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Old 26th September 2002, 01:57 AM   #1
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Default is my heatsink enough

i got two 1000w transformers with two winds of 30vac each, and i got 8
heatsinks of 35cm*23cm*5cm. can i use them to build alephX?
i think 30vac maybe a little high. i am afaid of my heatsink can not sink
500 w of one channel. pls give me some suggestion. how can i do.
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Old 26th September 2002, 03:30 AM   #2
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If your tranformers have primaries for 120/240 you can connect them in series effectively lowering the output in half. But I doubt they are like that, are they?
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Old 26th September 2002, 04:52 AM   #3
hifiZen is offline hifiZen  Canada
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John,

What you need is the thermal coefficient (or theta) value in degrees C / W for those heatsinks. Otherwise, it's a bit difficult to say if they'll be enough. If you don't know the value, you can look through manufacturer catalogues online to find a matching extrusion profile and pull the data from that. In many cases, you can find the exact extrusion you've got. This is what I do when I get heatsinks from surplus or scrap etc, and with a little patience, it works well. If not, please post a photo and perhaps someone here has used a similar extrusion and give you a ballpark figure to work with.
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Old 26th September 2002, 05:05 AM   #4
hifiZen is offline hifiZen  Canada
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BTW - just based on the dimensions you gave (and this is just an off-the-cuff guess here...), I don't think 4 of those sinks will be nearly enough for one channel of Aleph-X with ~40V rails, expecially if you want to try setting the current bias to allow for loads below 8 ohms (most "8 ohm" speakers have a dip down to 5 or 6 ohms, or even as low as 4 ohms).

Be careful to account for your loudspeaker's actual impedance in your power dissipation calculations. This can affect your idle dissipation tremendously!

You may do better as Peter suggested to connect the primaries in series, thus halving your output voltage to a more reasonable 15VAC per secondary. Bear in mind that the X amp will have double the output voltage to your speakers due to the balanced outputs. Thus, if you're running 40V rails, peak voltage to your speakers will be around 76V !!! At 8 ohms, you'll need around 10A standing current, for a total idle dissipation of roughly 800W per channel! Power into 8 ohms would be something like 350W per channel. But count on much higher power dissipation for 4 ohms. Yikes!!!
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Old 26th September 2002, 05:49 AM   #5
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Quote:
Originally posted by hifiZen
for a total idle dissipation of roughly 800W per channel! Power into 8 ohms would be something like 350W per channel. But count on much higher power dissipation for 4 ohms. Yikes!!!
And in this case your 1000VA transformer is not enough. Your only choice is to either use primaries (if it's possible) in series or build Aleph 2 (and this is what you probably intended originally with all that stuff) .
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Old 26th September 2002, 09:48 AM   #6
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Default is 20vac ok

if i want alephx to output above 100w, how much volt of EI transformer is ok ? is 20vac ok?
if i put these two transformer's primaries in series , i will get 15vac
,but will this effect sound quality?
i regret that i bought these transformers too earlier!
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Old 26th September 2002, 11:58 AM   #7
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Hi John,

Quote:
i regret that i bought these transformers too earlier!
All is not lost.

I'm assuming your in China. Where ever you are, you can sell these transformers on the forums Trading Post to someone who wants to build a pair Aleph 2's. Then go an buy the correct transformers for the AlephX.

Rodd Yamas***a
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Old 26th September 2002, 02:37 PM   #8
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Default Re: is 20vac ok

Quote:
Originally posted by john-china
if i want alephx to output above 100w, how much volt of EI transformer is ok ? is 20vac ok?
if i put these two transformer's primaries in series , i will get 15vac
,but will this effect sound quality?
i regret that i bought these transformers too earlier!
When putting them in series, from 15V AC you'll get around 20V DC, and that's fine for 100W Aleh X. That's exactly what I'm doing on my Aleph X. I asked Nelson if that would affect anything and he replied that it wouldn't.
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Old 26th September 2002, 03:36 PM   #9
herm is offline herm  United States
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John-China;

Just as an estimate, look at this link:

http://www.aavidthermalloy.com/bin/e...LengthUnits=in

Roughly .33 degrees C per watt.

Hope this helps.
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Old 27th September 2002, 02:51 AM   #10
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Default thanx

0.33c/w . maybe my 8 heatsink only sink 400w per channel.
i think i should sell them on forum. but these transformers weigh 16kg.
from china i post them to foreign country, i think post fee is more than
price of these trnsformers in china less people diy hifi,specially solid state diy, only someone play tube amplifier. well,well, i do a try.
HPetter 's word encouraged me, maybe is good idea.
while talking about transformer, i got a question. in hifi design, is industrial
power transformer ok for it. whether or not need special design of transformer? in china only big factorys produce transformers, but they are for
industrial application .
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