Solid State Amplifiers > Amplifier Discussion

Heatsinks for your poweramp

(1/16) > >>

joecool85:
First - Have a good power supply circuit and a big enough/proper voltage transformer
Second - Big heatsink, there is no such thing as too large of a heatsink

Proper heatsink size for two LM1875 chips, or one LM3886:


Overkill(which isn't a bad thing though):

skey:
Neither of the above heatsinks above seem to take advantage of thermal airflow. 
Sometimes smaller is better if it's less bulky.  Is there any convenient way to figure out a useful minimal size you'd need?

RDV:

--- Quote from: skey on June 14, 2006, 11:36:54 PM ---Neither of the above heatsinks above seem to take advantage of thermal airflow.
Sometimes smaller is better if it's less bulky. Is there any convenient way to figure out a useful minimal size you'd need?

--- End quote ---
The one in the 1st picture does not take advantage of thermal airflow(though it's big enough to not need it), but the 2nd one is outside the cabinet. How much airflow do you need? It's in free air.

Please don't say that a smaller heatsink is better because it's not. The smallest heatsink you can get away with is best for space saving purposes, but there is no heatsink that is "too big".

There is no convienient way to calculate heatsink size other than doing the math from the datasheet.

Regards

RDV

joecool85:
The first one does, maybe poorly, but it does.  I drilled 16 holes in the bottom, then 9 holes in the top to allow cold air to come in the bottom and hot air to rise out the top.  It works, trust me I've never had it over heat.  That amp is my computer speaker amp and I've had it on 3/4 volume (really really loud btw, I had no neighbors at the time  :tu: ) for 2 hours or so and no problems.

teemuk:

--- Quote from: RDV on June 15, 2006, 07:14:06 AM ---The one in the 1st picture does not take advantage of thermal airflow(though it's big enough to not need it), but the 2nd one is outside the cabinet. How much airflow do you need? It's in free air.

--- End quote ---

Free air means no "concentrated" airflow. Imagine this: Do you feel cooler on a sunny day when it breezes or when it doesn't? It's the same thing with heatsinking, thus fans are the ultimate solution. If you channel the airflow through the heatsink fins (hot air automatically tends to rise up when cool air replaces it) it will be a lot more efficient than when the heatsink is just in free air. For same reason vertical fins are better than horizontal. (Unless the air flows horizontally for some reson i.e. fan). In the first pic I see some holes at the bottom of the chassis, which means there will be a cooling airflow through the fins. IMO this is better than picture 2 solution. However, the heatsink in picture 2 is massive and therefore dissipates more heat. Same size sink in picture 1 configuration would dissipate heat even more efficiently. If you want a very efficient cooling, channel the airflow up through the fins and use a fan to push a huge amount of air for the heatsink. The cool air would replace the warm by itself but the fan just speeds up this process. If the cool air has paths to "leak" away from the fins you loose efficiency. Thus free air heatsink is always less efficient. However, temperature in the chassis may rise higher than temperature outside it. Best solution would be to isolate fins to a separate and well ventilated (airflow from down to up only) compartment in the chassis.

Navigation

[0] Message Index

[#] Next page

Go to full version