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CC2MC
09-08-2013, 10:33 AM
I helped a buddy to get his tower speakers going as they have not worked since he has owned the boat. It has an MTX marine 900watt amp. I found out that the 4 channel option was not working for some reason so I switched it to 2 channel and turned the gain up. I was able to get sound by soon that. I set the tower speakers a little louder than the speakers in the boat and they sound good. However, after being on for 45 mins or so, the amp gets hot and goes into protect mode, turning the tower speakers off. It will come back on after it cools back down but will get hot again. What is the problem? Is there an easy fix?

Traxx822
09-08-2013, 11:00 AM
Sounds like a blown amp. I had an RF amp in a thunderbird back in highschool that did the same thing. Sounds to me like the amp is bad if it is not working in 4 channel and it overheats regularly.

I'm not a guru on this stuff but there isn't any setting on the amp that should hurt the amp. The amp should be able to put out what it says it can. I mean there may be a couple switches that if both are on then it could cause damages, but simply changing channels output and gain should have no affect on the amp. It would maybe blow speakers if overpowered but never the amp.

So it sounds like the amp is bad.

Maybe Earmark or Jim can chime in. They are the resident experts here.

MLA
09-08-2013, 12:40 PM
Class-A/B id guess?
Is it set to full-range or Hi-Pass? If hi-pass, whats the cross-over frequency dial set at?
How many speakers per chnl?
is it bolted directly to a carpeted wall?
Gain too hi also adds to the amps work load, so setting it at optimal or below is best.

CC2MC
09-08-2013, 01:18 PM
Unsure what class. Not sure what that means exactly. I think it was set on the FR setting. There are two speakers per channel, actually only two speakers total. When it first went out, it sitting on the seat, which I just thought was the reason for it getting hot. The next time, it was just sitting propped up in the storage under the seat, out of the water and on the trailer. It was previously mounted to the side of the subwoofer box and now it is unmounted. I did tell my buddy to put a spacer between the wall and the amp to let some air flow behind it. Could it help to just put one speaker on each channel and adjusting the gain?

JimN
09-08-2013, 02:25 PM
I helped a buddy to get his tower speakers going as they have not worked since he has owned the boat. It has an MTX marine 900watt amp. I found out that the 4 channel option was not working for some reason so I switched it to 2 channel and turned the gain up. I was able to get sound by soon that. I set the tower speakers a little louder than the speakers in the boat and they sound good. However, after being on for 45 mins or so, the amp gets hot and goes into protect mode, turning the tower speakers off. It will come back on after it cools back down but will get hot again. What is the problem? Is there an easy fix?

Use a multi-meter, set to Ohms, to check the speaker wires on each speaker, then from one speaker to another (if separate wires were run to each speaker, then from the speaker wires to the tower. If you see any continuity from the speaker wires to the tower, it will cause problems, especially if you see it on both channels- you can't combine ANY connections between the channels. It is possible that the amp has a problem- what model? It could also be a problem with at least one speaker- if you can substitute other speakers, do that.

What is the gauge of the power cables, does it have distribution blocks, were the ring terminals crimped, or crimped AND soldered (the best way)?

Do a voltage drop test on the power wires and write the results on paper- set the meter to DC Volts and connect from the battery post (NOT the terminal) to the terminal, then turn the system on. If you see voltage, you have a resistive connection. If you see no voltage (set it to the lowest scale), move the probe from the terminal to the next connection down the line, whether it's at a distribution block or the amp. If you see voltage, you have a resistive connection. Once you get all the way to the amp, look at the measurements- anything more than .1VDC total is a problem, more is a bigger problem. Repeat this on the ground cable- it's very possible to have a problem on one without having a problem on the other, but the solution MUST be found because both sides affect the amp's performance, longevity, your speakers and your ears.

If you don't see a problem when the boat isn't running, run the engine and repeat the tests. Wiggle wires while you test each connection.

If the amp doesn't work in 4 channel mode, is this with two, or four speakers? If it's with two, make sure the connections are on the correct terminals- most amps use L+/R- when in bridged mode but the switch must be in the correct position.

MLA
09-08-2013, 02:54 PM
Unsure what class. Not sure what that means exactly. I think it was set on the FR setting. There are two speakers per channel, actually only two speakers total. When it first went out, it sitting on the seat, which I just thought was the reason for it getting hot. The next time, it was just sitting propped up in the storage under the seat, out of the water and on the trailer. It was previously mounted to the side of the subwoofer box and now it is unmounted. I did tell my buddy to put a spacer between the wall and the amp to let some air flow behind it. Could it help to just put one speaker on each channel and adjusting the gain?

Class-A/B is the least efficient. A lot of the battery power consumed is converted to heat. Having all 4 chnls driven at a 2 ohm (2 4 ohm speakers wired in parallel per chnl) is a real work out for amp. This can add to the heat. With the amp playing for awhile, shutting down, then returning to service, does sound like thermal shut down. Moving the cross-over filter to HP, will also reduce to load on the amp. Just a few simple adjustments that might help out.

JimN
09-08-2013, 03:54 PM
Class-A/B is the least efficient. A lot of the battery power consumed is converted to heat. Having all 4 chnls driven at a 2 ohm (2 4 ohm speakers wired in parallel per chnl) is a real work out for amp. This can add to the heat. With the amp playing for awhile, shutting down, then returning to service, does sound like thermal shut down. Moving the cross-over filter to HP, will also reduce to load on the amp. Just a few simple adjustments that might help out.

An amp that's Class A/B operates in Class A at low power levels, only. It's designed to operate more efficiently at higher power levels. A Class A amp is the least efficient because it operates at about 70% bias level at all times.

MLA
09-08-2013, 04:58 PM
Great info Jim, thanks for sharing. So who in the mobile 12v amp world is currently producing Class-A only amps? This way, others would know what to steer clear of.

JimN
09-08-2013, 05:04 PM
Great info Jim, thanks for sharing. So who in the mobile 12v amp world is currently producing Class-A only amps? This way, others would know what to steer clear of.

I can't think of any because it's such an inefficient design and with 12VDC systems, efficiency is (theoretically) king. I took your comment as more of an absolute.

MLA
09-08-2013, 05:21 PM
I can't think of any because it's such an inefficient design and with 12VDC systems, efficiency is (theoretically) king. I took your comment as more of an absolute.

I thought so..........no worries. It was more of whats currently available in the retail market.

EarmarkMarine
09-08-2013, 05:58 PM
Just speculation but I am a little doubtful that the MTX amplifier is defective since it plays for 45 minutes before shutting down. Usually an amplifier with an internal failure won't make it that long. The issue is more likely to be an external issue like voltage, impedance/load, wiring, implimentation, or a combination.

There certainly are topology differences between Class A and Class AB other than the amount of applied bias. The original SoundStream company made pure Class A automotive amplifiers for a short time in the late '80s and it didn't last long.
Class AB is less efficient at lower power levels and more efficient at higher power levels since the bias current is a higher percentage of the output at lower power levels. There is simply less waste as a percentage at full output. But the topology is still inherently wasteful at any level and produces a ton of heat.

David

JimN
09-08-2013, 06:59 PM
I thought so..........no worries. It was more of whats currently available in the retail market.

A couple of years ago, I saw a car amp that used tubes for the output, but it was push-pull.

CC2MC
09-08-2013, 07:51 PM
Jim, not sure on the exact model. I did not have a multi meter handy when I was working, so I had to just get a 9V battery to make sure the speaker wire connections were good. I got a pop from each speaker, so I confirmed the speakers were at least hooked up. I will bring my meter back over to his house, the next chance I get and check the wires. I can't really answer any of the other questions either unfortunately without having the boat in front of me. When I get back over there, I will try to get some pics. Not sure if it matters but there are two MB Quart 6x9 speakers in some Titan cans. Unsure of model or any specifics though. I know this is not much help for now, but thanks for the detailed reply.

swatguy
09-08-2013, 08:07 PM
Far from the expert here as the few have chimed in. What model amp and speakers are you running. I am a bit confused as you say there are two speakers on each channel but then you say he only has two speakers. I am guessing maybe the speakers are not 4ohms and you are over loading the amp possibly.


The exact amp or speaker models would def help

EarmarkMarine
09-08-2013, 08:18 PM
A couple of years ago, I saw a car amp that used tubes for the output, but it was push-pull.

http://www.butleraudio.com/

Earmark carried the above brand years ago as purely a novelty along with some fullrange ribbon tweeters. Not sure if it was a hybrid. Silly in a car, I know.

David

CC2MC
09-08-2013, 08:21 PM
Far from the expert here as the few have chimed in. What model amp and speakers are you running. I am a bit confused as you say there are two speakers on each channel but then you say he only has two speakers. I am guessing maybe the speakers are not 4ohms and you are over loading the amp possibly.


The exact amp or speaker models would def help

Will see what I can get. As I said, I will get some pics next time with some details. I did not mean to say that I have two speakers on one channel. There is a front and a rear, so I have both speakers on the front L and R.

JimN
09-08-2013, 09:57 PM
http://www.butleraudio.com/

Earmark carried the above brand years ago as purely a novelty along with some fullrange ribbon tweeters. Not sure if it was a hybrid. Silly in a car, I know.

David

It was someone else. I'm familiar with the Tube Driver and would have made the connection.

Here it is-
http://milbert.com/bam235ab

skitilldark
09-21-2013, 10:59 AM
Sounds like a blown amp. I had an RF amp in a thunderbird back in highschool that did the same thing. Sounds to me like the amp is bad if it is not working in 4 channel and it overheats regularly.

I'm not a guru on this stuff but there isn't any setting on the amp that should hurt the amp. The amp should be able to put out what it says it can. I mean there may be a couple switches that if both are on then it could cause damages, but simply changing channels output and gain should have no affect on the amp. It would maybe blow speakers if overpowered but never the amp.

So it sounds like the amp is bad.

Maybe Earmark or Jim can chime in. They are the resident experts here.

I agree with traxx, the amp I blew this past summer did the same exact thing.