Rack Mounting Instructions - SWR 350x Owner's Manual

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 signal at very low levels). The tube in your 350x
should last one to three years, depending on usage.

RACK MOUNTING INSTRUCTIONS

RACK MOUNTING INSTRUCTIONS
To preserve the beauty and reliability of your amplifier, we recommend that you install your amplifier in a rack
case. The 350x is completely ready to be rack mounted and needs no additional parts or accessories other
than the rack screws and the case itself.
The 350x takes up two full rack spaces (3 1/2"). If the rack in which you mount your 350x 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 350x should be mounted as close to the bottom of the rack case as possible. If you must mount the
350x 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 chassis 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 350x and with your rack case rails. We recommend
that at least once a month you remove the 350x 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 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 350x at a 2 or 2.6 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 obviously 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 350x 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 350x 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 playing 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 continuous vibration or by
any large jolt received in shipping, etc.
FINAL ENGINEERING SUMMARY FINAL ENGINEERING SUMMARY
The two preamp gain stages utilize a specially-selected 12AX7A. The tone controls incorporate ICs, 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 350x 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.
350x OWNER'S MANUAL • 15