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Old 10th December 2003, 03:38 PM   #11
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Quote:
Originally posted by moe29
Scott,

sounds like you are describing the Chatham heatsink. I use two
of those for 1 channel of Aleph 2... and they get toasty! I remember
thinking that it was overkill to use 2 sinks per channel, but it
actually worked out quite well. So the rule of thumb is, when in
doubt, double it! - you can never have too much heatsink. I think
the Chatham heatsink suffers because it's cooling fins are to small
at 1.5"... i bet it would help a lot if they were 3".

m.

Yes, that's them. If they had 3" fins, according to the spreadsheet they would go from .17 C/W to .07 C/W..so yeah that would help. ;-)

Scott
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Old 10th December 2003, 03:43 PM   #12
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Quote:
Originally posted by cowanrg
wow, i wasnt aware an aleph 5 had THAT much heat! would i be fine then with an aleph 3 in stereo? i was hoping to get a bit more power out of this then just 60 watts into 4 ohms, but it looks like thats the most i could get

oh, and yes, they are anodized black.
Oops...I guess I didn't answer your question...

Going by the Aleph 3 service manual each fet is biased for 1A, making 2A of current. With 25V rails that works out to 100W dissipation...which if the spreadsheet is right should be reasonable for your heatsinks. If they run too hot, take one of those new fangled super quiet PC fans and run it under the recommended voltage. They are silent when doing this, and you'd be surprised at how much it helps.

Scott
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Old 10th December 2003, 04:53 PM   #13
cowanrg is offline cowanrg  United States
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that sure is a lot of heat put out by two little transistors!

i guess an aleph 3 would be fine powering the top end of my maggies, with the aleph 2's powering the bottom end...
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Old 10th December 2003, 05:04 PM   #14
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Quote:
Originally posted by cowanrg
that sure is a lot of heat put out by two little transistors!

i guess an aleph 3 would be fine powering the top end of my maggies, with the aleph 2's powering the bottom end...

Well actually it's 4. Two in the constant current source, two in the output stage. So 25Watts each isn't so bad. With a thermal impedance from junction to sink of 1.2 C/W or less youre going to keep the junction temp at 80 degrees...which is hot...but the IRF FETS do pretty good with temp so they should be okay.

(I should have said each FET leg, or something like that, sorry.)

Scott
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