Atomic Reactor 50/50
2×50W STEREO RACKMOUNT FULL RANGE TUBE POWER AMP
OWNER’S MANUAL
www.atomicamps.com
WARNING!
TO PREVENT FIRE OR SHOCK HAZARD, DO
NOT EXPOSE THIS UNIT TO RAIN OR
MOISTURE.
NO USER SERVICABLE PARTS INSIDE, REFER
SERVICING TO QUALIFIED PERSONNEL ONLY.
SERVICE BY PERSONS OTHER THAN ATOMIC
AUTHORIZED SERVICE TECHNICIANS MAY
VOID WARRANTY.
THIS UNIT MUST BE
EARTH GROUNDED.
Atomic Amplifiers, Atomic Reactor Series, and Reactor FR are trademarks of Atomic Amplifiers LLC.
Any other product names, trademarks or names are the property of their respective owners
which are in no way associated with or affiliated with Atomic Amplifiers LLC
© 2011 Atomic Amplifiers LLC. All rights reserved.
Atomic Amplifiers LLC • info@atomicamps.com • www.atomicamps.com
ATOMIC AMPS REACTOR 50/50 MANUAL
2
The Atomic Reactor 50/50 Stereo Power Amp
3
Panel Features & Functions
5
Using the Reactor 50/50
8
Rig Diagrams
10
Maintenance
11
Service
10
Troubleshooting
13
Specifications
18
Warranty
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ATOMIC AMPS REACTOR 50/50 MANUAL
THE ATOMIC REACTOR 50/50 STEREO POWER AMP is a rackmount, 2 × 50W
amplifier designed for use with guitar or full range speaker cabinets. The
Reactor 50/50 was inspired by the demand for a stereo version of our
popular MB-50 “mono block” amplifier, created with the stage or studio
guitarist in mind. It is also ideal for acoustic guitars, vocals, electronic
instruments, and any other application where a high quality stereo
amplifier is needed. The 50/50 delivers full-rated power over a fullfrequency response, with high headroom and very low distortion. In other
words, this is an amp without an opinion; it amplifies but does not alter the
character of the sound.
Each channel of the 50/50 is a fully independent 50W amplifier with
independent level and presence controls, balanced and unbalanced inputs,
an XLR thru, plus two speaker jacks per side with independent selectable
impedance, allowing a range of speaker cabinets to be connected. It comes
with two 12AX7s and a stereo set of “JJ” 6L6 power tubes. The Reactor
50/50 is also capable of using EL34 tubes. Convenient frontpanel perchannel bias controls make it possible to perform fine adjustments on-thefly and even allow the unit’s channels to operate with two different sets of
tubes.
The Reactor 50/50 is ideal for the modern digital guitar rig. Together
with Atomic Reactor FR Passive Cabs or Wedges (or the traditional guitar
cab(s) of your choice) it ensures that your preamp, modeler or simulator
will sound great, with plenty of power, presence, and punch. It is built to
last, with a heavy duty steel chassis and ¼” brushed aluminum faceplate.
Even as guitar tone processing technology advances, the Reactor 50/50 will
remain a valuable investment in great tone.
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ATOMIC AMPS REACTOR 50/50 MANUAL
Figure 1: Controls & Connections of the REACTOR 50/50 Front Panel
Power Switch – Switches both channels of the amplifier ON or OFF. The
power light will glow when power is ON.
Unbalanced (¼") Input (×2) – Unbalanced input of the amplifier (one per
channel). The ¼” input overrides the balanced XLR input if both are
connected.
Standby Switches (×2) – These control high voltages to the tubes,
independently for each channel. Allow 60 seconds after powering up before
setting standby to the ON position.
Warning! If you are only using one channel make sure that the other
channel is set to STANDBY, regardless of whether or not input signal is
present in the unused channel.
Level Control (×2) – These knobs set the output volume for each of the
amplifier’s 2 channels.
Presence Control (×2) The active presence circuit alters the high
frequency component of a signal, adding “brightness” or “sparkle” while
retaining a pleasant high-end quality. The presence circuit is completely
disengaged for true flat response with the knob fully counterclockwise.
Channel Fuse – These dual compartments house the 250A Fast blow
type fuses which protect the left and right channels.
Bias Controls – Each channel is equipped with a front panel bias adjust
trim pot, plus its own test point. A common ground serves both channels.
For more on how to adjust the bias of the Reactor 50/50, see p. 7.
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ATOMIC AMPS REACTOR 50/50 MANUAL
Figure 2: Controls & Connections of the REACTOR 50/50 Rear Panel
Power Input - Connect the supplied AC line cord here. The power inlet
also houses the Fuse Compartment which must be opened to replace the
fuse. In order to convert the power amp from 115v (US) to 230v (EU)
operation (or vice versa) change the fuse to the appropriate value (see
specs on pp. 13–17), then rotate and replace the fuse compartment.
Cooling Fan (×2) – These quiet fans spin while the amp is on.
Balanced (XLR) Input (×2)– This female XLR-type connector accepts a
balanced or unbalanced line level signal.
Unbalanced (¼") Input (×2) – Unbalanced input of the amplifier. The ¼”
input overrides the balanced XLR input if both are connected.
Balanced ( XLR) Thru (×2) – Signals appearing at the Balanced (XLR) Ins
will be output at the Balanced (XLR) THRUs for connections to a recorder,
mixer, or other device. The ¼" inputs do NOT connect to the THRUs!
Ground Lift Switch (×2) – May be used to eliminate the hum or buzz
from a ground loop in either channel of the Reactor 50/50.
Dual Speaker Outputs – Each channel of the Reactor 50/50 has two
speaker output jacks.
Output Impedance Selector Switch (×2) – 4/8/16Ω selectable per side,
sets the impedance in Ohms for each of a channel’s dual speaker jacks.
WARNING! The total impedance of the speaker load connected to a jack
must match that jack’s switch setting, or damage may result!
Tip: Two 8-ohm speakers in series present a 16-ohm load, Ωt = Ωa + Ωb
while two 8-ohm speakers in parallel present a 4-ohm load. Ωt = (Ωa × Ωb) / (Ωa + Ωb)
It is safe to use a channel with speaker(s) connected to only one jack.
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ATOMIC AMPS REACTOR 50/50 MANUAL
The Reactor 50/50 is easy to use and offers the controls needed for a great
range of music performance situations. NOTE: Always lower the output
level knobs on any connected devices before beginning to operate the
power amp.
1. Connect one or more speakers to the Speaker Output Jacks and
set the Impedance Selector Switch to match their rating(s).
2. Using a high-quality cable, connect a signal source to either the
Unbalanced (¼”) Input or the Balanced (XLR) Input.
3. Connect the supplied Power Cable to your unit’s Power Input
located on the back panel.
4. Turn the Power Switch to ON. The power light should come on.
5. Wait at least 60 seconds for the amplifier to warm up, then set the
Standby Switches to ON for ONE or BOTH channels.
IMPORTANT! Never take a Reactor 50/50 channel out of standby
when input signal is present and no speaker or load connected to
the speaker output. Doing so will damage the amplifier.
6. Increase the level of your instrument or processor and set the
Master Level of the Reactor 50/50 to the desired level. Adjust the
tweeter level to taste.
WHO’S DRIVING? Whether you like to run your source signal “Hot” and
lower the master volume of the Reactor, or turn up the Reactor and lower
the output level of a connected instrument or processor, you will find that
the Reactor operates quietly and sounds great.
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ATOMIC AMPS REACTOR 50/50 MANUAL
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ATOMIC AMPS REACTOR 50/50 MANUAL
Your Atomic Reactor 50/50 is vacuum tube driven, and therefore requires
maintenance. Power tubes have a life expectancy of approximately 1000
hours. Regular play requires regular service.
Tube Replacement: The 50/50 utilizes 2 × 12AX7 tubes and four high
quality JJ brand 6L6GC tubes, selected because they offer excellent sound
quality. You will notice degradation when tubes need to be replaced. The
power section is built to work with any properly biased 6L6 or EL34 tube.
When tubes need to be replaced, use a qualified amplifier technician.
Output Tube Bias Adjustment: A technician will bias your amp when new
tubes are installed. However, you may find bias drifts over time. You can
check and adjust this yourself. Each channel of the Reactor 50/50 is
equipped with a front panel bias test point and adjustment point. A
common ground serves both channels. The bias trim sets the idle current in
the output tubes, properly matching the amp’s performance characteristics
to the type of tubes used. Each tube type and brand may require a slightly
different bias, and settings should be checked when tubes are replaced. A
properly biased amp will sound great and will run reliably and safely. An
amp’s bias can drift with extended use. To bias the Reactor 50/50, turn
main power ON and take the desired channel out of STANDBY. Touch the
negative lead (black) of a VU Meter to the common ground on the front
panel of the Reactor 50/50. Touch the positive lead to the test point for the
channel you plan to adjust. Adjust the trim with a small flathead
screwdriver until the meter reads in the range of 70–90ma. Once the first
channel has been properly biased, put it in standby and repeat the bias
adjustment process for the second channel.
Front panel bias controls of the Reactor 50/50.
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ATOMIC AMPS REACTOR 50/50 MANUAL
WARNING! The internal voltages of tube type amplifiers are
potentially lethal and capacitors are capable of storing these
lethal charges. The Reactor 50/50 allows you to bias the amps without
removing the panel to expose componentry but you should still exercise
caution or refer to the services of a qualified professional.
The Fuse: The fuse protects the amplifier in the event of an electrical fault
or tube failure. If a fuse blows, replace it only with one of the required type
and rating. The main fuse is in a compartment built into the AC inlet of the
amplifier and can be accessed by opening the fuse compartment with a
small flat-head screwdriver or similar tool. In order to change the voltage
specification from 115v (US) to 230v (EU), or vice versa, the fuse module
must be rotated 180° and the fuse changed to the correct specified value as
marked above the AC inlet. The secondary per channel fuses are accessible
through the front panel.
WARNING! Always disconnect the amplifier’s power cord from
the AC outlet before attempting to change the fuse. Refer to the
specification pages (pp. 13-17) to determine the correct fuse type and
rating. NEVER use a fuse with a higher rating as this could damage the amp
and present a serious safety hazard. If the fuse blows repeatedly, the amp
should be taken to an authorized service center.
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ATOMIC AMPS REACTOR 50/50 MANUAL
Reactor 50/50 does not power up.

Is the power cord firmly inserted into the AC input socket?

Is the power cord firmly plugged into a working electrical outlet?

Are one or more of the fuses blown?
The Reactor 50/50 powers up but produces no sound.

Is the Reactor really turned on? (“Tubes glow and fan blows.”)

Is the standby switch also set to the ON position?

Is the output level control on your source device turned up?

Is there a problem with your audio connector cable?

Is/are your speaker(s) properly connected?
IMPORTANT! Operating either channel of the 50/50 in the absence of a
load on the output transformer can cause serious damage and may
void your warranty. ALWAYS ensure that a speaker or load is
connected for any channel that is taken out of Standby.
Amp Produces a Hum or Buzz

Try the Ground Lift switch.
If after performing all of the troubleshooting steps above your Reactor FR is
still not performing correctly, please contact Atomic Amplifiers.
(See Obtaining Service on p. 10.)
How do I know when to replace tubes?

When the Reactor is suddenly noisy with hiss, pops, or hum

If your Reactor 50/50 develops a high pitch microphonic squealing.

When you experience a loss of output power

When the amp continually blows fuses

When tubes visibly look “shot” (strong whitish cast, no warm glow)

Sound is “dirty” on what you expect should be clean settings
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ATOMIC AMPS REACTOR 50/50 MANUAL
Q:
How do I go about getting my Reactor product repaired?
A:
For repairs within the amp’s warranty period (1 year or 90 days for
tubes) please email info@atomicamps.com for service instructions. You
must first contact us for a RETURN AUTHORIZATION NUMBER and shipping
instructions.
Q:
A:
Is there a charge for repairing my Reactor Series Product?
There may or may not be. If you have not done so already, read the
WARRANTY beginning on page 18 for information on coverage, duration,
and what is required of you the purchaser in order to obtain Warranty
Service.
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ATOMIC AMPS REACTOR 50/50 MANUAL
Intended Applications:
Guitar/FRFR Sound Reinforcement
Power Requirements:
115V AC, 50/60 Hz 105w
OR 230v Ac, 50 Hz 105w
Remove/rotate/replace fuse holder to select between 115 (US) and 230 (EU)
Main Fuse:
US Model 115V AC, Slow Blow, 3.15A
EU Model 230V AC, Slow Blow, 1.6A
Channel Fuses:
2 x 250mA (same for US/EU)
Amplifier Power Output:
2x 50w into 8 ohms at 3% THD
Power Amp Input
2x 270 mv (-9.5db) at 1000 Hz
Sensitivity (Return):
for 50 watts output ×2
Power Amp Input Impedance:
2x 100K ohm
Tubes:
(2) × 12AX7A tube
(4) × 6L6GC tubes
Connecting Speakers:
2 × 1/4" jacks per side (4 total)
4/8/16 Ω selectable impedance
50-200W recommended
Chassis Construction:
Heavy duty powder coated steel
Radiused/Milled Aluminum 1/4" face
Fan:
2 × 80mm quiet fans
Dimensions:
Width:
Height:
Depth:
Weight:
11
17.25" (panel 19")
3.75"
11.75"
26 lbs.
ATOMIC AMPS REACTOR 50/50 MANUAL
Atomic Amplifiers warrants to the original purchaser that this product
(exclusive of tubes) will be free of defects in material and workmanship for
a period of 1 year from the original date of purchase. Atomic Amplifiers
warrants to the original purchaser of this product that tubes will be free of
defects in material and workmanship for a period of period of 90 from the
original date of purchase by the original purchaser. It is understood that
Atomic Amplifiers reserves the rights to inspect any warranty part prior
replacing or repairing them to insure that their defect is not a result of user
error. These warranties are subject to the conditions, exclusions, and
limitations hereinafter set forth.
This limited warranty is transferable and is valid only when accompanied by
a copy of the original sales receipt or packing slip with legible purchase
date, purchase price, and when product is purchased from an authorized
dealer in the United States or Canada and must be returned to the same for
any warranty services required. All exported products are subject to
warranty and services to be specified and provided by the authorized
distribution center for each country or region. Excluded from this warranty
are defects caused by wear and tear, accident, misuse, neglect, failure to
follow all operating instructions (including the OVERPOWERING of
speakers), alterations and modifications, or act of nature. Such
determinations will be made by Atomic Amplifiers. This limited warranty is
also void if: the original retail purchase is not made directly from the
company or an Authorized ATOMIC AMPLIFIERS’ dealer, or if repairs,
alterations, or modifications are performed by anyone other than Atomic
Amplifiers or an Atomic Amplifiers Authorized Service Center, or if the
original serial number affixed to the product is altered, defaced, or
removed.
All parts costs for repairs covered under this limited warranty will be borne
by Atomic Amplifiers so long as the repairs have been requested within the
applicable warranty periods described above. It is understood that all repair
charges and costs incurred by Atomic Amplifiers for all periods following
the applicable warranty period will be borne and paid for by the purchaser.
All labor costs incurred by Atomic Amplifiers for repairs covered under this
limited warranty will be borne and paid for by Atomic Amplifiers within the
applicable warranty period according to rate schedules established by
Atomic Amplifiers. All labor costs and expenses above these rates will not
12
ATOMIC AMPS REACTOR 50/50 MANUAL
be the responsibility of Atomic Amplifiers. Atomic Amplifiers MUST perform
all warranty services. Transportation charges involved in warranty services
are the sole responsibility of the purchaser.
A copy of the original sales receipt or packing slip must accompany all
products being presented to an Atomic Amplifiers Authorized Service
Center for warranty service. All products being returned to Atomic
Amplifiers for warranty service must be accompanied by a copy of the
original sales receipt or packing slip, a detailed description as to needed
repairs, and an Atomic Amplifiers Return Authorization number. Atomic
Amplifiers reserves the right to repair or replace the affected piece of
equipment at their option but it is understood that repair or replacement
as provided under this limited warranty is the sole and exclusive remedy to
the purchaser for defective or non-conforming products.
Atomic Amplifiers will not be held liable for any incidental consequential,
special, punitive, or exemplary damages resulting from any defect or failure
of this product other than the repair of the Atomic Amplifiers product
subject to the terms of this limited warranty. Any product repaired or
replaced under this limited warranty will, itself, be warranted only for the
remainder of the limited warranty period of the original product being
repaired or replaced. Products used for dealer rental purposes shall be
warranted from the date of the original invoice to dealer and if sold will be
warranted only for the remainder of the limited warranty period of the
original product.
This warranty gives you specific legal rights, and you may have other rights
which vary from state to state, and province to province, and to the extent
required by law, any limited warranty shall be limited to the duration of this
limited written warranty.
OTHER THAN AS STATED ABOVE, ATOMIC AMPLIFIERS MAKES NO
WARRANTIES EITHER WRITTEN, EXPRESSED, OR IMPLIED WITH RESPECT TO
THE PRODUCT. THIS WARRANTY IS EXCLUSIVE, AND ATOMIC AMPLIFIERS
MAKES NO OTHER WARRANTY, EXPRESSED OR IMPLIED, INCLUDING
IMPLIED WARRANTIES OR MERCHANTABILITY OR FITNESS FOR ANY
PARTICULAR PURPOSE, ALL OF WHICH WARRANTIES ARE HEREBY BEING
DISCLAIMED.
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