• The Metal Master utilizes a two-stage tube preamplifier. The two stages can be controlled separately by means of the GAIN 1 and GAIN 2 knobs.

• An infinite number of sound combinations can be attained depending on the relationship between these two knobs, from clean or crunch to heavy overdrive.

• The MID control takes its place in the signal chain before the tube stages and its main purpose is to adapt to the characteristics of the guitar and pickups.
• To avoid undesirable distortion in the bass or treble range, the BASS and TREBLE controls function in the signal chain after the pre-amp tube stages.
• There is a separate headphone jack (PHONES), which is turned ON or OFF with a back panel push-button switch.
• The Phones switch serves a second function as well. At the same time that it switches the headphone jack on, it also applies CABINET SIMULATOR circuitry (like in the Hughes & Kettner Red Box) to the signal appearing at the SPEAKER OUT jack. This will give hi-fi speakers or full-range P.A. speakers connected to this jack the sound character of a guitar loudspeaker. 
• There is an integral 4½-watt solid-state power amp for connecting a guitar loudspeaker cabinet or – in the manner described above – a hi-fi speaker cabinet.