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Old 12th December 2003, 11:06 PM   #1
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Question aleph 2

Hey everybody,
I finally decided what to build after reading countless posts and studying, an Aleph 2. And I highly recommend reading Teach Yourself Electricity and Electronics by Stan Gibilisco, very helpful.

I am purchasing 4 pcs 10"X18" 1/2" baseplate w/4" fins for alpeh 2 monoblocks. I plan on mounting KRISTIJAN's FET boards squared and centered on the sink, 1 on each sink of course. I'm not great with formulas, so I am wondering if this size heatsink is sufficient? I am assuming it is.

Also planning on purchasing Plitron's 1500VA 38v sec transformers for each block. I will be using a Pi filter per KRISTIJAN's PS schematic. What value should I use for the coil? I've seen people using 3.9mh coils with that secondary voltage, just wondering if i'm the ballpark.

Many thanks,

John
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Old 13th December 2003, 12:03 AM   #2
moe29 is offline moe29  United States
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heatsinks sound big enough.

FETS mounted in the middle is ideal.

1500 VA toroids are fine... so would 1000 VA, up to you. i think the
original had 750VA? (i think i remember reading that somewhere)

38 volt secondaries are fine.

i used 2mH coils in my Aleph 2... 4mH would be fine too. Kristijan's
PSU shematic is a good one to follow. Check out mcmelectronics.com
for them.

sounds like you've done your homework! Good Luck, you will not
be disappointed
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Old 13th December 2003, 12:14 AM   #3
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I think 2mH should be ok.
If you haven't used the coil 38VAC might be a bit too high,but with coil should be allright.
1500VA should be just fine.
I know (from good source) that original Aleph 4 uses 2KVA transformer,so I think Aleph 2 monoblock uses at least 1,5KVA,and I wouldn't be supriced if it's more.
Good Luck with your project!

Bartek
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Old 13th December 2003, 04:49 AM   #4
moe29 is offline moe29  United States
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Aleph 4 is a stereo Aleph 2 in one chassis, thus 2KVA transformer.

1K VA is plenty for an Aleph 2. More is overkill, but that's up to
you and your wallet.
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Old 13th December 2003, 09:14 AM   #5
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Quote:
Aleph 4 is a stereo Aleph 2 in one chassis
Not exactly.
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Old 13th December 2003, 12:36 PM   #6
grataku is offline grataku  United States
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This is an old subject but with the different AC freq the low pass should be a little bit different betwen US and EU. In practice 4mH in EU is equivalent to 2mH in the US.
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Old 13th December 2003, 12:39 PM   #7
moe29 is offline moe29  United States
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Quote from the service manual:

The Aleph 4 is a stereo 100 watt audio power amplifier which
operates in single-ended class A mode.
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Old 13th December 2003, 05:03 PM   #8
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I meant that Aleph 4 is not exactly two Aleph 2 in one chassis.
The power requirements might be a little bit diffrent becouse of the small diffrances in schematics.

Bartek
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Old 5th January 2004, 01:15 AM   #9
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True, the Aleph 4 and the Aleph 2 were both 100W amps, but the Aleph 2 ran higher bias. All things being equal, more bias is good, so the nod goes to the Aleph 2.

Grey
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Old 5th January 2004, 01:44 AM   #10
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And the power supply voltage is totally non critical. I've ran mine all the way from +- 25V to +- 65v with very little sound difference (except power output) I had to tweak the bias back (I have a pot)a bit to keep temp down at 65v.

The amps sounded more open with the higher rails an lower bias. Best compromise was around 4.5A and +- 50V

I strongly considered putting my 22A variac in an enclosure and using it as a soft start and heat adjustment for non critical listening so I could choose not to put almost 1 kw of heat into my balmy Houston livingroom.
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