amps getting hot

Hi, New here and new to audio, so go easy on me.

I've been lurking for a while. I installed a dual amp setup last weekend. Here's the specs.

99 Jeep cherokee XJ without the factory amp. Rockford Fosgate T600-4 amp running my infinity mid/highs connected to a rockford 1 farad cap. I have an alpine mrp550 bridged to run 2 10" alpine type E's.

JL battery terminals. 2 gauge marine grade wire for all my battery/alt power and ground. I put a 100amp anl fuse between the alt and battery. The ground to chassis is under 6 inches and the motor ground is as short as possible with the factory motor to chassis ground in excellent condition. All connections are clean and secure.

I have 10ft of 1/0 cable (from a stereo shop) for the amps with a good quality fuse holder within 6 inches of the battery. At the end of the 1/0 I have a fused distribution block with 4 gauge wire going to a Rockford 1farad cap then to my T600-4. My mrp550 amp only accepts 8 gauge. I ran 8 gauge to that amp.

Both amps and the cap are located on the floor behind my drivers seat. with plenty of room for ventilation.

My system sounds great. I'd like to add a capacitor for my subs amp and replace the bridged alpine mrp f550 4 channel amp with an amp that is better suited for subs.   

Now the problem.

I connected the cap and both amps with as short as possible ground cables, using wire gauges that match the corresponding power wire. I initially connected everything to the nearest seat bolt using eye lugs. The amps got hot real fast. I redid the ground by drilling out the 5/16 threaded hole in the floor to 1/2 inch. I slipped a 1/2-13 socket cap head screw with a washer through the floor and seat bracket and welded the bolt head and washer solid to the underside of the floor. I was hoping that this would make my ground real good. there is a lot of layers of sheet metal layered and spot welded together where the seat bolts are located on the cherokee's uni-body.

I am a machinist. I read that it is ideal to connect all the grounds to one connection. I made a block from 6061 aluminum that allows me to strip, slip and pinch my ground cables with set screws. Piece of cake for me. That helped a lot, but my amps are still getting pretty hot very fast when the volume is up.

Both amps get hot. I tried each amp individually. Both amps get hot regardless of what is connected or disconnected. Nothing else in the system ever feels hot.   

My next step is to pony up for a block of 360 brass and remake my ground block. I understand that most circuit aluminum is 1000 series. I'm wondering if 6061 has to much resistance or if my layout is flawed.

Any suggestions?

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The ass of my art form is always exposed

Brass - no way! Unless you know it's conductivity and size appropriately. Brass has ~30% the (electrical) conductivity of copper but can be lower than 10%.

Compared to Cu electrical conductivity as 100%:
Brass (generally) is ~30%
Aluminium is ~60%
Gold is ~70%.


However, considering steel is only 15% or far less, maybe it doesn't matter. (LOL - find out your conductive cross-sectional areas or voltage drops - not that that necessarily causes amp overheating.)


And can you confirm you have NOT connected a cap across the outputs of an amp - I assume (do'h) that the caps are on the DC power side of the amps. But the caps are most likely better off in a bin anyhow if you can afford a 1.2AH or bigger AGM battery in their place.

I'm wondering if aluminum's resistance varies greatly from alloy to alloy? My aircraft wing aluminum has to have different electrical conductivity than circuit board aluminum.

I thought many stereo components/terminals were made from plated 360 brass? I assumed that is the way to go. I'm surprised to see the ratings.

I began researching ground resistance and hope to take measurements asap.

I have my cap wired with a 4gauge + from my distribution block to + terminal on the cap. The neighboring + terminal on the cap is wired to the amp + with 4 gauge. I have a 4 gauge ground wired in the - terminal on the cap to my aluminum ground block and a separate 4 gauge ground wire from the - terminal on the amp to the same ground block.

The second amp is on a separate fuse from the distribution block. It is not wired to my cap, but shares the same problems. It is also ground on my aluminum block. The amp only accepts 8 gauge +/-. Both wires are in the correct terminal on the amp.   

I have an optima red top in the factory location. My alt is fairly new and stock 90 amp. I'd like to find a grand cherokee 117, 136 or 160 amp alt and add a second isolated deep cycle battery. My Jeep is offroad equipment with the every day amenities of electric windows/locks, AC, ect. I also have an electric winch, electric air compressor, fans and additional lights coming up. I travel to remote areas and camp. The second battery offers excellent peace of mind, not really for additional power(I'll take it though).

Thanks

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The ass of my art form is always exposed

If Al is like Cu alloys, then conductivity usually drops (markedly). I think it's the same with iron (eg steel is under 30% & down to ~3%).

Silver conducts better than Cu, but Cu is amongst the best. (have you Google'd or Wiki'd?)
(LOL! I was expecting a "so why gold plate if it conducts 30% WORSE than Cu?"!)

I have written often enough about AGM batteries that are wasted in the original location so I won't repeat. Nor will I repeat "wasted" money on caps....

i am an idiot wrote:

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How many speakers do you have connected to the amps?  Are your multi-channel amps bridged?  What Ohm are the speakers connected to the amp?

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My Rockford Fosgate T600-4 is not bridged. I am using all 4 channels on the amp. My front speakers are infinity reference 6.5 component speakers. Apparently each component is 2ohm, but when connected correctly with the crossover, tweeter and mid woofer it produces a "true 4ohm" according to infinity. My rear speakers are 4ohm sony xplod 5.25's

My 4 channel Alpine MRP F550 is bridged to 2 channel. I am running 2 Alpine 4ohm 10 inch type E's.

All my speaker wire is new, high quality speaker wire. All my power/ground wire is brand new, high quality wire. I got all the wire from the most reputable stereo shop near me.

I got nice RCA's, my head unit is a new Alpine IDA-X303. All my speakers are new or near new. My battery is not new, but puts out good voltage and holds it's charge superbly. All my battery wiring is new.

I'm new at this, but I've double-double checked my wiring and can't find anything incorrect. It's all very straight forward to me.



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The ass of my art form is always exposed

oldspark wrote:

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If Al is like Cu alloys, then conductivity usually drops (markedly). I think it's the same with iron (eg steel is under 30% & down to ~3%).

Silver conducts better than Cu, but Cu is amongst the best. (have you Google'd or Wiki'd?)
(LOL! I was expecting a "so why gold plate if it conducts 30% WORSE than Cu?"!)

I have written often enough about AGM batteries that are wasted in the original location so I won't repeat. Nor will I repeat "wasted" money on caps....

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I like the Absorbed glass mat battery in the stock location for no other reason than it doesn't leak acid. I pull the battery regularly to power a mobile welder for trail repairs. It's just nice to not tangle with toxins while camping in the wilderness for extended periods. Aside from pulling the battery, the jeep gets air born on occasion and crashes into rocks on a monthly basis. Not that I plan on it, but I have been in a roll (a friends bronco) that was bad enough that the front passenger fender, rim, and hood got ripped off. The battery came out still clamped to the tray. The group of 10+ jeeps teamed up and got the bronco rolling. The optima was dusty and scuffed but fired the engine right back up.

I want my stereo to have an excellent sound quality. Which it does. I'm tickled that the stereo sounds good from Henry Mancini to Megadeath to Beastie boys. It's nice that it gets loud enough to hear every note over the mud tires and all the rattles. I'd also like to blast the stereo in the desert while camping at night during the winter. The battery and alt need only supply the enough to do those things. I'm not competing in anything. I'm not likely to get into any winch fest's either. What I have seems to perform worry free and has done so for many years.

I am curious to read your point of view. I will search your posts at my leisure. You have peaked my interest on caps. I will be removing the rear bench seat when I finish my cage install. I'm planning to adapt a bucket seat to one side and build a tool box, spare tire rack and stereo equipment enclosure to the other side. I hope to have room for additional batteries in the enclosure.



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The ass of my art form is always exposed

With the amps cool, power them up and leave the volume at Zero, leave them on for about 10 minutes.  Are they hot?  If they are only barely warm, they are working properly.  If one or both heat up even with no volume, the dias adjustments may be off. 

Have you ever removed the cover of the amps and adjusted any controls that you could not get to with the cover on the amp?

i am an idiot wrote:

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With the amps cool, power them up and leave the volume at Zero, leave them on for about 10 minutes.  Are they hot?  If they are only barely warm, they are working properly.  If one or both heat up even with no volume, the dias adjustments may be off. 

Have you ever removed the cover of the amps and adjusted any controls that you could not get to with the cover on the amp?

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I did the 10 minute test. I could not feel any change in temp. Seems good.

what is "dias adjustments"? My gains are at .5 volts.    

I bought the amps used. I can't know for sure if the amps are unmolested. Are there further tests to make a diagnosis? I feel like I'm learning a lesson here.    



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The ass of my art form is always exposed

If they did not heat up, your bias adjustments are fine.  Do not take it apart and look for them.  They do not need to be adjusted, if you like your amps they do not need to be adjusted. 

JP - AGMs use as you describe are totally cool.
At first I was thinking "what spills" - but mine are semi-sealed (unlike the old capped ones that used to wreck my chrome every time I dropped my bike) without leaks - not that I have inverted them or had them tipped over for long.

My anti-AGM comments are for audio buffs that get them for their low ESR (or internal resistance), but instead of mounting next to or near the amps, they mount them in the engine bay which usually defeats much of that purpose (path resistance (and inductance?) from batt+ to amp and then back via GND). Add to that, wasting an AGM with engine starting when normal batteries may tolerate it better...
Granted that for audio, an AGM is better than a wet cell, but all that for a 10 milli-Ohm gain or less?

IMO the best is an AGM near the amps, and normal battery for the engine. Hence can concentrate on low resistance between the AGM & amp (with arguably less critical alternator/battery to AGM depending on alternator and amp capacities etc.)    


The cap argument is straight forward. You may need a cap if the amp is far from its low-impedance power source. But even a small AGM battery will usually outperform cap of several Farads. So why not a $20 1.2AH or $35 7AH AGM next to the amp instead?
Arguably paralleling batteries has issues, but so too does charging a BIG discharged cap. And either cap or AGM can drag down and ruin the prime battery - though that is far more likely with the AGM.

In short - ignoring parallel battery issues - an cheaper AGM battery or similar will outperform a cap (for dips; and both are likely to result in lower SPL).
(And if the AGM is big enough - say (maybe 7AH else) 15AH or bigger, it's a handy emergence cranking battery.)

But you'll find heaps of posts & refs on that... (sales people included).

Looks like 6061-t6 (the state of the alloy I used) has 40% + conductivity. It doesn't seem terrible.

Any other suggestions on possible causes?

The amps really can get hot when the volume is up. Just below to hot to touch and just above to hot to hold.

Thanks for all the Help BTW!

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The ass of my art form is always exposed