Shar Plug ‘n Play Amplifier These portable amps are ideal for practicing in the house or studio at low volumes. The 10-watt Violin/Viola amp includes a 5″ speaker, volume, bass, and treble controls, an overdrive switch, input jack, and headphone jack. The all new 30-watt cello-bass amp has a 10″ speaker, volume, bass, middle, mid-frequency, and treble controls, low and high input jack, and headphone jack. Which Amp? They’re portable, and are ideal for practicing in the house or sutdio at low volumes. Bowed string instruments have such a variety of frequencies and dynamics that we suggest an “acoustic” instrument amplifier for live performances. Violins and violas enjoy the most efficient results with amps that have a tweeter to accommodate the higher frequencies, whilst cellos and basses will have to use bass amplifiers.