My recently purchased audio amplifier is now toast. Why? Did I mess up; or is this just a bad amplifier?
While conducting a test run on my new audio amplifier (used in "mint condition"), using a signal generator as input, the smell of smoke filled the air. This was on the third run, using purely resistive loads: 8 Ohm, 4 Ohm, and finally 2 Ohm. Power measured was significantly lower than specification, at full gain/power: all power leds lit up, but the clipping led did not. My resistor, a heater element, did not heat up noticeably. The amplifier maintained 100% gain for a minute or two, prior to failing. The amplifier's 10 Amp fuse did not blow (marked 8 Amps on the rear panel). Visual inspection of the amp revealed at least 3 burned out resistors on one channel. Trying out the second channel, I found it no longer puts out any signal/power (verified with oscilloscope).
SetupThe signal generator output was via BNC/alligator clip leads. The amplifier Channel A audio input was via an 1/4" to 3.5mm jack adapter, hooked up to about 4' of 3.5mm TRS cable. The alligator clips were clipped on to the TRS cable connector, with negative to sheath & positive to tip. Output from the amplifier was via two wires, from an old extension cord, attached to Channel A binding posts, which was then clipped to heating element via alligator clips.
Load: 2 Ohms resistive (heater element)
Input: 1.54 Vp-p, 400 Hz, sinusoidal
Measured Power @ 100% Gain: 4.0 Amps (amp clamp), 8.3 Volts (DMM)
Equipment SpecsSignal Generator:
Output Impedance: 50 Ohms
Frequency Range: 0-25 MHz
Amplifier:
Make: GTD Audio
Model: Q3000 "2U Professional Power Amplifier"
Channels: 2 (non-bridgeable)
Frequency Response: 10Hz-50KHz @ 1.5 dB
Input Sensitivity: 0.77V
RMS Power @ 2 Ohms: 1,500 Watts
Link:
Manufacturer Product/Specification Page with PicturesDMM (Volts): GB Instruments GDT-11
DMM (Amps): Radioshack 22-172 Clamp Amp
Thanks!