22 • 550x
INTERNAL FEATURE: VACUUM TUBE (VALVE)
SWR installs a specially selected 12AX7A dual triode on the preamp circuitboard of every 550x. If this tube needs replacing,
we recommend that you replace it with a similar high quality product. This tube will need replacing only if it becomes noisy or
microphonic (which sounds like glass tinkling in the background of certain notes), or completely fails (causing no signal or sig-
nal at very low levels). The tube in your 550x should last one to three years, depending on usage.
COOLING FAN
The power amp in your 550x is cooled by two methods: 1) an internal extruded aluminum heatsink; 2) an internal fan. This fan
runs constantly to ensure proper cooling of the amplifier at all times and cannot be defeated. Be sure to leave at least a 1/2"
clearance between the vent on the sides of your 550x and the sides of any rack case or enclosure in which you install your
amp. This will allow for the heat generated by internal components to escape. SWR also recommends at least one empty rack
space in your rack to allow for the best possible airflow.
NOTE: It is normal for the cooling fan to be audible at low levels. In situations where absolute quiet is
necessary (such as in a recording studio when a cab is being miked), simply place the amplifier in a
separate room from the microphone being used for the speaker cabinet.
RACK MOUNTING INSTRUCTIONS
To preserve the beauty and reliability of your amplifier, we recommend that you install your amplifier in a rack case. The 550x
is completely ready to be rack mounted and needs no additional parts or accessories other than the rack screws and the
case itself.
The 550x takes up two full rack spaces (3 1/2"). If the rack in which you mount your 550x requires that the rubber feet on the
bottom of the chassis be removed, please remember to keep the screws handy in case you wish to reattach the rubber feet
at a later date.
The 550x should be mounted as close to the bottom of the rack case as possible. If you must mount the 550x in an area of
the rack other than the bottom space, a piece of wood or similar solid 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 chas-
sis can damage the amplifier and is not covered under the warranty.
Please do not forget about your amp after it has been installed in a rack case. Continuous transportation and vibration can
cause screws to become loose, both on the 550x and with your rack case rails. We recommend that at least once a month
you remove the 550x from the case and tighten all outside screws and wipe off the outside of the chassis with a damp cloth.
Then check all the connections in your rack case and reinstall the unit.
A FEW WORDS CONCERNING 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 operating your 550x near maximum poten-
tial at a 4 ohm total impedance. This is because these low impedances are introducing the least efficient condition of the unit
(in terms of 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 obvi-
ously get quite hot.
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