SWR Sound 350x - Manual (Page 18)

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 intro-
ducing 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 con-
duct 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 star ts 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 ser vice technician. A power amp can become over-biased through continuous 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 ICs, and
the power amp is designed with extremely high quality bi-polar devices. Each type of device was chosen for
its per formance and reliability in the application used. The front panel and chassis of the 350x are com-
prised of aluminum, because of its superior electrical and thermal characteristics and light weight. All pri-
mar y 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 factor y in Southern California.
SUGGESTED SETTINGS
The following page includes examples of tone control options for various styles of music. These settings are
intended for use as a starting point for dialing in your own individual sound, so feel free to make adjustments
based on your own playing style, instrument and speaker cabinet configuration. After you find combinations
you like, don’t forget to try adding in the SubWave™… as much as you feel is necessary.
16 • 350x OWNER’S MANUAL