20 • 550x
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.
Most musical instrument amplifiers on the market today use steel for their chassis, which does not conduct heat as well as
aluminum. The 550x uses an all aluminum chassis and front panel because it has less impurities than steel, is less susceptible
to rust, and is a better conductor of heat. This results in the chassis acting as an additional 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 the 550x will get warmer than cases made out of steel.
The one 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 "idle" (without speakers plugged in and without play-
ing it). If your unit starts getting hot under these conditions, it may be over-biased. This situation should be attended to and can
be easily remedied in about 15 minutes by a qualified service technician. A power amp can become over-biased through con-
tinuous vibration or by any large jolt received in shipping, etc.
FINAL ENGINEERING SUMMARY
The two preamp gain stages utilize a specially-selected 12AX7A. The tone controls incorporate I.C.'s, and the power amp is
designed with extremely high quality bi-polar devices. Each type of device was chosen for its performance and reliability in the
application used. The front panel and chassis of the 550x are comprised of aluminum, because of its superior electrical and
thermal characteristics and light weight. All primary electrical components are U.L. approved, and SWR uses Beldon Cable for
all shielded wire. All units are assembled by hand and individually soundtested in the U.S.A. at our factory in Southern
California.
SUGGESTED SETTINGS
Содержание 550x
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