Aiken Amplification Sabre User manual

Sabre
User's Manual
Aiken Amplification, Inc.
1225 Montague Avenue
Greenwood, SC 29649
Tel: [phone]
http://www.aikenamps.com

Contents
Contents...............................................................................................................2
Getting Started.....................................................................................................3
Front Panel Controls and Switches...................................................................4
Rear Panel Controls and Switches....................................................................7
Tube layout and replace ent...........................................................................10
Biasing................................................................................................................11
Speakers.............................................................................................................12
Troubleshooting................................................................................................13
Specifications....................................................................................................17

Getting Started
Congratulations on purchasing your new
Aiken Sabre amplifier!
The Sabre is a 50W channel switching
amplifier featuring two EL34 tubes in the
output stage. There are two completely
separate channels, each featuring Gain,
Bass, Middle, Treble, and Master controls,
with a common Presence control, as well as
two separate effects loops allowing
individual effects to be used for each
channel. The clean channel is capable of
tones reminiscent of the finest old Fenders,
while the gain channel takes you into
modern modded high gain territory. The
gain channel also features a footswitchable
gain boost to take the amp from crunch to
over the top sustaining distortion almost
like having a three channel amplifier.
Features include:
All tube signal path. Preamp tubes are 12AX7/ECC83. Output tubes are EL34. The rectifier
uses massive 3 amp 1000V ultra fast recovery diodes (Ultra FREDs), for utmost reliability
and a tight low end, without the RF noise interference "spikes" inherent in standard rectifiers.
Front panel controls/connections: Input jack, Channel 1 Gain, Treble, Middle, Bass, Master,
Channel 2 Gain, Treble, Middle, Bass, Master, and Presence (affects both channels). There
is also a bright switch for channel 1, a channel select switch, a gain boost switch for channel
2 (footswitchable), and a red and green LED to indicate which channel is active. A jeweled
pilot lamp completes the look.
Rear panel controls/connections: AC mains input, international voltage selector switch
allowing operation at 100V/120V/200V/220V/230V/240V 50/60Hz, impedance selector switch
for 4, 8, or 16 ohm operation, two 1/4" speaker jacks, and a footswitch jack to control the
channel switching and channel 2 gain boost functions. Also includes a locking mil style RV6L
bias pot and three tip jacks for easy bias setting without having to remove the chassis from
the cabinet. There are also two separate line level (+4dBu) effects loops (one for each
channel) using a single 1/4" TRS jack for each (tip is send, ring is return, and sleeve is
ground).
Solid, finger jointed, void free birch ply cabinets. The head is 25 1/2" wide, 10 1/4" tall, and
9" deep.
Hefty 16 gauge steel chassis, zinc plated, yellow chromate conversion coated for durability,
corrosion resistance, and appearance. Front and rear faceplates are gold anodized
aluminum for a durable, classic look.
All hand wired "military style" turret board construction, using chassis mounted tube sockets,
for ease of maintenance and reliability. Built to last. Finally a high gain channel switching
head that is not wired on a flimsy PC board!
Premium, tight tolerance parts are used for lowest noise operation, including 2W carbon film
and metal film resistors where appropriate for best tone and lowest noise, 5W metal oxide
power resistors, 630V axial leaded polypropylene film/foil capacitors, and low noise, sealed,
2W mil style RV4 pots.
SabreManual.doc 12/08/11 Page 3 of 17
Copyright 2004 2011, Aiken Amplification, Inc.

Front Panel Controls and Switches
Input jack:
Plug your guitar in here and you are ready to rock!
Ch1/2 select switch:
This switch selects either the clean channel or the distortion channel. It should be in the
“up”, or channel 2 position to enable normal footswitch operation, as it will override the
footswitch setting. The red and green channel indicator LEDs will alternately illuminate
when their channel is selected.
Ch 2 gain switch:
This switch turns on the gain boost function of channel 2. It should be left in the
“up”, or boosted position to enable normal footswitch operation, as it will override the
footswitch setting.
Ch 1 bright switch:
This switch changes the voicing of channel 1 to make it brighter for more high end
“sparkle”. Unlike the bright switches on most amplifiers, it does not lose effectiveness as
the volume is turned up.
Ch 1 Gain:
This is the clean channel gain control. It is primarily designed to compensate for guitars
that have lower output single coil pickups or high output humbuckers. Turning the gain
all the way up will give a bit of crunch with higher output pickups if desired, or a more
even clean tone when switching between lower output single coils and higher output
humbuckers in the same guitar. For the cleanest possible tone, turn the channel 1
Master up all the way and use the channel 1 Gain control as the overall channel volume.
For the most clean sustain, turn the channel 1 Gain control all the way up and use the
channel 1 Master to control the overall volume.
Channel 1 Bass:
The bass control adjusts the low frequency equalization of the clean channel.
Channel 1 iddle:
The middle control adjusts the midrange frequency equalization of the clean channel.

Channel 1 Treble:
The treble control adjusts the high frequency equalization of the clean channel.
Channel 1 aster:
The output level control is the overall level control for the clean channel. It should be
used to equalize the volume between the clean and distortion channel when switching
between them.
Ch 2 Gain:
This is the distortion channel gain control. For the cleanest possible tone, turn the
channel 2 Master up all the way and use the channel 2 Gain control as the overall
channel volume. For the most sustain and distortion, turn the channel 2 Gain control all
the way up and use the channel 2 Master to control the overall volume. The “normal”
setting for the gain control is around the 1 to 2 o’clock position. This will give a good
crunch tone, and when the gain boost is turned on, it will give a very noticeable
distortion/sustain increase for leads. If the gain control is turned all the way up, there will
be much more distortion in the non boosted mode, so the additional distortion added by
the gain boost may not be as apparent. Of course, this setting is all dependent on guitar
type and playing style, so it should just be used as a starting point for experimentation.
Channel 2 Bass:
The bass control adjusts the low frequency equalization of the distortion channel.
Channel 2 iddle:
The middle control adjusts the midrange frequency equalization of the distortion channel.
Channel 2 Treble:
The treble control adjusts the high frequency equalization of the distortion channel.
Channel 2 aster:
The output level control is the overall level control for the clean channel. It should be
used to equalize the volume between the clean and distortion channel when switching
between them.
Presence:
The presence control adjusts the high frequency equalization in the output stage. It is a
"shelving" control that operates by cutting the amount of high frequencies in the global
negative feedback loop, which results in a boost in the output high frequency range and a
subjectively "brighter" and more "open" tone in the highs due to the lower negative
feedback at those frequencies. The presence control frequency range is higher than
most presence controls, and is primarily designed to add “sizzle” to the distortion
channel, acting as a fourth eq control voiced above the treble control range. The treble
and presence controls should be interactively adjusted to voice the top end of the
distortion tone. Since it is a global control (it affects both clean and distortion channels
simulataneously) if it is turned up too high, you may want to turn off the channel 1 bright
switch or use less channel 1 treble to compensate.

Note that a small amount of noise during rotation of the presence control is normal, and is
due to a small DC voltage present on the control. This was deliberately done, in keeping
with the "old style" presence control circuitry that we feel sounds best.
Pilot lamp:
The pilot lamp lights when power is applied to the amplifier and the power switch is on.
The pilot lamp features a screw on “jewel” that can be removed from the front panel to
replace the bulb without having to remove the chassis. The bulb is a standard #47
“bayonet” style bulb, available at most electronics supply stores.
Power switch:
The Power switch turns the amplifier on in the up position and off in the down position.
Glory switch:
What good is power without the glory? The Glory switch allows muting of the amplifier
output when not in use. When the switch is in the up position, the amplifier is on, and
when it is in the down position, the amplifier is on standby. The tube filaments remain on
and warmed up, so the amplifier is ready to play as soon as it is taken off standby. The
correct powerup sequence is to turn the amplifier on with the power switch and then, after
it has had time to warm up, the Glory switch is turned on. When turning the amplifier off,
the Glory switch should first be turned off, then the power is turned off after a few
seconds.

Rear Panel Controls and Switches
AC ains:
Plug the supplied IEC mains cord into this outlet to provide power to the amplifier.
ains Fuse:
2A slo blo for 100V/120V operation, 1A slo blo for 200V 240V operation.
AC ains voltage selector:
Set this switch to the appropriate position to match the mains voltage in the country in
which you are using the amplifier. WARNING: Do not adjust this control with the AC
mains cord plugged in and the power on!!! Damage to the amplifier will result if the
switch is set to the wrong position. If you have any doubts as to which is the correct
voltage for the country you are in, call the factory or inquire with someone locally who will
know the correct mains voltage.
HT Fuse:
500mA fast acting fuse
Impedance Selector:
The impedance selector allows selection of 4, 8, or 16 ohm output impedance to match
the speaker in use. Be sure to set this switch to the appropriate setting for the speaker or
speakers connected to the amplifier. All amplifiers are shipped from the factory with a
single 16 ohm speaker or a pair of speakers wired in series to provide a 16 ohm load.
This allows connection of an external 16 ohm cabinet to be used simultaneously with the
internal speaker by setting the impedance selector to 8 ohms, or four 16 ohm cabinets
can be used by setting the impedance selector to 4 ohms.
Speaker Jacks:
Two speaker jacks are provided to allow use of the amplifier with either the internal
speaker (combo units only) or up to two external speaker cabinets. More than two
external cabinets may be safely used with the amplifier, but this will require the use of "Y"
cables for the extra two cabinet connections. Be sure to use only quality speaker cable
do NOT, under any circumstance, use guitar cable to connect the amplifier to a speaker
cabinet. Doing so may cause damage to the amplifier.

Bias Test Jacks:
Three standard tip jacks are available to allow easy bias current measurements without
removing the chassis. Refer to the section on biasing for instructions on the use of these
jacks.
Bias control:
A locking mil style RV6 trimpot is provided to allow adjustment of bias current. The outer
locknut must be loosened before adjusting the screwdriver slot control. Refer to the
section on biasing for further instructions.
Effects Loops:
This is a 1/4" TRS (tip/ring/sleeve) insert style jack. There is a separate loop for each
channel, and they function completely independently. The nominal 0dBu level allows use
of line level (pro) effects for lowest noise levels. The TRS insert jack allows use of a
single TRS cable to connect the effects, instead of the two 1/4" cables normally required
for an effects loop. The TRS cable (also called an “insert” cable) is a cable that has a
stereo ¼” jack on one end and breaks out into two mono ¼” jacks that go into the input
and output of the effects unit. These insert cables are available at most music stores
(they are typically used to connect compressors or other effects to a single channel on a
mixing board). Alternately, you can make or buy a stereo to two mono “pigtail” adapter
cable (available from places like Radio Shack) and use standard ¼” cables to connect
the effects.
Once properly connected, adjust the effects unit’s input level control so the signal
presence LED is lit (if there is one) and the clip LED occasionally lights on peaks or
doesn’t light at all, depending on the effect’s requirements. Then adjust the effects unit’s
output level so the Sabre’s volume is the same with the insert cable plugged into the back
of the amp or unplugged. Refer to the effects unit user manual for proper adjustment in
case it differs from these instructions.
Although there are two independent effects loops, it is not necessary to use two separate
effects units with the Sabre. Most rack mount effects are stereo, and have independent
channels when both are used. To use a single stereo effects unit with the Sabre, simply
connect two TRS cables, one from each effects loop jack, to the inputs/outputs of the
stereo effects unit. Of course, the same effects patch will be active for both channels, so
you will have to change channels and effects patches at the same time to have different
effects on each channel. There are midi footcontrollers on the market that will allow
control of amplifier channel switching and effects patch changes at the same time.
There is, however, a more elegant solution to using a single effects unit: the TC
Electronics G Major multi effects processor. This is the recommended effects unit for
use with the Sabre. It has a unique relay output jack feature that is perfectly suited for
use with the Sabre’s footswitchable functions. This is a stereo output jack that has two
indepent patch controllable relays connected to a single stereo jack on the rear of the
unit. By simply connecting a stereo cable from the relay output jack on the G Major to
the stereo footswitch jack on the rear panel of the Sabre, and connecting two TRS cables
from the effects loop jacks of the Sabre to the inputs/outputs of the G Major, you can
program and control G Major effects patches, Sabre channel selection, and Sabre boost
switch functions all at the same time with a single patch change on the G Major (or single
step on the G Major’s footcontroller).

For more information on programming the G Major relay function, refer to the TC
Electronics manual*.
*Aiken Amplification is in no way affiliated with TC Electronics, we just were told about this effects
unit from a customer, and decided that it looked like it was tailor made for use with the Sabre!
Footswitch jack:
This is a 1/4" TRS (tip/ring/sleeve) insert style jack. The tip connection controls the
channel switching function, and the ring connection controls the gain boost function of the
distortion channel. Shorting the tip or ring to the sleeve connection enables that
particular function. The sleeve connection is not at chassis ground potential, so be
careful to only use isolated contact closure functions, i.e. relay switching or standard
footswitches. Shorting the sleeve connection to chassis ground or AC mains ground will
damage the amplifier.
Below is a schematic of the recommended Sabre footswitch wiring, should you decide to
build your own. This is the schematic of the footswitch that ships with the Sabre from the
factory.

Tube layout and replacement
The Sabre uses five 12AX7/ECC83 tubes and EL34. The preamp tube function is as follows,
starting at the side closest to the input jack: CH1 preamp 1/CH2 preamp 1 (12AX7/ECC83), CH1
effects recovery amp/CH2 preamp 2 (12AX7/ECC83), CH2 preamp 3/CH2 preamp 4
(12AX7/ECC83), CH2 effects recovery amp/CH2 cathode follower (12AX7/ECC83), and phase
inverter(12AX7/ECC83). The chassis top view layout is shown in the diagram above.
The preamp tubes are housed in removable "bayonet" metal shields. The shields can be
removed by pushing down on them and rotating the shield to the left, then pulling it upwards off
the tube. The tube can then be pulled out of the socket.
You may freely sub any 12xxx type tube in the preamp and phase inverter positions. It won't hurt
anything, and you may find some different tones you like. The 12AU7 is a good lower gain tube,
as is the 5751. Other choices are 12AY7, 12AT7, or 12AZ7. In addition, different manufacturer's
tubes will sound different. Some people prefer the tone of various Ei, Sovtek, or other tubes, and
some insist on NOS tubes for a true vintage tone. The JJ/Teslas are the least microphonic, but
are a bit compressed sounding when compared to the longer plate tubes. The Chinese 12AX7’s
are a good compromise between microphonics and a more “open sounding”, or less compressed
tone. Feel free to experiment!
Note: vacuum tubes, especially output tubes, can get very hot in normal operation, and may
cause burns if removed before they have a chance to cool down. Be sure to wait several minutes
before replacing tubes to allow them to cool down. Do not, under any circumstances, remove or
replace the tubes with the power on, as this could cause a deadly electrical shock should the
glass break, exposing the high voltage plate terminals. Also, be sure to pay attention to the
orientation of the tubes when putting them back in the socket. The tube pinout is keyed so it can
only be placed in the socket in one direction, and if the tube is forced in incorrectly, it can damage
the tube or the socket. The octal output tubes have a phenolic key that fits a corresponding
keyhole in the socket. If this key is broken off, it will allow incorrect placement of the tube in the
socket, which could result in damage to the amplifier. Be sure to carefully examine the tube
before replacing it.