Greetings One and all
I'am a complete newbie to DIY electronic, thus the Grasshopper. I'am taking a stab at building a 25 watt SON and wondering if any one has a cheap source for heatsinks in the eastern Canada area or further afield if need be. I know it will require massive amounts of HS.
Homebrewed designs are most welcome.
I'am a complete newbie to DIY electronic, thus the Grasshopper. I'am taking a stab at building a 25 watt SON and wondering if any one has a cheap source for heatsinks in the eastern Canada area or further afield if need be. I know it will require massive amounts of HS.
Homebrewed designs are most welcome.
Thanks for the site. Similar to the idea I had in mind, although, I believe I will need three to four times the amount of sq. inches shown to meet the HS requirements for a 25 watt SON. Now to aquire to raw material.
Cheers, Gustavo
Cheers, Gustavo
You might want to isolate the MOSFETSs heatsinks with the power resistors's heatsinks as you can run the resistors closer to its limits.
Check out the thread titled heatsinks just a short scroll down from your post. I posted a link there for some pretty big sinks you can buy surplus.
Rob
Rob
Sorry I rushed for time the other day, that link was
http://www.aaaim.com/cgi-local/shop991/shop.pl/SID=18889125752/page=THUN>htm#HD9800
http://www.aaaim.com/cgi-local/shop991/shop.pl/SID=18889125752/page=THUN>htm#HD9800
I checked out the site with heatsinks. I'll need at least 10 of that type, at $35 US per unit, way too rich for my blood. Scrapyard scrounging for the next few weekends.
Gustavo
Gustavo
at least 10?
What in hell are you building if you don't mind me asking?
And do you realise how BIG 10 of those is?
What in hell are you building if you don't mind me asking?
And do you realise how BIG 10 of those is?
sorry, just read your first post again....but damn, TEN??
You might want to do those calculations again....I only need 2 of those at $35 a piece for my Aleph 4 and that's with quite a bit of room to spare....so 10 sounds OBSCENE...its not THAT inefficient is it?
You might want to do those calculations again....I only need 2 of those at $35 a piece for my Aleph 4 and that's with quite a bit of room to spare....so 10 sounds OBSCENE...its not THAT inefficient is it?
jduncan,
you must be missing out the big picture, it's a 25W SOZ....or should i say an amplifier from hell...🙂
you must be missing out the big picture, it's a 25W SOZ....or should i say an amplifier from hell...🙂
its TEN 17" lengths of heatsink (thats 170") that have a thermal resistance of roughly 0.8 degrees C/W/3" ...so assuming you're not stupid and spread out the devices evenly thats absolutely ridiculous....
It's not an amplifier...it's a space heater that makes music. That's part of why I've got the SOZ w/current sources thread going. Dreadfully inefficient.
Good thing that winter's coming on--at least here in the Northern hemisphere. (Just ask me if I love having a pair of Alephs and a pair of tube amps to help warm up my listening room.)
Grey
Good thing that winter's coming on--at least here in the Northern hemisphere. (Just ask me if I love having a pair of Alephs and a pair of tube amps to help warm up my listening room.)
Grey
alright i'll accept this...it just shocked me initially...i knew it was inefficient, but wow....my aleph 4's dissipate almost 600W and as i said, 2 of these heatsinks is plenty.....so you're saying for 10, you're dissipating roughly 3000W? 25W out, 3000W dissipated?
i think that defines horribly inefficient....
😉
i think that defines horribly inefficient....
😉
Jduncan:
Are 2 of those really enough for a stereo aleph 4?
What temps do you get on your machine?
//kasra
Are 2 of those really enough for a stereo aleph 4?
What temps do you get on your machine?
//kasra
you have 12 devices per 17" length right?
that means you have roughly 2 devices for each 3 inch length....
that's 48W...the Rjc is 0.83, Rcs is 0.2 and the Rsa for each 3 inch length is 0.8. So 48W * (0.83 + 0.2 + 0.8) = about 88 degrees difference between ambient and junction temperature....thats perfectly ok! It's actually a bit better than this as the 48W per 3" length aren't centered at one particular point and are spread pretty much evenly over the 3 inches....
that means you have roughly 2 devices for each 3 inch length....
that's 48W...the Rjc is 0.83, Rcs is 0.2 and the Rsa for each 3 inch length is 0.8. So 48W * (0.83 + 0.2 + 0.8) = about 88 degrees difference between ambient and junction temperature....thats perfectly ok! It's actually a bit better than this as the 48W per 3" length aren't centered at one particular point and are spread pretty much evenly over the 3 inches....
jduncan
How do you get Rcs (R case to sink) at 0.2C/W?
When you need to electrically isolate the FET from the sink reaching 0.2C/W is quite a challenge. Readely available materials such as mica with silicon grease or silicon pads will not come close. BeO, Kapton are very hard to come by.
In practice I can get 0.5 to 0.6C/W with mica and silicon grease. In your example this would mean very hot sinks and probaly a short lifespan for the amplifier, or am I missing something?
How do you get Rcs (R case to sink) at 0.2C/W?
When you need to electrically isolate the FET from the sink reaching 0.2C/W is quite a challenge. Readely available materials such as mica with silicon grease or silicon pads will not come close. BeO, Kapton are very hard to come by.
In practice I can get 0.5 to 0.6C/W with mica and silicon grease. In your example this would mean very hot sinks and probaly a short lifespan for the amplifier, or am I missing something?
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