Does it happen immediately when you use the system for the first time each day, or only after the amp has run for awhile? Is the amp warm to the touch when it is happening?
I would not bet on the head unit, but if you could test using any other source it would eliminate or confirm the possibility.
Googling around a bit I see a few instance of Alpine KTP-445u cutting out - usually on one side - at high volume, but no definitive fixes except what we are already discussing here - low voltage / poor grounding.
There is no light, or any visible feature that would help indicate of the amp is doing anything, much less going into protect mode.
Iāve been running these most recent tests with the engine off. In any case, the results seem consistent with the engine on. It happens anytime I play a high sound (like a cymbal crash) when the radio is nearing itās highest volume. The cutoff occurs at varying points on the volume dial. In other words some songs I can play closer to 60 (the max) than others, because of the high notes involved. So itās not at a consistent point on the volume dial across all different songs. Does that make sense?
The amp ground appears clean, tight and separate from the subwoofer.
I did test the amp as a 2 channel amp by switching the dip switch for that. No difference.
Perhaps it is the amp. I hadnāt thought about it previously, but I donāt think I bought this new, I think I remember buying this amp used, from eBay. I hadnāt considered that previously.
Itās a little bit unusual that an amp would go in to protect mode on a high note. I would expect it on a bass note, when itās drawing more current. Or whatever the lower notes that your front amp is expected handler, 60 Hz and above, I think in your case.
I think your next steps are to either try a different head unit / source, or a different amp.
Referring back to a previous post, you can use anything with an RCA output for your head unit. Doesnāt have to be another car head unit. For the purposes of testing.
OK, so I plugged in an old iPod that I had lying around. I had a RCA to headphone jack adapter so I was able to unplug the front speakers (still in 2 channel mode) and plug in the iPod and play the same song. (Ashes to Ashes, David Bowie)
Hereās the problem with that test.
How do I know the volume coming out of the iPod is the same as the head unit? I was able to play Ashes to Ashes without it cutting out, but then I switched to some random Van Halen song, and it went back to cutting out?
Can I use a multimeter to check that the output from the ipod is the same? Itās an ancient 5th Gen iPod Video. I have no idea what itās output audio specifications are.
I donāt think it matters what the output of the iPod is.
What matters is that the amp is still cutting out with a totally different source. So it is not a head-unit problem, itās something to do with the amp.
(If you had said you used the iPod cranked to max and got no cutout then the output of the iPod could matter b/c maybe it is not driving the amp as hard, and we get into a subjective conversation about what āloudā means. But that didnāt happen.)
I feel like we have eliminated voltage drop as a problem, you have ensured a good power feed to the amp via the 8ga cable, the grounds are good, youāve tried reducing the load on the amp (2 channel mode) and itās still not happy.
So now I am thinking the amp is āfaultyā. I say āfaultyā because it could be going in to some sort of āself-protectionā mode and the cutout could be by design. Meaning you buy same amp brand new and get same behavior. Which would suck.
Or.
The amp is legitimately ābroken.ā
When you are in two channel mode are all four speakers still hooked up?
Here is where my head is at with 2 vs. 4 channel.
The spec on the amp says any single channel is ok for 2 ohms.
In 4 channel mode you have 2 ohms on each front channel and 4 ohms on each rear channel. So far so good.
IF switching to 2 channel mode causes the two speakers each side to be run in parallel, you are now showing the amp less than 2 ohms. The formula for resistance in parallel is: 1/Rt = 1/R1 + 1/R2
So you have 1/2 + 1/4 = 3/4. The inverse is 4/3, or 1.25 ohms.
If running the amp in 2 channel mode with all four speakers means you are showing your amp 1.25 ohms it would not surprise me that it cuts out or overheats.
As a final test I would be curious if it cuts out using only the 4 ohm speakers in 2 channel mode.
If YES, then definitely an amp problem. It should handle that load easily.
If NO, then perhaps your setup is just asking too much of the amp. Yes, it should work fine with your 4 channel setup, but maybe you are just too close to the edge.
I swapped it over, simply swapping RCA connections at the ampā¦while set to 2 channel. Still cuts out.
I will addā¦ while it still cuts out, I think it doesnāt cut out as quickly when the car is on with the engine running. It will still cut out, but I may be able to eek out another one or two numbers on the volume dial. I donāt suppose that would make a difference.
I may just upsize and go with the 75W KTA-30FW amp. That should easily handle what I need.
Is there any chance that the head unit is starved for power at the top end of the volume knob which is why Iām not seeing a difference when I use the #8AWG wire to the amp.
I did not use that 8AWG wire for the tests above, but I will. Iām sorry. I donāt know why I didnāt, it was such a perfectly warm day to run tests yesterday.
When running 2 channel, I tested with and without the other two speakers plugged in. That seemed to make no difference at all. (Dip switch on amp set to 2 channel)
Veekay, letās take a couple steps back and walk this thru. I feel like I am missing something. If you are willing, let me make sure I understand the baseline, then we can change one thing at a time and see what we learn.
Step 0: Current configuration:
Head Unit
4 channel high end amp
Powered subwoofer
You have 3 pair of RCAs leaving the head unit:
2 pair to the 4 channel amp for front and rear speakers
1 pair to the powered sub
The head unit is connected to a 12v battery (should be yellow) and a 12v switched power (should be red).
Both ampsā positive wires are connected to a yellow wire that connects to the head unit.
THIS is a key point: Previously I think you said that the amps are connected to the yellow wire that comes āoutā of the deck. I think I took this wrong and confused myself. I have never seen a deck that has a power āoutputā for amplifiers. That would go against pretty much every principal of high-end audio, and I got a bit wrapped around the axle thinking about it.
I think that this yellow wire is the 12v battery wire, and you are using it for the deck and both amps.
This means that the deck and both amps get power directly from the battery.
Am I correctly describing your system?
Am I correct about the yellow wire?
Now 2 questions:
Assuming that I have described the yellow wire above correctly, and that it is a 12v battery connection, what it is connected to? Fuse box, something under the dash, something else?
Please describe exactly how each amp is grounded: How long are the ground wires, and what do they connect to?
Once I understand the above Iāll have more questions and suggestions
You are correct for your understanding of my system. Both amps are currently connected to the same yellow wire for power, which is also connected to the head unit. Iām sorry I confused you with the how I described the circuiting.
The yellow wire gets (switched) power from the battery through a fuse block. That fuse block was originally 10A (which is lower than the fuse in the head unit, at 15A). I need to check the fuse rating for that circuit, but it certainly seems that it is now overloaded, even at 10A! The head unit carries a 15A fuse, and the powered subwoofer carries a 10A fuse. There should be nothing else on this circuit. Just the head unit, and currently the powered subwoofer and amp.
I do have a question here. I canāt figure out how the switched power is circuited based on the diagram. It seems that battery power is circuited through the Seat Heater Relay and then feeds fuses for the radio, driverās seat heater and passengers seat heater. Iāve attached the diagram for the switched power.
I am determined t run a new (fused) 8AWG wire directly from the battery post in the trunk to serve, at the very least, the amplifier. Iām willing to hook up anything else to that wire, or even upgrade that to a 4AWG if needed. That will leave the head unit on itās current yellow-wired circuit, along with the powered subwoofer, which I will probably bring over to the 8AWG wire as well, once we figure this whole thing out.
The unswitched, or radio memory power has itās own 10A circuit as well. Nothing else on it after the fuse.
My references show that the yellow wire on the head unit should be 12v constant, and the red wire should be switched. Are you sure the yellow wire is connected to a switched source?
I will have to study these. Are the red and yellow highlights your red and yellow wires?
This is the right answer. 8 or 6 awg is plenty. Be sure to fuse it close to the battery, there are lots of cool high-current fuses out there. Iād go something like 40-50 amp. The purpose of this fuse is to blow if this power cable gets shorted to ground. It is NOT to protect the amps.
You should hook the sub and high-end amp both to this new power wire.
You should then have individual fuses of the appropriate sizes in the individual power wires for the amp and sub.
Each amp should have its own ground wire that is as short as practical (say 24 inches or less) and at least the same size as the power wire to the amp. These should be ground directly to a bare metal spot on the body.
I would do all of this next. itās the right way to wire the power side of the system, and if you end up upsizing the amp, youāll need it ever more. If you still get cut-out with this new power set up when the car is running then we look further.
Youāre right, yellow wire is constant power. My mistake. They cannot be switched, otherwise the headunit would either (a) lose all memory settings when the car is off, or (b) stay on with the car shut off.
No, yellow just indicates the circuit to the radio. The red is just shared circuiting. I should have picked different colors.
I will fuse it to 40A. Thatās well above the sum of the fuses on that circuit (15A + 10A = 25A) I will tie both amp and subwoofer to this new wireā¦also fused once I stepdown wire sizes.
I will measure and clarify the wire gauges for the ground wires.
Iāve found that eBay does a better job of having things Iāve needed. The toughest was a fused splitter, carrying both fuses before downgrading wire.
I have everything I need, I just need to pull the 8AWG from the trunk into the passenger compartment.
Iām pretty sure itās a faulty amp. I have the same exact amp, same 2 ohm front speaker brand, model and size, a set of 4 ohm midranges for the rears, same Kenwood subwoofer. I have done nothing special for power. No direct line to the battery, just tapped off existing power wires. Iāve played a variety of hard rock music, loud, with no cutouts at all. Iām running off the RCA outputs of my JVC headunit.
I did not deviate from using the harness that came with the amplifier, so power and ground wire gauges and lengths are no longer than what cam with the amplifier.
Iām still going to run that 8AWG into the passengerās cabin to connect both the amp and the powered subwoofer to. Thatās never going to hurt either way.
Will conduct more tests when the weather gets a little more pleasant. Thank you for taking the time to help!
I replaced the amplifier with a larger one. I bought the Alpine KTA-30FW. Still a Class D compact amp. It has solved the problem. It now goes louder than I need it to (Gain is at just below half) without any cutting out. If something changes, I will come back to update this thread.
I did run a fused 8AWG wire straight from the battery to a secondary fused splitter, where both the sub and the amp get direct power.
Thank you for your help and analysis. I learned a great deal from this, so it wasnāt a complete waste!!!
