Adding a cathode current meter?

[HighFidelityGuy]

I'm currently working on a guitar amp project and I'd like to add a simple analogue panel meter that will display the output valve cathode current for the purposes of biasing the valve. It seems that there are two ways to achieve this. The first is to insert a 1 Ohm resistor between the cathode and ground and then measure the voltage across this, where 1mV = 1mA. The second is to simply add a current meter between the cathode and ground. Obviously a switch would also be added in each case to allow the meter to be taken out of the circuit during normal amp usage and a high wattage potentiometer will be used to actually set the bias.

So what I'd like to know is whether either of these two approaches is more accurate than the other or otherwise better? What would you recommend?

Cheers. :)

[Trickie_Dickie]

Well, I'm building a pair of Mullard 5-20 amps with negative bias on the EL34s. In their cathode circuits, I have a 10 ohm resistor to measure the cathode current. A simple voltmeter across this resistor on 1V range will give the current value via Ohms Law. Any effects that the meter leads cause will be damped by the 10 ohm resistor. A 100microamp panel meter with 10k resistor in series, wired permanently across the 10ohm will work very well. :cool:

[HighFidelityGuy]

Hi Richard, I don't quite follow you with your ammeter suggestion. What's the 10K resistor for and why would you but it and the ammeter in parallel with the 10ohm resistor? :scratch: Cheers. :)

[Trickie_Dickie]

Connect one end of the 10k resistor to the "+" meter terminal and the other end of the 10k resistor to the cathode. The "-" meter terminal is connected to ground. This will measure the volts across the 10 ohm resistor which is connected between the cathode and ground. :cool: