Setup at friends house ... fried amp!

[BarryV]

Hi guys,

This is my first attempt at a whole-house system debug, please bear with me.

His setup is 5 pairs of speakers, each with its own impedance-matched volume control. The jumper on each control is set to 8x. The speakers have nominal impedance of ~8 ohms (~5 ohms resistance with ohmmeter). All wire that runs from the amp to the volume controls are paralleled.

His amp is an NAD 325BEE. This system has worked for more than 5 years without issue.

One day a few weeks ago he said "it wouldn't turn on, so I kept hitting the ON button, then it smoked". I cracked the amp and found a blown fuse ... its a smaller one that is near the power switch.

1) Is this a "typical" install? From what I understand, it seems like this should work, as-is.

2) Is there any part within this system (not including the amp) that would cause this fuse to blow?

3) The NAD is probably good to 4 ohms, so I would think that it is well within spec (5 pairs, 8x on impedance-matched volume control). Is that right?


Thanks for any help you can give.

BTW ... I got involved with the local "geek squad" gave my friend an estimate of $4000; the original installer is retired.


BarryV

[Paul O]

Re: Setup at friends house ... fried amp!

This system has worked for more than 5 years without issue.

With that info I'd suspect the amp just up and died unless something changed recently with the speaker system, amps die for lots of reasons that have nothing to do with what's connected to them, so have it looked at to see exactly what blew up and unless they can trace it to shorted speaker outputs then you know you don't have a speaker problem.

[BarryV]

Re: Setup at friends house ... fried amp!

With that info I'd suspect the amp just up and died unless something changed recently with the speaker system, amps die for lots of reasons that have nothing to do with what's connected to them, so have it looked at to see exactly what blew up and unless they can trace it to shorted speaker outputs then you know you don't have a speaker problem.

Thanks for the reply and the vote of confidence. This is what I was thinking too. I have checked 6 out of 10 speakers, and they were all ~5 ohm resistance. I could check the others as well.


BarryV

[envisionelec]

Re: Setup at friends house ... fried amp!

Thanks for any help you can give.
BarryV

It's not the install. Good amps die, too.

[[email protected]]

Re: Setup at friends house ... fried amp!

Thanks for the reply and the vote of confidence. This is what I was thinking too. I have checked 6 out of 10 speakers, and they were all ~5 ohm resistance. I could check the others as well.


BarryV

Also make sure to check the resistance seen by the amplifier itself, at the outputs. Disconnect the leads from the amplifier outputs and connect the ohmmeter across them. If it reads less than about 3 ohms, then you've got a problem. (More than that, and you're groovy.)

[dcibel]

Re: Setup at friends house ... fried amp!

Also make sure to check the resistance seen by the amplifier itself, at the outputs. Disconnect the leads from the amplifier outputs and connect the ohmmeter across them. If it reads less than about 3 ohms, then you've got a problem. (More than that, and you're groovy.)

Yes, this is the right path. Disconnect amp from speaker load, and check resistance at the amp output, and check resistance at all speaker loads. Be confident nothing is shorted.

Sound like the fuse didn't protect the amp very well though, since you mention it "smoked". So likely some amp repair or replacement is in your future. But definitely check all speaker loads before throwing another amp in there, or you may end up with two smoked amps.

I'd even go as far as testing the load with the in-wall volume control at either end. Check lowest setting as well as max setting.

[dcibel]

Re: Setup at friends house ... fried amp!

It's not the install. Good amps die, too.

Don't jump to conclusions. It's a stupid game.

[fireplace]

Re: Setup at friends house ... fried amp!

It's been know for a nail to be shorting out a speaker cable if anything has been recently attached to some dry-wall for example - your ohm meter will reveal any issues like this.

[Joegtech]

If this type of project interests you and you might do it again, maybe it makes sense to invest in a DATs test system. You can then get an impedance test of the speaker cables before you attach them to the amp.
https://www.parts-express.com/dayton...ystem--390-807