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Old 28th January 2013, 05:06 AM   #1521
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r27 as a pot to jack up the bias. more bias makes it sound better. but adds heat.
heat sink temp. the lower the better. nelson says 55 or 50 deg C.

here is what i would do. jack the bias up till the sinks are 50-55deg C and the fan noise is low enough to live with if you have fans.

the temp of the fets dosent make it sound diffrent (temp will change how the fets mesure so i supose it could but i couldnt hear it) but the hotter the chip the shorter it will last. or it could overheat and fail, then it will sound bad.
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Old 28th January 2013, 05:44 AM   #1522
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Quote:
Originally Posted by sakellogg View Post
r27 as a pot to jack up the bias.
Many thanks! The enclosed fan is very silent with rear exhaust. I will see how heat at the stock bias is managed and take it from there. [I would like 8-10 degrees of spare cooling capacity for higher room temperatures during summer.]

Also, each heat sink will have 75 degree thermal cutoff switches to the mains in case of fan problems...

Last edited by francolargo; 28th January 2013 at 05:54 AM.
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Old 28th January 2013, 05:54 AM   #1523
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Many thanks! The enclosed fan is very silent with rear exhaust. I will see how heat at the stock bias is managed and take it from there. [I would like 8-10 degrees of spare cooling capacity for higher room temperatures during summer.]
Wise.
50 deg is very safe.
But I don't wanna pay ur ac bill! In the summer. I use mine in the winter only, kinda sad but I don't have time in the summer anyway.

Keep in mind the extra draw on your powersupply.
Don't fry your xformer. More curent will raise the ripple in your ps.

So in short... Find your sweet spot. Powersupply/heat/sound you like. good luck. Worth the time
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Old 28th January 2013, 06:01 AM   #1524
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Originally Posted by sakellogg View Post
Wise.
Keep in mind the extra draw on your powersupply.
Don't fry your xformer. More curent will raise the ripple in your ps.

So in short... Find your sweet spot. Powersupply/heat/sound you like. good luck. Worth the time
Good point. I'm using one 400VA toroid per channel, each with 88,000 uF of Panasonics plus a couple nice nonpolars for good measure. Should be good there, no?

Rectifiers are FREDs - 3020s. They might be touchier...

Last edited by francolargo; 28th January 2013 at 06:10 AM.
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Old 28th January 2013, 06:20 AM   #1525
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Off the top of my head I would say yes a bit higher would be ok.

Off the cuff math and spelling are not my strong suit.
400/secondary Vac = ROUGH current rateing.

Lots of fun to be had
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Old 28th January 2013, 06:28 AM   #1526
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let`s say i will use same heatsinking from actual aleph which holds 140w dissipation at 30C above ambient per channel
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Old 28th January 2013, 11:38 AM   #1527
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keep sissy IRFP240 happy at the bay , with no more than 40W of dissipation/per piece and no more than 55C at heatsink - where you can touch it with your palm
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Old 28th January 2013, 11:44 AM   #1528
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12v should lend itself to about 2.5A, coming in at about 30W dissipation
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Old 28th January 2013, 12:51 PM   #1529
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still thinking at that battery system ... and how my speakers are current hungry I guess it is better for them to lower the voltage and raise the current
maybe one day this dream becomes reality but this after I will find and substitute input fets ..
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Old 5th February 2013, 04:58 PM   #1530
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One more detail before power-up, if you please... I accidentally ordered the wrong cap for C4 so made do with what was on hand: one used Elna SilmicII and one new Panasonic. I'm not sure of the role played by that cap, which parallels the 9.1v zener diode. So, wait and order new&good 10 uf caps, put in new&good 22uf caps, or forge ahead with whats in there now? TIA
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