Sad, sad story

[tboooe]

Oh man, this one made me almost cry. My buddy who has some 800D recently purchased some very expensive used interconnects going from his cdp to pre. When he plugged them in, a VERY loud sound was produced through his tweeter. OF course he shut everything down immediately but it was too late. The diamond tweeter on his right speaker had died. Thought it looked fine, no sound was coming from it.

I am not an electrical engineer so I am not sure how this could happen but boy....what a bummer.

[Karma]

HI tboooe,
Sad indeed. This should be a warning to all of us to shut our systems down when plugging or unplugging equipment. Further, turn the volume down before power is reapplied. My guess is the offending cable had a missing ground. Not uncommon.

We should also note that the design of the majority of RCA jacks break the gound connection before the signal connection. It's a recipie for disaster.

Sparky

[audioqueso]

It's too bad for him, but wow... I would think people who buy speakers of this caliber would be smarter.

- Unplug power whenever connecting electrical devices.
- Disconnect the car battery whenever working on anything electrical.
Simple rules like that.

[Eliav]

Oh man, this one made me almost cry. My buddy who has some 800D recently purchased some very expensive used interconnects going from his cdp to pre. When he plugged them in, a VERY loud sound was produced through his tweeter. OF course he shut everything down immediately but it was too late. The diamond tweeter on his right speaker had died. Thought it looked fine, no sound was coming from it.

I am not an electrical engineer so I am not sure how this could happen but boy....what a bummer.

Hi
I hope it is not going to be something more serious than simple replacement of the tweeter.
Things like this, makes me very meticulous about the way i operate my system :system OFF whenever changing cables/ interconnects.
routinely, I switch the cd/ pre amp first, after a while each monoblock is turned on to minimize speakers damage .when switching off - monoblocks go first, followed by pre/ cdp. kind of a pain in the neck since a trigger cord would have made it easier to switch everything on at one remote button hit,however,in order to prevent possible speaker damage - that's the way ( Classe way) to go..
Regards
Eliav

[georgev]

When you say turn everything off, do you turn them off from the unit itself or from the mains as well?

[bigburner]

When you say turn everything off, do you turn them off from the unit itself or from the mains as well?

Always at the mains.

Eliav's rule is a good one too - amps should be switched ON LAST and OFF FIRST.

Nigel.

[Karma]

HI georgev,
There is no question that unplugging from the mains is the very best way to avoid problems. However, I think it is overkill and over cautious in many cases. I have been messing around with audio systems for well over 40 years and never had a problem by simply turning the power switches off. When I ran my hi fi repair shop I would unplug because I was working inside the chassis and wanted to avoid damge to the circuits from a slipping tool or shock to myself.

Before folks jump on me, I must caution that modern equipment that use remote contols do not shut off completely with the power switch. There is a small "standby" power supply that remains on even when the main power is off. It allows the remote control to turn the main power on with the remote. However, the standby supply poses no direct problems such as we have seen above because the main power supply for the audio circuits really is turned off.

But if there is a possibility that a pet, child, spouse might try to turn the system on with the remote while you are working on it, by all means unplug the equipment. For me this is not a problem so I don't bother to unplug.

Also, the order of turning on equipment mentioned above is an excellent practice. It can save speakers. I do that too.

Sparky

[caleb]

Just out of interest, does anyone know why the design of the RCA plug and socket makes the positive connection before the earth?

If it were the other way round where the earth or ground makes contact before the live pin - would this not stop these dangerous pops and cracks when you connect??

[misterdoggy]

I'm curious......

NO sound from the tweeter, but the tweeter dome is intact. Usually the tweeter dome explodes first when you blow a tweeter (I've done it)

Might we not look elsewhere ?

[tboooe]

mrdoggy, we thought the same thing. Our initial guess was that we fried the cross over. We have not ruled out this possiblity. I think my friend is going to have his dealer look at it and determine if its the tweeter, crossover, or both.

[misterdoggy]

Lets hope crossover and not tweeter. The tweeter repalcement cost $1100. The Crossover has to be less

[Eliav]

When you say turn everything off, do you turn them off from the unit itself or from the mains as well?

Off power = turn the power conditioner off, no current is available, not even for stand by mode, this is when I change cables/interconnects. on everyday's use I switch between standby and on.
Eliav

[dknightd]

Bummer! Plugging in to a live system can cause problems, but not often. IMO if there is no obvious physical damage then b&w should cover the failure. If there is obvious physcal damage, then maybe not. If the speakers are out of warentee then either figure out what is wrong yourself, or take it to a dealer.
I try not connect/disconnect cables to a live system, but have done it by mistake. So far I've been lucky and nothing has blown. At least turning things off is a good idea.
I suppose unplugging might also be a good idea (on the other hand sometimes
having a ground wire from the plug is a good idea). If what you are doing requires unplugging, then it also requires either discharging the capacitors, or, waiting till they self discharge. (When I'm worried about a potential connection, I unplug the units but leave them on - this helps discharge capacitors - them I plug in through a variac so I can slowly turn up voltage. But this is very rare, and should not be needed)
I hope your friends speakers are OK. Let us know what you find. And next time at least turn off all pieces before changing cables. . .

edit: as a postmortem, was the cable bad? If so how?

[misterdoggy]

I turn everything off but don't unplug. If its major work I unplug.

I also ground my hand before touching equipment even from accidental carpet charge causing a spark.

[Karma]

Just out of interest, does anyone know why the design of the RCA plug and socket makes the positive connection before the earth?

If it were the other way round where the earth or ground makes contact before the live pin - would this not stop these dangerous pops and cracks when you connect??

HI caleb,
Yes, I know. It's because someone at RCA had their head up their A**. It's a bad design but because they are cheap and simple, they have been adopted by everybody for as long as time flows.

Actually, Tiffany RCA's are designed to breaks the signal lead first. And Mark Levinson used CAMAC (LEMO) connectors for a few years which are wonderful connectors. But the world, in all of its wisdom, did not follow. Eventually, Levinson went back to RCA's. CAMAC connectors are a lot more expensive. But still we are only talking a few dollars even for a preamp which has a lot of connectors.

Sparky