Andrews Amplification Spectraverb User manual

OPERATION MANUAL
08/07/13

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Thank you for purchasing an Andrews Amplifier The Spectraverb
name signifies a full spectrum of tones and reverberation The
Spectraverb amps feature extremely sweet reverb and work very
well with a variety of pedals As with all Andrews amps, these
models are built to the highest standards of craftsmanship and are
finely tuned for the ultimate tone This manual will help you to get
the most from your new amp Please feel free to contact us with any
questions at andrewsamps com

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FEATURES;
• BEAUTIFUL CLASSIC TUBE TONE WITH LUSH SPRING REVERB - Featuring
tube driven spring reverb with an innovative reverb drive limiter control
• HAND-WIRED CONSTRUCTION – Also sometimes called “point-to-point” wiring,
the Spectraverb amps utilize a very high quality turret board made of super-
tough G10 composite This glass-epoxy laminate is specified for its extremely
high strength and high dimensional stability over temperature The extra-thick
board material will never warp or melt, and there are no copper traces to peal
away from the board over time All wiring and soldering is done by hand and
quality-checked to ensure many years of trouble free operation
• OPTIONAL BUFFERED SERIAL EFFECTS LOOP – See the rear panel explanation
for more information
• AMERICAN-MADE TRANSFORMERS – We utilize only the best transformers to
meet our specifications They are chosen for superior tone and are rated to
withstand extreme heat for high reliability Output impedance is switchable to 4,
8 or 16 ohms and 2 speaker jacks are provided
• CUSTOM DESIGNED CHASSIS – Our durable welded steel chassis is designed
specifically for our amp models so that every part can be mounted in the optimal
location for lowest noise and highest stability
• CUSTOM DESIGNED CABINET – Our cabinets are specially designed for
maximum durability and superior tone We use high-grade woods for our
cabinets The cabinet components are precision cut using high-tech equipment
and are hand assembled with care Dovetail or finger joints are used at the
edges for maximum strength
• EXTERNAL BIAS TEST POINTS – The Spectraverb amps are equipped with
external bias test points and an externally accessible adjustment control This
makes output tube replacement fast and economical In fact, with a low cost
multi-meter you can adjust bias yourself This can be a real advantage in case of
a tube failure during a performance or recording session See the section about
the rear panel for more information

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Warnings and Precautions
During operation, vacuum tubes can reach temperatures over 400 degrees F Do
not touch hot tubes Insure plenty of ventilation behind the amp Keep the amp
away from children as well as curtains and other flammable objects
Do not expose your amplifier to rain Never set any cups, glasses, bottles or
cans of liquid on your amplifier
Do not use any solvents to clean your amplifier
Never operate your amplifier without a proper speaker load or damage may
occur See the section about the rear panel features for more information
Make sure the amplifier is always properly grounded Never remove or defeat
the ground pin from your power cord Always unplug the amplifier before
changing tubes or fuses
Use only correctly rated fuses See the rear panel and this manual for proper
fuse ratings
This amplifier can create high sound pressure levels Please use proper hearing
protection and/or maintain an adequate distance from the amplifier to avoid
hearing damage
Tube amps contain lethal voltages (even when unplugged) There are no fuses
or other user serviceable parts inside Please refer servicing to qualified service
personnel
Never insert any tool or other object into ventilation holes, tube sockets or other
openings unless instructed to do so in this manual Otherwise, you may come
in contact with dangerous high voltages inside the chassis

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Front Panel
1 INPUT JACKS – For maximum versatility, we have provided two input jacks
(la eled HI and LO). The HI jack provides a it more drive and sensitivity. The LO
jack provides a slight (6dB) attenuation and is useful when a cleaner and slightly
darker tone is desired, especially with high output pickups.
2 VOLUME CONTROL – Use this control to adjust the volume and gain of the
amp. Try using the other input jack to widen the range of the Volume control
3 BRIGHT (BRT) SWITCH – This switch is used to slightly increase the alance
of rightness (tre le) when playing at lower volume settings. The “up” position will
produce a it more sparkle and tre le articulation.
4 TREBLE CONTROL - This control varies the amount of tre le.
5 MID CONTROL – The Midrange control adjusts the midrange level. Keep the
setting low for vintage American tones. Turn it up for a warmer tone or to add more
midrange grind at higher gain settings.
6 BASS CONTROL – This control varies the amount of ass. In general, it is
suggested to increase the ass setting as volume is decreased to compensate for
the way the human ear hears ass at different volume levels and to allow for
tighter high-volume usage. Bass is generally turned down at high volume settings
to keep the low end “tight”. If playing at extremely high volume settings, the est
tone can e achieved ut turning the Bass almost all the way down.
7 REVERB LIMITER CONTROL – An Andrews Exclusive! When the LIMIT
control is turned fully clockwise, the rever functions as it would on classic amps
with spring rever . This will provide maximum drive to the spring unit resulting in a
very thick, long lasting rever eration. As you play louder or drive the amp harder
with an external pedal, the rever sound will increase. When playing cleaner or at
lower volume, the rever level will e reduced ecause the rever tank is not
driven as hard. When you adjust the rever level get the perfect rever setting for
clean tones, you may find the rever too strong when you turn up for a solo. This
can e annoying when playing dynamically. This is why we have added our
exclusive Limiter control. When the rever LIMIT is turned fully counterclockwise,
the rever is limited so that there will e very little increase in rever when your
volume is increased. The range of settings in etween “0” and “10” allow for
varying degrees of limiting. Use in conjunction with the rever MIX control (see

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elow). The Limit control allows you to set your level for clean tones and keep the
same level for higher volume settings such as solos.
8 REVERB MIX CONTROL – For adjusting the mix of rever signal compared
to the dry signal. Use in conjunction with the rever (Limit) control (see a ove).
On many amps, this control is la eled simply “rever ”. Turning the control
clockwise increases the volume of the rever signal as it mixes with the dry signal.
9 STANDBY SWITCH – This switch turns on the high voltage for the tu es. If
your amp is equipped with an optional solid state rectifier, o serve the instructions
elow *. If equipped with the standard tu e rectifier, it is not necessary to start the
amp in the stand y mode. However, it is a good idea to place the amp in stand y
when taking a reak to extend the life of the tu es and to allow the amp to cool.
*If equipped with a solid state rectifier: When turning on the amp, make sure
the STANDBY switch is in the off (down) position. Turn on the POWER (up
position) switch first. The pilot light will light up. Wait at least one minute to allow
time for the tu es to warm up completely efore turning on the STANDBY switch.
After the tu es are warmed up, turn on the STANDBY switch (UP position) to
operate the amp.
10 POWER SWITCH – This switch turns on the main power to the amplifier.
Always turn off the POWER switch when not using the amp for a couple of hours
or more.
11 PILOT LIGHT – This light indicates when the main power is turned on. For
ul replacement, simply unscrew the red lens, gra the ul with your fingers,
push in while turning counterclockwise and release. Replace with a standard #47
ul . The lens thread fits many standard lamp lenses and “jewels” allowing you to
customize the color if you desire.

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Rear Panel
1 FUSES – Always use correctly rated fuses or severe damage to the amp may
occur. Refer to the rear panel for fuse ratings. Always unplug the amp efore
replacing any fuses. When installing a new HV fuse, first insert it into the cap of the
fuse holder, then while holding only the cap, insert the fuse into the holder, push in
and turn clockwise to lock the cap and fuse in place. The main AC fuse is located
in the AC cord jack. Use a small screwdriver to remove the fuse holder.
2 OPTIONAL TRIODE/PENTODE SWITCH – In the PENTODE position, the
amp will operate normally with full output power. In the TRIODE mode, the output
power will e reduced roughly y half. This will allow the volume controls e set
higher for a more “cranked up” tone while slightly reducing the actual volume of the
amp. Always e sure to stop playing efore switching. Operating this switch while
playing could cause damage to the amp or tu es.
3 BIAS TEST POINTS AND ADJUSTMENT CONTROL – These are
provided to simplify measurement and adjustment of the idle current of the output
tu es. Bias adjustment is necessary whenever the output tu es are replaced.
See page 10 for ias adjustment instructions and precautions. The adjustment
control is located on the underside of the chassis near the test points.
4 SPEAKER JACKS – Always use the jack la eled MAIN first. If an additional
ca inet is to e used, meaning that two ca inets will e connected at the same
time, connect the second ca inet to the jack la eled EXT. Make sure any speakers
you connect can handle more than the output power of the amp. Always set the
impedance selector switch to match the correct speaker load. See chart elow.
NEVER OPERATE THE AMPLIFIER WITHOUT A SPEAKER CONNECTED OR
DAMAGE MAY OCCUR AND THE WARRANTY WILL BE VOID.
Speaker “Break-In” – New speaker cones may e tight and stiff. This results in a
righter tone with less ass and may even e considered “harsh” at times. By the
time your speaker has een played hard for 20 to 30 hours or more, its true
character and tone will ecome apparent. Until your speaker is fully roken-in, you
may find that you can achieve etter tone y reducing the TREBLE control slightly.

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5 IMPEDANCE SELECTOR – Always set this switch to the proper speaker load
according to the chart elow. Note: The Spectraver 1X12 com os incorporate
uilt-in 8 ohm speaker loads so leave it set to 8 when not connecting another
ca inet.
Setting For One Cabinet For Two cabinets
4 One 4 ohm cabinet Two 8 ohm cabinets
8 One 8 ohm cabinet Two 16 ohm cabinets
16 One 16 ohm cabinet
6 OPTIONAL FOOTSWITCH JACK – Insert the plug from the footswitch ca le
here. The footswitch will allow the rever circuit to e turned off remotely. A
specially modified volume pedal can e used in this jack to adjust the rever mix.
7 OPTIONAL BUFFERED SERIAL EFFECTS LOOP – Use the loop for
connecting effect units such as rever , delay, tremolo and chorus to avoid the
noise and distortion that sometimes occurs when connecting the certain effects in
the input jack if using high gain settings on the amp. Effect loops are generally not
recommended for overdrive and distortion effects.
a) Send – Connect the input of your effects chain here.
b) Return – Connect the output of your effect chain here.
c) Level – Adjusts the level of the loop signal. For est results, first try the
LOW level setting. The LOW will work est for most applications. The HIGH
setting may produce slightly less ackground hiss ut is only usa le for “line
level” effects and may cause distortion or volume reduction under certain
conditions, especially when the clean channel volume or overdrive channel
gain is set very high. See notes belo .
d) Bypass – To completely ypass the loop circuit and maintain a 100% tu e
signal path, set this switch to the “out” position.
Notes on the effects loop – Some 9 volt “stomp box” type effects are not designed
to be used in effect loops and can not handle the levels present in the loop ithout
distortion. If your effect distorts even hen the loop is s itched to the LOW level
setting, your effect unit may not be compatible. Try upgrading to an effect that can
handle higher levels or one that runs on a higher supply voltage. You may also
encounter higher levels of hum if using effects in front of the amp and effects in the
effects loop if they share the same po er supply. This is cause by the ground loop
that is created bet een the signal ground connections and the po er supply
ground connections. It is recommended to use separate supplies for each group of
pedals or a high end supply ith isolated DC outputs for each group of pedals.

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FOR TECHNICAL TYPES
We have provided this information for those who have a technical interest,
proper equipment and a DIY attitude CAUTION! GUITAR AMPLIFIERS
CONTAIN LETHAL VOLTAGES If you have any doubt about your ability to
safely perform this procedure, refer the job to a qualified technician!
Bias Adjustment Procedure:
Precautions:
• Lethal voltages are present inside the chassis and at the tube pins. Do not
open the chassis or insert any objects into any openings other than here
directed by these instructions. The entire procedure can be accomplished
ithout opening the amp.
• Vacuum tubes get very hot. Al ays allo the tubes to cool completely before
touching them.
• When replacing output tubes, use only the very highest quality tubes or the
amplifier may be damaged. For more details, see the section belo regarding
tube replacement.
Bias Adjustment
1) Unplug the amplifier and allow the tu es to cool. The output tu es are the two
matching tall tu es.
2) Spread open the retaining clips that hold the output tu es in place and remove the
tu es. Install a new matched pair of the same type of output tu es that came
installed in your amp. ie: 6V6 or 6L6 (5881 can e used in place of 6L6 tu es).
3) Utilizing a digital multi-meter, set the switch for DC Volts or millivolts measurement
and select a range that will show 0-100 millivolts. Insert the lack meter lead into
the lack test point terminal and insert the red meter lead into the red test point
terminal.
4) Insert a small flat lade screwdriver into the adjustment control hole and gently
turn the control to its mid position. The adjustment control is located on the
underside of the chassis near the ias test points.
5) Plug in the AC cord and turn on the amplifier’s main power switch. After waiting at
least one minute, turn on the stand y switch. The meter should display a few
millivolts (mV).
6) While taking care not to touch any hot tu es, insert the screwdriver into the
adjustment control slot and very slowly turn the adjustment until the meter reads
65mV to 90mV for 6L6GC tu es or 50mV to 70mV for 5881 tu es. The test point
shows the com ined reading for oth output tu es.
7) It’s a good idea to re-check the ias periodically (every 500 hours of use) as the
idle current can drift over time as the tu es age.
NOTES: Adjusting ias to the higher end of the scale will provide a warmer more
driven sound ut will shorten the life of the output tu es and increase the chances of a
tu e failure. Adjusting to the lower end of the scale will increase tu e life while
providing a “colder” less driven sound. Try different settings and listen for differences
and make your choice. Factory settings are in the middle range.