Ohms math

Frankee

Wartime Consigliere
Messages
25,469
In parallel or separately? How many speakers in the extension cab? You can use a 16ohm load safely with an 8ohm output if that's what you're asking. If you're planning on running it in parallel, that will result in a 5.3 ohm load.....which I wouldn't recommend doing.
 

Kyle B

Member
Messages
5,073
You got it backwards bro. You can drop the ohms on a tube amp, but it's the opposite for a transistor amp.

Most tube amps will short-circuit (0 ohms) the output if you turn it on with no speaker connected. It's to protect the OT from inductive voltage spikes. Short-circuit a SS amp and you'll let the smoke out. But you can run a SS amp with no load (infinity ohms) forever with no ill effects.

Doesn't matter how many speakers are in the extension cab. 16 ohm load is a 16 ohm load. 16 paralleled with 8 will be 5.3, that's correct. With a nicely oversized OT (physically large), a 5.3 ohm load would not be a problem on an 8-ohm tap. It'll get warmer is all. But modern amps tend to put in OT's that are just barely large enough to handle the power... PROBABLY OK, but no promises.

Some people like to view the grand canyon from 10 feet away. Some like to get right up on the edge.
 

csweet08

Member
Messages
383
I guess I could just disconnect the built in speaker and just run the extension can to be safe. The Budda has 4, 8, and 16 ohm taps
 

mabruk

Member
Messages
60
I guess I could just disconnect the built in speaker and just run the extension can to be safe. The Budda has 4, 8, and 16 ohm taps
You can do whatever you like but I would connect the external 16ohm cab to the 16ohm amp output while kipping the internal 8ohm still connected. What "Kyle B" told you is totally correct, apart from showing a deep knowledge on that matter.
 

Frankee

Wartime Consigliere
Messages
25,469
Doesn't matter how many speakers are in the extension cab. 16 ohm load is a 16 ohm load.
I asked because it's possible to easily rewire the 16 ohm cab to suit his needs.

And I don't have it wrong. I wouldn't dip the impedance of the load my amp is seeing.
At least not too far.
 

oldhousescott

Gold Supporting Member
Messages
2,731
Plug your internal 8 ohm speaker into the 4 ohm jack. Plug your external 16 ohm cab into the 8 ohm jack. This will match the load to the amp.
 

IM4Tone

Member
Messages
3,770
If by "taps" you mean OT taps and a selector switch (4/8/16) and two output jacks, then attach the 16 ohm cab in the second jack (with the internal in the other) and set the switch to 4 or 8. Either are close enough to 5.3 to not be an issue (though technically, 8 is a 'safer' choice). Having said that, you're probably not going to like the results since the 8 ohm speaker will receive 2/3 of the wattage and the 16 ohm 1/3 (due to ohms law). There will be volume imbalance, but no harm done in trying.

EDIT: Be sure to use a speaker cable and not an instrument cable in connecting the extension cab.
 
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