Expert: Cleggsan - 11/12/2009

Question
Hello I have a qsc gx3 and was wondering.Since it puts out 450 watts at 4 ohms what would the input signal have to be(in db), so that the amplifier does put out the 450 perside .Thanks:)

Answer
I guess this is a trick question.  According to QSC it does not put out 450 watts into 4 ohms.  According to their specifications published on the net it will produce:

Stereo Mode
8Ω / both channels driven / 1 kHz* 300W
8Ω / single channel driven / 1 kHz* 350W
4Ω / both channels driven / 1 kHz*  425W
4Ω / single channel driven / 1 kHz*  500W

and:

Input Sensitivity
1.2 Vrms
Voltage Gain (8Ω)
32.2 dB

Input Impedance (Ω)
Greater than 20k (balanced)
Maximum Input Level
+24 dB (16 Vrms)

Normally we think of audio power amplifiers as voltage devices and the universal standard among most amplifier manufacturers throughout the world is an input sensitivity of 1v to 1.5v. In this case they chose 1.2v of signal level.  The input impedance is high, like 10k or 50k so as to think of it as virtually no input power needed.

For professional applications some amplifiers use XLR inputs with a 600 ohm impedance.  This configuration is done for proper balancing in professional I/O applications.  This model has both inputs as you can read from the specifications given by the company.  

The input gain may vary slightly with different loads, but not more than a couple of db.

The input sensitivity in professional terms is generally designed to be 0 dbv or about 6.3v rms ac.

Contact QSC for further information......  or let me know if you have more questions.