# HELP: Amp Randomly goes into protect mode



## xspl14x (Oct 26, 2017)

Hey guys, I have a problem with my amp going into protect that I cant track down and I figured someone on here might have some insight as to how I can solve it.

*Setup*: 

2009 Subaru Legacy w/ factory Harmon Kardon 1000W stereo system (not sure if this matters)

Line out converter from back of factory HU

*Power*: Memphis Audio 16-sr1.250 Monoblock Amplifier, 250 Watts at 2ohm, 125 watts at 4 ohm (rated stable 1 ohm). Power wire is 10 awg and comes directly from battery with inline fuse block about 6" from battery through the firewall, and fished back to the amp. Its grounded to the metal trunk floor pan where I have removed all of the paint. 

*Subwoofer:* Rockford Fosgate Prime R1L-2X10" Pre-built, sealed subwoofer enclosure, (300W RMS 600W Peak, 2 Ohms total impedence) with spring post connectors. The wire going from the amp to the spring post is 14 awg.

This setup worked perfectly and kicked really hard when I first got it, but now I am running into issues. The protect mode on the amp keeps randomly kicking on. Sometimes it will make it through a whole song without doing it, sometimes it stays in protect for the majority of a song. Occasionally, it will go into protect for 30 seconds, kick back on for a second and hit one note, and then go right back into protect. This issue happens at any volume, any gain setting, and at any EQ setting. Some songs its alot worse, some songs have no issue at all. I did some troubleshooting with a DMM and confirmed that my voltage at the positive and ground terminals stays above 12.5 volts when it is kicking the hardest. Voltage at the battery and at the terminals is 14.6 with no music on and car running. 
The amp doesnt get hot at all, and none of my wires are getting hot either. 

Other than the equipment being no good, what do you guys think the problem could be?

Any help/insight/advice would be greatly appreciated

-Thank you


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## xspl14x (Oct 26, 2017)

Update: The amplifier does not go into protect mode with the RCA inputs and subwoofer wires disconnected...sounds to me like an issue with the subs themself, but its a box made by rockford that is fairly new. If need be I could pull the subs out of the box and inspect the connections but Id rather not have to do that. Let me know what you guys think


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## miniSQ (Aug 4, 2009)

assuming there is no stray wires? either speaker wires or power wires, i would turn the gain completely counter clockwise and play some music if it does not trip, then turn the gain up a bit and repeat until the amp goes into protect.


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## SPLEclipse (Aug 17, 2012)

Is it possible that the power wire has loosened up over time either at the battery, fuse connections, or at the amp? Is the ground still good? I think your voltage is dipping more than you realize but it might not show itself consistently on the voltmeter.

It's also possible the remote connection is making intermittent contact.


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## xspl14x (Oct 26, 2017)

miniSQ said:


> assuming there is no stray wires? either speaker wires or power wires, i would turn the gain completely counter clockwise and play some music if it does not trip, then turn the gain up a bit and repeat until the amp goes into protect.


 nope, no stray wires. I even replaced the speaker wires going from the amp to the sub to see if that made a difference and it didn't. It did it about 3 times on my 30 minute commute to work today. I'll try what you said, but I have a feeling its not going to trip. It only seems to trip when the bass is hitting.


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## xspl14x (Oct 26, 2017)

SPLEclipse said:


> Is it possible that the power wire has loosened up over time either at the battery, fuse connections, or at the amp? Is the ground still good? I think your voltage is dipping more than you realize but it might not show itself consistently on the voltmeter.
> 
> It's also possible the remote connection is making intermittent contact.


Yes, since the problem started occurring I periodically checked and tightened my battery and ground connections, they are as tight as possible. Previously, I had tried wiggling around the remote wire at the amp with music playing and nothing happened. Removing the remote wire all together just shuts the amp off, it doesnt put it into protect. 
I hope its not an issue with any of the wiring at my headunit, because that would be a pain in the ass.


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## xspl14x (Oct 26, 2017)

Does anyone else have some insight on this topic? The sub box reads exactly 2ohms when tested with a dmm. I've heard of issues with very thin remote wires actually breaking inside the insulation when pulled to hard around a tight corner. Is there any way I could test if the remote wire is my issue without removing my head unit?


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## xspl14x (Oct 26, 2017)

I am open to the possibility of it being an issue with the way I wired my line-out converter. Is there anyway to test if I am getting a short/clipped signal from my RCA's inputs? I feel like that may be the issue. I used those stupid t-tap connectors (insulation displacement connectors, the ones where you put the two wires side-by-side and the blade cuts the insulation, making a mediocre splice connection). I know that is a noobish move but has anyone else used these to wire an LOC before?


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## SPLEclipse (Aug 17, 2012)

xspl14x said:


> I've heard of issues with very thin remote wires actually breaking inside the insulation when pulled to hard around a tight corner. Is there any way I could test if the remote wire is my issue without removing my head unit?


If you are very careful you can use a small wire to connect the B+ terminal on the amp to the REM terminal. Make sure you disconnect the remote wire you have in there now and properly protect it from grounding out. You will need to be VERY careful when doing this - don't let the screwdriver touch the case of the amp or any ground point. Do not let any wire slip out and touch the ground terminal or amp case. If you find it easier to disconnect the ground terminal while you're doing this and then reconnect the ground terminal last do that. This will cause the amp to be on all the time, even when the car is off, so only use it during a single drive for testing and don't leave it connected if the car will be sitting for more than 30 minutes or so.

Alternatively you could use any wire that has 12v+ to connect to the remote terminal to turn the the amp on. If you happen to have another 12v+ wire somewhere near the amp you could tap off of that to connect to the remote terminal.

I have a feeling like miniSQ is on the right track. That's a small amp, and if your gain is too high because you are trying to squeeze every last drop of power from it that would cause it to go into protect.


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## syc0path (Jan 23, 2013)

The OP already said he has this problem at any volume or any gain setting. 

How are the subs wired in the box? If u have 2 sets of speaker wire, I would try hooking up 1 sub at a time. I suspect the problem is in the box itself -- there may be some metal debris, stray strands of speaker wire, or possibly a partially shorted coil. My guess is that the amp will play fine w/ 1 sub but will continue to go into protect w/ the other. If that's the case, then u'll have to pull that sub and investigate further. If the amp goes into protect w/ either sub, then the problem is probably elsewhere.

If your subs share the same airspace, don't run them too hard when only 1 is hooked up or u might overdrive them.


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## xspl14x (Oct 26, 2017)

SPLEclipse said:


> If you are very careful you can use a small wire to connect the B+ terminal on the amp to the REM terminal. Make sure you disconnect the remote wire you have in there now and properly protect it from grounding out. You will need to be VERY careful when doing this - don't let the screwdriver touch the case of the amp or any ground point. Do not let any wire slip out and touch the ground terminal or amp case. If you find it easier to disconnect the ground terminal while you're doing this and then reconnect the ground terminal last do that. This will cause the amp to be on all the time, even when the car is off, so only use it during a single drive for testing and don't leave it connected if the car will be sitting for more than 30 minutes or so.
> 
> Alternatively you could use any wire that has 12v+ to connect to the remote terminal to turn the the amp on. If you happen to have another 12v+ wire somewhere near the amp you could tap off of that to connect to the remote terminal.
> 
> I have a feeling like miniSQ is on the right track. That's a small amp, and if your gain is too high because you are trying to squeeze every last drop of power from it that would cause it to go into protect.



Thanks for the advice man, thats a good idea. I will give that a shot and make sure I am very careful in doing so.


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## xspl14x (Oct 26, 2017)

SPLEclipse said:


> If you are very careful you can use a small wire to connect the B+ terminal on the amp to the REM terminal. Make sure you disconnect the remote wire you have in there now and properly protect it from grounding out. You will need to be VERY careful when doing this - don't let the screwdriver touch the case of the amp or any ground point. Do not let any wire slip out and touch the ground terminal or amp case. If you find it easier to disconnect the ground terminal while you're doing this and then reconnect the ground terminal last do that. This will cause the amp to be on all the time, even when the car is off, so only use it during a single drive for testing and don't leave it connected if the car will be sitting for more than 30 minutes or so.
> 
> Alternatively you could use any wire that has 12v+ to connect to the remote terminal to turn the the amp on. If you happen to have another 12v+ wire somewhere near the amp you could tap off of that to connect to the remote terminal.
> 
> I have a feeling like miniSQ is on the right track. That's a small amp, and if your gain is too high because you are trying to squeeze every last drop of power from it that would cause it to go into protect.





syc0path said:


> The OP already said he has this problem at any volume or any gain setting.
> 
> How are the subs wired in the box? If u have 2 sets of speaker wire, I would try hooking up 1 sub at a time. I suspect the problem is in the box itself -- there may be some metal debris, stray strands of speaker wire, or possibly a partially shorted coil. My guess is that the amp will play fine w/ 1 sub but will continue to go into protect w/ the other. If that's the case, then u'll have to pull that sub and investigate further. If the amp goes into protect w/ either sub, then the problem is probably elsewhere.
> 
> If your subs share the same airspace, don't run them too hard when only 1 is hooked up or u might overdrive them.


Big thanks to both of you guys for this advice. These are some great things to try and I will give them a shot. Within the box, the subs are wired in parrallel. One set of wires connecting the second sub to the first sub, and another set of wires connecting the first sub to the spring post terminals on the box. I have already taken those out of the box and the wiring looks great, and I checked their impedence, and they both check out.
But I may have stumbled upon something that might be my problem. 

This is the Metra line out converter I bought: https://www.bestbuy.com/site/metra-two-channel-line-output-converter/1265702.p?skuId=1265702

I didn't realize this when I first installed it, but I just found out today that this LOC has individual signal gain adjustments for both the left and right channels. I did not touch those at all when Installing my setup, so whatever they were set at when they were packaged is what they are at right now. So here is my train of thought.

Would my amp go into protect in any all of these situations :
A) The gain on both of these channels is too high, causing a clipped signal, tripping the protect circuit
B) The gain on both of these channels is too low, causing an almost undetectable signal with not enough voltage for the amp to distinguish and that is why its tripping the protect circuit
C) The gain on one channel is significantly higher than the other channel (not sure if that would affect anything)

Another update to my theory is the fact that if I turn the Fader on my HU biased to the rear (the line out converter takes the signal from the rear left and right channels) I have no issues with my amp whatsoever and can play at any gain/volume/eq setting.

Is there any way I can test this theory without pulling my head unit back out? I know you can measure the signal with an oscilloscope using test tones, but unfortunately I don't have access to one. Can I use a multi-meter?
To me this feels like a eureka moment, but I dont want to jump the gun, so let me know what you guys think.  :bowdown:


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## xspl14x (Oct 26, 2017)

Update: 

I measured the AC voltage output of my RCA's (unplugged from the amp) with a 60hz test tone at a high volume, using a Fluke True RMS Multi-meter and I was getting .83V (which is 1.224 at peak) on the left channel, and .77v (1.08V at peak using the equation "RMS Volts" multipled by sqrt(2) ) 

Is this too low of a voltage for a input signal?


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## SPLEclipse (Aug 17, 2012)

That is really odd. ~1v is enough signal to drive any amp, although the gain on the amp might have to be turned up quite a bit to match that signal voltage.

Perhaps try increasing the gain on the LOC to 2-3v if possible and adjust the gain on the amp if necessary to match. I don't know what could be causing your issue but that might fix it, lol.


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## syc0path (Jan 23, 2013)

No, low input voltage isn't the problem. Voltage that low might not give u the best sound quality, but it's not gonna cause the amp to go into protect mode. For the sake of argument, let's say u have a 3V input. Well it's 3V at high volume. At low volumes, the input will be much lower -- maybe as low as .1V.



> Another update to my theory is the fact that if I turn the Fader on my HU biased to the rear (the line out converter takes the signal from the rear left and right channels) I have no issues with my amp whatsoever and can play at any gain/volume/eq setting.


How long did u run it before u came to this determination? Since this is an intermittent problem, it may have worked simply becuz it happened to be working at the time u did this testing rather than the fader actually having something to do w/ it. What happens if the fader is set to the middle?

If u really want to rule it out, u could temporarily hook up a different source to the RCA inputs to see if the problem continues.

A tip for bypassing the remote turn-on wire is to get a paper clip, straighten it, cover it w/ electrical tape or heat shrink, and then bend it into shape. Becuz it's a single strand, it's a lot easier to maneuver w/o shorting out.


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## xspl14x (Oct 26, 2017)

syc0path said:


> How long did u run it before u came to this determination? Since this is an intermittent problem, it may have worked simply becuz it happened to be working at the time u did this testing rather than the fader actually having something to do w/ it. What happens if the fader is set to the middle?
> 
> If u really want to rule it out, u could temporarily hook up a different source to the RCA inputs to see if the problem continues.


I got the setup back in august. It worked perfectly and sounded really nice, and kicked really hard when I wanted it to, but I usually never play that loud. This issue only started happening two weeks ago, and it seems to be pretty intermittent. But you make a good point in saying that the fader has nothing to do with it and this could've just been coincidence. When the fader is set to the middle, with all EQ settings at flat (+0db), the amp will trip the protection surface at any volume above 5. The range of my head unit volume control is 0-40, and I never usually play music past 18 or so. HOWEVER, this furthur complicates the problem. If I play at volumes ABOVE 18, with the Bass EQ setting at +1 or +2, it will not trip the protection circuit once. As soon as the volume or EQ setting dips, it will start doing it again. Thats not a coincidence, I know that for a fact. I just dont like playing at those volumes because: 1) I bet distortion is occuring, its just hard to distinguish, 
2) I dont want to damage my subwoofers or amplifier
3) Ill look like a a*****e.....

Why would it work at loud volumes but not low-medium level volumes?


Other than hooking up a different amp/sub setup, what could I hook up to these RCAs to see if the problem continues?
If my spliced connections at the head unit are loose, or the splice t-connectors arent making enough contact, will these kind of issues occur?


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## xspl14x (Oct 26, 2017)

SPLEclipse said:


> That is really odd. ~1v is enough signal to drive any amp, although the gain on the amp might have to be turned up quite a bit to match that signal voltage.
> 
> Perhaps try increasing the gain on the LOC to 2-3v if possible and adjust the gain on the amp if necessary to match. I don't know what could be causing your issue but that might fix it, lol.


Yeah that's what I am going to try this weekend. the LOC is buried behind the dash so I will have to take all of that apart. But im probably going to inspect all my splice connections and make sure nothing is shorting. And possibly find a way to make it so that my LOC is easily accessible, maybe in the passenger footwell or something, in case these problems occur again. 

I figured 1v is enough. The Memphis audio manual says the input range is 200mV (.2V) to 6V so i feel like that might not be my problem. It is weird because the amp doesnt get hot, and even when the subs were working fine, I always had the gain set at less than half, and never used bass boost of any kind. Maybe I just have some crappy RCA cables? Maybe the female RCA jacks on the amp are dirty or just going bad? what is weird is that it works fine at high volumes, but those are volumes that I dont want to listen at.


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