Need Help! My Class A Amp Is Running Very Hot

the cabinet over or around the vents  it is burning hot , I even feel the heat on the sides of the cabinet,

Can you measure with a thermometer?

Contact the dealer or manufacturer directly and explain the situation.

This is not normal.  Don't take any chances.

Doesn't matter what the problem is, and there is a problem.  If you aren't prepared to fix it your self, then an authorized service center or the manufacturer is the way to go.

It appears to me that the bias is way off. However, a simple solution (not the best) is to adjust the bias back to where it should be.  However, what caused the bias to float way off in the first place.  This is not normal.

enjoy

How hot is too hot, how hot is burning hot?

Measure with a thermometer !

You probably shouldn't have it placed inside of a poorly ventilated cabinet. My Class A amp is warm but not burning hot to the touch but I choose place it on an amp stand, not even within a rack.  Ventilation is important.

The L-590AX is spec’d as consuming 220 watts at idle (310 watts max). The L-590AXII is spec’d as consuming 260 watts at idle (330 watts max). Both models weigh about 63 pounds. The amp’s heatsinks are entirely enclosed within its metal cabinet, and are immediately adjacent to the side-panels, as can be seen here:

http://www.luxman.com/asset/product/L-590AXII/gb4.jpg

So the escape route for the heat corresponding to those power consumption numbers is almost entirely via the vents on the top, supplemented to a small extent by radiation through the side panels.

Given all of that it seems to me to be very possible that what you have described is normal, but it’s hard to say for sure. Perhaps another owner of one of these models will chime in.

@three_easy_payments, I believe the OP’s reference to "cabinet" pertained to the metal enclosure of the amp itself.

Regards,
-- Al

@almarg 

I believe the OP's reference to "cabinet" pertained to the metal enclosure of the amp itself.

Ah yes, I see I likely misread.

Have you talked to your dealer? What did he say?

Although others hear are diagnosing your amplifier with positive, absolute, definitive assessment they cannot know what might/could be wrong with your amplifier without a firsthand inspection or more information than you have provided it may well be functioning completely, fully, and entirely within the manufacturer's intended operating parameters at the very least/minimum you need to measure the temperature of the unit itself.

Actual temperature? "Burning hot", is very subjective! No one can(possibly/correctly) answer your question, without that fact/measurement. Not even the manufacturer. btw: your amp has a protection circuit, that will turn it off, if it senses over-current, abnormally high temperature, or DC drift(per the first page of the Owner's Manual).

The L-590AX is spec’d as consuming 220 watts at idle (310 watts max). The L-590AXII is spec’d as consuming 260 watts at idle (330 watts max). Both models weigh about 63 pounds. The amp’s heatsinks are entirely enclosed within its metal cabinet, and are immediately adjacent to the side-panels, as can be seen here: 

http://www.luxman.com/asset/product/L-590AXII/gb4.jpg 

So the escape route for the heat corresponding to those power consumption numbers is almost entirely via the vents on the top, supplemented to a small extent by radiation through the side panels.

Given all of that it seems to me to be very possible that what you have described is normal, but it’s hard to say for sure. Perhaps another owner of one of these models will chime in.

@three_easy_payments, I believe the OP’s reference to "cabinet" pertained to the metal enclosure of the amp itself.

Regards,
-- Al

Hi there, the cabinet on the top temperature is 28C which I think is just a little warm but acceptable but when I put my hand on top of the plastic vents (over the heat shrinks) it is extremely hot, way over my thermometer maximum temperature of 50C 

what kind of speaker cables are you using?  I about roasted a Classe CA200 20 years ago using Goertz spkr cables.....caused the amp to oscillate and overheat....can't remember what the tech explanation sorry 

the cabinet on the top temperature is 28C which I think is just a little warm but acceptable but when I put my hand on top of the plastic vents (over the heat shrinks) it is extremely hot, way over my thermometer maximum temperature of 50C

To add perspective, my Pass XA25 amp operates in class A and consumes an amount of power (240 watts at idle) that is very similar to yours. The XA25 is stated to be designed such that after it warms up to a stable temperature its heatsinks will be about 25 degrees C higher than the temperature of the room. (Elizabeth makes a good point about the significance of room temperature, btw. Each degree of difference in room temperature will make the same difference in the temperature the amp stabilizes at, following warmup).

So under typical room temperature conditions the heatsinks on my amp will approach 50 degrees C. Very significantly, however, in contrast to yours the heatsinks on my amp are on the outside of its cabinet:

https://www.passlabs.com/amplifier/xa25#lg=1&slide=8

The heatsinks on my amp also appear to have much greater total surface area from which to radiate the heat than the heatsinks that are inside of your amp.

So, again, it seems to me to be very possible that what you have described is normal, although I am not in a position to be certain about that.

Regards,
-- Al

If you just bought the amp and are that worried, perhaps Class A isn't for you.  In that case, I would return the amp and buy the Class AB version instead.

Questions: How much SPACE is open above the amplifier? How much space is under the amplifier? How much space is open behind and to the sides of the amplifier. Is it on the floor, on carpet? Is in on a hard shelf?     
Ambient temps? This is how HOT is your ROOM? If you live in the tropics or like me, regularly are at 80F/ 27C or higher, then the amp will be hotter. just the way it goes... If you room is at 74F / 23C that is not an issue.   
Does the 'too hot' mean if you left you fingers on it for thirty seconds you would have a second degree burn? Or just a bit of pain??    
If just some pain. then I say it is NOT too hot.     
I own a PREAMP that is a blast furnace. It gets really hot. I spoke to the guy who built them, and he said, normal.  
Things you can do: Raise it up a little higher off the shelf or floor. So small bits of wood under the feet. 1/2inch .. 10 to 15 mm is all you need. If the amp is on a shelt, it needs at least three or four inches free space above it. If it has less, you need to solve the lack of free space above it.    
All the "Danger Will Robinson Danger" nonsense spouted in other folks posts means nothing if the amp is designed to run that hot.

 Thanks for the feedback, to answer your questions, the Amp is placed on a  open wood shelf, the top and the sides are wide open, the room temperature is about 70 degrees. I can put my hands on the cabinet for a period of time no issue but when I put my hand on the vents it is very hot can’t hold it for 30seconds I will get burn

If it is so hot on the vents that you would get burned, I find it hard to believe, that Luxman would use a material such as plastic, as vents. 

Given what you have reported and Al's usual helpful stats it sounds like the amp is operating at normal temps for a Class A design. This is the main reason I am not a big fan of some of these designs--it's not so much the heat they produce and the impact on room temperatures. I have concerns about parts longevity in an enclosure that produces so much heat. Things get stressed at those temperature levels regardless of what specs they might cite and the repeated heating and cooling as you power up and down will also likely take their toll over time. I feel the same way about tube units that are not designed to allow the heat to dissipate easily from inside the cabinet. One of the reasons I love a ZOTL design like my LTA Ultralinear is that it runs remarkably cool for a tube unit. This will likely contribute to less parts failure down the road.

If you can hold your hand on it for 30 seconds, then it's not that hot.  Still, it's best to talk to the manufacturer/distributor if it really concerns you.

IF it is an used unit, make sure it is a 115v model ( not a 100v Japan model ) if you are in US otherwise a transformer is needed!

Read the paragraph under ’PROTECTION CIRCUIT’, on Page 1 of the Luxman AX590 manual: https://onahighernote.com/oahn/wp-content/uploads/2015/01/L590AX.pdf Luxman probably knows, how hot is too hot, for their product and have taken precautions.

IMO it probably is running as it is designed to run.  I have a Luxkit amp that runs hot, very hot to the touch so you wouldn't leave your hand on the unit and it has open vent slots but small heat sinks.  The kit has been around 30 years and works fine, sounds fantastic also.  One of the best sounding amps I have ever heard or built myself.  Oh course mine is slightly modified by me!

BTW the Luxman will wipe the floor with the First watt amp so I wouldn't even consider that move.

Happy Listening.

Perfectly normal. The amp has over temp protection. If it were abnormal it would be shutting itself off. This is what class A amps do. 

Read the paragraph under ’PROTECTION CIRCUIT’, on Page 1 of the Luxman AX590 manual: https://onahighernote.com/oahn/wp-content/uploads/2015/01/L590AX.pdfLuxman probably knows, how hot is too hot, for their product and have taken precautions.

Thanks for the info, it is very informative 
so many nice and helpful people here, love this site.

My experience with this amp is exactly that, it runs like a house on fire. But it sounds pretty good too. As some note, Class A amps typically run hot.

I replaced my Mc integrated with a Lux 590AX about a year ago. Wanted to try Class A. My equipment had always been in cabinets. That did not work with the Luxman. Even though the cabinets were pretty well ventilated the Luxman ran so hot that it would shut down after about an hour. So, I moved it to the cabinet top where it has lots of fresh air and I’ve had no further issues. Great sound and good looking unit with all the retro knobs but it needs LOTS of breathing space as it definitely runs hot. Maybe all Class A units do but this seems excessively hot to me.

You can check this with an inexpensive watt meter:

https://amzn.to/2nhr6Iv


Set it to watts and compare to your spec.
And yeah, class A gets very hot.

https://www.amazon.com/dp/B07R4W5DS7/ref=sspa_dk_detail_6?psc=1&pd_rd_i=B07R4W5DS7&pd_rd_w=G...=

Get one of these - a properly designed Class amp should not run any hotter than 50 to 55 Degrees C  

Good Listening

Peter

This is a funny amp, @pbnaudio


Look at the power rating, and look at the idle/max wattage.
Tell me what they say to you. :)

I've had Class A amps for years so to me what you're describing sounds normal. Looking at a picture of the inside of the 590, each of those massive heat sinks is for only four power transistors. That tells me the designers expected all that heat.

@khmyjy- Luxman has it covered. Just relax and enjoy your music.

I'd still be interested in having you take a few temperature readings at various locations using an infrared thermometer.

My WA33 woo runs extremely hot to ... to the point where if I put my hand on the chassis it will burn my hand ...literally...  I bought a fan to cool it off so it runs warm all the time now....

I have a 100 watt per channel pure class A Threshold SA/4e. There are large heatsinks along both isides of the amplifier. The heavy front face of the amp, and the large rack handles, are also part of the heat sink system. After it's been working for a half hour or so, the heat sinks get up to about 114 degrees F. 

Different amps, different temps! I am using 2 mcintosh 2205s and noticed one running hotter on one channel of heat sink then all of the others. After a thermogun and amp meter, I reset the bias and found a dirty connection. Read true maintenance manual from manufacturers to get specs. If you are technically apt, do it yourself! If not, find reputable repair or service. 

I have four Class A amps. I run two of them bridged in one system and each one is over 100 pounds of radiating fury.  That system is not one I listen to frequently during a hot summer - they would drive you out of the room in a bit of time.  Great in winter, though.

I doubt that you have anything to be concerned about - that is just the way Class A normally works.

OP--for a definitive assessment on operating parameters by someone who is really going to steer you in the right direction whichever situation unfolds---Join Luxman vintage yahoo group. The moderator there Hans is invaluable for info on Luxman. He is an archivist and a wealth of knowledge on anything Luxman.
I had a vintage class A/AB Luxman once. It did not  get hot enough ---there is so called class A and then there is true CLASS A---which may all that is going on here and coupled with internal heat sinks most assuredly results in higher temp. Although I did not read enough to gather whether you bought this used .. As Correct bias is paramount. Contact Hans for his 2c. Actually not sure he is moderator but that doesn’t matter. He is based in Europe I think. One time ordered a manual from him if I recall correctly. Long time ago. Be sure though that you actually communicate with Hans himself.

OP, all amps are different, so don't be sidetracked too much by remarks about other products. As some above have recommended, I would first want to find out how hot your amp actually gets. Terms like 'hot', 'burning hot', etc, are all subjective.That being said, I own the L-590AX, and was concerned about heat before the purchase. After owning it for a couple of years now, my assessment is that the amp gets what I would describe as "pretty warm". Certainly nothing approaching burning hot, I could put my hand on it anywhere, for any amount of time.Good luck, please let us know what you find out.

Get a KILLAWATT AC power measuring device for $20. It will tell you how many watts you are drawing. End of story. Its a very useful device, logs yoiur KWHr, time, voltage current, watts VA. I have 6 of them

We're cooking a roast tonight. How many kilowatts should it be?

+1 @ramtubes and erik,

Plug in the L-590 to a KILLAWATT to verify if the bias as specs

Power consumption 330W
260W (under no signal)

Thanks I just bought the Killawatt and plug the L590 to measure, the reading is fluctuate between 332W to 340W 
I assume is within specs?

@khmyjy,
Is the 332 to 340 watts with the amp idle, not playing any music but powered on? That’s how I’d recommend you test it, because the power draw should be “only” 260W in that case. If 332-340 is at idle, then It seems prudent to question the heat output. Do you have a local shop you trust to look at it?

http://www.luxman.com/
I don't know why peeps don't rely on manufacturer's websites. :)

Per this, it should be ~ 260 at idle, and ~ 330 at full power.

Disconnect all inputs, and outputs.  You may have some ultrasonic oscillations going on. 
If that does not drop the power, contact the manufacturer.

Best,
Erik

If OP's (khmyjy) amp is L-590AX and not the AXII, there's a possibility his amp is a 100v japan model.

The L-590AX is spec’d as consuming 220 watts at idle (310 watts max). The L-590AXII is spec’d as consuming 260 watts at idle (330 watts max).

Yeah, running a 100V model at 120V will absolutely cause this problem!

Hi I checked the reading it is about 332 Watts at idling with no volume and the same with music on

As I noted, disconnect the speakers, and all inputs, and measure again.

If it's still 330, and you are sure you are running a US model, contact the manufacturer.

They are pretty responsive.