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Is it okay to push an 8 ohm cabinet with a 4 ohm head?


eeddings

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Quote Originally Posted by dparr View Post
No problem at all.

You can always go higher but never lower.
It never fails. Sigh. With tube amps, it really depends on the amp. You can't make general assumptions one way or the other. Check the owner's manual.

Solid state amps will have a minimum impedance. Anything equal to, or higher than the minimum is okay.
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I used to use a 1400w 2ohm Class D subwoofer amp in my car wired at 0.5ohms...It was fine for over 6 years and was loud as {censored}. I don't recommend it, but it can be done. It really just depends on the amp.

Personally, I wouldn't do it with a tube amp as components are much more sensitive and volatile then solid state components.

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I used to use a 1400w 2ohm Class D subwoofer amp in my car wired at 0.5ohms...It was fine for over 6 years and was loud as {censored}. I don't recommend it, but it can be done. It really just depends on the amp.

Personally, I wouldn't do it with a tube amp as components are much more sensitive and volatile then solid state components.

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Quote Originally Posted by GCDEF View Post
It never fails. Sigh. With tube amps, it really depends on the amp. You can't make general assumptions one way or the other. Check the owner's manual.

Solid state amps will have a minimum impedance. Anything equal to, or higher than the minimum is okay.
I've never heard of a amp (tube or SS) where you can't use a higher ohm cab.

If you know of one please share.
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In some cases that is an OK mismatch,but it does not apply to all amps. I know Mesa usually says it is ok with their amps, but I know some Marshall's and older Fenders can be ruined in offset ohm loads. What amp are you wanting to do this with? Most modern amps can handle the higher mismatch, but I would still make sure.

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Quote Originally Posted by dparr View Post
I've never heard of a amp (tube or SS) where you can't use a higher ohm cab.

If you know of one please share.
Any tube amp into an infinite load (aka no speakers hooked up) is asking for a new OT, especially with insulated output jacks (Marshall). SS can tolerate this, but will likely damage output transistors running into a very small load.
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older Fenders can be ruined in offset ohm loads.

 

 

 

 

I recently learned this. Evidently there's a lot of old 4 ohm Bassmans out there with replaced output transformers. Story goes some OTs were produced that were closer to 2 ohm spec than 4. So if plugged into an 8 ohm cab, the mismatch is even worse. They are tough old amps but they can only take so much. So most experts will tell you its best to run your tube amps to the specified cab load so as to not overwork the OT. It will last a lot longer.
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Quote Originally Posted by paul88lx View Post
I've been told you can go 4ohm into 8ohm or 8ohm into 16ohm. But not 4ohm into 16ohm. And definitely never ever higher amp impedence into lower cabinet impedence.

Please, correct me if I am wrong.
Just partly, going low into high can be risky for some tube amps, esp older ones.
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Jesus suffering {censored}. How many times does it need to be explained that mismatching into a higher load can create large flyback voltages that can destroy an output transformer in a tube amp? It will also generate massive screen currents and blow your tubes.

Edit - not a dig at the op, just people who churn out the same misinformation

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Quote Originally Posted by DARKMETL/

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I believe this is generally ok. Just makes the amp work a bit harder. I used a 8ohm Mesa .50 Cal head for a long time with a Marshall 16ohm cab with no issues...

 

Mesa amps generally don't have this issue because the quality of transformers used. Most other amps, I'd reccomend that the ohms match accordingly. Short answer...depends on amp.
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Quote Originally Posted by PlayboyChris View Post
Another short answer: don't do it.

Just look at the responses in this and every other thread like it that's ever been posted here. Half the people say one thing, the other half say the opposite.
I'd believe the people who can produce graphs and don't rely on anecdote wink.gif
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