Electrical and electronic audio equalizer apparatus; electronic sound mixing, processing and synthesizing apparatus; sound reinforcement systems comprised of amplifiers; sound amplifiers; electrical sound amplifiers; electrical amplifiers for use with musical instruments; electro-acoustic amplifiers; power amplifiers for use in sound reproduction; sound amplifiers; valve amplifiers; tube amplifiers; valve amplifiers for sound amplification; solid-state sound amplifiers; solid-state sound amplifiers for sound amplification; hybrid sound amplifiers; hybrid sound amplifiers for sound amplification; combination sound amplifiers; head sound amplifiers; pre-amplifiers; public address systems comprised of sound amplifiers; public address systems comprised of passive speaker enclosures; public address systems comprised of powered speaker enclosures; public address systems comprised of mixer sound amplifiers; guitar amplifiers; acoustic guitar amplifiers; loudspeakers; mixing desks in the nature of electronic sound mixing, processing and synthesizing apparatus; audio mixing apparatus in the nature of electronic sound mixing, processing and synthesizing apparatus; audio mixing desks in the nature of electronic sound mixing, processing and synthesizing apparatus; mixing consoles in the nature of electronic sound mixing, processing and synthesizing apparatus; master audio mixing desks in the nature of electronic sound mixing, processing and synthesizing apparatus for use in an audio recording studio; loudspeaker cabinets; electric switches and footswitches for use with amplifiers, musical instruments and sound reproduction equipment; sound and musical effects apparatus and equipment, namely, electronic effect pedals for use with sound amplifiers and sound effect pedals for musical instruments; electrical and electronic audio interfaces for use with musical instruments, amplifiers and loudspeakers; sound effects pedals for musical instruments; batteries and power packs; chargers for batteries and battery power packs; USB interfaces in the nature of USB hardware; stands, bags and cases, all specifically adapted for use with loudspeakers and amplifiers