What did I do wrong

[eharri3 10+ year member]

I keep hearing the best way to set gains on an amp with a DMM is with the sub hooked up. I have an Alpine CDA 9883, and the amp is MRP-M500, pushing a Pioneer Premier 10 inch shallowmount at 4 ohms, should be 300 watts rms. I disconnected the mid/high amp, turned the HU down, turned the gain all the way down, then popped in a 50 HZ 0 db test tone. With the sub wires in, I turned the HU up to the best undistorted volume. I touched the DMM probes to the speaker terminals, got an immediate spark, and the amp shut down and stopped playing (I assume protection mode). It fixed itself when I turned the truck off and back on. This doesn't happen when I disconnect the sub but does when I connect it. I did it twice, decided not to push my luck so I reconnected everything and just set it all as best I could by ear. What did I, or could I have done wrong? Various tutorials have made it sound so simple to check with a sub connected but I seem to cause my amp to go haywire when I try this. If anybody can make a good guess as to what I did I might try it again, otherwise things sound good enough and I don't want to touch anything again and do permanent damage so I'll just live with leaving a little bit of output on the table.

Id pay someone to do this but around here all anybody does to set gain is play whatever's on my ipod and tune by ear, even the high end shops.

Thanks

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[BoxdGM 10+ year member]

you have to do it with the sub unhooked

 

[Haunz 10+ year member]

^ wrong.. the amp should have a load..

Sounds like he is shorting the amp out somehow.. are you sure the DMM is set to AC volts and not amps ???

 

[Rashaddd 5,000+ posts]

only way a dmm could really spark is if you are on the wrong setting, they usually have ridiculously high input impedences so as not to fry anythin its hooked up to, or itself

 

[skateboardkid 10+ year member]

^ wrong.. the amp should have a load..

Sounds like he is shorting the amp out somehow.. are you sure the DMM is set to AC volts and not amps ???

x2

 

[Immacomputer 10+ year member]

You may have the wires in to read current (amps). When the probes are connected to the DMM in a fashion to read voltage, there is a very high impedance. When the probes are connected to read current, they are a very low impedance.

Plug the DMM leads into the holes that read common (negative terminal) and the one that reads voltages (positive terminal). In this picture, these are the black and red circled spots:

The spot with the yellow X through it should only be used when wiring in series to read current. Also make sure the switch is set to read volts and not amps as others have mentioned.

 

[02accord 10+ year member]

You may have the wires in to read current (amps). When the probes are connected to the DMM in a fashion to read voltage, there is a very high impedance. When the probes are connected to read current, they are a very low impedance.
Plug the DMM leads into the holes that read common (negative terminal) and the one that reads voltages (positive terminal). In this picture, these are the black and red circled spots:

The spot with the yellow X through it should only be used when wiring in series to read current. Also make sure the switch is set to read volts and not amps as others have mentioned.

Thats a good picture right there //content.invisioncic.com/y282845/emoticons/veryhappy.gif.fec4fed33b4a1279cf10bdd45a039dae.gif

 

[Immacomputer 10+ year member]

I stole it from this site:

http://www.ferner.se/Prod/GI-Multimeter.shtm