SCIENCE Street Sweeper MkII User manual

Contents
Intro...................................................................................................................................................................... 1
Front Panel.......................................................................................................................................................... 1
Rear Panel........................................................................................................................................................... 2
Tube Life & Biasing............................................................................................................................................ 5
Safety................................................................................................................................................................... 9
Limited Lifetime arranty............................................................................................................................ 10
Care and Maintenance.................................................................................................................................... 11
Tube & Bias Diagram........................................................................................................................................ 11

Intro
Thank you for purchasing the Street Sweeper MkII amplifier! This manual covers the amp’s
different features, maintenance, tube, and warranty information in detail.
Front Panel
Input Jack: ¼” jack for your guitar.
Gain: Controls the overall gain of the amplifier, ranging from crystal clean to vintage crunch.
Voice: 4- ay Rotary switch, that alters the voicing of the amplifier. The Voice switch interacts
with 3-band EQ section, changing their frequency response. Position 1 (most counter-
clockwise) provides classic balanced American clean tones with open mids and round lows
and increased headroom; Position 2 adds treble brilliance to the voicing of Position I; Position 3
has a similar tonality to Position 1, but is slightly thicker and with more gain available; and
Position 4 adds gain, lower-mids, and upper-mids to the tone for a more “British” tone.
Treble: Adds treble frequencies when turned clock-wise, and reduces treble when turned
counter-clockwise.
Middle: Adds mid-range frequencies when turned clock-wise, and reduces mid-range when
turned counter-clockwise.
Bass: Adds bass frequencies when turned clock-wise, and reduces bass when turned counter-
clockwise.
Reverb Section
The Street Sweeper features two independent 2-control reverb sections that can be switched
between or bypassed via the 2-button footswitch. ith no footswitch plugged in, only Reverb
I is active by default. (Note: Both reverbs are voiced identically, so no functionality is lost). To
mute the the reverb entirely with no footswitch plugged in, simply turn Reverb I's “Level”
control to minimun (fully counter-clockwise).
ith the footswitch plugged in, both reverbs become active. Button 1 (left) turns on or
bypasses both reverbs. Button 2 (right) switches between Reverb I and Reverb II.
Tip: While in bypass/off mode, you can you Button 2 to pre-select everb I or everb II!
Level I: Adjusts the overall amount of reverberation for Reverb I.
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Color I: Adjust the tonal characteristics of Reverb I. hen turned clock-wise the tone of the
reverberation will become brighter with a longer 'tail'.
Level II: Adjusts the overall amount of reverberation for Reverb II.
Color II: Adjusts the tonal characteristics of Reverb II. hen turned clock-wise the tone of the
reverberation will become brighter with a longer 'tail'.
Loudness: Adjusts the overall volume of the amplifier.
OFF/STBY(Standby)/ON switch: 3- ay switch: down is OFF, middle is Standby, and up is ON.
About Standby: Standby mode mutes the sound and allows the tubes to heat up before
applying high voltage to amp when turned ON. Leave in Standby for 30 seconds to a 1 minute
before switching ON. Standby can also be used to mute the amplifier while leaving the tubes
warm for short breaks. For long breaks it is best to turn the amplifier completely off.
To turn OFF, follow the same turn-on procedure – but in reverse order – allowing the amp to
idle in Standby mode for about 30 seconds before powering down. hile it is perfectly okay to
turn the amp OFF immediately, idling in standby before powering down lets the filter
capacitors inside the amp fully discharge. If turned off immediately, there will still be some
sound as the filter caps continue to discharge, which may be annoying.
Note: Amps fitted with the Ghost Effects Loop will experience a short delay when switching from
Standby to ON. This is normal.
Indicator lamp: Attractive red neon light to indicate the amp is ON.
Rear Panel
WA NING: Use with grounded power outlet only! Discard power cord immediately if ground
pin is damaged/broken. The ground connection is for your safety in case of a fault condition!
120 VAC power input: Plug in the included standard IEC power cord here. For use with120 VAC
only unless otherwise specified. Canadians, you are good to go too!
Fuses
WA NING: Only check/change fuses with amplifier unplugged from the outlet!
Your amp is fitted with fuses for safety and to protect the amplifier’s most expensive parts.
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Fuses are user-replaceable, and if a fuse does need replacement, always replace with the
correct type and rating (as designated on the rear panel of the amplifier).
To check if a fuse is blown, push and twist counter-clockwise to remove the fuse holder and
see if the small wire inside the glass is broken. There may also be a burnt area the inside of the
glass.
If you replace a fuse, and it blows again, there is likely a more serious problem. Please contact
us before changing the fuse again at [e-mail] so we can further assist you with
the trouble-shooting.
Mains Fuse: 1 ¼” x ¼”, Slow Blow, 250V glass cartridge fuse. This fuse is fitted for safety, but
can still blow under some normal amp faults. If the indicator lamp does not come on, then it is
likely the Mains Fuse has blown (otherwise the lamp itself has burned out).
HT Fuse: 1 ¼” x ¼”, Slow Blow, 250V glass cartridge fuse. If the amp produces no sound at all
then it’s most likely the HT Fuse has blown. The most common reason for this is a shorted
output tube.
Output Tube Fuses (200 model only): 1 ¼” x ¼”, Fast Blow, 250V glass cartridge fuse.
200 models are fitted with extra fuse protection. If either of these fuses blow, a red LED
illuminates on the back to indicate a failure. The output tubes work in pairs, a nd if an output
tube fuse blows, power is cut off to one pair of the four KT88 output tubes (even though only
one is likely damaged). This allows the amp continue to run safely on the remaining pair of
tubes at half power with change in tone.
If you would like to keep running on half power until the faulty tube(s) can be replaced, it is
optimal to set the impedance selector one setting below what the cab’s impedance rating. For
example, when running at half-power into an 8 Ohm cab, switch the impedance selector to 4
Ohms.
Tip: You can run your 200W amp at half power by simply removing one of the fuses. Just
remember to turn down the impedance selector one setting as stated above -if doing this for a
prolonged period.
Speaker Jacks and Impedance Selector
Note: Speakers must be rated for at least the full rated clean output power of the amplifier (50W,
100W, or 200W depending on your model). Under overdrive conditions, the clean power can be
exceeded by tens of watts, and therefore it is preferable to use speakers whose combined power
rating exceeds the clean power rating. This topic is up for debate as some speaker manufacturers
rate their speakers with this in mind (i.e. four 25W rated speakers may be OK for a 100W amp),
however it is still better safe than sorry!
CAUTION: Always verify a speaker cabinets impedance before using with the amplifier. An
impedance mismatch can potentially damage the amplifier and is not covered under
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warranty.
Using one speaker cabinet: ith the amp OFF, plug in speaker a cabinet either
Speaker Output jack.
Using two speaker cabinets: hen using with two speaker cabinets, both must be the
same impedance (i.e. two 8 ohm cabs), and the impedance selector should be set for
half each cab's impedance. For example:
•hen using two 8 ohm cabs: Set the impedance selector should be set to 4 ohms.
•hen using two 16 ohm cabs: Set the impedance selector should be set to 8 ohms.
•Using two 4 ohms cabs: This configuration is not supported.
Footswitch Jack:
¼” jack for the included 2-button footswitch. Use with TRS ¼” cable.
Effects Loop (optional):
The Ghost series effects loop is designed to work ideally with instrument level effects (i.e.
effects pedals) and some line level equipment (i.e rack effects units) gear. In general, time-
based effects such as reverb and delay are best placed in the effects loop. The effects loop is
located after the preamp section of the amp, where most of the overdrive/distorted tone is
generated. This allows time-based effects to be be heard more cleanly and clearly. For
example, plugging a delay into the effects loop allows you to delay your distorted tone, giving
a clear delay effect. Conversely, plugging a delay into the input of the amplifier would
overdrive the delay, giving a murkier, washed-out delay sound. There is no correct way to use
your effects, it's all a matter of preference.
Note: The eturn jack of the Effects Loop may also be used as a power amp input, and in
conjunction with a separate preamp unit.
Tip: A volume pedal also works well in the effects loop, acting as an overall master volume, which
can be extremely useful in a live setting, however a buffered pedal is preferred to prevent treble
loss.
Send Jack: Connect to the input of your effects via ¼” shielded instrument cable.
Return Jack: Connect to the output of your effects via ¼” shielded instrument cable.
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Tube Life & Biasing
WA NING: Tubes can become extremely hot during normal operation. Make sure the
amplifier is OFF, and always allow tubes to cool before handling to prevent burns.
P reamp Tubes:
Preamp tubes typically last many years, but fail occasionally. Typically they will become noisy
or “microphonic” before they wear out. This is characterized by ringing, static, or popping
noises.
Changing Preamp Tubes:
V1, V2, V3, V4 (see tube diagram on pg. 12)
To remove tubes, gently pull upward using a very slight circular motion if necessary. hen re-
inserting a preamp tube, mind the pin/socket orientation as they are “keyed” to insure proper
installation.
O utput Tubes:
Output tubes (See tube diagram on pg. 12 ) generally produce a strong output for 6 months to
a year when played regularly, then they may become dull sounding, and/or the amplifier may
begin to loose some power. Output tubes may last much longer depending on how hard the
amp is played. Sometimes they die gracefully, sometimes abruptly causing a fuse to blow,
which in turn protects the amplifier from further damage.
It's sometimes possible to see in plain view which power tube(s) is damaged. If necessary,
remove the output tubes to inspect them by grabbing the plastic base, and gently pulling up in
a shallow circular motion.
Here are things to look for:
•The shiny silver area on top of tube has turned white (tube has lost vaccuum).
•Burned spot(s) on the large gray structure inside the tube (tube has “red-plated”/drawn
excess current.
•The filament is not lighting up (not common, but can happen).
Like preamp tubes, sometimes output tubes can become “microphonic.” This occurs when
some part internal part of the tube becomes physically loose. In turn, this noise then gets
amplified. The noise can be anything from static, a high-pitched ringing, or intermittent
sputtering noises. This is usually exacerbated by vibration from the speaker cabinet. If you
think a tube may be microphonic, try isolating the amplifier from the speaker cabinet to see if
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the noise stops.
Tip: If you think you have a microphonic tube, you can very gently tap on each tube with a pencil's
eraser to see if the sound becomes worse, stops, or changes. All tubes will amplify the sound of a
tap little, especially preamp tubes, but for example, if you hear an intermittent ringing sound and
tap each tube to find V7 (for example) is causing the ringing to start/stop, you can be sure it's the
problematic tube!
Changing Output Tubes:
V5, V6 (100 & 200 version only) and V7, V8 (see tube diagram on pg. 12)
In general, it's best to change all output tubes at once and preferable to buy a “burned-in”
matched set from a reputable dealer.
Output tubes can be replaced and biased by a qualified technician, however if you would like
to replace and bias the output tubes yourself, please see the detailed information about your
amp’s biasing system and bias procedure in the following sections.
Bias Control & Test Points
Every Science Amplifier comes equipped with user-accessible bias test points and bias
control located on top of the chassis, adjacent to the output tubes. They can be accessed by
removing the rear panel of the amplifier.
Please see the diagram on pg. 12 to identify the controls and test points.
Bias Control: The bias control is a recessed slot adjustment (looks like a ¼” jack at first
glance), which can be adjusted with a normal flathead screwdriver.
Test Points (for use with standard multimeter probes):
•Ground 1, Black: Plug in negative multimeter probe here while measuring bias
for V5 and V6.
•V5, Red: Plug in positive multimeter probe to measure V5 output tube bias.
•V6, Red: Plug in positive multimeter probe to measure V6 output tube bias.
•Test points below are only fitted on 100 & 200 models:
•Ground 2, Black: Plug in negative multimeter probe here to check bias for V7
and V8.
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•V7, Red: Plug in positive multimeter probe here to measure V7 output tube bias.
•V8, Red: Plug in positive multimeter probe to measure V8 output tube bias.
Bias easuring & Biasing Procedure
hat is bias?
Simply put, bias refers to the idle current flowing through the output tubes. In fact, all tubes
need to bias, but in guitar amps the bias of the preamp tubes is permanently set and does not
need adjustment. Here we will be only discussing the measurement and adjustment of the
output tubes’ bias current.
CAUTION: Maladjustment of the bias controls can lead to output tube failure. The bias
adjustment is not fool-proof, and output tubes can be under-biased (i.e. too “hot”). The bias
control needs a wide enough range to accommodate different tube types and sets (tubes
vary from set to set), and therefore it is possible to under-bias the output tubes in some
cases. If under-biased for a sustained period, the output tubes will likely fail. Science
Amplification is not responsible for output tube failure due to maladjustment of bias
controls.
Please familiarize yourself with the bias procedure before making bias adjustments. If you
feel uncomfortable making adjustments, take the amp to a qualified technician. We do,
however, encourage you to bias yourself. It is easy once you get the hang of it, and can save
you quite a bit of cash!
WA NING: Adjusting the bias requires the amplifier to be ON. The output tubes adjacent to
the test points and adjustment control get very hot during normal operation and there is a
potential burn hazard. Be careful near those hot tubes!
Here are some situations where you may need to check and/or adjust the bias:
•You are changing tubes.
•You are changing tube type from EL34 to 6L6 or vice versa (applies to 50 and 100
models only).
•The amp is quieter than normal.
•The amp has a hum that is not affected by the setting of the Loudness control.
hat you’ll need:
•A phillips screwdriver to remove the amp’s back panel.
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•An electronic volt meter (a digital model is preferred) with a millivolt setting. These can
be found inexpensively and just about any one will do.
•A small to small flathead screw driver to adjust the bias control.
•A speaker cabinet to plug into.
Biasing Procedure
(Please reference the tube diagram on pg. 12)
easuring & Adjusting Output Tube Bias:
1. Use a phillips head screw driver to remove the rear panel of the amplifier.
2. ith a speaker cabinet plugged in, turn the amp to Standby, let it warm up for about 1
minute, then turn ON.
3. Set your multimeter to DC millivolts (mV).
4. Insert the negative/common test probe into the black test point (ground). On 100
and 200 models use the black test point that adjacent to the tubes you are
measuring.
5. Plug the positive probe into the red test point behind the tube you are measuring.
6. Take note of the reading on the meter.
7. Remove the probe from the red point, and repeat the procedure for each tube. On
100 and 200 models, move the negative probe to the other black test point nearest
the tubes you are measuring.
Your readings should be the same within 10 millivolts, which means the tubes are
reasonably matched. If a reading on a particular tube is below the safe/suggested
ranges (see below) by more than 10-15mV, then it's possible a tube has gone bad and
needs to be replaced.
Here are the bias settings/ranges for each tube type and model. Biasing on the lower,
“cooler” side will slightly increase headroom and tube life. Biasing higher, or “hotter”
will encourage quicker power tube distortion, but slightly decrease tube life. These
differences are very subtle, however.
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•50 & 100 model:
EL34: 30mV to 40mV
6L6: 36mV to 46mV
•200 model:
KT88: 25mV to 35mV
8. If adjustment is necessary, turn the bias control with the small flathead screwdriver
while monitoring the number on the multimeter to obtain the desiered setting.
Changing Output Tube Bias:
1. If ON, turn the amplifier OFF and wait for tubes to fully cool. To remove, gently grab
the plastic or metal base and pull upwards, using a very slight circular motion if
necessary.
2. Insert the new tubes, minding the “key” on the bottom of each tube so that it matches
with the socket.
3. Turn the bias control to minimum (All the way counter-clockwise).
4. Follow steps 2-7 from the “Measuring & Adjusting Output Tube Bias” instructions
above.
1. Turn the bias control clock-wise with a small screwdriver until you reach the desired
bias setting listed above and also on the Tube Chart & Bias Diagram on pg. 12
2. Allow tubes to idle for 15 minutes, then recheck bias and adjust if necessary.
Safety
•Always use a 3-prong cable into a grounded outlet. This makes sure the amplifier is
always grounded and safe during the rare occurrence the chassis should become "live"
(electrified).
•Tubes become very hot during normal operation. Allow them to cool before handling
to prevent burns.
•Never change tubes with the amplifier ON.
•Always make sure the amp's vents are open, allowing heat to escape and air to flow
freely.
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•Keep the amp away from moisture, and never put any beverages on top of the amplifier,
no matter how convenient it may seem!
•Only change fuses with the amp unplugged from the outlet!
•There are potentially lethal voltages present inside the amplifier. Do not open the
amplifier chassis unless authorized and are a qualified technician.
Limited Lifetime Warranty
Science Amplifiers are warranted to be free from defects in workmanship for the lifetime of
the original owner. Electronic components such as capacitors, resistors, transformers, jacks,
and potentiometers are warranted for 3 years (not including tubes, see below). Any part
determined defective by Science Amplification within the 3 year period shall be repaired or
replaced by Science Amplification without charge for parts and labor provided the unit is
returned and transportation costs prepaid. Science Amplification will pay return shipping
costs to the original owner. Any unauthorized repair, modification, or tampering voids this
warranty.
The warranty excludes:
•Normal wear and tear: worn out tubes, jacks, cosmetic damage, etc.
•Misuse and abuse: operating the amp without a speaker connected (although the amp
has some built-in protection against this), operating the amp into the wrong speaker
load, improper tube installation, using the wrong value fuses, maladjustment of bias
controls, etc.
•Accidental damage: Dropping the amp, spilling liquid inside, etc.
•Acts of "God”: Natural disasters and other non-preventable/foreseeable events that
damage the amplifier.
•Tubes, unless within manufacture's warranty period of 90 days (replacements offered
at manufacturer's discretion).
•Any damage caused by authorized or unauthorized repair or modification that is not
performed by Science Amplification.
For warranty service, please email [e-mail] for return authorization. Amplifiers
must be sent back in the original packaging or equivalent packaging. The cost of return
shipping to Science Amplification is to be prepaid by the owner. Science Amplification is not
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responsible for damage caused in return shipping. Science Amplification will pay for the
shipping back to the customer after the warranty work is completed.
In general, we will be able to fix your amp for free, and help with tube changes, etc. if needed.
e will also be happy to modify the amp in any way possible until the amp is perfect for you.
Non-warranty repair is also available – please inquire for shop rates.
Care and aintenance
Do not use household cleaning products. If control panels need cleaning, use only a soft clean
dry or damp cloth to wipe off smudges. To clean tolex, wipe with a damp cloth.
Periodically check the 4 mounting screws on the bottom to make sure they are tightened.
These screws secure the chassis to the head cabinet, and also insure contact to the aluminum
RF shielding plate inside the cabinet.
If possible, move the amplifier when the tubes have had the chance to cool down for a couple
minutes. Because the tubes get very hot, the elements inside become more vulnerable to
physical damage until the tubes have cooled. In general, try to move the amp off stage last.
Tube & Bias Diagram
Birds-eye view of the Street Sweeper's tube layout and bias controls:
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