is it big enough?

[henry zhang]

i think the heat sink is too small,but it still can work for about 2 hours when the volume is not too high.so i wonder if i need to change a bigger one.thanks very very much!
i'm Chinese from Beijing.

[Cloth Ears]

Hi Henry,

Maybe try on the Chip Amps forum. Also, explain what chip and maybe an indication of the size of the heatsink.

Basically, if you can put your fingers on it for a few seconds when it's reached operating temperature, then it's probably OK. If it's too hot for your fingers, then it's probably not big enough.

[henry zhang]

Hello,Cloth Ears
It si said that the temperature of heatsink will not be higher than 75 ¡æ if I can put my fingers on heatsink for more than 3 seconds.right?Thank you very much.

[Cloth Ears]

You're probably wanting to look at 50 degrees as a better option. It's a law of diminishing returns once you go beyond that...

[henry zhang]

Hi,Cloth Ears!
Thanks for your reply!But what's 'diminishing returns'?

[Cloth Ears]

Hi Henry,

This is an example of 'diminishing returns' from the Wikipedia:
Suppose that one kilogram (kg) of seed applied to a plot of land of a fixed size produces one tonne of harvestable crop. You might expect that an additional kilogram of seed would produce an additional tonne of output. However, if there are diminishing marginal returns, that additional kilogram will produce less than one additional tonne of harvestable crop (on the same land, during the same growing season, and with nothing else but the amount of seeds planted changing). For example, the second kilogram of seed may only produce a half tonne of extra output. And diminishing marginal returns also implies that a third kilogram of seed will produce an additional crop that is even less than a half tonne of additional output. Assume that it is one quarter of a tonne.

With your heatsink, I possibly used the term a little incorrectly. If the chip you are using is rated at 100watts, then that will generally be at 25 degrees Celcius. If it heats up to 150 degrees, then it probably will not be rated at more than 0watts. So, using the calculator, at 50 degrees, you've probably got 80watts, and at 75watts you've probably got 60watts.

So, literally, when your temperature is higher, you get diminishing returns (watts, in this case). If you can cool it better, it will last longer and you will have more available power.

[henry zhang]

Hi,Cloth Ears!
No matter how hard I tried,it was impossible for me to understand your reply clearly.So I must improve my English as soon as possible.Though it will take years of hard work to speak good English,I will try my best.
Thanks for your reply.

[Christer]

I am not sure about the chip you are using, but I think most of those amps have built in temperature protection and shut themselves down if they get too hot. Of course, if that happens often you should get a better heat sink.

[sangram]

It looks small. Maybe you need twice the size and a thicker piece also.

I use a 5" Extrusion with 6 spaced fins, made of 3 mm aluminium for a pair of 2030 chips. The overall size should be about 5" by 3", and the fins should be about 3-4 cm.

That should keep the chips cool.

Like many other things, chips are happy if you are. So if you can't keep your hand on it for too long, aim for lower temperature. You should be able to comfortably keep your hand on it say for 5-6 seconds, unless you're running it full blast all the time.

[ozonek]

Henry, the heat sink is just too small (comparing with the chip size) and the result is the output power will decrease as the case temperature rise above the point when the SPIKE protection circuitry is triggered. You will hear click and pop and the IC will not last long under stressing high temperature.

PS, i came from Shanghai