Hello. I got a 50w evh amp recently with cab but I’ve been playing through my Marshall cab instead since it’s broken in. Yesterday I decided to start breaking in the new cab. Marshall is 8ohm EVH cab is 16ohm. No problem amp has a switch for either, but I left my 8ohm attenuator plugged in(in the off position) I ran the amp and cab for an hour or so. When I realized what I had done, I shut it down and unplugged the attenuator and realized I was still losing about 10db with it through the off attenuator. So it’s possible I did damage to the amp I guess. I’m wondering what you guys think? I played it a little today and nothing odd but I’m wondering if I could/should send it in for repair at my local shop to prevent a full melt down.
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Amp ohm and attenuator damage
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Are you measuring decibels with a meter ?
Just curious.
id say plug in one amp / one cab / one guitar and see if everything works.
If it does then get rid of everything else and consider yourself lucky.
To be honest an attenuator with 2 cabs makes no practical sense.
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My understanding is you might have just shortened the life of some components by running a 16ohm amp into an 8ohm load for a little while, but if it didn't completely fail, you'll probably be able to just keep going as long as you don't do that again.
But if you're worried and can afford a service call, it wouldn't hurt to have a tech measure the components and circuit and check how they are performing, just to make sure there isn't any indication of an imminent failure.
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IME tube amps are pretty forgiving and I think it's unlikely that you've done any real damage.
I've run 8 Ohm outputs into 16 Ohm cabs for years of heavy gigging without any problems.
The opposite mismatch might be more stressful however - I don't recommend running a 4 Ohm cab off a 16Ohm output, for instance.
I think it's likely that even with the attenuation off, the impedance matching part of your attenuator is still active.
The slight volume drop you're hearing might simply be due to the impedance.
When I used to run my 16 Ohm Marshall cab from an 8 Ohm output of my Boogie, I did it to reduce the volume a bit.
I suggest trying your rig with the attenuator plugged in but turned off, then trying again with the amp plugged straight into the cab.
There might be a difference. Then again, there might not. But at least you'll know if your attenuator is full bypass..
"You should know better by now than to introduce science into a discussion of voodoo."
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If you hurt anything you would instantly know it. Even Dave Freidman said on his podcast that you could run a tube amp for awhile without anything for load, granted the volume wasn't turned up on the head for a long time. It would eventually overheat but would take awhile, and if the volume was turned down it is unlikely to build much heat for awhile.
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Originally posted by beaubrummels View PostI think 16ohm amp into 8ohm attenuator, the amp would have been trying to open up, but you weren't hearing it, because...
...8ohm attenuator into 16ohm cab, that lowered your volume.
I don't think it hurt the amp any more than running it wide open on 11 with a proper 4x12 would
Sent from my SM-A115A using Tapatalk
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Originally posted by dave74 View PostIf you hurt anything you would instantly know it. Even Dave Freidman said on his podcast that you could run a tube amp for awhile without anything for load, granted the volume wasn't turned up on the head for a long time. It would eventually overheat but would take awhile, and if the volume was turned down it is unlikely to build much heat for awhile.
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Originally posted by JMP/HBE View Post
Friedman would tell you "for best results always correctly match impedance."
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A mismatch is a mismatch regardless of volume.
Mesa Boogie amps can tolerate certain mismatches because their output transformers are spec'd for it by Randall Smith.
EVH amps are made in Mexico or Indonesia and are not on par with Mesa Engineering.
Last edited by JMP/HBE; 06-22-2022, 07:54 PM.
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Originally posted by devastone View PostNo, current = volume, current is what would do damage. You can leave an amp on for a week without a speaker plugged in as long as you have the volume on zero.
Feel free to ask Dave.
So lemme get this starlight you're actually telling a noob [OP] who has just about fried his amp by doing the wrong thing that David Friedman of all people [in a 3rd party sense] is telling him to hook up his amp with no speaker load and leave it on for days ?
My how internet amp forums have gone down the sheeter.
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