running my Ampeg with a 4ohm load?

[BassGreaser]

So I have a show tonight up in Hollywood and the club has a Ampeg 410HLF.. Now I know the cab is a 4 ohm cab and I was wondering could I safely run my Ampeg B25B that runs at 16 ohm load.. I would perfer to run my head as it has the tone i know i can get from it rather than use someone elses

[username1]

I wouldnt run a tube head into a cab with that much of an ohmage mismatch.

[Wes Whitmore]

I have never seen that head, but it should have a ohm selector switch on the back...look for it and switch it to 4 ohm. You won't have a DI built into the head, so you will either have to Mic the cab or use an outboard DI.

[BassGreaser]

Originally Posted by Wes Whitmore

I have never seen that head, but it should have a ohm selector switch on the back...look for it and switch it to 4 ohm. You won't have a DI built into the head, so you will either have to Mic the cab or use an outboard DI.

Wes the B25B has no ohm selector switch just two speaker outs. I can put a dumby 1/4" jack in one of the speaker out and that will switch the ohm load of the head to 8 ohms.

Oh this is an all tube head BTW

[christw]

No, no, no! Do not do that unless you want to risk transformer damage or worse. Tube amps are tough, but should not be used in way they aren't built for. Impedance mismatches are a big deal. I killed a Marshall head as a newb once with an 8 ohm cab on a 16ohm tap

[dmusic148]

If you're ABSOLUTELY SURE that 'dumby' plug will switch it to 8 Ohms, it's almost certainly safe. Read the 'Amps/Ohms' FAQ.

[nicfargo]

It's still not safe. Going from an amp running at 8ohms into a 4ohm cab is a bad idea. Increasing resistance is a bad idea, I've heard decreasing it isn't as big of a deal...but I still wouldn't do it. If you want to damage your head, then by all means plug into that 410.

[BassGreaser]

well i am just going to play it safe an not bring my head.. as I get people saying either that it is safe to do or that it isnt safe to do.

[BigOldHarry]

16 ohm head? Far out. Never heard of such a thing - rather limits you to a 16 ohm cab, doesn't it?

[JimmyM]

Originally Posted by BigOldHarry

16 ohm head? Far out. Never heard of such a thing - rather limits you to a 16 ohm cab, doesn't it?

no, you can trick it into doing 8 by sticking an empty 1/4" jack into the first speaker out. but it does kind of limit you to 8 ohms unless you want to play fast and loose with the rules of output transformers.

however, if jess oliver is to believed, a 4 ohm cab will not hurt an 8 ohm head. he used to replace speakers in b-15's he worked on with 4 ohm speakers because it tightened up their sound in a way he liked, and he said as long the ot sees at least some sort of load, it'll be ok. if you're not comfortable with that, no problem...can't blame you. i don't do it with my stuff. i have done it with rentals, though, and nothing bad ever happened...that day

[thumpbass1]

I wouldn't want to risk it, if it was my decision to make. I've been there to see a few tube amps go down, or suffer from this sort of thing. I can still recall the smell of burnt wiring, and cooked transformer, in the case of an Orange guitar head that some guy had back in the 70's. The other one was an old Bogen tube p.a. head that some clown wired up the speaker cable to the wrong impedance tap on the output strip. That thing smoked, literally, before the mistake was caught. My fellow old timers would remember those old, funky, all tube Bogen p.a. heads. Again, some amps are more robust than others and might not break a sweat at being tapped for 8 ohms, while seeing a 4 ohm load. Is there any other amp head you could use or borrow just to get through this gig? Do what you think you should do, and if you go ahead with it, for good or bad, please keep us posted. I wish you a great gig, no matter what you decide.

[JimmyM]

yeah, go buy an svt

i agree...for one short gig, i wouldn't risk it either.