and ouput is found on the connectors in the 500 rack corresponding to the left hand slot of the two rack slots that the COMP-554 occupy. Since
the unit is transformer balanced, it usually doesn´t matter if you use a balanced or an unbalanced unit before and after it.
CONTROLS
THRESHOLD: This sets how high the signal must reach before the compressor kicks in.
RATIO: This sets how much compression is applied in ratio to the dB rise in
signal level above the threshold.
ATTACK: This sets how fast the compressor kicks in once the threshold has
been breached.
RELEASE: This sets how fast the compressor lets go, once the input signal
has dropped back below the threshold.
HPF: Adds a high pass fi lter in the sidechain circuitry unless “OFF” is selected.
Frequencies below the fi lter cut off will trigger compression to a lesser
degree.
GAIN: This changes the make-up gain between 0 to about 20 dB so that the
ouput level can be adjusted to a suitable level.
LINK: Is used to synchronize the compressor action in two COMP-554 units
working as a stereo pair to prevent image shifting that could occur if each
channel is compressed individually and content in one channel is louder than
that in the other.
Connect a cable between the CZ4 jacks (located at the bottom of the left hand
circuit board) on the back of the unit. Make sure the cable is not damaged
when mounting the units in the rack.
Set the LINK switches in the upward position and match the controls on both
units.
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I would like to thank you for chosing the COMP-554!
I wish you much joy with the unit and I hope that it will help you in making a
lot of great sounding music.
Yours, Bo Medin
Vintage character
for modern ideas!
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