Radial SB-15 Tailbone - Combination Buffer Active direct box for acoustic guitarUltra compact to fit in your guitar casePlug &amp; play easy to use feature set48V phantom powered, no batteries needed! The ultra-compact design begins with a standard Hi-Z instrument input The signal is then 'tamed' using Radial's unique Dragster load correction circuit to replicate the tone and feel as if connected directly to the amplifier The signal is then buffered via a 100% discrete, class-A unity gain amplifier Unlike most others that employ ICs or integrated circuits to buffer the signal, the discrete design reduces the need for phase-cancelling negative feedback producing a more natural and pleasing tone