Andrews Amplification Spectraverb 16 User manual

OPERATION MANUAL
16
01/10/16

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Thank you for purchasing an Andrews Amplifier. The Spectraverb
name signifies a full spectrum of tones and reverberation. 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;
•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 peel
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.
•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 available at 4, 8
or 16 ohms.
•HIGH QUALITY CABINET –The cabinet is made of solid pine with a Baltic birch
plywood baffle. The components are precision cut using high-tech equipment
and are hand assembled with care. Finger joints are used at the edges for
maximum strength.
•EXTERNAL BIAS ADJUSTMENT POT –The Spectraverb amps are equipped with
an externally accessible adjustment control. This makes output tube
replacement fast and economical. 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
(labeled High and Low). The High jack provides a bit more drive and sensitivity.
The Low 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 each input jack to widen the range of the Volume control.
3. BRIGHT SWITCH –This switch is enabled when the volume control is pulled
outward. It is used to slightly increase the brightness (treble) when playing at lower
volume settings. The “pull” position will produce a bit more sparkle and treble
articulation, especially when the control is set to the lower numbers.
4. TREBLE CONTROL - This control varies the amount of treble.
5. MIDRANGE 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 bass. In general, it is
suggested to increase the bass setting when volume is decreased to compensate
for the way the human ear hears bass at different volume levels and to allow for
tighter high-volume usage. Bass should generally be turned down a bit at high
volume settings to keep the low end “tight”. If playing at extremely high volume
settings, the best tone can be achieved by turning the Bass control down a bit
more, especially when playing on the neck pickup with humbucking pickups.

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7. REVERB LIMITER CONTROL –An Andrews Exclusive!
When the LIMIT control is turned fully clockwise, the reverb functions as it would
on other amps with spring reverb. At this setting, you are operating without any
limiting. This will provide maximum drive to the spring unit resulting in a very lush,
long lasting reverberation. As you play louder or drive the amp harder with an
external pedal, the reverb sound will increase. When playing cleaner or at lower
volume, the reverb level will be reduced because the reverb tank is not driven as
hard. When you adjust the reverb level to get the perfect reverb setting for clean
tones, you may find the reverb too strong when you turn up for a solo. This can be
annoying when playing dynamically so we have added the option to limit the reverb
drive. This is why we have added the limit control.
When the reverb LIMIT is turned fully counterclockwise, the reverb is limited so
that there will be very little increase in reverb when your guitar or pedal volume is
increased. The range of settings in between “0” and “10” allow for varying degrees
of limiting. Use in conjunction with the reverb MIX control (see below). The Limit
control allows you to set your level for clean tones and keep approximately the
same level for higher volume settings such as solos.
8. REVERB MIX CONTROL –For adjusting the mix of reverb signal compared
to the dry signal. Use in conjunction with the Reverb Limit control (see above). On
most amps, this control is labeled simply “reverb”. Turning the control clockwise
increases the volume of the reverb signal as it mixes with the dry signal.
9. PILOT LIGHT –This light indicates when the main power is turned on. For bulb
replacement, simply unscrew the red lens, grab the bulb with your fingers, push in
while turning counterclockwise and release. Replace with a standard #47 bulb. 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. BIAS CONTROL –see below
2. FUSE –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 before
replacing any fuses. When installing a new 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.
3. POWER SWITCH –The power switch has 3 positions. They are “off”, “standby”
and “on”. The standby position keeps the tubes warmed up while silencing the
amp. The amp can be warmed up in the standby mode or it can be turned fully on.
The rectifier tube will provide a delay in delivering high voltage to the other tubes
until they are warmed up. It is unnecessary to put the amp in standby mode before
powering off. Standby mode is most useful for silencing the amp during breaks/.
4. SPEAKER JACKS –The Spectraverb 16 is equipped with 3 speaker jacks
labeled 4, 8 and 16. These provide properly matched output impedances for 4, 8
and 16 ohm speaker cabinets. Always use the jack labeled “8”for the built-in
speaker. If an additional cabinet is to be used, unplug the built-in speaker and
connect the external speaker cabinet to the jack that matches the ohm rating of the
cabinet. If operating two cabinets at the same time, it will be necessary to connect
a junction box or “Y” cable. See chart below. NEVER OPERATE THE AMPLIFIER
WITHOUT A SPEAKER CONNECTED OR DAMAGE MAY OCCUR AND THE
WARRANTY WILL BE VOID.
5. USING VARIOUS SPEAKER COMBINATIONS –Always use the proper speaker
jack to match the speaker(s) being used according to the chart below. When using
2 cabinets, it will necessary to connect them through a junction box or “Y” cable.
Jack
For One Cabinet
For Two cabinets
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One 4 ohm cabinet
Two 8 ohm cabinets
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One 8 ohm cabinet
Two 16 ohm cabinets
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One 16 ohm cabinet

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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!
TUBE REPLACEMENT
Precautions:
Always unplug the amplifier and allow the tubes to cool completely before
touching them.
It is absolutely necessary to adjust the bias (see below) when replacing the
output tubes.
When to replace tubes:
Preamp tubes such as 12AX7 and 12AT7 will generally last for many thousands of
hours but occasionally problems can development before they “wear out”. If you hear
crackling, popping, humming, ringing, or other strange noises, try replacing your
preamp tubes one at a time. This may resolve the problem. Preamp tubes can be
replaced at any time without any adjustment.
Output tubes usually have a shorter life. They will often start to sound bad long before
they fail. If you notice that your amp is gradually loosing volume, headroom or
“punch”, or if you notice that low notes are sounding a little “flabby”, it might be time
for a new matched set of high quality output tubes. This could happen after a several
months or it might take several years depending on how much and how hard the amp
is played. Don’t forget about biasing the output tubes when replacing them. Rectifier
tubes generally fail all at one time causing a fuse to blow. Also, some brands of 6V6
tubes, even brand new ones, tend to develop high pitched mechanical rattles. The
rattling may sound metallic or glassy and is not heard through the speaker but will be
heard coming from behind the amp. This sound generally does not indicate a failure or
danger to the amp but is common to modern 6V6 tubes. Installing a new pair of tubes
may or may not provide better results.
Sometimes an output tube will fail before it “wears out”. A tube failure will usually
result in blown fuse. If you find a blown fuse in your amp, the most likely cause is a
bad output tube or rectifier tube. If your amp is blowing fuses, try a new rectifier tube
or a matched set of output tubes and adjust the bias. Always use the correct fuse
rating.

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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 where
directed by these instructions. The entire procedure can be accomplished
without opening the amp.
•Vacuum tubes get very hot. Always allow 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 below regarding
tube replacement.
Bias Adjustment –Necessary when replacing 6V6 tubes output, regardless of
brand.
1) Unplug the amplifier and allow the tubes to cool. The output tubes are the two
matching tall tubes labeled 6V6.
2) Spread open the retaining clips that hold the output tubes in place and remove the
tubes.
3) Connect a “bias probe” (available online) to the empty tube sockets and install 6V6
tubes into the sockets on the bias probe.
4) Insert a small flat blade screwdriver into the adjustment control hole and gently
turn the control to its mid position. The adjustment control is located on the back of
the chassis between the power cord and the fuse.
5) Plug in the AC cord and turn on the amplifier’s main power switch. After waiting
about one minute, switch the amp into play mode and observe the reading on the
bias probe.
6) While taking care not to touch any hot tubes, insert the screwdriver into the
adjustment control slot and slowly turn the adjustment until the probe shows a bias
current of about 22mA (milliamps) per tube. Allow the amp to warm up for about
10 minutes and check again.
7) It’s a good idea to re-check the bias periodically (every 500 hours of use) as the
idle current can drift over time as the tubes age.