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Old 8th July 2009, 02:14 PM   #1
wicked1 is offline wicked1  United States
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Default mini aleph transformer question

Well, I think I'm at the point where I have read too much. I know this question has been answered, but its been answered so many different ways, I need to ask again.

Transformer for mini aleph. 12v or 15v? I'm thinking 12 w/ higher bias, but let me know what others think works best.

VA? I've seen posts that say the mini aleph doesn't use much power and will run perfectly off a 200va or even less tx. Then I read the next post, and someones using 500va, and wouldn't go smaller. (Ive noticed talk about the mini and the 30 always end up in the same thread, so maybe thats the difference in va.. let me know)
I'm most likely going stereo, sharing one power supply. It's just for some desktop/computer speakers, so doesn't need to be the very best aleph out there, and probably won't ever need to be turned up all the way.

Thanks!
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Old 8th July 2009, 03:31 PM   #2
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I have a stereo miniA running from a single 225VA transformer with 2*12V secondaries (CLC PSU) and it has plenty of power (FE108EZ fullrange). The power-meter in the socket reads 80W when the amp is switched on and the transformer gets warm (~30°C) after a some hours of playing music through the amp.

Use whatever transformer you can get, I'd say 150VA or bigger, with secondaries matching your heatsinks.
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Old 8th July 2009, 07:57 PM   #3
wicked1 is offline wicked1  United States
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I'm just starting to understand the differences between different power supply designs.
Do you have 2x bridge rectifiers, or only one? Do you know how much voltage you get out of your power supply?
Do you know the technical details on your chokes?

I've got the briangt board, and looked up the original parts list from diyamps.com. They say to leave the resistor out! ( so whats that? a C,C ps) So, that would make the voltage higher at the output of the PS.
I was just reading a post somewhere and a person used 2x18v transformers, and after the resistors and chokes in the power supply only got 13v out!

Thanks, -still trying to get the idea of amp power supplies.
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Old 8th July 2009, 11:03 PM   #4
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Hi,

I use two bridges, like in the F3 service manual:

http://www.firstwatt.com/downloads/F...-manual-sm.pdf

The voltages of my PSU are +12.66V and -12.70V. You can see all the voltages and pics of my amp here, in the original Mini A thread (or search for Austin Powers):

http://www.diyaudio.com/forums/showt...68#post1536468

The air-core coils are 2.2mH, have a resistance of 0.84 Ohms and are made of 1mm thick copper wire. They're from Intertechnik and are basically intended for use in crossovers. Just measured, they have a voltage drop of 2V across them. They get warm but definitely not hot. I use 29 Panasonic FC 2200µF50V caps in parallel per rail, in a CLCC configuration, plus bypass-caps inside the amp.

Leaving out the resistors would result in a higher supply voltage, yes, but not much I'd guess. What value do/would they have and how many are there?

So much rum...
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