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The
front panel features include, for each channel, a four segment
dot display indicating headroom, separate volume controls and
an on/off switch. The back panel features include separate balanced
and unbalanced inputs for each channel, a ground lift switch
for the balanced inputs, a stereo/bridge switch, and individual
slave outputs for each channel so that several power amps may
be driven from a single signal source. Speaker outputs include
two 1/4" phone jacks, one banana jack and one speaker protection
fuse for each channel. Also included on the back panel is an
external line (mains) fuse.
After
the initial design was completed in May, 1991, we spent the
following months testing and improving reliability, noise, power
bandwidth, and distortion for use in sound reinforcement, studio
and stereo systems. For use with musical instruments, we made
sure it gave the immediate and full response needed for all
instruments played by real musicians in the real world. Another
parameter important to musicians is the characteristics of an
amp when driven into clipping or saturation. The Stereo 800
sounds very smooth under this condition with no unwanted chirps,
whistles and crackling (unless
your speaker produces them mechanically). Remember that constant
clipping of any power amplifier can eventually damage loudspeakers
of any wattage rating.
Part
of the process we used to insure reliability was to heat up
the power module to over 100 degrees centigrade (yes, we boiled
water droplets) then turned the unit off, then on again with
a signal that drove the amplifier well into clipping. We have
done this at least 17 times with our original prototype and
it still works perfectly. It was after these tests that we added
a thermostatically controlled fan to insure thermal stability
under any circumstance we could think of.
As
a historical note, the first "production" unit was
shipped overnight to New York for use by Rob Wasserman touring
with Lou Reed. After several hours of rehearsing with the Stereo
800, they compared it to the power amp they used on the last
tour. Rob and the sound tech felt the Stereo 800 was superior
to the competition to the extent they ordered a second Stereo
800 as a back up rather than use the other unit.
RACK
MOUNTING TIPS
If you intend to rack mount your Stereo
800, be sure that after installation that neither of the vent
holes on the sides are obstructed. When the fan is in operation,
air flows in the unit from the right side (when facing the front
panel) and exits from the left side. Try and allow for at least
one inch of clearance between the inside of the rack case and
the outside of the Stereo 800.
The
rubber feet on the bottom of the Stereo 800 were chosen so that
the unit may be installed in the bottom position of most racks
without having to remove them. In this manner, the rubber feet
can act as a shock absorber if the rack is dropped upright.
If you need to remove the rubber feet, unscrew the feet with
a #2 phillips screwdriver, remove the foot from the screw, and
REPLACE THE SCREW IN THE VACANT HOLE. This is VERY IMPORTANT
as the screws help to hold the bottom panel assembly to the
main chassis. Mechanical damage can occur to your amplifier
if these screws are not in place.
If
you intend to mount your Stereo 800 in a position other than
the bottom of the rack, we recommend supporting the rear of
the unit. This can be done by securing a block of wood or metal
bracket to the inside of the rack case in such a position that
it acts as a "shelf" for the rear of the unit to rest
on. Although we added an additional steel support bracket near
the rack ears of the Stereo 800, a rack that is dropped from
a couple of feet can cause the unit to flex at this point and
distort or even crack the chassis.
Once the unit is installed in the rack case, don't forget that
your amplifier will be subject to vibration from music and transportation.
For this reason, you should periodically remove your Stereo
800 from the rack case for cleaning and making sure all external
screws are tight. Remember, nobody needs a loose screw!
ELECTRICAL
CONSIDERATIONS
In a rack system with a large power amplifier
such as the Stereo 800, placement of effects units and preamplifiers
with respect to the power amplifier may be important as hum
induction may occur. Generally speaking, install a preamplifier
so that it is farthest away from the power amplifier with line
level effects units, tuners, etc., in between. Whenever possible,
leave an empty rack space between the power amplifier and other
accessories in the same rack.
All
patch cords should be made as short as possible using high quality
shielded cable and plugs. Placement of patch cables should not
run next to AC power cords and should not be routed in-between
different components. In other words, do not run a patch cable
from the front of a preamplifier over the top or under the bottom
and then to the rear input of a power amplifier. This can also
cause hum in the system. If you must run patch cables in this
fashion, experiment with the routing so that ideal placement
is achieved.
Another
consideration in a rack system is a ground loop caused by the
chassis' of several pieces of equipment electrically "tied"
together by the metal rack rails. Some equipment is built with
this situation in mind, such as the Grand Prix Preamp from SWR.
It comes with an option of separating certain electrical grounds
from chassis earth grounds thus isolating the chassis from the
inner workings. This method is far superior than that of using
a three prong to two prong adapter on your AC cord. These adapters
"lift" the earth ground from your chassis and could
make for an unsafe condition. If you are experiencing a system
grounding problem (each piece of equipment works good by itself,
but connecting them together causes undesirable hum), and using
a ground adapter on one piece of equipment solves the problem,
consult the manufacturer of that piece of equipment to see if
there is a way to isolate the secondary grounds from the primary
or chassis earth ground.
The
fuse ratings for the AC line fuse, internal fuse and speaker
fuses were selected so that they would blow (open) quickly under
adverse conditions. If, for some reason, outside testing is
done for maximum power readings, especially in the bridge mode,
one of these fuses may open NOT due to any electrical problem.
The fuses will not blow under normal use with music sources,
but it is always wise to have spare fuses on hand. Refer to
the Speaker fuse and Line fuse section of this manual for proper
size and ratings.
We
sincerely hope that the Stereo 800 exceeds your expectations
in the area for which it was chosen.
FRONT
PANEL FEATURES
RACK
HANDLES
The rack handles were chosen to comfortably
carry your Stereo 800 from place to place. They will also protect
the front panel controls in the event the unit is dropped on
its face. In some type of racks, the handles may need to be
removed before installation. The handles may be removed by the
four screws holding them to the front panel.
VOLUME
CONTROLS
Individual volume controls are supplied
for both the left and right channels. The Volume control affects
the amount of signal driving the power amplifier. With the knob
indicator in the full counter-clockwise or "min" position,
turning the control clockwise will gradually increase the level
the power amp sees and thus increase volume. In most cases,
we suggest you run the Stereo 800 with the volume controls set
near maximum and control the level from your signal source (i.e.
preamplifier, console, etc.). This will result in less knobs
to worry about and insure repetitive gain structures. In any
event, always keep an eye on the dot bar display to make sure
the Stereo 800 is not being over driven (+3 red LED continuously
lighting) as this can result in damage to your speakers due
to DC content in a clipped wave-form. Turning down the Volume
control will alleviate this situation.
FOUR
SEGMENT DOT BAR DISPLAY
Each channel of the Stereo 800 has its
own dot bar display. The Dot Bar Display can be thought of as
a "headroom" indicator whose markings are in dB increments.
For example, running the Stereo 800 with the "0" yellow
LED lighting on the musical peaks or transients gives the user
a maximum of 3db of headroom available before the amplifier
reaches clipping or maximum undistorted power as indicated by
the following red LED marked +3. The user has reached maximum
power from the Stereo 800 when the red LED is activated. Running
the Stereo 800 with the +3 LED lighting continuously will not
harm the power amp but can eventually harm your loudspeaker
components.
When
the Stereo 800 is used in the Bridge or mono mode, both Dot
Bar displays will be operational.
POWER
ON/OFF SWITCH
Pushing the ON/OFF switch to the top position
will activate the electronics in the Stereo 800 as indicated
by the red LED being lit.
REAR
PANEL FEATURES
INPUTS
NOTE:
IF YOU INTEND ON USING THE STEREO 800 IN THE BRIDGE MODE, YOU
MUST USE THE BALANCED OR UNBALANCED LEFT CHANNEL INPUT ONLY.
BALANCED
INPUTS
Electronically balanced inputs are provided
for each side of the Stereo 800. Input impedance for the balanced
input is 10K ohms. Maximum input level is 8 volts RMS.
Pin
out for the Balanced inputs is:
Pin 1 = ground Pin 2 = + Pin 3 = - (American standard)
GROUND
LIFT
A ground lift is provided for the Balanced
inputs. In the normal (out) position of the push switch, pin
1 on the XLR connector is grounded. In the Lift (in) position,
the ground on Pin 1 is disconnected. When using the Balanced
inputs, always be aware of the position of the ground lift switch.
This function does not affect the unbalanced inputs.
UNBALANCED
INPUTS
One unbalanced input is provided for each
channel of the Stereo 800. This input utilizes a 1/4" standard
phone jack. Input impedance for the unbalanced input is 33K
ohms. Maximum input level is 16 volts RMS.
STEREO/BRIDGE
PUSH SWITCH
The Stereo/Bridge switch selects the mode
you wish to operate your Stereo 800. Check the position of this
switch each time you operate the Stereo 800 to be sure it is
in the desired position. In the Stereo (out) position, the Stereo
800 operates as any stereo power amplifier. If you have a stereo
source, run two shielded patch cables from the left and right
outputs of the source (preamp, electronic crossover, etc.) to
the left and right inputs of the Stereo 800. Use the appropriate
Volume controls on the front panel to set individual levels.
Use the stereo speaker output jacks for your loudspeaker hookups.
To
operate the Stereo 800 in the Bridge/Mono mode, the Stereo/Bridge
switch should be in the "IN" position. In this mode,
one set of banana jacks are provided for your speakers. These
are the top two jacks indicated + and - on the back panel in
the "speaker outputs" section. Next, make sure your
signal source is connected to one of the LEFT speaker inputs
(balanced or unbalanced). The volume in the Bridge mode in controlled
by the Left volume control on the front panel. Any signal source
plugged into the Right inputs will not be heard through your
speakers.
CAUTION!!
Be sure that the speakers you connect to the Bridge output can
handle the wattage delivered by the Stereo 800. Under clipping,
the Stereo 800 delivers a MINIMUM of 700 Watts RMS @ 8 ohms
and 800 watts RMS @ 4 ohms. We recommend consulting the manufacturer
of your speaker system if you are unsure BEFORE using them in
this mode.
SLAVE
OUTPUTS
Left and right Slave outputs are provided
in the event you want to "daisy chain" more than one
power amp at a time. To use the slave output(s) to run an additional
power amp, run shielded patch cords from either or both the
left and right slave outputs to the inputs of the additional
power amp(s). The Volume controls on the Stereo 800 DO NOT affect
the level of the Slave outputs.
If
you have a mono signal source and wish to run the Stereo 800
in the stereo mode, plug your signal source in the left channels
balanced or unbalanced input. Now run a short shielded patch
cable from the LEFT slave output to the RIGHT channel unbalanced
input. Make sure the Stereo/Bridge switch in is the out (stereo)
position.
The
Slave outs can also be used as an unbalanced record out or a
monitor send.
SPEAKER
OUTPUT SECTION
RIGHT
AND LEFT SPEAKER FUSES
The left and right speaker fuses are provided
to protect the power amplifier from faulty speaker cables, improper
loads or hookup procedures. They will also protect your speakers
in the unlikely event of a power amp failure. Proper size and
rating of the speaker fuses is 3AG (physical size), 10 amp fast
blo. Depending on the load, a large transient or spike sending
the power amp well into clipping could cause the speaker fuse
to open (blow). It is always wise to carry extra speaker and
line fuses with you at all times.
Do
not defeat the purpose of this feature by using a fuse of a
higher amperage. It can only cause more misery if a fault lies
in the system.
RIGHT
AND LEFT STEREO SPEAKER JACKS
Two 1/4" phone jacks and one banana
jack is provided per channel for speaker hookups and connections.
Your speaker cable should be made with a minimum of 18 gauge
wire or heavier (the heavier the wire, the LOWER the gauge).
When hooking up several speakers, especially if your using the
banana jacks, always double check to make sure all speakers
are in phase. Two (or more) speaker cabinets out of phase with
each other will cancel and cause a tinny sound with no body.
If you are suspicious of phasing, unplug one cabinet. If one
cabinet sounds louder than both together, chances are they are
out of phase. At this point, check the connections of your phone
jacks and/or the polarity of the banana jacks.
Minimum
load per channel on the Stereo 800 is 2 ohms. This is the equivalent
of 2- 4 ohm cabinets, or 4- 8 ohm enclosures. In the STEREO
mode, the Stereo 800 will work on all loads from two ohms to
infinity (no speakers at all, which is how your parents would
probably prefer it). Therefore, you may operate the Stereo 800
using the speaker outputs of just one channel and not the other.
In the MONO/BRIDGE mode, minimum load is FOUR (4) ohms. If you
try and use a load of less than 4 ohms in the bridge mode, one
or more of the protection fuses will probably blow (open).
In
the STEREO mode, and as indicated on the back panel, the banana
jacks should be used in the vertical positions (+ or hot being
on the top, ground or negative being on the bottom. In the BRIDGE
mode, use the top two banana jacks (horizontally). Plus (+)
polarity is on the left and minus (-) is on the right. Once
again, this is all indicated on the rear panel. The two bottom
banana jacks are NOT used in the bridge mode.
CAUTION:
As mentioned under the Stereo/Bridge switch section, each time
you use your Stereo 800, check the position of this switch (out
for stereo, in for bridge). With speakers plugged into the bridge
output and the switch in the stereo mode, essentially shorts
out both power amps and may result in one of the speaker fuses
opening. Speakers plugged into the stereo outs with the switch
in the bridge position will cause the left and right channels
to be out-of-phase with each other causing your Stereo 800 to
sound like a cheap transistor radio.
A/C
(MAINS) FUSE
This fuse is provided to protect the amplifier
from possible power surges, improper use, etc. It can also open
if there is a fault within the amplifier. If, when you turn
on the power switch, the red LED does not come on, check the
condition of this fuse. Proper size and rating of the AC fuse
is 3AG (physical size), 8 amp slo blo.
Do
not defeat the purpose of this fuse by using a fuse of a higher
amperage rating.
A/C
LINE CORD RECEPTACLE
Accepts a standard A/C power cable (supplied
with the Stereo 800), used with almost all current musical,
professional and household electronic devices. We recommend
taking great care when packing up. If you disconnect the AC
cord from your amplifier, put the cable in your instrument case,
accessory case, etc. If it does become misplaced, replacement
will be easy at almost any appliance store, super market or
the like.
PLEASE
NOTE: the rating for this cable is 3 conductor, 10 amperes minimum.
This is a rating of the current capacity of the cable, designated
for higher power-drawing devices like amplifiers. If replacement
is necessary, or if you wish to buy a longer cable, look for
the rating on the cable and be sure it is at least 10 amps.
CAUTIONARY
ADVISEMENTS:
CAUTION:
TO PREVENT ELECTRIC SHOCK. DO NOT OPEN THE CHASSIS OF THE STEREO
800. NO USER SERVICEABLE PARTS INSIDE. REFER SERVICING TO QUALIFIED
SERVICE PERSONNEL.
WARNING:
TO PREVENT FIRE OR SHOCK HAZARD. DO NOT EXPOSE THIS APPLIANCE
TO RAIN OR MOISTURE.
CAUTION:
TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK HAZARD, REPLACE
ALL FUSES WITH THE SAME TYPE OF FUSE AND RATING.
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