For a ten ohm, 2W requires 2W/10R = 200ma. The current needed to dissipate 2W in a 1 ohm resistor is 2W/1R = 1A. Use a 2W or 3W metal oxide type resistor. Neither will cause any bad effect in your circuit's normal operations. You can use a ten ohm 1%, and get 10mV/ma if you like. Now when you bias, connect your meter between ground and the test point. Bring both ground and the top of the 1 ohm resistor out to a test point you can reach without removing the chassis. Put this between cathode and ground (in the standard circuit at least). Anybody know a good place to get one?Make it easy on yourself. Anybody know a good place to get one? Thanks Bob Might of been a coincidence but I remember reading an old post from John Philips? about ma probes and possible oscillation. I then replaced the resistor that got hot(even though it measured fine and still worked). New set of tubes worked fine and I checked the bias with a 1 ohm resistor I installed instead. I quickly shut off the amp and removed the probe. The ma drawn just kept climbing and a resistor inside the amp started to smoke. The tube was fine for months previously and I was just checking the bias again for drift. I have a ma type but havent used it since a 6L6 went 'runaway' on me while using it. Miliamp bias probe put your DMMs amp circuit in series with the cathode, and since you've got alot of wire between the socket and ground, you can get oscillations, though I've never had a problem with them.I think I will stick to the mv type. Milivolt bias probes put a 1ohm resistor in series with the cathode, and we use Ohm's law to calculate bias current.

Bias guitar amp without probe