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Old 5th December 2012, 03:57 PM   #611
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Quote:
Originally Posted by BigE View Post
Are the sinks from heatsink USA more appropriate? You can order them as tall as you like.
yes. sort of. they have more spacing between the fins but they come only in raw aluminium
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Old 5th December 2012, 05:18 PM   #612
dazed2 is offline dazed2  Canada
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yeah but the difference is that Antek can also custom build a case for you with their heatsinks integrated to it.
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Old 5th December 2012, 05:20 PM   #613
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but most of the sinks are made for forced cooling thats why the spacing between the fins are so smal.
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Old 6th December 2012, 05:54 PM   #614
BigE is offline BigE  Canada
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I think this is correct now. Comments?

Prms is the Watts RMS output.
I^2 = Prms/8R0
Irms = Sqrt(I^2)
Vrms = Irms * 8
Vpk = Vrms * 1.414
Vrect = Vpk + 5.6 V
Vac = 1.3 * Vrect

Loss/droop of 5.6 volts. This is Class A.

Prms I^2 Irms Vrms Vpk Vrect Vac

20 2.5 1.581 12.649 17.885 23.486 18.066
50 6.25 2.5 20 28.28 33.88 26.062
100 12.5 3.535 28.284 39.993 45.593 35.072
150 18.75 4.330 34.641 48.98 54.582 41.986

As far as the VA for each transformer, that is a different story.

Please note, I take no responsibility that these will work in your amp, as I'm just trying to learn this stuff and could be very wrong.

AudioSan,

The table suggests you are going to get 135 Watts from a 40 V transformer. In real life, a little less.

The table also suggests that 50 V caps should be OK for a 100watt amp.

Last edited by BigE; 6th December 2012 at 06:18 PM.
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Old 7th December 2012, 04:00 PM   #615
BigE is offline BigE  Canada
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Who do I speak to about getting my login name changed to "Threadkiller"?
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Old 7th December 2012, 04:44 PM   #616
flg is offline flg  United States
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Personally, I think your first equation is Irms^2= Prms/8R0,
But this is backwards???
SqRt (Irms^2) *1.414=Ipk
Ipk*8R0=Vpk
Vpk+(2V MOSFET Drop)= powersupply DC
DC/1.3=Secondary Vrms
You could experience MOSFET drop closer to 4V but it depends on your VAS drive and or other factors.
Depending on the load and the rectifier Vf I ussually see about 2.5V drop from the unloaded condition. YMMV
I ussually use schottky rectumfriers with about .3-.4Vf @ load.
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Last edited by flg; 7th December 2012 at 04:46 PM.
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Old 7th December 2012, 09:02 PM   #617
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I am thinking with 32V rails, you are real close to 100W unless you have an undersized trafo and overly large smoothing resistors in the PSU
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Old 7th December 2012, 09:38 PM   #618
Variac is offline Variac  United States
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Heatsinks over about 6" tall have diminishing returns. I wouldn't bother going over 8" tall. I think its because the lower part of the sink heats the air traveling up the slots to the point that the upper part of the sink doesn't cool much.
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Old 7th December 2012, 09:40 PM   #619
Variac is offline Variac  United States
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The PCB's are ordered and should be in the store within the month. We got expedited shipping and production.

I know this has been an incredibly long time, but we don't have full time people helping here at the forum or at the store and I have been swamped with work at my "real Job" Also, there were issues with getting the order right with the maker, which is really important !
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Old 7th December 2012, 10:14 PM   #620
BigE is offline BigE  Canada
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Quote:
Originally Posted by flg View Post
Personally, I think your first equation is Irms^2= Prms/8R0,
But this is backwards???
SqRt (Irms^2) *1.414=Ipk
Ipk*8R0=Vpk
Vpk+(2V MOSFET Drop)= powersupply DC
DC/1.3=Secondary Vrms
You could experience MOSFET drop closer to 4V but it depends on your VAS drive and or other factors.
Depending on the load and the rectifier Vf I ussually see about 2.5V drop from the unloaded condition. YMMV
I ussually use schottky rectumfriers with about .3-.4Vf @ load.
It does not really matter when you do the calculation for Vpk, just so that you do it somewhere.

My guestimate for 5.6 needs some looking at.

A great read, from page 64 and on.

http://www.onsemi.com/pub/Collateral/HB206-D.PDF
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