| Destroyer OS. |
The chips are bolted to the plate you see with RCAs and binding posts.
It is just cheap sheet metal from Ace.
Should I some how add more heatsink?
It does get hot with only under a minute of play time. Not so hot I can not touch it, but hot.
This is sort of project use everything laying around. |
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| Destroyer OS. |
| Oh yeah it is a 330va 25v transformer being used, into 8 ohm speakers. |
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| Nordic |
Not a chance in hell....
A nice 2.5C/W heatsink may set you back $5.... |
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| mateo88 |
| What chip? Is that 25v single supply or is it two 25v rails? |
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| I_Forgot |
Everything lasts longer and works better at lower temperatures. If it gets any more than slightly warm, it's too hot. Surplus heat sinks are cheap. Get a couple of them.
I_F |
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| Nordic |
| I'm glad I upgraded my heatsinks... we had a 40C day in the week... went to feel the sinks... they were HAWT... |
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| Destroyer OS. |
I added some heat sinks but I fear they are not enough.
Damnit I want this done in a day. Where can I buy local heatsinks?
25v per channel before recitifcation. 3875 chips |
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| janneman |
| quote: | Originally posted by Destroyer OS.
The chips are bolted to the plate you see with RCAs and binding posts.
It is just cheap sheet metal from Ace.
Should I some how add more heatsink?
It does get hot with only under a minute of play time. Not so hot I can not touch it, but hot.
This is sort of project use everything laying around. |
If you can touch it for 10 secs or more (really touch, not touch-and-go) you're OK. It means <50 degrees heatsink.
Jan Didden |
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| CarlosT |
Nice butch project :D
You got a perfect opportunity there to bolt something to the outside... go to a scrap yard and look for a piece of copper or something...heck...even bonding some 1/2" copper tubing pieces vertically from the Home Depot would help.
I was thinking that mixing metal powder with regular silicone caulk would make a decent DIY adhesive for a "heatsink"...you know...in the spirit of the butch look and all :D |
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| burnedfingers |
| Lets stay with the rustic look shall we? How about some surplus drainage spout or something along that line for heat sinking? |
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| impsick |
| :D you guys are too funny. drainage pipe would be a good touch. wait ... do... um...:hot: smell smoke? |
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| azira |
IMO, go with previous suggestions and get a real heatsink. I don't like that one because you've picked up sheetmetal that isn't garenteed to be flat. OTOH with a real heatsink, it's milled perfectly flag. A flat service will go a long way for ensuring heat transfer to the sink.
I bet you could find one or two old Pentium 2 heatsinks for really cheap. You didn't mention what kind of chips they were but,I used a P2 sink for my stereo LM3875 and it works great.
--
Danny |
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| shallbehealed |
| quote: | Originally posted by azira
IMO, go with previous suggestions and get a real heatsink. I don't like that one because you've picked up sheetmetal that isn't garenteed to be flat. OTOH with a real heatsink, it's milled perfectly flag. A flat service will go a long way for ensuring heat transfer to the sink.
I bet you could find one or two old Pentium 2 heatsinks for really cheap. You didn't mention what kind of chips they were but,I used a P2 sink for my stereo LM3875 and it works great.
--
Danny |
I walked into a computer gamers store and asked for some old copper heatsinks, they handed me a bag of them and didn't charge me anything. I think they were glad to get rid of them. |
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| lineup |
these chips
does not require much heatsinking
As they work in low Class AB current
it is not much heat generated.
Except for if you play it very very hard!
But if you do, chip is well protected for high temperatures.
So, I say, if you use your set up in image nothing bad can happen.
You may 'upgrade' with a heatsink later, if you wish,
when you can find a nice buy.
I have seen people report, that these LM3875 get barely warm as you can notice it.
We see them often attached to aluminium chassis, as only cooling.
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This is one of Pedja Rogic's gainclones.
He is a very good diy builder.
Notice that 2 chips uses very little metal for cooling.
More detail pictures at Pedja homepage:
http://www.pedjarogic.com/
http://www.pedjarogic.com/gc/pics.htm |
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| abid_rehan |
| Nice way for advertisement of people running their own "HIFI" board |
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| lineup |
| quote: | Originally posted by abidr
Nice way for advertisement of people running their own "HIFI" board |
yes,
and the heatsink in picture is Not very large
as you can see
:)
But as I recall it,
Pedja was going to make some holes in that round can he used for 'chassis'
all amplifiers with heatsinks inside the chassis
will benefit from having some inlet and outlet holes
to improve air circulation and cooling
Regards
lineup |
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| Nordic |
Just stay away from 4 ohm loads then... instant heat in a box...
I did use my chipamp on too small sinks before... I eventualy relented as it was not going to last at those temperatures... and I probably halfed the shelflife of the caps etc... due to the heat given off....
Now it stays cool, unless we have close to 40C weather...like it did last week.... and even then I can hang on to the sinks forever...they don't get too hot anymore... |
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| abid_rehan |
Answer to the question that whether mentioned heatsink is enough or not could be:
If you want to take the risk of thermal shut downs due to continued operations, which over the period of time will damage the chip, then the heatsink is good enough.
Otherwise as it seems that ur chip amp is a P2P, get an old heatsink as mentioned in one of the replies, put the chip on it and tie it to the plate.
But if you want to make things look more appealing make a hole in the plate about the size of heatsink and then fit the heatsink in that.
I hope i could make a photograph of one of my GC in which i used heatsink the way i ve mentioned, if only i could find it in my store.
:D |
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| Destroyer OS. |
| I am getting two chunks of aluminium that are 2x3x1/2 and then I am going to bolt them to the sheet metal, which will suck it in straight, then bolt the chip through both of them. That ought to cover it. The expansion of heat through the sheet metal should make up for the inch or so short of Peter Daniels recommendation. |
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| CarlosT |
I'd add some heatsink grease between all layers for extra measure.
I think that the chunk of aluminum lineup uses is not insignificant and now your revised heatsink sounds much better, too.
My point about copper tubing was twofold...extra surface area for a given weight of metal and copper as a superior heat conductor.
Also...painting aluminum in heavy black enamel can help it to radiate heat...I think the heatsink gurus call this emmissivity :D |
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| tamasic1 |
| Go to a computer repair place. They will have plenty from old computers and probably give you what's lying around. |
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| lineup |
We can think and guess
and it will only be guessing.
When I say that LM3875 at normal listening levels
'does not require very much heatsinking'
.. it is based on my experiences and knowledge.
Now the young ones wants to stress and get to the limit of
as much MAAXXXXIMALLLL POWEEEERRR!!!! as possible.
These, not always the young!, should have enormous heatsinks in whatever amplifier they use.
Even in preamplifiers .....
I guess they will calm down, when they get older and sensible
in their audio listenings.
When they can start enjoy nice music instead :)
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Furthermore
it is not at all difficult to determine like what heatsink you need.
Not if you use the excellent documentation and applications information
in the LM3875 PDf datasheet.
Let's stop guessing now :cool:
http://www.national.com/ds.cgi/LM/LM3875.pdf
See for example, the great heatsink
info in my attached figures and tables.
They are captured from LM3875 PDF Datasheet
Regards everybody
lineup |
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