Dual rectifier using 2 power tubes only. What ohm jack to use?

[KLINKDETROIT]

I have a Dual rectifier with4 power tubes and 2 rectifier tubes. I want to use only 2 power tubes and 1 rectifier tube to do comparisons of different tubes as I only have sets of 2 on some of the different brands I own.. What ohm jack to use? 4 or 16? I know you dont use 8 with a 8 ohm cab if you rmove tubes to make the amp 50 watts.
I know the ohmage is different than 8 ohms if you only use 2 outer power tubes and 1 rectifier tube to make a 100 dual rectifier into 50 watts but I am not sure what to plug my cab into. The 4 ohm out or the 16 ohm out of the head? I use a 8 ohm Mesa cab. I also wonder if I used a 16 ohm cab if I should plug into a different jack on the head? Thanks for your help

 

[Kent S.]

Re: Dual rectifier using 2 power tubes only. What ohm jack to use?

I have a Dual rectifier with4 power tubes and 2 rectifier tubes. I want to use only 2 power tubes and 1 rectifier tube to do comparisons of different tubes as I only have sets of 2 on some of the different brands I own.. What ohm jack to use? 4 or 16? I know you dont use 8 with a 8 ohm cab if you rmove tubes to make the amp 50 watts.
I know the ohmage is different than 8 ohms if you only use 2 outer power tubes and 1 rectifier tube to make a 100 dual rectifier into 50 watts but I am not sure what to plug my cab into. The 4 ohm out or the 16 ohm out of the head? I use a 8 ohm Mesa cab. I also wonder if I used a 16 ohm cab if I should plug into a different jack on the head? Thanks for your help

When using two tubes instead of four (not sure about the dual rectifier thing though) adjust the amp imedance or speaker load so that the load is twice what the amp is looking for ... if the amp is at 8ohms and can't be changed use a 16ohm speaker load, if the amp can be cahnged to 4 ohms then you can use the 8ohm speaker load. I don't think the mesa actually changes to 4ohms though ... rather than to guess you'd can run the 8ohm amp jack into a 16ohm cab ... Rule is the speaker load needs to be twice what the amp wants to see. If you want to know more, go ask Lord Valve.