Need Some Amp Advice

Good Morning,
Last year I installed a JL Audio Stealthbox in my Tacoma powered by a Alpine PDX M6 Amp. About a week ago the subs stopped playing and there was a bad smell coming from them. I took the subs out of the box, hooked them up on the bench and they’re both blown. Immediately started to smoke. When I test the output voltage of my amp its at 89 volts, should be around 35. When I turn the gain dial the voltage does not change. (I’m using a 40hz test tone when testing the output.)
So I ordered another M6 amp and this one is showing .7 volts on the output and again voltage does not change when I turn the gain.
I checked all connections. I have good power and ground going to the amp so I’m at a loss at this point.
Is it possible both amps are bad, or is there something else you would recommend checking? Could bad RCAs be causing these issues?

 

Are you running a loc or dsp or anything between your head unit and amplifier? Also I’m sure you’re aware but be sure your dmm is set to AC Voltage and within the range you plan to measure for. I’ve found my auto ranging dmm gives me low voltage readings like you speak of at times

 

What are you using for a source to test? Head unit, portable player, etc? Tones or music? You should be using tones which don't change levels - want a constant output.

To test your cables, test voltage at your output device, then test at the other end of the cables. You should have very close to the same voltage. Also test the cables' resistance. It should be near zero.

 

FWIW these amps have some serious headroom...not surprised to see smoked subs from it. Never seen the M6 on a dyno, but BigDWiz tested the M12 and got some ridiculous numbers out of it - over 2900W in a dymanic run at just under 2 ohms - well over double rated power.

 

Thanks for the replies. I’m using a 40hz test tone on a cd to do the testing playing through the head unit. Nothing in between. RCAs go straight from the radio to the amps.
Testing with a multimeter. I can confirm I am on AC. I did see online that the m6 amps have had some internal failures that cause the voltage to spike. I’m thinking the amp has gone bad. The other one showing very low voltage I bought used so may be bad as well.
I’ll pull the radio and check on the cables.

 

Damn that sucks if That’s the case

 

If it winds up being the amps, Alpine will repair them for a fair sum. $85 IIRC and you get a warranty with it. It has been a while since I used that rate, so YMMV. Turn-around was quick. Pretty sure I wound up with a different serial number since the amp I got back looked better than the one I sent in.

 

I would like to know if the replacement amplifier is powering up correctly because you could have just popped a fuse or something during the swap.

 

It seems to be. It lights up blue like they usually do when they power on. I checked my fuses and the fuses on the amp and they’re all good.
Just to follow up from a prior post, I did check the RCAs and they seem to be good as well. I checked them with a multi meter and as I turned up the volume the voltage went up, same as when I check directly at the radio. At full volume I was at 5 volts which seems correct. The radio is a Kenwood DNX893S with 5volt pre-outs.