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torsom 14th November 2005 02:53 PM

Aleph 1.2
I am going to bulid a Aleph 1.2. I have bought
Heatsinks H=50cm L=30cm W=4cm.
2 X 4KVA /45 Volt transformer.
12 x 100000uF Evox REFA
4 x 68 A 600V Bridge Rectifier
50 X IRFP 240(Same production)
Solen Capacitors
Tantalm resistors
And so on!

I am planing to reduce the 1.5 ohm resistor that is placed on the drain of IRFP 240 to 1.2 ohm. I am doing this so I can get even more out of this already powerful amplifier.

Is there anybody that have any experience in doing so?

Best regards Torsom

GRollins 14th November 2005 11:07 PM

You won't get more power out of an Aleph by reducing the Source resistor (I am assuming that you meant Source resistor, as there is no resistor on the Drain of the output devices)...unless you are using a low impedance load. The power into 8 ohms will remain the same. Increasing the bias can make it sound better, however. I have a pair of Aleph 2s running at roughly 10% higher bias than stock and they sound quite nice.
If you want to increase the amp's power into 8 Ohms, you'll need to increase the rail voltage. Yes, it can be done, but you'll have to pay close attention to the thermal dissipation of the MOSFETs.


jleaman 15th November 2005 05:44 AM

why do yoneed so much power ? I'm running 4 aleph mini's witch = 15watts each Class a.. ANd have tons od power WHY do you need a aleph 1.2 plusmore power ? Do you really have so much money to run them and the hydro bill up. ? Do yo have huge huge huge heat sinks ?

torsom 15th November 2005 05:28 PM

Thanks for correcting me GRollins! Yes, I meant the source resistor.
Ok! So reducing the resistor vil mostly cause higher thermal dissipation and maybe better sound.
I got the tips from KRISTIJAN KLJUCARIC, maybe i misunderstood him. He talked about 900W and right below 8A BIAS. I guess he meant 900 W in heat dissipation.
And when I think about it, as long as you have the same voltage and the same impedans(load) the effect will be the same. Ohms lov:)

And for "jleaman"! You asked me if I need the extra power. No! I don't need it. Somethings you just do for the fun of it and the satisfaction of getting things to work. And about the money! It's an expensive hobby and I hope I don't blow all the MOSFET's:)

Best regards Torsom

GRollins 15th November 2005 08:45 PM

So long as you go into it with realistic expectations, chances are that everything will turn out just fine.


folkeb 18th January 2006 10:31 PM

I'm in the process of finding appropriate heatsinks for the aleph 1.2. If I'm not mistaken I am also thinking of having heatsinks just on the sides. However, I've been troubled with getting the C/W ratio low enough. I figure I can have the amps running at 35 degrees above idle, but only a few, and very expensive heatsinks, can give me these low numbers and only just. We're talking about a two heatsinks for $800 (500 mm W, 200 mm long and 85 mm high).

The question is this: Have you calcultated the temp for the heatsinks under normal operation, and if so - where can I get these heatsinks?!?

GRollins 18th January 2006 11:39 PM

I sidestepped the whole problem. Fooey on convection heatsinks. I went water-cooled for my big Alephs. Works wonders and it's much, much cheaper than buying a zillion dollars worth of heatsinks.
I did a thread on this a couple of years ago if you're interested. Bang on the search feature a while and it'll turn up.
If you decide to go with normal air-cooled heatsinks, you might want to consider fans. It'll help keep your costs down. If you don't want to use fans, then you'll be spending a lot of money. That's just the way things are, I'm afraid.


Anvil 19th January 2006 07:16 AM

Hi. Look from elfa, they have austerlitz heatsinks, KS300.6 might be good for you.

Duck-Twacy 19th January 2006 11:58 AM

Four Seifert KL273 or something like that

apogee_diva 12th February 2006 01:56 AM

I'm also planning to build a pair of Aleph 1.2 to use with the Apogee Diva's. It'll be my first DIY project though.

Can someone (Torsom ?) email me your parts list ? Any rough indication of how much the parts only will cost ? (besides the PCB's from KRISTIJAN KLJUCARIC).

I've considered smaller Alephs, but the Diva's are power hungry and quite inefficient (3 ohms, 87 db). I'm currently using the Diva's with a Krell KSA-200S, but would like to bi-amp. The Krell's bass is excellent, but the MRT could be improved. I've read wonderful reviews about the Aleph's MRT sweetness (a recurring trait since earlier designs such as the STATIS). So, I'm keen to give it a try and hope that it won't cost too much :whazzat:

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