I'm looking at doing my own biasing at home, and notice some probes read different metrics. This probe measures plate voltage and plate current: https://www.ebay.com/itm/2-in-1-Tub...Voltage-test-probe-6l6-el34-kt88/282672928476 It looks more convenient in that it has a switch to flip between its modes. I wonder if that can be switched between modes without powering down the amp or putting it into standby. This probe measures plate voltage and cathode current: https://www.tubedepot.com/products/tubedepot-bias-scout-kit It seems less convenient because the amp needs to be turned off to change the connectors for each metric. What it more comes down to, though, is whether plate current or cathode current is a more useful metric for biasing. If using the following formula to bias an amp, is the final mA reading of the tubes the plate current or the cathode current?: 70% max dissipation of 25 watts divided by tube plate voltage = 0.00whatever mA you should try.