Amp head being used with other cabs

Force · #1 05-12-2010, 06:41 AM

I blew up my Hartke LH500 bass head about a month ago at gig because I used it with another guy's cabinet. It also blew up his speaker cabinet. I took the head in to get repaired and got it back today and it's working, but that's not the point.

What I'm asking is how in the future when I use a different cab with my head, can I prevent this from happening again. From what I've heard it's something to do with the red switch at the back of the amp head, the ohms thing.

I apologize if this is in the wrong section.

duderasta · #2 05-12-2010, 06:57 AM

as far as I can tell, that amp will do 2 ohms stereo, and there is no bias switch, it's a SS power stage. Chances are it was a direct short in his cab that caused the problem. the only way do kill it with an impedance mismatch would be lower than 4 ohms bridged?
(I don't know this first-hand looking at the manual pdf)

Force · #3 05-12-2010, 10:02 PM

So it may have been his cab that blew the head up?

JimmyM · #4 05-12-2010, 10:27 PM

hard to say without more info. you should be able swap speakers in and out of that head all day as long as you stay within its minimum impedances, though.

Stumbo · #5 05-12-2010, 10:55 PM

Which cab was it? Ohms? Pics?

Force · #6 05-13-2010, 12:48 AM

No idea, but I don't really need to know how it destroyed my head, I wanna know how to avoid this in the future.

bongomania · #7 05-13-2010, 01:24 AM

Can't have one without the other. Generally speaking there is no reason that amp, working properly and set up properly, should have had a problem with any cab. However, if the total cab load was lower than the rated minimum for the bridging setting you used, then yep--you get fire. Again though, the only way to tell you how not to do it again is if we know exactly what you did--and that is the same as finding out how the amp got destroyed.

In case you don't want to think about that, the answer is to read the manual. If you follow the directions in the manual, your amp will probably not blow up. And if the amp doesn't blow up, and you use common sense about the levels you feed into the speaker cab, then the cab shouldn't blow up either.

Force · #8 05-14-2010, 02:55 AM

I sat the amp on top of the cab, plugged the speaker cable from the cab into the amp, plugged the power cable into a powerboard. Turned the amp on, no output, kept strumming the bass, still no sound. Smelt a burning smell, felt the back of the amp and it was really hot. Amp ****ed. Also, I used his speaker cable as mine didn't fit into his cab. His cable was thicker and didn't seem to sit right in my speaker input. It was a little wobbly.

Force · #9 07-04-2010, 03:30 AM

My band's got a gig on this Saturday and I'll be using the backline speaker cabinet which is an Ampeg (8x10 I assume). Now, I have a bit more of an idea of this whole impedance thing (still a bit confusing though) and I think my Hartke Lh500 will work fine with the Ampeg using the mono 1/4" speaker jack on the cab.

Using it that way it will be 4 ohms and according to the manual of the LH500 I should only use cabs that are 4 ohms or higher. I'm just confirming if you guys think it should be fine. I don't wanna blow my head up again lol... Am I on the right track with this here?

countrybass007 · #10 07-04-2010, 05:54 AM

I agree with the direct short idea. That caused a speaker and amp to fry at a gig once, the repairman said it caused DC voltage that fried the speaker and some amp components. A guitar player friend of mine caused a similiar situation once, and burnt a hole in one PA speaker and melted the cord going to the other one. Again, they told us it was a DC voltage back-up into our system.

**bass4worship** · #11 07-04-2010, 03:51 PM

I know that sometime we need to borrow at a gig but next time use his hold setup this way if there a problem you're not out a head, but you may be responsible for his rig if it's go out.

By the way was he using the cab before you got to it. Sound like that cable was bad and causing a dead short.

Jaco who? · #12 07-04-2010, 04:08 PM

Quote:

Originally Posted by Force

Also, I used his speaker cable as mine didn't fit into his cab. His cable was thicker and didn't seem to sit right in my speaker input. It was a little wobbly.

Next time it's a little wobbly, trust your intuition, don't turn anything on until you have a solid connection.

R Baer · #13 07-04-2010, 04:15 PM

Stupid question, but are you positive another head wasn't also plugged into the cab at the same time? That never turns out well.

BassmanPaul · #14 07-04-2010, 05:30 PM

I/m guessing that the cable was not plugged into the amp properly and presented a short. The amp died. If you're getting no sound DON"T KEEP PLAYING! As you found out, this is not a good thing to do.

Yes YOU DO NEED to identify what went wrong. With out how are you going to prevent it happening again. I'd not connect any of my amps to a cabinet that I am unaware of the history behind it.

Paul