Bench tool
Total cabinet load
4.0 Ω
exact: 4.000 Ω
W
Match against output transformer taps
Most tube amp OTs are tapped for 4, 8, and 16Ω. Pick whichever tap sits closest to your total load.
Running a load slightly higher than the selected tap is generally safe — the output stage sees a bit less current and power transfer drops slightly. Running lower than the tap raises reflected plate current and stresses the output tubes and transformer; avoid it, especially on amps without a fixed load already installed. This assumes matched speakers of equal impedance — mixing different speaker impedances in one cabinet skews power distribution unevenly between drivers.