operational amplifier - Guitar signal with opamp boost - Electrical Engineering Stack Exchange
ammoon Electric Guitar Headphone Amplifier Amp 1/4 Inch Plug 3.5mm Headphone Jack & Aux In with Classic Rock Distortion Effect Built-in Rechargeable Battery - Walmart.com
ElectroSmash - 1Wamp Electroc Guitar Amplifier.
100W Guitar Amplifier (Mk II)
Electric Guitar Amplifier + Preamplifier – Electronics Projects Circuits
Amazon.com: LyxPro 40 Watt Electric Guitar Amplifier | Combo Solid State Studio & Stage Amp with 8” 4-Ohm Speaker, Custom EQ Controls, Drive, Delay, ¼” Passive/Active/Microphone Inputs, Aux In & Headphone Jack :
mixer - Headphone amplifier for guitar with stereo MP3 input - mixing - Electrical Engineering Stack Exchange