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®
Chandler Limited
RS124 Compressor
User Manual
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For more information, visit www.chandlerlimited.com. © 2016 Chandler Limited, Inc. All Rights Reserved. RS124_UM_070116
Abbey Road Studios, EMI, RS and their associated logos are trademarks of EMI (IP) Limited.
OFFICIAL
EQUIPMENT
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Chandler Limited
®
RS124 Compressor
User Manual
Thank you for purchasing the Chandler Limited TG Microphone Cassette, you now own a
piece of EMI / Abbey Road Studios official
equipment.
The Chandler Limited RS124 Compressor is
a recreation of the rare EMI / Abbey Road
Studios RS124, and reimagined for the modern era. The Chandler Limited RS124 is a
mono tube compressor, and incorporates
an extended feature set over the original
equipment.
Each historic Abbey Road Studios’ RS124
compressor is unique in more ways than
one, and Chandler Limited’s incarnation of
the equipment includes the three favorite
original units still in use at the historic
studios, in one device for the first time.
HISTORY
First designed in 1960 by Abbey Road Head
of Technical Bill Livy, Deputy Head Len
Page and seasoned EMI Audio Designer Mike
Bachelor, the EMI RS124 compressor is one
of the most coveted pieces of recording
gear ever developed.
During the late 1950’s, EMI acquired Altec 436B compressors, and soon realized the
units were insufficient for critical recording applications. Livy, Page and Bachelor worked to modify the Altecs to meet
their standards and ultimately ended up
designing an entirely new compressor in the
process, the EMI RS124.
The RS124 was popular with Abbey Road Studios’ engineers. The RS124 added its unique
character to single instruments, rhythm
busses and entire mixes. So integral to the
recording, mixing, and mastering process,
a pair can be seen in almost every control
room photo in Abbey Road during the 60s period.
Still in use today at Abbey Road Studios,
and most recognized for its use at virtually every Beatles session, the RS124’s true
inner-workings have remained an enigma,
until now.
Your Chandler Limited RS124 Compressor has
been carefully crafted and built by hand at
Chandler Limited in Shell Rock IA, U.S.A,
using through-hole components for the ultimate analog experience.
At Chandler Limited we are proud of our
American made products and we hope you like
them!
Please feel free to call our shop anytime
for help or questions. Phone: (319) 8854200
For more information, visit www.chandlerlimited.com. © 2016 Chandler Limited, Inc. All Rights Reserved. RS124_UM_070116
Abbey Road Studios, EMI, RS and their associated logos are trademarks of EMI (IP) Limited.
OFFICIAL
EQUIPMENT
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INPUT
000001
RS124
Chandler Limited
FUSE
FUSE .25 AMP
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MAINS VOLTAGE
110-120V
220-240V
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OUTPUT
LINK
TIP- CV
SLEEVE- 0v
OUTPUT IMPEDANCE
200
600
CONNECTIVITY
POWER
The Chandler Limited RS124 Compressor features an internal power supply. Connection is
made using the supplied IEC power cable. Power is preset internally to operate at either
120V or 220V.
INPUT/OUTPUT
On the rear panel of the RS124 compressor exists two XLR jacks (wired pin 2 hot), one for
input, and the other for output. Both input and output connections are +4, transformer
balanced.
Output impedance is 600/200ohms switchable, both offer tonal and gain differences. The
600ohms setting is more amenable to the modern studio environment. The 200ohms impedance
setting was Abbey Road Studios’ standard.
STEREO LINK
Chandler Limited RS124 Compressors are stereo linkable via a standard ¼” cable, using
the female ¼” connector available on the rear of the unit. While “Stereo-Linked”, each
compressors control-set would still be managed individually.
For more information, visit www.chandlerlimited.com. © 2016 Chandler Limited, Inc. All Rights Reserved. RS124_UM_070116
Abbey Road Studios, EMI, RS and their associated logos are trademarks of EMI (IP) Limited.
3
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pulls it in an equal fashion. Over time,
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the “push/pull” balance may become irregu-
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lar, and as a result, unwanted artifacts
will occur in the audio. This is common to
most tube based compressors, including the
RS124.
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ON/OFF
Cycling power to the RS124 is achieved by
turning the ON/OFF power switch (located
far right of the front panel) to the desired position. When the RS124 is powered
on, the jewel light on the front panel will
illuminate.
When the “push/pull” circuit becomes unbalanced, it may exhibit subtle rumbling
or distortion and modulation of the source
signal; this is more noticeable at quiet
sections of music, and low frequencies.
Located at the far left of the front panel
is the “BAL.” control-set, a circuit rebalancing utility. If the RS124 is suspected of having become unbalanced, simply depress the silver colored momentary switch.
This action will induce a ticking sound
heard in the monitors. Use a small flathead
screw driver and slowly adjust the trim pot
(located above the “BAL.” label) back and
forth across the range, until the ticking
sound is barely audible; the ticking sound
will not fully disappear. Once the ticking
sound is at its minimum audible level, rebalancing of the RS124 has been achieved.
HISTORIC NOTE: Early versions of the EMI /
Abbey Road Studios RS124 did not have front
panel “BAL.” functionality. As a result
when the circuit became unbalanced, the
compressor would have to be pulled during
the session and rebalanced by Abbey Road
technical staff. This was scenario was cumbersome, and the resultant session interruption not ideal.
BAL.
STOP: The balance feature is preset at the
factory and should not need to be adjusted.
In any “push/pull” amplifier, one side
pushes waveform, while the other side
For more information, visit www.chandlerlimited.com. © 2016 Chandler Limited, Inc. All Rights Reserved. RS124_UM_070116
Abbey Road Studios, EMI, RS and their associated logos are trademarks of EMI (IP) Limited.
Abbey Road engineer Len Page had a proverbial ‘Light-Bulb’ moment, coming up with an
ingenious modification.
A small balancing circuit “BAL.” including a neon bulb, momentary switch, and trim
pot was added to the RS124. When the momentary switch was activated, a ticking sound
was sent to both amplifiers, with one being
phase reversed. If the circuit in a balanced state, the ticking would be canceled
out. Otherwise, the engineer would adjust
the trim pot until the audible ticking was
virtually removed. This allowed for convenient in-session rebalancing of the compressor by the recording engineer in a matter of seconds.
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INPUT CONTROL
The “INPUT CONTROL” is variable*, and allows adjustment of input signals applied at
the XLR input connector on the rear of the
compressor. The “INPUT CONTROL” is labeled
0 to10 from left to right.
The RS124 is a variable transconductance
compression circuit. Clockwise adjustment
of the “INPUT CONTROL” simultaneously raises incoming signal level, while lowering
the compressor’s threshold and increasing
the amount of compression applied to the
source material.
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OUTPUT ATTENUATOR (db)
The ‘OUTPUT ATTENUATOR (db)’ control is
variable*, use this control to lower the
overall output level of the RS124. Rotation
in a counterclockwise motion from right to
left, beginning at 0 and continuing to -10
will attenuate the output signal of the
RS124 to the desired level.
*NOTE: If a switched output attenuation
control is desired, it can be pre-ordered
at time of purchase for an additional fee
from an authorized Chandler Limited dealer.
Counterclockwise rotation of the “INPUT
CONTROL” simultaneously reduces incoming
input level, while raising the threshold
and lowering the amount of compression applied to the source material.
*NOTE: If switched input control is desired, it can be pre-ordered at time of
purchase for an additional fee from an authorized Chandler Limited dealer.
For more information, visit www.chandlerlimited.com. © 2016 Chandler Limited, Inc. All Rights Reserved. RS124_UM_070116
Abbey Road Studios, EMI, RS and their associated logos are trademarks of EMI (IP) Limited.
5
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enough so that Abbey Road engineers would
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request a specific serial numbered unit depending upon the source material it was to
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be applied to. Furthermore, historic EMI/
Abbey Road Studios RS124s featured a fixed
attack time, i.e. the attack timing was
hardwired internally to a set time constant. Overall, not all RS124s shared the
same values
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ATTACK
Chandler Limited’s RS124 Compressor provides adjustable attack time via the
stepped switch, labeled “ATTACK”, a feature
not available on historic units.
There are nine attack time settings available, the fastest setting is achieved at
the far left position labeled “1”, each
subsequent position is slower.
The Chandler Limited RS124 includes three
favorite historic RS124 compressors still
in use at Abbey Road Studios today, in a
single unit for the first time ever.
Included amongst the nine attack options
are three positions marked in red. These
red colored settings reflect the serial
numbers (60070B, 60050A, and 61010B) of
historic RS124s. To dial up one of Abbey
Road’s favorite historic RS124s, simply set
the “ATTACK” switch to the desired serial
number.
HISTORIC NOTE: Each historic RS124 was
unique, exhibiting its own character and
personality, variances between units were
RECOVERY
“RECOVERY” is an eleven position stepped
switch which controls the compression release time.
The “RECOVERY” switch provides six recovery
or release time options, starting left to
right and from slowest (6) to fastest (1),
including five identical “HOLD” positions
denoted by a red colored dot.
Adjusting the “RECOVERY” switch to any of
the “HOLD” positions, will keep the source
signal compressed to the most recently processed peak level.
HISTORIC NOTE: The “HOLD” feature was an
ingenious way to prime or preset the compression level of the incoming signal as a
way to overcome potential processing issues.
During mastering, to prevent abrupt compression onset at the beginning of a track,
Abbey Road engineers would roll tape forward to the highest peak level and set the
RS124 to the nearest available “HOLD” position from the desired “RECOVERY” setting.
Now with the compression level held or
preset, the engineer would rewind the tape
and begin from the top of the track, and any
artifact of initial compression onset was
removed.
Another use of the “HOLD” facility was
to prevent level in-rush when there was
a precipitous drop in level during quiet
passages of a track below the compression
threshold. Here again, engineers would
switch the “RECOVERY” control to the nearest “HOLD” position until the quiet passage
had passed, before setting it back to the
previous release value.
For more information, visit www.chandlerlimited.com. © 2016 Chandler Limited, Inc. All Rights Reserved. RS124_UM_070116
Abbey Road Studios, EMI, RS and their associated logos are trademarks of EMI (IP) Limited.
6
Page 7
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METER
The Chandler Limited RS124 features compression level monitoring facilities via
the large ‘db COMPRESSION’ meter located at
center of the front panel.
The ‘db COMPRESSION’ meter illustrates the
amount of compression applied to the incoming signal, and is labeled right to left, 0
to 30db.
When compression is induced, the ‘db COMPRESSION’ meter’s needle will move from
right to left, indicating the amount of
gain reduction applied to the source signal.
NOTE: The meter will move faster or slower
depending upon attack and recovery time
settings. However, the meter is analog and
ultimately slow in nature, as a result the
amount of compression applied to the source
signal may be greater than visibly observed.
NOTE: The vintage RS124 and new version
RS124 as well as the Altec 436, have an
unregulated power supply. Because of this
design there can be some variation in the
resting place of the meter’s needle, this
is normal. For example, if your AC voltage
is a bit high, the meter may rise slightly
above the meter’s thick black zero bar.
SUPERFUSE
Available on the far right of the RS124
front panel, exists what appears to be a
fuse cap, it is not, it’s a switch!
This switch disguised as a fuse cap, is a
feature dubbed the ‘Superfuse’.
Turning the switch to the left will activate ‘SuperFuse’ mode and the RS124 power
jewel light becomes brighter indicating the
feature has been engaged.
What is ‘Superfuse’ mode?
While we will not divulge the inner-workings of this special feature, it does
change the personality of RS124 to become
faster and more aggressive overall. When
activated, the source material may become
more lively and appearing to jump out of
the monitors. WARNING- “Superfuse” is addicting!
For more information, visit www.chandlerlimited.com. © 2016 Chandler Limited, Inc. All Rights Reserved. RS124_UM_070116
Abbey Road Studios, EMI, RS and their associated logos are trademarks of EMI (IP) Limited.
7
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MAINTENANCE
INTERNATIONAL SERVICE
TUBES
From time to time, replacing vacuum tubes
may be necessary. The RS124 compressor requires three vacuum tubes: 6BC8, 6CG7, and
6AL5.
WARNING: HIGH VOLTAGES are present! Before
replacing any tubes, please power off the
unit, disconnect the power cable and wait 5
minutes for the voltage to discharge.
FUSE
On the rear of the unit exists a circuit
protection fuse. If fuse replacement is
required, cycle the power switch to ‘OFF’,
and use a 250mA Slow-blow type.
U.S. SERVICE
Prior to sending in your gear for repair,
please contact our shop at the number below. We will assist you in troubleshooting
the problem and, if needed, we will issue
you an RMA# to send in the gear.
Repair of Chandler Limited products purchased outside of the United States, is
provided by local or regional authorized
Chandler Limited distributors. To obtain
service or repairs, please contact your local dealer or regional distributor for further instruction.
Visit chandlerlimited.com for a list of authorized International Distributors.
CE Certification
Chandler Limited declares under its
sole responsibility that all products manufactured by them are in compliance with Electromagnetic Compatibility
(EMC) Directive 2014/30/EU; Standards:
EN55103-1:2009+A1:2012; EN55103-2:2009;
EN55013:2013 and Low Voltage Directive
(LVD) 2014/35/EU; Standards: EN60065:2002+A
1:2006+A11:2008+A2:2010+A12:2011.
Send repairs to:
Chandler Limited, Inc.
Attention: Repairs
222 S. Cherry St.
PO Box 38 (if sending via the postal service)
Shell Rock IA 50670
Phone: (319) 885-4200
Email: support@chandlerlimited.com
For more information, visit www.chandlerlimited.com. © 2016 Chandler Limited, Inc. All Rights Reserved. RS124_UM_070116
Abbey Road Studios, EMI, RS and their associated logos are trademarks of EMI (IP) Limited.
8
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Product Limited Warranty
During the rst year from the date of the original purchase, this product is warranted to be free from
defects in materials and workmanship under normal use, service and maintenance. This warranty applies to the original purchaser and is subject to the following terms and conditions:
What Is Covered: The product’s components as originally installed by the manufacturer that are defective in materials or workmanship under normal use, service and maintenance.
What Is Not Covered By This Warranty: This warranty does not extend to or cover:
1. Any defect due to the negligence of others; failure to install, operate or maintain the product properly; unreasonable
use; accidents; alteration; use of unauthorized or non-standardized parts; acts of God; theft; vandalism; electrical
malfunctions (i.e., resulting from power surges, shorted or overloaded circuits, etc.), use of any power source other
than supplied by manufacturer; repair by anyone other than an authorized Chandler Limited representative; or
damage resulting from improper packing or mishandling by a shipper.
2. Normal wear and tear of parts.
3. Shipping, handling, packaging and delivery costs of the product.
Who Is Covered: The original purchaser.
Repair During The First Year: During the rst year, all defective product components that are cov-
ered by this Limited Warranty will be repaired free of charge including parts and labor. The purchaser
will pay shipping costs AND a $35 handling fee per unit.
What You Must Do for Warranty Service (in the United States): If you live in the United States and
your product was purchased through a U.S. Dealer, please contact your dealer OR call 319-885-4200
or e-mail support@chandlerlimited.com.
What You Must Do for Warranty Service (outside of the United States): For warranty service if you live outside
of the United States, please contact the dealer where you purchased the product.
Any products returned to Chandler Limited for repair should include: (1) complete description of the
problem; (2) name, address, phone number, fax number, and/or e-mail address; (3) receipt of original
purchase; (4) power supply and all accessories and cables. The purchaser is responsible for the shipping costs to and from Chandler Limited. Chandler Limited is not responsible for damage resulting
from improper packing and/or mishandling by a shipper.
If sent by UPS or Federal Express, ship to: Chandler Limited, 222 South Cherry Street, Shell Rock IA
50670
If sent by Postal Service, ship to: Chandler Limited, PO Box 38, Shell Rock IA 50670
The foregoing expresses Chandler Limited’s obligations and liabilities with respect to the quality of
the product, its components and accessories. All other warranties, express or implied, including the
warranties of merchantability or tness for a particular purpose are disclaimed. Chandler Limited shall
not be liable for the loss or use of the product, its components and accessories, inconvenience, loss
or any other damages, direct or consequences arising out of the use of, or inability to use the product
or its components or damages resulting from or attributable to defects in the products or its components. No one other than Chandler Limited has authority to extend or modify the terms of this limited
warranty in any manner whatsoever.
For more information, visit www.chandlerlimited.com. © 2016 Chandler Limited, Inc. All Rights Reserved. RS124_UM_070116
Abbey Road Studios, EMI, RS and their associated logos are trademarks of EMI (IP) Limited.
9
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DISCLAIMER OF WARRANTY
EXCEPT FOR THE FOREGOING WARRANTIES, CHANDLER LIMITED HEREBY DISCLAIMS AND EXCLUDES ALL OTHER WARRANTIES, EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO
ANY AND/OR ALL IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
PURPOSE AND/OR ANY WARRANTY WITH REGARD TO ANY CLAIM OF INFRINGEMENT THAT
MAY BE PROVIDED IN SECTION 2-312(3) OF THE UNIFORM COMMERCIAL CODE AND/OR IN ANY
OTHER COMPARABLE STATE STATUTE.
LIMITATION OF LIABILITY
THE LIABILITY OF CHANDLER LIMITED, IF ANY, AND PURCHASER’S SOLE AND EXCLUSIVE REMEDY FOR DAMAGES FOR ANY CLAIM OF ANY KIND WHATSOEVER, REGARDLESS OF THE LEGAL THEORY AND WHETHER ARISING IN TORT OR CONTRACT, SHALL NOT BE GREATER THAN
THE ACTUAL PURCHASE PRICE OF THE PRODUCT WITH RESPECT TO WHICH SUCH CLAIM IS
MADE. IN NO EVENT SHALL CHANDLER LIMITED BE LIABLE TO PURCHASER FOR ANY SPECIAL,
INDIRECT, INCIDENTAL, OR CONSEQUENTIAL DAMAGES OF ANY KIND INCLUDING, BUT NOT
LIMITED TO, COMPENSATION, REIMBURSEMENT OR DAMAGES ON ACCOUNT OF THE LOSS OF
PRESENT OR PROSPECTIVE PROFITS OR FOR ANY OTHER REASON WHATSOEVER.
For more information, visit www.chandlerlimited.com. © 2016 Chandler Limited, Inc. All Rights Reserved. RS124_UM_070116
Abbey Road Studios, EMI, RS and their associated logos are trademarks of EMI (IP) Limited.
10
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