Well - my speakers caught fire.

[Slevage]

Something in the signal chain (including the amp/preamp) might be "passing DC".

Mathematically speaking:
Current x current x resistance = watts in the form of heat

 

[ThisBass]

Something in the signal chain (including the amp/preamp) might be "passing DC".

Mathematically speaking:
Current x current x resistance = watts in the form of heat

Far too much of coupling C's in the system chain that block any DC,
at least at OT there is zero DC, sorry, pardon, did I mentioned that EVERY power amp input blocks DC?

 

[Slevage]

Far too much of coupling C's in the system chain to block any DC

Maybe DC offset? The 41 Hz of the E string has to get to the speaker, so all of the low stuff can't be blocked.

 

[B-string]

Yes, any DC at the output of an amplifier is strictly a fault of the amp's output section.

 

[B-string]

Maybe DC offset? The 41 Hz of the E string has to get to the speaker, so all of the low stuff can't be blocked.

41 Hz is an AC signal, not DC. DC (Direct Current) has NO frequency.

 

[Slevage]

41 Hz is an AC signal, not DC. DC (Direct Current) has NO frequency.

DC offset? Could be pushing the speaker "farther" in one direction.

 

[B-string]

DC offset? Could be pushing the speaker "farther" in one direction.

Yes, that is why the amp must be checked. DC offset from the amp's output is a failure in the output section of the amp.

 

[Slevage]

Yes, that is why the amp must be checked. DC offset from the amp's output is a failure in the output section of the amp.

I'll drink to that

 

[ThisBass]

Yes, any DC at the output of an amplifier is strictly a fault of the amp's output section.

Must be a very faulty amp that can't restrict DC due to clipping by feedback loop.

 

[Slevage]

Yes, that is why the amp must be checked. DC offset from the amp's output is a failure in the output section of the amp.

Now I've gotta try something.

Put a 9V battery to the input of my amp (I'll limit the current)---- then see it the speaker moves in one direction (I better use an old speaker)

 

[delta7fred]

From post #1

The speakers were original from the 80s and I heard one rattling around last week but didn't think much of it.

It sounds like one VC was already scraping before the gig, it could only get worse.

 

[B-string]

Now I've gotta try something.

Put a 9V battery to the input of my amp (I'll limit the current)---- then see it the speaker moves in one direction (I better use an old speaker)

I would use only a 1 1/2 volt or you may damage your amp. Expect a tick or pop but the speaker to return to center. Do not contact the battery or leads for the battery/cable or you will inject 60 or 50 Hz hum.

 

[B-string]

Must be a very faulty amp that can't restrict DC due to clipping by feedback loop.

Not where the DC would come from, but you know that already. You must be misunderstanding me (or the translation was bad).

 

[tedious1]

Also im proud of TB for not saying the reason it burst into flames was mixed drivers.

Well, since you broached the subject...

But to be fair, the mixed driver folks are always citing sound as the major issue, even when they start talking about splitting the power between cabs, the major issue they are concerned about is one cab farting out. I can't recall anyone in the anti-mixed drivers camp predicting that you would turn one of your cabs into a Guy Fawkes Day celebration...

 

[-Asdfgh-]

So I recently added a second cabinet to my rig and played it out for the first time the other night. I use a Sunn Concert Head (100w, 4ohms), an SWR Goliath 410 (8ohms, with the tweeter off) and a GK 212 (8ohms, so the power is cut to 4 all around). Everything was hooked up properly the same way it was in our practice space, except that I was playing around 7-8 volume rather than around 4-6. Towards the end of our set, my rig starts smoking - badly. I quickly shut off my head and a buddy let me borrow his (Orange, much higher powered) head for the few songs we had left. By the end there was smoke BILLOWING out of my 4x10 and probably the worst smell that I've ever smelled.

I've had a similar power tube head catch fire, but it takes extra dedication to make the cab catch fire! Truly rock and roll.

Seriously, I hope you can get it fixed.

 

[-Asdfgh-]

I have never heard of a pedal burning up a speaker. Ever.

Now, your 100w head pushing two cabs that are clearly designed for more power... and I know those old Sunn heads (I had a concert bass head when I was a kid) - I suspect something wrong with the head that spiked your cabs. Those old amps depend on very large, very wet capacitors that, unless you have replaced them at some point, might have dried out... I'd be VERY careful about using that head with any other speaker until I had a tech check it out.

With the amp I had catch fire it was the output transformer that failed.

 

[SanDiegoHarry]

With the amp I had catch fire it was the output transformer that failed.

Sure - a coil short can cause all kinda mischief. That's how I wrecked my Sunn (or rather, how it died!)

 

[killjeats]

Update: the head is in perfect condition. So I guess I'm going to chalk this up to a few speakers that were on their way out anyway and me cranking everything as the mail in the coffin.

 

[ThisBass]

Not where the DC would come from, but you know that already. You must be misunderstanding me (or the translation was bad).

No concern,
I guess there is more important stuff out there

 

[ThisBass]

Sure - a coil short can cause all kinda mischief. That's how I wrecked my Sunn (or rather, how it died!)

wrecking amp yes, wrecking speaker improbably.