Brand
JOYO Technology is a Shenzhen music-gear company whose range goes well beyond stompboxes. Its official catalogue covers guitar and bass amplifiers, acoustic and busking amps, effects, power supplies, interfaces, wireless systems and accessories. JOYO also says it develops acoustic-core technology and has applied for utility patents. JustPedals listings include the JF-21 Splinter distortion and JF-319 Green Legend overdrive, alongside mini amps and power adapters. That breadth matters when comparing products under the JOYO name: some are effects, while others support the rest of a guitar or bass rig.
Category
A preamp brings an instrument signal to a controlled level and shapes its impedance, gain and frequency balance before amplification or recording. A DI converts the signal for a balanced, low-impedance connection and may include ground lift, pad and transformer isolation. Combined units can add drive, cabinet filtering, effects loops and parallel outputs while keeping the direct path stable.
Tags
The signal is shaped by continuously varying electronic circuitry rather than being converted into a digital effect algorithm. Component choice, operating voltage and circuit tolerances influence headroom, noise, clipping texture and the small variations in response between designs.
Raises or lowers defined frequency regions. Fixed-band graphic controls provide direct visual shaping, while parametric controls vary centre frequency and bandwidth; the available range and filter width determine whether the change is broad tonal balance or narrow corrective filtering.