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Post by qdtjni on Dec 6, 2017 15:19:16 GMT -5
Gary, What measurements have you made? Cheers Johan |
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Post by Gary Cook on Dec 6, 2017 17:13:16 GMT -5
Gary, What measurements have you made? Cheers Johan In my race team kit I have a pyrometer with high and low temperature probes. We mostly use it for checking tyre temperatures (around 80 degrees C) but it also gets used for water and oil cooler in and out temp checks (up to 125 degrees C) plus brake temperature checks (up to 800 degrees C) and exhaust gas temperature (up to 1100 degress C) that use the high temp probe. It's certified and checked annually for accuracy/consistency. I use the electrically insulated probe to check the temperature of the heat sink, in a multi channel amp its useful in identifying issues with individual channels as their heat sink temp will commonly vary from the others. I can detail the process, but simplified I check the temp of the heat sink/s at various time intervals and various volume settings with a shelf at various spacing or no shelf. I have done this for decades on many different amps. For the XPA-1L with the shelf ~ 50 mm above they idle up to around 45 Degrees C in Class A relatively quickly and get to around 60 degrees C at fairly high listening volumes after 30 minutes or so. If I go really high in the listening levels they switch to Class AB and the temp drops down to low 50's and doesn't climb, no matter how long I listen. That's the test for effective convection cooling, if it keeps climbing then there's not enough airflow. Ambient temperature does have an effect and outdoors it gets to 40 degrees in Sydney occasionally, but then inside the air con is on  Cheers Gary |
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Post by garbulky on Dec 6, 2017 19:46:51 GMT -5
The 1L and the XPA-1 are different in terms of heat output. And the heat sinks in the XPA-1's are about 4 times the size ie, the watts to heat sink ratio is about the same. Cheers Gary Not disagreeing with that though I'm not sure about the figures. (Not saying they're wrong, I just don't know). Heatsinks is about its ability to dissipate heat. The heat output is greater with the XPA-1 I think you'll agree. Having used both the 1L and the 1, the XPA-1 gen 2 simply puts out tons of heat. It especially needs some ventillation some space despite its heatsinks. It's gotta go somewhere! Mine is in a wide open rack right now but I still wonder about the long term effects on the wood it's sitting on. Since class A amps are not normal and amps which put out miniscule amounts of heat are common, I can definitely see people not realizing the issues with space and class A. I remember somebody having a thread remarking that the XPA-1 gen 2 was hot. Even Big Dan was confused by it! |
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Post by novisnick on Dec 6, 2017 19:59:27 GMT -5
And the heat sinks in the XPA-1's are about 4 times the size ie, the watts to heat sink ratio is about the same. Cheers Gary Not disagreeing with that though I'm not sure about the figures. (Not saying they're wrong, I just don't know). Heatsinks is about its ability to dissipate heat. The heat output is greater with the XPA-1 I think you'll agree. Having used both the 1L and the 1, the XPA-1 gen 2 simply puts out tons of heat. It especially needs some ventillation some space despite its heatsinks. It's gotta go somewhere! Mine is in a wide open rack right now but I still wonder about the long term effects on the wood it's sitting on. Since class A amps are not normal and amps which put out miniscule amounts of heat are common, I can definitely see people not realizing the issues with space and class A. I remember somebody having a thread remarking that the XPA-1 gen 2 was hot. Even Big Dan was confused by it! I really think that placing my XPR-1’s on paving stones has been great for heat disruption. Perhaps you should give them a shot. They are porous and heat neutral. |
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Post by novisnick on Dec 6, 2017 20:01:46 GMT -5
The 1L and the XPA-1 are different in terms of heat output. And the heat sinks in the XPA-1's are about 4 times the size ie, the watts to heat sink ratio is about the same. Cheers Gary I agree with you Gary! 👍 |
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Post by garbulky on Dec 6, 2017 20:16:23 GMT -5
Not disagreeing with that though I'm not sure about the figures. (Not saying they're wrong, I just don't know). Heatsinks is about its ability to dissipate heat. The heat output is greater with the XPA-1 I think you'll agree. Having used both the 1L and the 1, the XPA-1 gen 2 simply puts out tons of heat. It especially needs some ventillation some space despite its heatsinks. It's gotta go somewhere! Mine is in a wide open rack right now but I still wonder about the long term effects on the wood it's sitting on. Since class A amps are not normal and amps which put out miniscule amounts of heat are common, I can definitely see people not realizing the issues with space and class A. I remember somebody having a thread remarking that the XPA-1 gen 2 was hot. Even Big Dan was confused by it! I really think that placing my XPR-1’s on paving stones has been great for heat disruption. Perhaps you should give them a shot. They are porous and heat neutral. I got bricks to support the front legs that stick out the rack on to the floor but the rest has to be on a shelf/rack which has some limitations in space. The way it is, paving stones would not work in the space. |
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Post by Gary Cook on Dec 6, 2017 20:56:46 GMT -5
And the heat sinks in the XPA-1's are about 4 times the size ie, the watts to heat sink ratio is about the same. Not disagreeing with that though I'm not sure about the figures. (Not saying they're wrong, I just don't know). Heatsinks is about its ability to dissipate heat. The heat output is greater with the XPA-1 I think you'll agree. Having used both the 1L and the 1, the XPA-1 gen 2 simply puts out tons of heat. It especially needs some ventillation some space despite its heatsinks. It's gotta go somewhere! Mine is in a wide open rack right now but I still wonder about the long term effects on the wood it's sitting on. Since class A amps are not normal and amps which put out miniscule amounts of heat are common, I can definitely see people not realizing the issues with space and class A. I remember somebody having a thread remarking that the XPA-1 gen 2 was hot. Even Big Dan was confused by it! Heat dissipation via convection is pretty simple (high school) physics, in a power amplifier the output devices are the big heat generators, plus a few other components. The amp design should take into account the amount of heat required to be transferred into the heat sicks to determine the size and lay out of the heat sinks (radiators). Then the heat sinks pass that heat onto the surrounding air via convection. Hot air rises to be replaced by cooler air, hotter air rises faster and is replaced by more cooler air. The 2nd Law of Thermodynamics (not High School Physics), the more the heat differential between the heat sink and the ambient air around it, the faster the air flows though the heat sinks. In the race cars, because of their often rapid forward motion, we do occasionally find that the air flows too fast through the radiator and the lack of contact time means that they aren't transferring the heat into the air passing through. Something that's not likely to occur in a convection heat sink in stationary power amplifier  Obviously an XPA-1 is going to require a higher heat dissipation capability than, say, an XPA-1L, which should be in proportion to its heat generation. In addition the XPA-1 has its heat sinks located along each side which helps with the airflow out of both sides of an open rack. They aren't in the middle where a close proximity shelf above would block the air low.  In comparison the XPA-1L has one (of its pair of heat sinks) at the side and one more towards the middle. In which case a too close proximity shelf above could block the air flow from 50% of the heat sinks.  In regards to the timber underneath a power amplifier, since the cooler ambient air is going to flow inwards from below, I wouldn't be too concerned. The hot air should be flowing out of the top. Cheers Gary |
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Post by garbulky on Dec 6, 2017 22:31:05 GMT -5
Not disagreeing with that though I'm not sure about the figures. (Not saying they're wrong, I just don't know). Heatsinks is about its ability to dissipate heat. The heat output is greater with the XPA-1 I think you'll agree. Having used both the 1L and the 1, the XPA-1 gen 2 simply puts out tons of heat. It especially needs some ventillation some space despite its heatsinks. It's gotta go somewhere! Mine is in a wide open rack right now but I still wonder about the long term effects on the wood it's sitting on. Since class A amps are not normal and amps which put out miniscule amounts of heat are common, I can definitely see people not realizing the issues with space and class A. I remember somebody having a thread remarking that the XPA-1 gen 2 was hot. Even Big Dan was confused by it! Heat dissipation via convection is pretty simple (high school) physics, in a power amplifier the output devices are the big heat generators, plus a few other components. The amp design should take into account the amount of heat required to be transferred into the heat sicks to determine the size and lay out of the heat sinks (radiators). Then the heat sinks pass that heat onto the surrounding air via convection. Hot air rises to be replaced by cooler air, hotter air rises faster and is replaced by more cooler air. The 2nd Law of Thermodynamics (not High School Physics), the more the heat differential between the heat sink and the ambient air around it, the faster the air flows though the heat sinks. In the race cars, because of their often rapid forward motion, we do occasionally find that the air flows too fast through the radiator and the lack of contact time means that they aren't transferring the heat into the air passing through. Something that's not likely to occur in a convection heat sink in stationary power amplifier Obviously an XPA-1 is going to require a higher heat dissipation capability than, say, an XPA-1L, which should be in proportion to its heat generation. In addition the XPA-1 has its heat sinks located along each side which helps with the airflow out of both sides of an open rack. They aren't in the middle where a close proximity shelf above would block the air low. In comparison the XPA-1L has one (of its pair of heat sinks) at the side and one more towards the middle. In which case a too close proximity shelf above could block the air flow from 50% of the heat sinks. In regards to the timber underneath a power amplifier, since the cooler ambient air is going to flow inwards from below, I wouldn't be too concerned. The hot air should be flowing out of the top. Cheers Gary Though I'm not an engineer, I do have a science background. I'm familiar with the concepts you mention. What are you getting at? Are you saying that what he has is enough partly due to the side heatsinks? We don't know how much space he has on the sides - I'm guessing not a lot. If so, I don't think it's good idea from my daily experience with it. It's a great amp, it just needs some minor TLC. |
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Post by Gary Cook on Dec 7, 2017 0:36:01 GMT -5
Though I'm not an engineer, I do have a science background. I'm familiar with the concepts you mention. What are you getting at? Are you saying that what he has is enough partly due to the side heatsinks? We don't know how much space he has on the sides - I'm guessing not a lot. If so, I don't think it's good idea from my daily experience with it. It's a great amp, it just needs some minor TLC. Spot on gar, we do not know if the rack is open on the sides, if it is then he is more than likely OK with ~50 mm clearance to the shelf above. It helps that the XPA-1 heat sinks are on the sides. But at 5 mm (as per post #1) it definitely won't. As per the picture, even with the heat sinks at the sides it still needs space above the vents (in the top), so the air can flow up (a bit) then out the sides of the rack. Personally I wouldn't put any XPA amp in a rack with any closed in sides, unless it had enough fans of course. Cheers Gary |
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