GR70 Class a Vacuum Tube 5654W 6X4 Dual Tube HiFi 3.5mm 6.35mm Jack Headphone Amp Tube Preamp Headphone Amplifier

Steps:(1) Insert the 5654W and 6AC7 tubes into their correct sockets. Align the tube pins with the socket holes; (2) Connect your source device to the GR70 using RCA cables; (3) Plug in your headphones, or connect powered speakers/amplifiers to the RCA output if using as a preamp; (4) Connect the supplied 12V/3A power adapter; (5) Turn the power/volume knob on while keeping volume low; wait 20 seconds for the tubes to warm up; (6) Play music and slowly adjust the volume.

Notes: - Allow 20 seconds for tube warm-up; - Avoid plugging/unplugging cables while powered on; - Only replace tubes after they cool down to avoid burns or damage.