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Old 17th December 2004, 08:36 PM   #41
guido is offline guido  Netherlands
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Last picture for those of you that don't know such a cool(ing?)-tunnel. I have another one on stock, but that one is for 8 TO3's.
The four heatsinks are isolated from frame, so you dont need isolators between the transistors and the metal (at least not in the 4 TO version, here it's two TO3's per heatsink).

For playing music these days, i have an amp with the same age: AudioAnalyse B90mk2. The 'black bat' class-a amp with tube pre.
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Old 17th December 2004, 08:50 PM   #42
Cobra2 is offline Cobra2  Norway
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Default It reminds me...

I built my first amp; ETI-5000 in 1983.
-just found a copy of the article, will scan it, if anybody is interested.
I still remember it, "killing" my neighbours with my C.W.-AT-123 speakers, and Rush "Moving Pictures" on my top-of-the-line Dual...


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Old 17th December 2004, 08:57 PM   #43
guido is offline guido  Netherlands
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I still have the svenska's to go with the amp. Jamo disco line before philips got involved. Also not a nice thing for the neighbours / neighbourhood. I needed to 'test' the amp now and then to see if it was ok for a party in the evening, at least that was my excuse. The woofers of those svenska's need fixing, the foam ring around the speaker turned to dust at my last 'testrun'.


Question for all: how far can i get if i use that cooling-tunnel with a quiet fan (or run a normal fan at reduced revs). Any good for a livingroom amp? The papst fan in the amp is not quiet
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Old 18th December 2004, 03:54 AM   #44
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Go ahead..Cobra..post it.I ve build one 100watts ETI amp using 2N3055/MJ2955 2 pairs some 18 years ago,but now dumbed as junk!
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Old 18th December 2004, 09:29 AM   #45
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Guido,

there is a heatsink excel calculator to download on one of the threads. Rod Elliot has a simpler one at his site.

Depending on the geometry of the heatsink the maximum obtainably with a cooling duct is a reduction of the static heat resistance of 1 : 6.
The parameters to obtain that are:
blank heatsinks, no air gaps in the cooling duct, high air velocity,
no laminair flows but pure turbulent.
With average heatsinks and normal fans it reduces to 1 : 3.
I did fluid flows and heat transfer colleges at Delft polytech, at the time i experimented some with heatsinks, ducts, and vents
for the fun and to see how far i could go with a class A amplifier and a cooling duct.
If you like to estimate it more accurately, there is a graph for thermal resistance versus air velocity here somewhere too.

Some time ago i bought 20 new alloy Papst 30dBA vents for $5
the piece.
With reduced air velocity that vent is hardly noticeable, and lasts a century.
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Old 18th December 2004, 09:31 AM   #46
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Martin,

i'll take a look for the schematic today, i'll post it this weekend.
jacco.
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Old 18th December 2004, 10:35 AM   #47
Cobra2 is offline Cobra2  Norway
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Default The ETI...

Schematics:

Arne K
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Old 18th December 2004, 10:37 AM   #48
Cobra2 is offline Cobra2  Norway
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Default Article

Attached: too big....

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Old 18th December 2004, 11:00 AM   #49
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Sorry COBRA !! Poor pic quality after compressing Can u please mail it to >> floyds_ec@gawab.com
THANX!!
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Old 18th December 2004, 06:52 PM   #50
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Default Elektor crescendo 1982

Thanks jacco, I'd really appreciate that.
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