PRS HDRX 100 Watt Head Guitar AmpDesigned to push the high end so it is very clear, but not so much that it's harsh, the PRS HDRX shines without glaring and allows for aggression that can be backed off for smooth, sweet tones. The PRS HDRX 100 is driven by four EL34EH power tubes, the best pre amp tubes available, and a custom designed Straight Edge output transformer. The power supply and filament design make the HDRX 100 remarkably quiet with little to no amp "hum or hiss."The PRS