aleph 2

[MEGA-amp]

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

[moe29]

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

[zygibajt]

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

[moe29]

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.

[zygibajt]

Aleph 4 is a stereo Aleph 2 in one chassis

Not exactly.

[grataku]

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.

[moe29]

Quote from the service manual:

The Aleph 4 is a stereo 100 watt audio power amplifier which
operates in single-ended class A mode.

[zygibajt]

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

[GRollins]

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

[Brian Donaldson]

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.