Safe operating temperature-range for solid-state amplifiers

[Boomzilla]

Assuming a relatively high-efficiency power supply amplifier (such as Emotiva's generation 3 units), what operating temperature range is appropriate for the component?

Obviously, more ventilation is better - but on an otherwise open shelf, what "minimum top clearance" is sufficient? A half inch? An inch? An inch and a half?

Rather than estimate the required clearance, I thought that since I have a temperature-measuring gun, I could work "backwards" and determine a "minimum clearance" by amplifier temperature.

The question could also be asked in this form: If the maximum temperature of the amplifier during normal service is X-degrees with fully open ventilation, then how many degrees above that temperature (X+?) are acceptable with a top shelf above the amp?

Obviously, with any restrictions on ventilation, the amplifier temperature needs to be periodically rechecked to ensure that dust accumulation inside the amp, aging of parts, etc. has not significantly increased the temperature from the baseline.

I've previously run other Emotiva (Generations 1 & 2) amps with about ½ inch overhead clearance without issue, but was interested in others' experiences. The clearance (temperature rise) for a Generation 3 amplifier may be less than for an XPR or previous-Generation XPA amplifier (that were more heavily biased to Class-A operation and that generated more heat).

So out of curiosity, at what temperature does your Generation 3 amplifier run (assuming an air-conditioned ambient environment) and is it in a cabinet / shelf or is it in a free-air location?

Thanks - Boomzilla

---

PS: Found Keith L's comment below in another thread:

Unfortunately, this is one of those questions that seems simple, but is actually rather complicated.

The heat is actually generated inside certain components, then conducted to their heat sinks (or their casings), and finally to the air.
What counts - as far as the electronics are concerned - is the temperature at the actual silicon junctions inside the components.
And the ability of heat sinks to transfer heat to the air (and so get rid of it) depends on all sorts of things, including mainly the temperature of the air, and how fast the air is moving.
That second factor is especially important with amps that don't use cooling fans.

Because of the way convection cooling works, all of the "calculations" are based on the inside temperature of the amp running a certain number of degrees "above ambient".
With any device, the inside will ALWAYS be hotter than the air outside; and, without fans, the difference will be greater.
AND that difference will depend on there being unrestricted air flow so air can get into and out of the cabinet.
AND you can make the same sort of calculations about a cabinet, or an "equipment closet", or a whole room.

Unfortunately, calculating "limits" on all this stuff can get very complicated.....

Some good safe guidelines are:

1)
You need to have "unrestricted airflow" around the equipment.
This means that you can't block the vents, and you need at least an inch or two of space on the sides with vents.
It also means that the air has to have someplace to go... it has to be able to move into the vents FROM somewhere and out of the vents TO somewhere...
This is true at EVERY level; you can't block the vents on the equipment; and you can't seal your entire rack; and the closet the rack is in must have some sort of air flow.

2)
Assuming you've met that requirement, none of the equipment itself (the hottest spot on the top plate) should ever get too hot to touch with your fingers.
If you can put your hand there, and hold it for half a minute without screaming, then you're probably OK (that's about 135 degrees F).
So, if you have two amps in a rack, squeeze your hand in between them; if it hurts to do so, then more cooling would be in order.
(And, since it takes a while for the heat generated by power amps to reach the outside of their cases, you should play those as loudly as you ever do, then keep checking the temperature.
It should never exceed that safe temperature limit AT ANY POINT IN TIME - and you should check it from about one minute to about a half hour after you turn the volume up. )

3)
Excluding safety and "damage" per se, with most electronic equipment, the cooler you keep it, the longer it will live (and, usually, minimizing the changes between hot and cold - "temperature cycling" - also helps there).
(This is not quite an absolute, but many electronic components have some sort of "temperature derating" which says that, however long they usually live before they fail, that life span gets shorter at higher temperatures.)
Incidentally, even with tube equipment, where the tubes themselves run at relatively high temperatures, many other internal components have this same sort of relationship between temperature and service life.

4)
Always remember that heat takes a while to "work it's way from the inside to the outside", and that the amount of heat made by components like power amps depends on how much power they're producing. A Class A/B amp has some minimum heat that it produces all the time, based on things like bias current. Added to that is the "waste heat" generated by the output it is producing. With most Class A/B amps, including ours, the efficiency runs between 50% and 70%. That means that, if your XPA-2 is putting out an average power of 300 watts, it's making about as much waste heat as a 200 watt electric heater... and that heat will eventually have to be "gotten rid of". Therefore, after you play your amp very loud for a period of time, it will heat up.... and you must make sure you have enough cooling to get rid of THE MOST HEAT THE AMP WILL EVER PRODUCE. (This is why things like thermostatic fans, which can rev up to remove a lot more heat if they sense it's necessary, are usually a good idea in enclosed areas.)

So the question is (at least partially) answered - Shoot for less than or equal to 135F when the amp is fully heated (less is better). And to achieve this, 2" or more clearance on all sides are preferred. But what isn't answered is "what minimum clearance is needed to achieve 135F?" Of course, that would vary with ambient temperature & the amount of heat generated by the specific amplifier - but at least I have a thermal target to shoot at - Thanks Keith!.

---

[DYohn]

Your thread title and your poll have nothing to do with each other.

The safe operating temperature for any piece of electronic equipment is not so high as it exceed the rating of the components or the PCBs. Normally in consumer electronics these things are rated to 80C, or 176F.

[KeithL]

Those minimum clearance numbers REALLY depend on the sort of air flow you have.

Convection cooling relies on the fact that hot air rises....
Because of this, the hot air inside the unit rises and leaves through the vents, pulling in more cool air from the sides or below.
However, in the vernacular, the hot air doesn't try to rise with a lot of enthusiasm.
Therefore, if you want to ensure adequate air flow, you must not do anything to impede it on its lazy journey upwards.
If your amplifier is 1" under a shelf, then the air leaving the top vents must "zig zag around the shelf"... which restricts the flow.
If it's sitting on a carpet, then the cool air won't be able to get in the bottom vents.
And, if your amp is shut in a warm rack, then the "cool" air that gets pulled in the bottom won't be very cool.

Also, since the convection is driven by the differences in air temperature, it relies on the inside of the amplifier being HOTTER than the air outside.
(The amplifier runs a certain number of degrees above ambient temperature.)
So, the higher the ambient temperature, the warmer the interior of the amp will run.

That's one reason why a sealer rack MUST have fans.....
By pulling the hot air out of the rack, they ensure that cool air flows into the rack.
This, in turn, ensures that the air inside the amplifier will be hotter than the air around it (in the rack)...
And it ensures that the air the amp pulls into itself from the rack will be somewhat cool as well.

Because the motion of air due to convection is so lazy...
Even a relatively small fan that FORCES the air to flow will make a major difference.

Most professional equipment includes fans to FORCE the airflow to be adequate...
They literally blow the hot air out the exit vents... and suck in new cool air to replace it.
However, because fans make noise, we prefer to avoid them for home equipment.
As a result, in order to keep things cool, you must be sure that your amplifier has "unimpeded easy air flow".

Mar 26, 2018 2:50:05 GMT -5 Boomzilla said:

Assuming a relatively high-efficiency power supply amplifier (such as Emotiva's generation 3 units), what operating temperature range is appropriate for the component?

Obviously, more ventilation is better - but on an otherwise open shelf, what "minimum top clearance" is sufficient? A half inch? An inch? An inch and a half?

Rather than estimate the required clearance, I thought that since I have a temperature-measuring gun, I could work "backwards" and determine a "minimum clearance" by amplifier temperature.

The question could also be asked in this form: If the maximum temperature of the amplifier during normal service is X-degrees with fully open ventilation, then how many degrees above that temperature (X+?) are acceptable with a top shelf above the amp?

Obviously, with any restrictions on ventilation, the amplifier temperature needs to be periodically rechecked to ensure that dust accumulation inside the amp, aging of parts, etc. has not significantly increased the temperature from the baseline.

I've previously run other Emotiva (Generations 1 & 2) amps with about ½ inch overhead clearance without issue, but was interested in others' experiences. The clearance (temperature rise) for a Generation 3 amplifier may be less than for an XPR or previous-Generation XPA amplifier (that were more heavily biased to Class-A operation and that generated more heat).

So out of curiosity, at what temperature does your Generation 3 amplifier run (assuming an air-conditioned ambient environment) and is it in a cabinet / shelf or is it in a free-air location?

Thanks - Boomzilla

---

PS: Found Keith L's comment below in another thread:

Unfortunately, this is one of those questions that seems simple, but is actually rather complicated.

The heat is actually generated inside certain components, then conducted to their heat sinks (or their casings), and finally to the air.
What counts - as far as the electronics are concerned - is the temperature at the actual silicon junctions inside the components.
And the ability of heat sinks to transfer heat to the air (and so get rid of it) depends on all sorts of things, including mainly the temperature of the air, and how fast the air is moving.
That second factor is especially important with amps that don't use cooling fans.

Because of the way convection cooling works, all of the "calculations" are based on the inside temperature of the amp running a certain number of degrees "above ambient".
With any device, the inside will ALWAYS be hotter than the air outside; and, without fans, the difference will be greater.
AND that difference will depend on there being unrestricted air flow so air can get into and out of the cabinet.
AND you can make the same sort of calculations about a cabinet, or an "equipment closet", or a whole room.

Unfortunately, calculating "limits" on all this stuff can get very complicated.....

Some good safe guidelines are:

1)
You need to have "unrestricted airflow" around the equipment.
This means that you can't block the vents, and you need at least an inch or two of space on the sides with vents.
It also means that the air has to have someplace to go... it has to be able to move into the vents FROM somewhere and out of the vents TO somewhere...
This is true at EVERY level; you can't block the vents on the equipment; and you can't seal your entire rack; and the closet the rack is in must have some sort of air flow.

2)
Assuming you've met that requirement, none of the equipment itself (the hottest spot on the top plate) should ever get too hot to touch with your fingers.
If you can put your hand there, and hold it for half a minute without screaming, then you're probably OK (that's about 135 degrees F).
So, if you have two amps in a rack, squeeze your hand in between them; if it hurts to do so, then more cooling would be in order.
(And, since it takes a while for the heat generated by power amps to reach the outside of their cases, you should play those as loudly as you ever do, then keep checking the temperature.
It should never exceed that safe temperature limit AT ANY POINT IN TIME - and you should check it from about one minute to about a half hour after you turn the volume up. )

3)
Excluding safety and "damage" per se, with most electronic equipment, the cooler you keep it, the longer it will live (and, usually, minimizing the changes between hot and cold - "temperature cycling" - also helps there).
(This is not quite an absolute, but many electronic components have some sort of "temperature derating" which says that, however long they usually live before they fail, that life span gets shorter at higher temperatures.)
Incidentally, even with tube equipment, where the tubes themselves run at relatively high temperatures, many other internal components have this same sort of relationship between temperature and service life.

4)
Always remember that heat takes a while to "work it's way from the inside to the outside", and that the amount of heat made by components like power amps depends on how much power they're producing. A Class A/B amp has some minimum heat that it produces all the time, based on things like bias current. Added to that is the "waste heat" generated by the output it is producing. With most Class A/B amps, including ours, the efficiency runs between 50% and 70%. That means that, if your XPA-2 is putting out an average power of 300 watts, it's making about as much waste heat as a 200 watt electric heater... and that heat will eventually have to be "gotten rid of". Therefore, after you play your amp very loud for a period of time, it will heat up.... and you must make sure you have enough cooling to get rid of THE MOST HEAT THE AMP WILL EVER PRODUCE. (This is why things like thermostatic fans, which can rev up to remove a lot more heat if they sense it's necessary, are usually a good idea in enclosed areas.)

So the question is (at least partially) answered - Shoot for less than or equal to 135F when the amp is fully heated (less is better). And to achieve this, 2" or more clearance on all sides are preferred. But what isn't answered is "what minimum clearance is needed to achieve 135F?" Of course, that would vary with ambient temperature & the amount of heat generated by the specific amplifier - but at least I have a thermal target to shoot at - Thanks Keith!.

---

[Boomzilla]

Computer fans are readily available (and in low-profile) that can move quite a bit of air. An "across the top" bank of fans blowing between the shelf above and the amplifier top plate should be sufficient to do the job.

[KeithL]

The thing to remember is that what we're interested in is AIR FLOW.... which is related to a lot more than clearance.

Think of the air flow as a very slow lazy current in a river.
We want to avoid anything that might slow it down, block it, or cause it to "back up".

So, for example, if you have a shelf 1/2" above the top of the amplifier.....
If that shelf is open on the front and back, but closed on the sides, air flow will still be more restricted than it would be if the shelf was open on all four sides.
And, if you have a ceiling fan that always moves, creating a steady breeze around the amplifier, that will also make a difference.

Mar 26, 2018 2:50:05 GMT -5 Boomzilla said:

Assuming a relatively high-efficiency power supply amplifier (such as Emotiva's generation 3 units), what operating temperature range is appropriate for the component?

Obviously, more ventilation is better - but on an otherwise open shelf, what "minimum top clearance" is sufficient? A half inch? An inch? An inch and a half?

Rather than estimate the required clearance, I thought that since I have a temperature-measuring gun, I could work "backwards" and determine a "minimum clearance" by amplifier temperature.

The question could also be asked in this form: If the maximum temperature of the amplifier during normal service is X-degrees with fully open ventilation, then how many degrees above that temperature (X+?) are acceptable with a top shelf above the amp?

Obviously, with any restrictions on ventilation, the amplifier temperature needs to be periodically rechecked to ensure that dust accumulation inside the amp, aging of parts, etc. has not significantly increased the temperature from the baseline.

I've previously run other Emotiva (Generations 1 & 2) amps with about ½ inch overhead clearance without issue, but was interested in others' experiences. The clearance (temperature rise) for a Generation 3 amplifier may be less than for an XPR or previous-Generation XPA amplifier (that were more heavily biased to Class-A operation and that generated more heat).

So out of curiosity, at what temperature does your Generation 3 amplifier run (assuming an air-conditioned ambient environment) and is it in a cabinet / shelf or is it in a free-air location?

Thanks - Boomzilla

---

PS: Found Keith L's comment below in another thread:

Unfortunately, this is one of those questions that seems simple, but is actually rather complicated.

The heat is actually generated inside certain components, then conducted to their heat sinks (or their casings), and finally to the air.
What counts - as far as the electronics are concerned - is the temperature at the actual silicon junctions inside the components.
And the ability of heat sinks to transfer heat to the air (and so get rid of it) depends on all sorts of things, including mainly the temperature of the air, and how fast the air is moving.
That second factor is especially important with amps that don't use cooling fans.

Because of the way convection cooling works, all of the "calculations" are based on the inside temperature of the amp running a certain number of degrees "above ambient".
With any device, the inside will ALWAYS be hotter than the air outside; and, without fans, the difference will be greater.
AND that difference will depend on there being unrestricted air flow so air can get into and out of the cabinet.
AND you can make the same sort of calculations about a cabinet, or an "equipment closet", or a whole room.

Unfortunately, calculating "limits" on all this stuff can get very complicated.....

Some good safe guidelines are:

1)
You need to have "unrestricted airflow" around the equipment.
This means that you can't block the vents, and you need at least an inch or two of space on the sides with vents.
It also means that the air has to have someplace to go... it has to be able to move into the vents FROM somewhere and out of the vents TO somewhere...
This is true at EVERY level; you can't block the vents on the equipment; and you can't seal your entire rack; and the closet the rack is in must have some sort of air flow.

2)
Assuming you've met that requirement, none of the equipment itself (the hottest spot on the top plate) should ever get too hot to touch with your fingers.
If you can put your hand there, and hold it for half a minute without screaming, then you're probably OK (that's about 135 degrees F).
So, if you have two amps in a rack, squeeze your hand in between them; if it hurts to do so, then more cooling would be in order.
(And, since it takes a while for the heat generated by power amps to reach the outside of their cases, you should play those as loudly as you ever do, then keep checking the temperature.
It should never exceed that safe temperature limit AT ANY POINT IN TIME - and you should check it from about one minute to about a half hour after you turn the volume up. )

3)
Excluding safety and "damage" per se, with most electronic equipment, the cooler you keep it, the longer it will live (and, usually, minimizing the changes between hot and cold - "temperature cycling" - also helps there).
(This is not quite an absolute, but many electronic components have some sort of "temperature derating" which says that, however long they usually live before they fail, that life span gets shorter at higher temperatures.)
Incidentally, even with tube equipment, where the tubes themselves run at relatively high temperatures, many other internal components have this same sort of relationship between temperature and service life.

4)
Always remember that heat takes a while to "work it's way from the inside to the outside", and that the amount of heat made by components like power amps depends on how much power they're producing. A Class A/B amp has some minimum heat that it produces all the time, based on things like bias current. Added to that is the "waste heat" generated by the output it is producing. With most Class A/B amps, including ours, the efficiency runs between 50% and 70%. That means that, if your XPA-2 is putting out an average power of 300 watts, it's making about as much waste heat as a 200 watt electric heater... and that heat will eventually have to be "gotten rid of". Therefore, after you play your amp very loud for a period of time, it will heat up.... and you must make sure you have enough cooling to get rid of THE MOST HEAT THE AMP WILL EVER PRODUCE. (This is why things like thermostatic fans, which can rev up to remove a lot more heat if they sense it's necessary, are usually a good idea in enclosed areas.)

So the question is (at least partially) answered - Shoot for less than or equal to 135F when the amp is fully heated (less is better). And to achieve this, 2" or more clearance on all sides are preferred. But what isn't answered is "what minimum clearance is needed to achieve 135F?" Of course, that would vary with ambient temperature & the amount of heat generated by the specific amplifier - but at least I have a thermal target to shoot at - Thanks Keith!.

---

[Casey Leedom]

Also, the critical maximum junction temperature for various ASICs are different from each other. In my company we produce 100Gb/s Ethernet chip. The shutdown temperature for it ranges from 115°C (239°F) to 145°C (293°F) depending on part lots. That's a lot higher than chips for other applications.

And of course, Keith is right about Ambient Air Temperature and Fans. In our case, our boards are almost always installed in computers which have fans and often located in temperature-controlled labs.

Casey

[Boomzilla]

My shelf is open on all four sides, but the overhead clearance will be but ½ inch. Two options seem feasible:

1. Close off three of the four sides at the bottom of the amp and pressurize the space with fans, forcing air into the amp, bottom to top or
2. Place a fan on one side of the amp at the bottom blowing air toward the amp and place another fan on the opposite side of the amp at the top blowing air away from the amp.

But another option does occur:

3. Place the amp on a different stand and have no shelf above it...

[DYohn]

My humble suggestion: use it however you need to or wish to. If it goes into thermal shutdown, then address the problem. If it doesn't then youa re worried about a non-issue.

[Boomzilla]

Thanks, David - I do agree & I'd planned to use the heat gun before doing any other junkyard-engineering. I'm curious to see what the actual temperature will run with only ½ inch of top clearance...

[Loop 7]

I'm a bit paranoid so my Parasound 5 channel amp is in a rack with all 4 sides open and 10" of space above the amp.

[Boomzilla]

For the price of an inexpensive heat gun, you'll not need any further anxiety. Just saying...

[Bonzo]

Well ya know, with all the in and out gear moving you do, why not spend some time and coin on a better / more flexible cabinet. Something with adjustable shelves would be better for you. Or make your own like I did. Using the 80/20 system makes shelf adjustment fully customizable. You want exactly 2.375 inches, you got it. Put some casters on the bottom and roll it where ever you need. Makes getting in the back side easy too. I can't believe you didn't do this a long time ago actually. Anyway, that's my suggestion to making heat issues go away, being more ergonomic, and probably better looking.

[hemster]

Mar 26, 2018 14:04:21 GMT -5 Bonzo said:

Well ya know, with all the in and out gear moving you do, why not spend some time and coin on a better / more flexible cabinet. Something with adjustable shelves would be better for you. Or make your own like I did. Using the 80/20 system makes shelf adjustment fully customizable. You want exactly 2.375 inches, you got it. Put some casters on the bottom and roll it where ever you need. Makes getting in the back side easy too. I can't believe you didn't do this a long time ago actually. Anyway, that's my suggestion to making heat issues go away, being more ergonomic, and probably better looking.

Anything that makes getting in the back side easy has to be a good thing!

[Bonzo]

Mar 26, 2018 14:28:02 GMT -5 hemster said:

Mar 26, 2018 14:04:21 GMT -5 Bonzo said:

Well ya know, with all the in and out gear moving you do, why not spend some time and coin on a better / more flexible cabinet. Something with adjustable shelves would be better for you. Or make your own like I did. Using the 80/20 system makes shelf adjustment fully customizable. You want exactly 2.375 inches, you got it. Put some casters on the bottom and roll it where ever you need. Makes getting in the back side easy too. I can't believe you didn't do this a long time ago actually. Anyway, that's my suggestion to making heat issues go away, being more ergonomic, and probably better looking.

Anything that makes getting in the back side easy has to be a good thing!

I like BUTTA myself. 😁

[Gary Cook]

As mentioned previously in several posts, I tried different shelf spacing in a 4 sides open rack and found that anything more than 50 mm above an XPA-2/3/5, XPA-1L or XPA-100 made next to zero difference. That's using a pyrometer probe on the top of the heatsinks.

That's a mix of Gen 1 and Gen 2 Emotiva amplifiers, since the only real difference to the Gen 3 is the power supply I don't see any reason why they would be different ie; the hot spots in an amplifier isn't the power supply.

Cheers
Gary

[DYohn]

Mar 26, 2018 13:03:11 GMT -5 Boomzilla said:

Thanks, David - I do agree & I'd planned to use the heat gun before doing any other junkyard-engineering. I'm curious to see what the actual temperature will run with only ½ inch of top clearance...

Heat gun? Those are used for warming things up such as when shrinking heat shrink. Not exactly what you want to do to a piece of electronic gear unless your goal is to drive it into thermal shutdown... ??

[Boomzilla]

Actually, it's a focused digital thermometer. It has a laser pointer attached. Point at the surface you want to measure & get a digital temperature in less than a second in either Celsius or Fahrenheit. About $15 on Amazon.

[DYohn]

Mar 26, 2018 15:20:48 GMT -5 Boomzilla said:

Actually, it's a focused digital thermometer. It has a laser pointer attached. Point at the surface you want to measure & get a digital temperature in less than a second in either Celsius or Fahrenheit. About $15 on Amazon.

Ah. That's not a heat gun. Those are called IR (or infrared) thermometers, or spot thermometers. They are useful and fun to play with, although I maintain if your gear does not protect itself then you have no heat issues to solve.

[Boomzilla]

They actually make those with a video screen as well. It's fun to see inside a tank or distillation column (or even a furnace) looking for proper mixing, hot spots, etc.

[DYohn]

That's similar to a FLIR camera, which I use a lot for my work.