Tip Jack 100w

[grtamp]

Hi , In a 100w D-stile amp with 4x6L6Gc I seen there are 4 tip jack test point ,but can I wired only 2 for side? must use different resistor value?
Thanks

[Firestorm]

You can use 2, same resistor, but different math. However, you'll have no way of seeing the behavior of each tube. What's wrong with using all 4?

[grtamp]

Hi Firestorm , there's nothing wrong to use 4 resistor 1 Ohm , but I'd like to know if is possible wired only 2 res...what value? 1 Ohm or 2 Ohm?

[gilgalad101]

You should still use a 1 ohm resistor there, from the cathode of each power tube to ground. This value just simplifies the math used to figure out cathode current. You use the tip jacks to measure the voltage across the 1 ohm resistor.

V = I * R

Therefore,
I = V / R

So, if R is a 1 ohm resistor, then:

V = I

[heisthl]

bear in mind individual measurements does not match your tubes - they will still conduct differently - the bias does not determine that. Better to just use matched quads which means 1 bias point is adequate.

[grtamp]

Hi , my question begin to this Dumble photo and I ask me :why 2 Ohm and not 1 Ohm...

[gilgalad101]

My guess would be that he ran out of 1 ohm resistors so he used 2 ohms. You don't even need a resistor there unless you are using the test points.