Nice amp, but the power out specs are pushing the envelope a little. What I found was the amp starts clipping at approximately the voltage feeding the amp. For a 12 volt input, this corresponds to a 24 volt peak to peak output voltage to the speaker. Clipping means the output goes no higher and flattens out. I opened up the unit (there goes the warranty) and found it contains a switching power supply, that basically doubles the input voltage to the output transistors. Thus you get a 24 volt peak to peak output voltage, to your speaker, from a 12 volt power supply input. Assuming you amplify a sine wave signal, doing the math, the rms output voltage is 0.707 times the peak voltage or 12 X .707 = 8.48 volts. The rms power is the rms voltage squared divided by the speaker impedance or 8.48 X 8.48 / 8 ohms = 71.9 / 8 = 8.99 watts. With a 2 ohm speaker the power would jump to 36 watts (8.48 X 8.48 / 2). Increasing the input voltage to the normal voltage of a running vehicle of about 14.6 volts raises the clipping point and thus the undistorted output rms power to 13.3 watts, into an 8 ohm speaker. To make the spec of 75 watts, into a 4 ohm speaker (assuming this is rms power), the power supply input voltage would need to be 75 X 4 = 300, the square root there of = 17.32 (rms speaker voltage), this times1.414 (to get the peak speaker voltage) which equals 24.5 volts. Thus, about a 24.5 volts power supply input, would get you 75 watts output, with no clipping. It might fry the amp, however. I did not measure the noise, but the flat frequency response looked good. I did notice a little crossover distortion, in the waveform, at higher frequencies. That’s what I saw in my "200 watt" unit. For about $26, it’s acceptable, as long as you keep in mind you’re not going to get 200 watts of true output power.
