Stupid Impedance Question

[GaryLC]

Guys,

I should know this, but wanted to ask. If I have an amp with a switchable impedance tap....4 ohm/8 ohm....and it's set to the wrong position, will it harm the amp? An 8 ohm cabinet with the amp set to 4 ohms, or a 4 ohm cabinet with the amp set to 8 ohms.
And....say I want to use an "in-between" load, an Epi UL310 that's rated at 5.3 ohms. Is it best to have the amp set at 4, or at 8?

 

[CL400Peavey]

What amp?

 

[GaryLC]

Music Man HD150.....tube power section, ss preamp.

 

[CL400Peavey]

Music Man HD150.....tube power section, ss preamp.

With a tube power section its best to match your impedances to preserve tube life. Im not sure where you should be running your amp with that cab. I would PM JohnK and see what he thinks.

 

[DiabolusInMusic]

You will burn out a power tube running an odd load but nothing major will happen in my experience.

I use to run my SVT-CL with a 6 ohm cabinet, I set the SVT to 4 ohm since the other option is 2 ohm. I did eventually blow a power tube.

 

[NightCat]

If I remember my electronics right.... Impedance mismatch will change the efficiency of the energy transfer. When the impedance of the source matches the impedance of load you have maximum efficiency.
I don't think there is a "danger" with mismatched impedance unless you approach a dead short, meaning if you connect parallel speakers and end up with two ohms or less.

 

[NightCat]

My guess is that the reason you would blow tubes or whatever is because inefficient energy transfer means the amp is not as loud as you expect it to be so you crank it up. This causes everything to run hotter and die sooner.