Locomotive Audio 286A User manual
USER’S MANUAL
MODEL 286A
DUAL CHANNEL TUBE MIC PREAMP & DI
HANDMADE IN ST. LOUIS, MO USA
INTRODUCTION
Thank you for your purchase of the Locomotive Audio Model
286A! This hand-built vacuum tube dual mic preamp and DI
is a product of so much time, research and development.
Inspired by many beautiful pieces of equipment from the
50s and 60s, we were able to design a exible circuit with
high quality components and modern features for today’s
engineers. With proper treatment, our products will be able to
give you many years of reliable service, so you can focus on
being creative and making the best recordings possible! We
thank you for your support of Locomotive Audio.
BOX CONTENTS
Your Locomotive Audio product should have been
shipped with the following contents:
(1) 286A unit
(1) User’s Manual
(1) IEC Power Cord
CONTACT INFORMATION
LOCOMOTIVE AUDIO, LLC
P.O. BOX 21751
St. Louis, MO 63109
suppor[email protected]
314.282.0133
LEGAL NOTICES
©2015 Locomotive Audio, LLC
Manual Revision 286A-3
All information provided in this manual is thought to be accurate and free of errors
at the time of printing. Locomotive Audio, LLC shall not be liable for any errors or
omissions in this manual.
All information in this document is protected by copyright. No part of this manual
may be reproduced without the permission of Locomotive Audio, LLC. Locomotive
Audio, LLC reserves the right to make changes or improvements to this product at
any time.
INSTALLATION
Vacuum tube equipment can get very hot, so thought and care should be taken
in how it is installed. The 286A will t in a 19” equipment rack, taking 2 units of
space (2U). The chassis for the 286A has vents punched out of the top and sides
for heat to escape. It is good practice to leave 1U of space above the unit for bet-
ter ventilation.
The Locomotive 286A has its tubes and transformers installed on the outside of
the unit. Route audio and power cords in a direction where they would be least
likely to touch these components.
DECLARATION OF CONFORMITY
Eric Strouth
President
Locomotive Audio, LLC.
November 1, 2014
ADDRESS:
P.O. Box 21751
Saint Louis, Missouri 63109
Year of Afxing CE marking: 2014
MANUFACTURED BY:
Locomotive Audio, LLC.
PRODUCT:
286A Dual Channel Tube
Mic Preamp & DI
CONFORMITY:
Low Voltage Directive 2006/95/EC
(EN 60065:2002/A1:2006 + A11:2008 + A2:2010 + A12:2011)
EMC DIRECTIVE 2004/108/EC
(EN 55103-1:2009 & EN 55103-2:2009)
WARNINGS & SAFETY
Before powering up your new Locomotive Audio unit for the rst time, please
understand the dangers of vacuum tube electrical equipment. The high voltages
within the chassis and around the tubes can SERIOUSLY INJURY OR KILL YOU.
Before plugging your unit into the wall, please make sure all tubes are properly
seated in their sockets. The base of the tube should be ush with the tube socket.
Also be sure to mount your unit in a stable, secure rack to reduce the risk of
movement and damage. The unit is grounded through the IEC power cord supplied
in the box. Always use a properly grounded outlet and never use a ground lift plug
adapter for a non-grounded outlet. Do not use unit near any liquid or excessive
moisture. If liquid were to enter the unit, unplug EIC power cord from wall and wait
at least 5 minutes before attempting to touch or clean the unit.
The user should not attempt to service this product beyond changing tubes. The
286A has a hinged front panel that allows for easy access of internal parts if is-
sues were to arise. Only a trained technician should make modications or adjust-
ments as the voltages within the chassis are very dangerous!
LINE VOLTAGE & FUSE
The unit is powered by 115v or 230v AC sources. The AC Voltage Slide Switch
(page 8) is preset by Locomotive Audio before leaving production. Before using
the 286A for the rst time, please make sure the AC Voltage Slide Switch on the
back of the unit (page 8) is in the correct position for your mains voltage. If oper-
ated set to the incorrect voltage, harm to the unit may result. With unit turned
off, use a at-head screwdriver to change the voltage selection if necessary.
All Locomotive Audio products contain a fuse in the IEC power entry module for
protection of both YOU and the unit. In order to check or replace the fuse, a small
at-head screwdriver is needed to open the fuse drawer. Be sure to unplug the
unit before beginning this procedure. Always replace the fuse with the same rating
and type as specied for your mains voltage on back of the unit. If replacement
fuses of the correct specications consistently blow, there may be an issue with
the unit and qualied service technician should be contacted. If within warranty
period, please contact Locomotive Audio for instructions.
POWERING UP
Once installed in a secure equipment rack and plugged into the AC mains power
source, the user may then power the unit on by ipping the power switch on the
front of the unit to the up position. At this point, the power lamp will light, and the
unit will need at least 5–10 minutes for the tubes to warm up for best results.
POWER LAMP & VU BULBS
The power lamp and backlit VU meter will illuminate after the unit is switched on.
If either of these do not light, the bulb may be burned out or there may be another
underlying issue. The rst step would be to replace the bulb. If replacement is
necessary, use a 14V .08A bayonet style bulb for the power lamp and a 12.6V
.3A fuse style bulb for the VU meter.
MAIN FEATURES
• Microphone and high impedance instrument inputs
• One EF86 & one 12AY7 per channel
• Polarity reverse switch
• 20dB pad switch
• 100 Hz low cut lter switch
• Microphone load impedance switch
• Mic/DI selection switch
• +48v phantom power switch
• 3-position VU meter switch: CH1 - Off - CH2
• Custom Sifam backlit VU meter
• XLR input and output connections
• Cinemag input and output transformers
• High-grade Solen capacitors in signal path
• Hand-built in USA with classic turret board technique
• Heavy 16 gauge steel chassis
• 115v/230v AC mains option on rear
• Backed by 2-year limited warranty parts and labor
286A SPECIFICATIONS
The technical data listed below may change without notice
as we are consistently trying to improve our products
•Microphone input load impedance: 500Ω or 1800Ω
• Output impedance: <600Ω
• 1/4” DI impedance: 169kΩ
• 66dB of gain
• Flat frequency response: 20Hz-20kHz
• THD+N: <1%
• S/N ratio: >70dB
• Dimensions: 19”w x 3.5”h x 10”d (2u rackspace)
• Shipping Weight: 18 lbs.
• Power Consumption (120/240VAC): 25 watts
ABOUT THE 286A
The dual channel 286A offers a huge sonic palette for engineers and
producers to explore. Its single-ended Class A tube signal path is what
makes this preamplier so special. Inspired by the great vintage Ampex
601 vacuum tube tape recorder, the 286A features four tubes; there is
one EF86 and one 12AY7 per channel. The 286A can play nice by acting
clean and natural with gentle even-order harmonics for a smooth, sweet
touch. Get more aggressive with the “Gain” knob and drive the rst
12AY7 stage for a warm and colored thickening effect. Go all-out and
slam the nal 12AY7 stage and output transformer through the “Level”
knob for a fully-driven, saturated tube amp sound! Clean and natural to
overdriven and fuzzy warm; your choice!
Along with its classic tube gain stages, the 286A has been given the
modern front panel features that allow for exible interfacing with today’s
studio equipment.
286A SETTINGS
At rst glance, there are many features on the Model 286A which may
be confusing, but in reality, the initial setup couldn’t be easier.
GAIN & LEVEL SETTINGS
The 286A is a very lively preamplier with a great deal of gain.
A good place to start when looking for a clean sound, is with
the GAIN positioned at a low setting and the LEVEL positioned
at a high setting. If too much distortion is experienced
at these settings, it is likely that the source is too hot. Drums,
for instance, may benet from switching the -20dB pad to
the up position. Rotating the gain knob to a higher level
will allow more signal to pass from the rst tube
(EF86) to the second tube (12AY7). This action will
create more color and a general thickening to the nal
sound. Of course, play with these settings to achieve
the effect you want. There is no right way. Be creative!
IMPEDANCE SETTINGS
It was our goal to design a versatile preamplier for many different
sound sources. The impedance control allows the user exibility in the
microphone they choose and in crafting the sound they want. As a
standard, microphones “favor” an input impedance 10x that of their own
output impedance. Therefore, a common modern microphone with an
output impedance of 150-200Ω will be “properly” loaded with the preamp
set to 1800Ω. This will give the best overall frequency response for the
microphone. Some low output/low impedance microphones will be better
off with the 500Ω setting. By all means, experiment with these controls
for the color/sound you are looking for!
FRONT PANEL
The front panel of the 286A features two identical sets of channel controls.
1. Power Switch: Switches unit on. Illumination of the power lamp and VU
meter will result.
2. +48 Switch: Supplies 48-volt phantom power to the xlr input of channel.
Use only with condenser microphones that require phantom power. Some
microphones can be damaged if exposed to 48-volt phantom power, so it is
a good idea to switch phantom power off after each session.
3. Gain: This controls the amount of signal that passes from the rst gain
stage (EF806 Tube) to the second gain stage (12AY7-1)
4. Level: This controls the amount of signal that passes from the second
gain stage (12AY7-1) to the nal gain stage (12AY7-2) and through the
output transformer, followed by the next device in your signal chain.
5. -20dB Switch: When in the up position, a resistive pad is switched in
between the xlr input and the input audio transformer. This setting does
not affect a DI source. The pad sets a 1500Ω load impedance for the mic
to work into. The output impedance of the pad is 150Ω and should be used
in conjunction with the 1800Ω setting for a flat frequency response.
6. Polarity Switch: Also placed before the input transformer, this switch
controls the polarity of the microphone signal and will not affect a DI source.
7. Impedance Switch: This switch allows the user to select between a
500Ω and 1800Ω transformer load impedance on the microphone. Typically,
users will choose a transformer load impedance that is around 10x the out-
put impedance of their microphone for best frequency response. There are
no rules, so please experiment with the tonal changes associated with this
switch. This setting does not affect a DI source.
8. Low Cut Switch: If switched to the up position, a 100Hz low frequency
roll-off lter is placed on the signal for either the xlr mic input or DI. Use
this control to lter our low frequency rumble or to combat proximity effect
from a microphone.
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BACK PANEL
1. AC Power Entry Module: Accepts standard IEC power cord (included)
for 115v or 230v AC mains supply. A fuse is included with each unit for
the voltage/current expected at the location being shipped to. Only use a
fuse with the same rating and voltage as marked on back of chassis.
2. AC Voltage Slide Switch: Each unit is factory set to the voltage ex-
pected at the location being shipped to. If voltage does not match mains
voltage at your location, switch to reveal the appropriate voltage. Do not
operate unit set to incorrect voltage. Harm to the unit may result.
3. Model/Serial# Tag: When registering your product for your 2-year war-
ranty, please use the hand stamped tag to obtain the serial number.
4. Transformer Balanced XLR Line Outputs
5. Transformer Balanced XLR Mic Inputs
CHANGING TUBES
Each Model 286A will leave Locomotive Audio with a new set of tubes
that should last for several years. We encourage you to utilize these
tubes, but also experiment with with other brands of New Old Stock tubes
to acheive your sounds! There are no rules with brands or age of tubes.
But be sure to use only EF86s or EF806s and 12AY7 tubes in the appro-
priate tube sockets. This will prevent any issue with the performance of
the 286A and damage to the unit.
USE ONLY WITH 250V FUSE
MODEL No.
DESIGNED & MANUFACTURED
IN SAINT LOUIS, MISSOURI
SERIAL No.
LOCOMOTIVE AUDIO
1
2
3
45
9. Mic/DI Switch: Allows for selection of either the xlr mic input on the
back of the unit or the DI jack on the front of the unit.
10. DI: The Direct Input jack is useful when connecting high impedance
instuments such as guitars and bass. This 1/4” instrument jack loads
the source with an impedance of 169kΩ.
11. VU Select Switch: The VU meter on the 286A is able to display the
output signal level of either channel 1 or channel 2. If set to the center
position, no metering of either channel will be displayed. This is especially
useful when slamming the nal gain stage and output transformer. An
analog meter is expensive and can be damaged if not treated properly.
VU METER CALIBRATION
The VU meters in our units have been pre-calibrated. When needle is de-
ected to 0dB on the VU meter, a signal voltage of +4dBu will be present
on the output of the unit. Turning the small calibration screw on the rear
of the VU meter will allow a qualied technician to adjust display levels.
WARRANTY
Each Locomotive Audio unit will be given a 60-day warranty from date
of purchase covering parts and labor, excluding tubes purchased with
unit. A 2-year warranty from date of purchase will be offered to original
owners who register their product within the rst 30 days of ownership.
Warranty is void if the product serial number has been removed or if the
product has been damaged due to misuse, accident, unauthorized modi-
cation or repair. Locomotive Audio, LLC. reserves the right to determine
when a problem or issue is eligible for warranty. Warranty is non-transfer-
able and applies only to the original purchaser.
In no event will Locomotive Audio, LLC. be liable for any incidental or
consequential damages resulting from any defect in the product, including
lost prots, damage to property and, to the extent permitted by law, dam-
age for personal injury, even if Locomotive Audio, LLC. has been advised
of the possibilities of such damages.
REGISTRATION
purchase to receive the full 2-year warranty from date of purchase.
• Purchaser Name, phone number, email and mailing address
• Legible scan or photograph of the original sales receipt
• Serial # from stamped metal plate on back of unit
SUPPORT & SERVICE
In the unlikely situation that something would go wrong with your unit, we
would be happy to x it up for you! Please visit our support page to gain
further instructions on how to contact us.
If it is determined your product requires repair, we’ll let you know where to
ship it and we’ll also issue a Return Merchandise Authorization number
(RMA). This number must be displayed on the outside of your shipping
box. Most repairs take approximately 1 week. We will match the shipping
method you used to get it to us. (If you shipped it to us UPS ground, we
will ship it back to you UPS ground; if you overnight it to us, we will ship it
back to you overnight). You pay the shipping costs to us; we ship it back
to you free of charge.
©2015 Locomotive Audio, LLC
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