Carvin FET1000 Instruction Manual - Page 39

FET Series Power Amplifiers About the FEY Series Amps Section 3 Speaker protection by the virtue of the MOSFETs negative temperature coefficient becomes a built in safety feature. However, Carvin has taken the FET Amp series one step further by incorporating our exclusive SpeakerGuardm' protection circuit that automatically removes any potentially damaging voltages from the speaker. Special high speed circuitry assures immediate disconnection of the load when a fault is detected. SpeakerGuardTm represents the best possible protection against speaker damage. Notable Advantages of the FET Series Amps We have discussed how MOSFET devices offer many significant advantages over conventional bipolar transistors. However, in addition to the advantages provided by the MOSFET devices themselves, the FET Series amps include innovations that further distinguish them as truly innovative even when compared to other high quality MOSFET amplifiers. Following are some of the engineering features that are incorporated into each FET series amplifier. They further ensure that you will receive performance without compromise from your new Carvin amplifier. Each FET amp is designed to perform well beyond the requirements of FTC power ratings. The FTC ratings specify very harsh operating conditions for home Hi-Fi amplifiers, but in our opinion are not tough enough to guarantee long term reliability for pro-sound applications. So we established more stringent test conditions for specifying output power ratings. We push the amps harder, and insist that they maintain adequate safety margins even when operated at extreme temperatures (such as might be encountered in a hot amp rack at a summer daytime concert). We also insist that the amplifiers operate continuously under heavy loads without reduced performance with respect to distortion. The FET series amplifiers feature heavy-duty linear power supplies with high current transformers and filters. The combination of these heavy duty power supplies with an extremely high current output amplifier allows these amps to drive low impedance loads without thermal stress. Carvin elected to use a linear power supply with massive iron core transformers instead of a "lighter" switching power supply because of the simplicity and reliability that a linear supply provides. These power supplies provide plenty of reserve energy for massive power bursts on low frequency transients. The output current capability of the FET amps is exceptional. Normally the FET 1000 amplifiers will deliver a continuous current of 23 amps when both channels are driven at full power into 4 ohm loads. However, the MOSFET devices used in the FET 1000 can safely deliver as much as 138 amps continuously. The FET series amplifiers are also short circuit protected. Shorted speaker cables (or intermittent shorts in cables) can kill some amplifiers but the FET series amplifiers will simply disconnect themselves from the load if a short exists. In order to resume operation just correct the cause of the short and turn the amp off for a few seconds and then back on. All FET amplifiers feature "turn on muting." This circuit mutes the output of the amplifier for approximately three seconds after the power is applied to the unit. This allows the amplifier (as well as gear feeding the amp) to stabilize before the output is connected to the speakers. FET amplifiers feature a thermally controlled fan. This circuit is unique in that it provides a continuously variable fan speed which responds according to the temperature of the unit. This means that as the amp is used, the fan speed will change smoothly to provide just the air flow required for the load, level and temperature conditions. This eliminates any thermal shock (as with fans that "switch on") and maintains the lowest fan setting that will meet cooling requirements. CAUTION: NEVER BLOCK INTAKE OR EXHAUST VENTS--KEEP A 3" MINIMUM CLEARANCE! Note: The advanced electronic fan speed control may not start the fan until the unit is warm. It is normal to hear a low level mechanical hum before the fan starts. 3-2