Amplifier Enters Protection Mode When Volume Is Up

skeeter007 · 04-11-2005, 08:57 PM

I have touched on this briefly in other threads, but have never gotten a solid answer to the question...

Here's my setup:
Alpine MRV-F450 5-Channel Amplifier
Audiobahn ALUM12Q 12" subwoofer (dual 6-ohm voice-coil @ 3-ohms)
iBase MB870 MotherBoard w/ P4 1.8GHz
Lilliput 7" touchscreen

Basically, whenever I am playing a song with a lot of bass and I turn the volume up, my amplifier will go into protection mode for a few seconds, and then return to normal. If I have not lowered the volume when it resumes, it will usually go right back into protection mode. I have tried grounding the amp to a different point on the car but am still having the same problem.

It was suggested that I was possibly overloading the amp but I don't think that's the case because the gain on the sub channel is turned below the half-way mark and the speaker does not sound like it is distorting. Any ideas?

Thanks.

Vchat20 · 04-11-2005, 09:00 PM

what about your power connection? are you using proper guage wire for your amp?

skeeter007 · 04-11-2005, 09:10 PM

Quote: Originally Posted by Vchat20

what about your power connection? are you using proper guage wire for your amp?

Yea, sorry about that...I've got 4 Gauge wire coming from the battery+ and 4 Gauge wire going to a grounding spot in the trunk.

Lazyflip · 04-11-2005, 09:20 PM

Make sure the ground point has been sanded down to bare metal and the connection is makeing good contact.

mbuchman · 04-11-2005, 10:28 PM

Possible errors -
- Short somewhere in the circuit (from speaker to amp)
- not getting enough power
- amp might not be stable at that ohm level
- might need to lower the gain a little to better match the headunit

Thats all I can think of right now

Matt

boomintrac · 04-11-2005, 11:02 PM

how is your sub wired?
nevermind i saw 3ohm

boomintrac · 04-11-2005, 11:10 PM

the 3ohm is where your prob is alpine amps dont like to see below 4ohms mono (unless it is a mono amp) you have a few choices to fix this you can run both coils in series will make a 12 ohm load drasticaly cutting power to the sub. use the rear channels to power the sub right side to one coil left side to another coil (if you do this make sure that you use a multimeter to make sure the output is the same on both channels)
or you could just buy a dedicated sub amplike the alpine 501 which would match the 5 channel nicely

dave2 · 04-12-2005, 04:59 AM

No, the alpine will handle 2 ohms just fine. I'm guessing your voltage is dropping out, below 10.5 or so will send it into protect. Hook up that multimeter to the power leads and have a friend turn it up until the amp cuts, check what the voltage is when that happens. If your electrical system can't handle it, you might need a new battery or a cap to keep it alive. That's a relatively powerful amp, and they aren't too efficient, so they need lots of power. Since the amp turns back on, I'll almost guarantee that it's a voltage protection, not a heat protection. Thermal shutdowns require the amp to reset, by turning the remote lead off and back on, plus the heat needs to dissipate.

Only other idea is that the audiobomb sub might be shorting out a coil under high excursion, or touching the tinsel leads. Hook up your multimeter to the speaker leads, push the sub all the way in and all the way out, see if the coils ever short.

Boomin track, both the first ideas are not very good advice, getting a sub amp makes sense, since it will put out much more power to that sub. But all of them defeat the purpose of buying a 5 channel amp, which was to run everything off of one amp.

Dave

WhiteRabbit · 04-12-2005, 11:09 AM

if you want to test what exactly is causing your problem, start disconnecting speakers one at a time, regardless of whether or not hte amp can handle the load. start by disconnecting the subwoofer fro the amp itself, leaving the sepakers hooked up. see if the amplifier goes into protect. you can work this way through until you have all your speakers disconnected. if it still goes into protect at a certain volume on the radio, then its time ot turn down the bass and treble boosts on the radio. If the amp still goes into protect, its time to test the am pon a bench, in someone elses car, anything to isolate the amp from your car and your charging system. And finally, if it still goes into protect after this, its time to get your amp repaired.

isolate and identify!

dave2 · 04-12-2005, 03:53 PM

What he said.

Zshopa · 04-13-2005, 10:34 AM

had the same problem, it wasnt grounded well enough

skeeter007 · 04-13-2005, 10:43 AM

Quote: Originally Posted by dave2

No, the alpine will handle 2 ohms just fine. I'm guessing your voltage is dropping out, below 10.5 or so will send it into protect. Hook up that multimeter to the power leads and have a friend turn it up until the amp cuts, check what the voltage is when that happens. If your electrical system can't handle it, you might need a new battery or a cap to keep it alive. That's a relatively powerful amp, and they aren't too efficient, so they need lots of power. Since the amp turns back on, I'll almost guarantee that it's a voltage protection, not a heat protection. Thermal shutdowns require the amp to reset, by turning the remote lead off and back on, plus the heat needs to dissipate.

Only other idea is that the audiobomb sub might be shorting out a coil under high excursion, or touching the tinsel leads. Hook up your multimeter to the speaker leads, push the sub all the way in and all the way out, see if the coils ever short.

Boomin track, both the first ideas are not very good advice, getting a sub amp makes sense, since it will put out much more power to that sub. But all of them defeat the purpose of buying a 5 channel amp, which was to run everything off of one amp.

Dave

This sounds right on par with what I was thinking. I'm gonna get a meter and test it. I really want to use my 5-channel amp for all 5 channels, as I don't have much more room in the car for another amp. Thanks for the good ideas.

skeeter007 · 04-13-2005, 10:45 AM

Quote: Originally Posted by WhiteRabbit

if you want to test what exactly is causing your problem, start disconnecting speakers one at a time, regardless of whether or not hte amp can handle the load. start by disconnecting the subwoofer fro the amp itself, leaving the sepakers hooked up. see if the amplifier goes into protect. you can work this way through until you have all your speakers disconnected. if it still goes into protect at a certain volume on the radio, then its time ot turn down the bass and treble boosts on the radio. If the amp still goes into protect, its time to test the am pon a bench, in someone elses car, anything to isolate the amp from your car and your charging system. And finally, if it still goes into protect after this, its time to get your amp repaired.

isolate and identify!

Thanks for the help...I've done this step and stopped at the subwoofer, because when I removed it the amp no longer went into protect even with the volume all the way up. So right now I'm pretty sure it has something to do with the subwoofer-amp combination.

skeeter007 · 04-13-2005, 10:48 AM

Quote: Originally Posted by Zshopa

had the same problem, it wasnt grounded well enough

I was worried a bit about this, but I've tried multiple grounding spots with the same results. Where did you end up grounding to? I tried sanding the paint around a large bolt in the trunk and connecting to it with a ring connector. Then I tried (based on a friend's suggestion) connecting to one of the seatbelt mounts.

SergeykoR · 04-14-2005, 10:36 AM

then playing music, in some cases internal resistance of sub low down to 1 ohm and lower for a few milliseconds. So current (and heat on amp output transistors) increases too. Amplifier protection system recognizes this (and may NOT) and then immediately enters protection mode. It happens sometimes then concrete copy of power amplifier or concrete copy of sub are uncompatible with each other. Try other sub with more then 3ohm. In this situation no matter point of grounding or less voltage at inputs - they may call only loosing sound level at peaks for a very short time (good capacitor may fix it up). Also check the heat level from amp (it must not to be hot). It may helps subsonic filter to turn on (the amp has it), or low down boost regulator (the amp has it, calls Bass EQ). But on my opinion (we had the same situation a few times) you should try to change subwoofer itself.

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