|
Although
this model takes up only two rack spaces (3 1/2"), we recommend
you use a three rack space case. This will prevent the vents
on the top and bottom of your amplifier from being covered and
allow for natural cooling of the power section(s). NO FAN is
needed in this condition and you will not have to remove the
rubber feet. If you still would like to remove the feet, REPLACE
the screws as they help to hold on the bottom of the amplifier
- THIS IS VERY IMPORTANT!
The
SM-400 should be mounted as close to the bottom of the rack
case as possible. The height of the rubber feet have been chosen
so that when you slide the unit in the bottom of the rack case,
the rack mounting holes on the front panel should line up with
the mounting holes of the rack rail. This prevents the SM-400
from flexing downward if the rack case is dropped. If you must
mount the SM-400 in the middle of the rack, a piece of wood
or similar material should be installed between the bottom of
the rack case and the bottom of the amplifier to prevent flexing
of the amplifier's chassis. Severe or constant flexing of the
chassis can cause the main chassis to crack and could void your
warranty.
MAKE
SURE ALL VENTS ARE UNOBSTRUCTED WHEN INSTALLING YOUR SM-400
IN A RACK CASE. THIS WILL ALLOW FOR COOL AIR TO COME IN AND
HOT AIR TO ESCAPE.
If
you should have any other questions that are not answered in
the owner's manual, feel free to email or call the factory (818)
253-4SWR at anytime.
GENERAL
INFORMATION AND DESCRIPTION
The
SM-400 Bass Amplifier provides the power, performance, flexibility
and portability needed by the professional bass musician for
every style of playing and nearly every situation he/she will
encounter.
To
accomplish our goals, we had to use almost every imaginable
type of electronic component available. This added up to an
all TUBE preamp section, a limiter using Field Effect Transistors,
tone and equalizer controls utilizing Integrated Circuits and
two individual power amps employing discreet, solid state devices.
The
power amplifiers in the SM-400 can be used individually to provide
full bi-amp capabilities when used with the built-in adjustable
electronic crossover or can function as stereo, 200 watt power
units. If you need more power, the amps can be bridged for 400
Watts @ 8 ohms or 420 watts @ 4 ohms.
Front
panel features include Hi and Low Gain input jacks, Gain and
Master Volume controls, Integral Limiter and an exclusive feature
we call an Aural Enhancer. Tonal flexibility is achieved with
Bass and Treble controls and a 4 band Variable Graphic Equalizer.
The Crossover Frequency Control adjusts the crossover points
of the electronic crossover and the Balance control adjusts
the levels of the two power amps when used in the stereo mode.
The
back panel features and XLR Balanced Out switchable for direct
and line out, Crossover High and Low Frequency Output jacks,
and Mono and Stereo Effects loops. A power amp assign switch
selects stereo or bridge mode and for speaker outputs, there
are two jacks each for left and right out or one banana jack
for mono operation.
The
SM-400 is rack mountable, taking up two rack spaces (3 1/2")
by 11 3/4" deep. It is housed in an all aluminum chassis
for light weight and lasting beauty and weighs just over 18
pounds. It is easily carried by the handles secured to the front
panel.
The
tube employed in the preamplifier is a specially selected 12AX7
and should not need replacing for one to three years depending
on usage and care of your unit.
We
truly hope you enjoy your amplifier and find it all you have
ever wanted in a bass amplifier and more. If you ever have any
questions or suggestions, please don't hesitate to call or email
us at the factory.
FRONT
PANEL FEATURES
HI
AND LOW GAIN INPUT JACKS
Both inputs accept a standard 1/4"
phone plug and both inputs can be used at the same time. Since
the two inputs are totally independent, no loss in volume or
tone will occur if two instruments are used simultaneously.
Keep in mind, however, that the Hi Gain input has five times
more gain than the Low Gain input.
GAIN
CONTROL AND PREAMP CLIP LED
The Gain Control adjusts the volume of
the preamp section. After tone controls, Variable Graphic Equalizer
and Limiter are set to your liking, the Gain Control should
be set to where the Preamp Clip LED barely flashes upon striking
your loudest note. Now adjust the Master Volume to the desired
volume level. Utilizing these controls in this manner assures
the user of maximum signal to noise ratio with no distortion
caused by the preamp circuits "clipping".
The
Preamp Clip LED will light if any portion of the preamplifier
reaches clipping or runs out of headroom. This can be caused
by the Gain Control being set too high or any tone or Equalizer
Control set in a high boost position. To correct this condition,
turn down one of the previously mentioned controls.
Note:
The Preamp Clip LED indicates that at some point the preamplifier
is clipping. No harm is being done to your amplifier but,
CLIPPING OF THE POWER AMPLIFIER CAN CAUSE DAMAGE TO YOUR LOUDSPEAKERS
AND IS NOT RECOMMENDED!
LIMITER
The Threshold Control sets the level at
which limiting begins to take effect. At that point the LED
will light. Maximum limiting will occur with the Threshold Control
set in the Maximum position. The limiter is
completely out of the circuit with the Threshold Control set
in the Minimum position. Loss in volume caused by extreme limiting
can be overcome by increasing the Master Volume control.
Note:
If the Threshold is set at maximum and still no limiting effect
occurs, the Gain Control is set too low and should be increased
to a desired level.
AURAL
ENHANCER
The Aural Enhancer was developed to help
bring out the fundamental notes of the bass guitar and give
a resulting frequency response similar to that used for recording
the bass in the studio. This effect becomes more radical as
the control is turned to maximum. The result is a more "transparent"
sound and is especially noticeable with a slap style technique
of playing.
BASS
CONTROL
The Bass Control is a shelving type tone
control that cuts or boosts the lower or bass frequencies from
mid-position. Starting at mid-position, turning the control
counter-clockwise cuts the bass response and turning the control
clockwise boosts the bass response.
VARIABLE
GRAPHIC EQUALIZER
Level
Control
The Level Control cuts or boosts the frequency
set by the Frequency Control directly beneath it. It is used
in the same manner as a Graphic Equalizer. Starting at mid-position
moving the slider towards +15 boosts and moving the slider towards
-15 cuts that particular frequency.
Frequency
Control
The Frequency Control select the center
frequency that will be cut or boosted by the Level Control directly
above it. If The Level Control is as "0" or mid-position,
moving the Frequency Control will have no affect on the sound.
The Frequency Control covers a three octave range.
To
better understand how the Level and Frequency Controls work
with each other, try the following example:
1.
Set the Gain and Master Volume Controls for listening level.
2. Set all tone and level controls at mid-position and turn
all frequency controls full counter-clockwise.
3. Strike the open "E" string on the bass and move
the Level Control on the first band of your Equalizer to +15
(the Frequency Control should be set at 40 Hz which is the fundamental
that the open "E" string produces). The change in
sound and pressure levels is a result of the fundamental "E"
note being increased by approximately 15db.
4. Keeping all controls in their present positions (Level Control
at +15 and Frequency Control at 40 Hz) strike your open "E"
string again and move the Frequency Control from 40 Hz to 160
Hz.
As
the Frequency Control is moved from 40 Hz to 160 Hz you should
hear two increases in volume. The first will be at 80 Hz or
your first overtone (harmonic) and the second will be at 160
Hz or the second harmonic of your open "E" string.
From
the above example a few things come to mind. One, there's a
lot of information contained in one note on your instrument.
Two, if one position of the Frequency Control give a much louder
sound or volume, you may have found the area of greatest efficiency
of your speaker cabinet. And, three, the tonal variations you
can achieve with the Variable Graphic are just about infinite!
TREBLE
CONTROL
The Treble Control is a shelving type
tone control that cuts or boosts the high frequencies. Starting
from mid-position, turning the Treble Control counter-clockwise
cuts the highs and turning the control clockwise boosts the
high frequencies.
MASTER
VOLUME
The Master Volume controls the volume
of the internal power amplifiers, the level at the crossover
high and low jacks, the effects send jack and the XLR out jack
when switch in the "line" position. It should be used
in conjunction with the Gain control to achieve maximum signal
to noise ratio.
CROSSOVER
FREQUENCY
The Crossover Frequency sets the crossover
point or dividing point of the "High" and "Low"
jacks. For example, if the Frequency Control is set at mid-position
or 500 Hz, all frequencies below 500 Hz will appear in the "Low"
output jack and all frequencies above 500 Hz will appear at
the "High" output jack.
If
you are still confused on how to set the crossover point, you
can refer to the owner's manual that should come with your speakers.
Another reference, which is probably best, is your own ears.
Once you have correctly set up the system, rotate the Crossover
Frequency control until the sound seems balanced or simply,
just sounds the best!
Crossover
slope is 12db per octave.
BALANCE
When the SM-400 is used in the stereo
mode, the Balance control sets the levels of the left and right
channels with respect to each other. Rotating the Balance control
to the "l" or left, cuts the level of the right channel
and vice-versa.
If
you are running your system in the bi-amp mode, and you have
selected the left channel for the low frequencies and the right
channel for the high frequencies, adjustments can be made as
follows:
BALANCE
CONTROL
More lows and less highs can be accomplished
by rotating the Balance control counter-clockwise (towards the
left). More highs and less lows can be accomplished by rotating
the Balance control clockwise (towards the right).
POWER
SWITCH
Moving the Power Switch to the "On"
position will turn on you amplifier as indicated by the LED
lighting.
REAR
PANEL FEATURES
BALANCED
XLR OUT
The Balanced Out is a true balanced output
and serves two functions. In the "Direct" position,
the Balanced Out serves as a direct box and can be used for
recording or patching into a house P.A. System. No controls
on the front or back panel affect the signal appearing at the
XLR connector except the "XLR Pad." In the "Line"
position, all controls on the front and back panels control
the signal appearing at the XLR connector and the level is set
by the Master Volume.
The
"Line" position can be used for recording directly
into a tape machine as well as going directly to the studio
board. An external power amplifier with a balanced input can
be driven in the "Line" mode.
Pin
out for the XLR connector are as follows:
Pin 1 = Ground Pin 2 = + Pin 3 = -
For
a few dollars, you can buy an AC wall socket tester. A light
comes on if the AC socket has been wired correctly. We recommend
having one of these if you value your equipment.
HIGH
AND LOW OUT JACKS
The Crossover "High" and "Low"
out jacks have been provided for bi-amping capabilities. Present
at the "Low" jack are all frequencies below the point
set by the Frequency Control. Present at the "High"
jack are all frequencies above the point set by the crossover
or Frequency Control. All patching from these jacks should be
done with shielded cable.
HIGH
AND LOW OUT JACKS
Using the SM-400 for Bi-Amping Using high
quality shielded cable, run a patch from the "Low"
out jack into the "Left" stereo effects return jack
and a patch from the "High" out jack to the "Right"
stereo effects jack. Next, make sure the Power Amp Assign switch
is in the "Stereo" position. Now, hook up your low
frequency speakers to the "Left" speaker output jack
and your high frequency speakers to the "Right" speaker
output jack. Correct levels or balance between highs and lows
can be achieved with the "Balance" control located
on the front panel.
The
SM-400 can be used for amplifying just the low or high frequencies!
To accomplish this, run a patch from either the high or low
crossover out jacks to the "Mono" effects return.
Switch the Power Amp Assign switch to "Bridge" and
use the banana jack for your speakers.
EFFECTS
The Effects Loop is provided for use with
any external effect such as a Chorus or Stereo Flanger, etc.
Using the Effects Loop lowers the noise heard at the speakers
generated by the effects unit. The output and input impedances
seen at the "Send" an "Receive" jacks were
designed to give optimum performance from effects units both
new and old.
If
you have a mono effect, run a shielded cable from the "Send"
jack to the input of the effects unit and another from the output
to the "Return Mono" jack. If a stereo effects unit
is used, run separate cables from the left and right outs of
the effects to the "Left" and "Right" return
jacks on the SM-400.
The
patching capabilities incorporated in the SM-400 are nearly
limitless. However, in some cases, wiring should be done by
a qualified technician. If you have any definite needs or questions,
please contact the factory for assistance.
POWER
AMP ASSIGN SWITCH
If you wish to run your amplifier in the
stereo mode, move the Power Amp Assign Switch to the "Stereo"
position. Operation in the bridge mode is achieved by the Power
Amp Assign Switch being in the "Bridge" position.
The
position of the Power Amp Assign Switch will be determined by
the way you wish to use the SM-400 or the impedance of the cabinets
you intend to use. If you don't find the information you need
in this owner's manual, please contact the factory for assistance.
LEFT
& RIGHT SPEAKER FUSES
The left and right speaker fuses are provided
to protect your speakers in the unlikely event of a power amp
failure or incorrect hook-up procedures. Size and rating of
the fuses are 3AG, 8 AMP, Fast Blo. Do not defeat the purpose
of this feature by using a higher rated fuse.
The
speaker fuses can open if there is a fault in the speaker cable
or the speakers themselves. Therefore, it is always wise to
carry extra fuses at all times.
SPEAKER
OUTPUT JACKS
When used in the stereo mode, the internal
power amplifiers of the SM-400 will deliver 300 watts @ 2 ohms,
240 Watts @ 4 ohms and 140 Watts into 8 ohms. Optimum performance
will be achieved by using a total of 4 ohms per channel. When
using 2 ohms loads, the amplifier will run hotter than normal.
Minimum load in the stereo mode is 2 OHMS!
When
used in the Bridge mode, the SM-400 will deliver 250 Watts into
16 ohms, 400 Watts into 8 ohms and 420 Watts into 4 ohm loads.
Make sure the speakers you use in this mode can handle the power.
Minimum load in the bridge mode is 4 OHMS!
LEFT
& RIGHT SPEAKER JACKS
The Left and Right speaker jacks are provided
for use in the Stereo Mode only. DO NOT use these jacks when
the SM-400 is switched to the Bridge Mode. Balance between left
and right channels can be obtained by using the Balance Control
located on the front panel. Make sure all speakers are hooked
up BEFORE turning on the SM-400. Never plug or unplug your speakers
while the unit is on. Always use speaker cable
(not shielded cable such as used for patching or your instrument)
of an 18 gauge rating or heavier. The heavier the wire, the
lower the gauge.
BANANA
JACK
The Banana jack is provided for use in
the Bridge Mode only. A six foot speaker cable is provided with
each unit for your convenience. Optimum performance from the
SM-400 will be obtained by using an 8 ohm speaker cabinet. More
than one cabinet can be used in the Bridge Mode by stacking
banana jacks. You can stack the banana plugs coming straight
out of the banana jack on the amp (Most banana plugs are made
so that you are able to plug one into the rear of the other).
Then connect the 1/4" ends to each respective speaker enclosure.
If you have any questions in this area, please consult the factory
for assistance BEFORE experimenting. Make sure all hook ups
are complete before turning the unit on.
Note:
The frequency response of the SM-400 is far greater than usually
found in musical instrument amplifiers (10 Hz to 40K Hz). This
is done to give the bass player the same punch and clarity on
stage as found in the studio or concert P.A. Systems. Therefore,
it is doubly important that the user be aware of the impedance
and power rating of the speakers they intend to use and that
they are compatible with the SM-400.
LINE
OR MAINS FUSE
The size and rating of the Line Fuse is
3AG, 7 Amp, Slo Blo. NEVER replace this with a fuse of a higher
rating as it will void your warranty.
INTERNAL
FEATURES
VACUUM
TUBE (VALVE)
As stated earlier, SWR installs a specially
selected 12AX7A dual triode from Groove Tubes. If this tube
needs replacing, we recommend you replace it with a similar
high quality product. This tube will need replacing only if
it becomes noisy or microphonic (sounds like glass tinkling
in the background of certain notes), or completely fails causing
no signal.
CONCERNING
CHASSIS HEAT
One
of the most asked questions about our amplifiers is why they
tend to get warmer than other amps. The chassis of your amplifier
can get quite warm during normal usage. This is especially true
if you are using a 4 ohm total impedance in the Bridged mode.
This is because a 4 ohm impedance (or 2 ohms per channel in
the Stereo mode) introduces the least efficient condition of
the unit (ie: power drawn from the outlet in relation to power
produced in the speakers). The difference in these two figures
can be as high as 300 Watts. This would be the equivalent of
putting a 300 Watt light bulb inside a metal box which would
obviously get quite hot.
Most
musical instrument amplifiers on the market today use steel
for their chassis which, in most cases, is considerably cheaper
than aluminum and does not conduct heat as well as aluminum.
SWR uses all aluminum chassis because they have less impurities
than steel, are less susceptible to rust and it is a better
conductor of heat. This results in the chassis acting as a heatsink
drawing heat away from heat producing components inside and
thus extending their life. In this manner, we feel we have produced
a more reliable amplifier, but, at the same time, the outside
of our units will get warmer than cases made out of steel.
The
only condition you should be aware of is if one or more of the
power amplifiers in your unit becomes "over biased."
This condition can be recognized by turning your amplifier on
and letting it sit without speakers plugged in and without playing
it. If, under these conditions, your unit becomes quite warm,
it may be over biased. This situation should be attended to
and can be easily remedied in about 15 minutes by a service
tech. A power amp can become over biased through continuous
vibration or by any large jolt received in shipping, etc.
NOTE:
UNITS MANUFACTURED AFTER SEPTEMBER, 1993 AND HAVING A SERIAL
NUMBER GREATER THAN #6125 HAVE AN INTERNAL COOLING FAN.
Back
to Products
|
