M-Audio M-Track Duo 2-Channel USB Audio Interface bass-overdrive-distortion The JJ 5U4-GB tube is

The JJ 5U4-GB tube is another affordable replacement rectifier tube for both guitar and hi-fi tube amplifiers

With 3/8" thread

but can accept the optional DTBR1535 backrest

baffles or wall panels to reduce reverberation and improve intelligibility

M-Audio M-Track Duo 2-Channel USB Audio Interface bass-overdrive-distortion The JJ 5U4-GB tube isThe M Track Duo is the best, most portable recording interface in its class. It delivers 24 bit 48kHz audio resolution in a compact and easy to use format that is ideal for creating music on any Mac, PC or iOS device. This versatile interface works great for recording any type of sound source and features two Combo Crystal Preamps with phantom power, making it compatible with any guitar or microphone. Plus, there is a dedicated switch to choose line