Pulling tubes question....

[tribi9]

If I pull 2 EL34's on my 100 watt amp, I should be able to still use my 8ohm cabinet by switching the impedance on the back to 16 ohms, right?

[martin manning]

You need to go the other way. Easy way to remember is if you pull half the output tubes all the numbers on your impedance selector are doubled. So a four ohm setting matches an 8 ohm cab.

[tribi9]

Awesome, thx. That is an easy way to remember.

[Phil_S]

I thought I'd mention, 100W is about 10% louder than 50W. If you are looking to cut volume in half, 10W (sqrt of 100) is about right. You won't get there from here. Temper your expectations.

[rdjones]

I thought I'd mention, 100W is about 10% louder than 50W. If you are looking to cut volume in half, 10W (sqrt of 100) is about right. You won't get there from here. Temper your expectations.

A MusicMan amp I used for quite a while had a supposed half power setting that didn't make difference at all.
I modified it to cut the voltage way down, maybe 12-15 watts. I used that low power all the time.

I played a Fender 75 that was 75/15 watts. That one was also very useful on low power.

rd
"More than 50 watts goes to waste"

[tribi9]

I thought I'd mention, 100W is about 10% louder than 50W. If you are looking to cut volume in half, 10W (sqrt of 100) is about right. You won't get there from here. Temper your expectations.

Actually Phil, the reason I asked is not because of volume. It's because the speaker Im using with the big 100 Watt amp is only rated at 80 watts, so i figured that if I can reduce the output to 50 watts, then that speaker should be able to handle the amp.

[Phil_S]

80W speaker. That's the best reason I've heard for pulling 2! Actually, a good idea.

[Gaz]

In theory, shouldn't the HT fuse be halved as well?

[rdjones]

In theory, shouldn't the HT fuse be halved as well?

Yes, "in theory" you could change the fuse value to something more in line with how you're using the circuit.
I don't think it would be a necessity because any catastrophic failure that would be enough to blow the fuse would pop the original value as well.

I'll let you try it to prove me wrong, though.

You also still have the preamps, drivers and inverter that are pulling the same amount of current as before.
And with tubes pulled the B+ will be higher so you'll have a bit more than half power.

Maybe 3/4 the original value ?

rd

[Luthierwnc]

Tribi9; you might even take a white or silver Sharpie (the kind you autograph guitars with ) and mark the half-power position on the switch. In the heat of the battle it is one less thing to remember. sh