SWR Sound 350x A Few Words Concerning Heat, Final Engineering Summary, Suggested Settings

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 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

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 com- prised of aluminum, because of its superior electrical and thermal characteristics and light weight. All pri- mary 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

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