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Old 23rd January 2009, 06:33 PM   #1
Bakmeel is offline Bakmeel  Netherlands
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Talking Aleph 2 - The Final Build

Hello all,

Today is a glorious day! The paintwork for my amplifier is done, and I am finally ready to assemble my Aleph 2 monoblocks. All pre-assembly and component gathering was done in the past 4 years, so in this weekend I expect to have two huge amplifiers rising....

For bringing up the appetite, below is the first picture of the platework just brought in... It is painted in a BMW metallic paint

Some specs:
- 1 kVA toroid transformer, 2x 42V / 11,9A secondaries.
- More than 198.000 uF capacitance on each rail
- Nominal rail voltage +/- 55V, 10mV ripple under 500W load.
- Bias current 0,5A on each fet pair, times 6 = 3A bias
- 330W dissipation per channel.

Apart from exaggerating on the power supply, the amplifier design is practically unaltered from the original Pass design.

First, I'm off to a cigar & whiskey tasting event... Tomorrow the big build will start....

Cheers!
Bakmeel
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Old 23rd January 2009, 07:58 PM   #2
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Old 24th January 2009, 12:19 PM   #3
Bakmeel is offline Bakmeel  Netherlands
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Goodafternoon y'all!

So here we go... All housekeeping tasks (groceries, laundry, etc) are now done, we can start...

First step is to mount the mainsboard on the baseplate. The baseplate is 10mm thick hardened aluminium.

The mainsboard contains a small auxiliary power supply and two large relais for the soft-start circuit I've alredy posted on this forum here
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Old 24th January 2009, 12:58 PM   #4
Bakmeel is offline Bakmeel  Netherlands
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Default Adding weight

Next part is the transformer and rectifier assembly.

The transformer is an Amplimo type Z8022 toroid. Amplimo also sells transformer pots, but they are normally used for tube amplifier transformers. A friend of mine potted it using a kind of soft potting material, also used for potting in-road LED lighting.

The two rectifiers are made with International Rectifer 63CPQ100 schottky diodes. They are mounted on 4mm thick ceramic plates for thermal coupling.
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Old 24th January 2009, 01:29 PM   #5
Bakmeel is offline Bakmeel  Netherlands
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Default Take to the skies

Next to mount the baseframe. Four aluminium rods, 20mm x 10mm x 555mm will keep the entire amp together.
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Old 24th January 2009, 01:55 PM   #6
Helmuth is offline Helmuth  Netherlands
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Bijna klaar Bouke?

Ziet er mooi uit allemaal. Looks great spacy.

Heb je mijn nieuwe boxes al gezien?nieuwe boxjes
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Old 24th January 2009, 03:35 PM   #7
Bakmeel is offline Bakmeel  Netherlands
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Heej Helmuth,

Speakertjes zien er puik uit! Mooi afgewerkt!

Next mount is the primary capacitor bank. 2 x 4 x 33.000uF / 63V Vishay BC Components. Copper strips to connect the lot together.

The primary capacitor bank is part of a CLC filter combination. More on the filter next post.

I've wired the capacitors in a kind of X- wiring. The current paths through the copper strips cross one another such that the impedance seen on each capacitor is identical, and they all filter an equal share of the ripple current.
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Old 24th January 2009, 04:27 PM   #8
Netlist is offline Netlist  Belgium
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Thread bookmarked. Looks very promissing.

/Hugo
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Old 24th January 2009, 04:51 PM   #9
Bakmeel is offline Bakmeel  Netherlands
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This is me wiring up the second stage of the CLC filter.

Since the A2 draws - like all other Alephs - a constant current under most conditions (neglecting the low-frequency modulation in the current source) I thought I could best use a CLC combination and put the filter frequency as low as possibl , the filter sizes: 132mF - 3mH - 66mF. Actually I've never calculated the filter frequencies, but
Duncan's Amp PSU Designer tool was all to handy, and I trust that it is accurate enough.

Behind the large inductor - there is another large inductor! :-) The two air-core inductors are placed back-to-back, putting them in a sort of magnetic coupling through air (and plastic). In essence, this makes them a weakly coupled DC common mode filter. I've never tested its benefit, but if the physics still work, there should be some good in it, shouldn't there?
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Old 24th January 2009, 05:09 PM   #10
Merijn is offline Merijn  Netherlands
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Te gaaf Bouke!!

Or for our English readers: Awsome!

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