Pass Aleph 4 Project out !!!

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Aleph4 Info

Hi Folks,

FYI. Desmond Harrington is the webmaster and PR person for PassLabs. If you want any info from PL he should be your first port of call rather than NP himself.

Being the said builder of the Aleph4 a little info. I am not a reseller. Anyone is welcome to any info re the amp.

You can get a PDF from the projects gallery which has the necessary info:

You can use IFRP244, IFRP240, IRF244 ..... NP states it doesn't matter. IFRP240s are what he would (and does) use now.

NOTE: there was an ERROR in the first PDF which omitted a join from C9-R26 to the base of Q3. I have sent Des a replacement file which should be on the site as we speak.
The Irfp 240 I think are the easiest to find.
The only problem is they need matching which is easy to do with 1 resistor and a good digital multimeter.
The only problem is that they cost more the input ones.
It´s just something you have to do if you want your amp to be perfect. That´s the whole idea anyway.
100 W class A Yees please!

I was triing to get the schematics.

But could not folow the tread.

Could you post them please.

PS I have started to work on the heat sinks

Plan is to use 2mm copper sheet and 4 mm thick buss bar + fans
for which is quite easy to make a speed controler (speed increse with temperature )

So far cost is around £30 for the copper (I have same good sources)

Copper is a beter conductor than alluminium it does oxidise with time but it can be Gold Silver or Crome plated again I shuld be able to get this cheap.

I will let you know but I am stuck witout the schematics.
Aleph 4 Heatsinking

Hi guys.

I am new to the Aleph series of amplifiers but I am contemplating an Aleph 4 project.

My problem is heatsinks.

I have a pile of 1.1 K/Watt Heatsinks. As the Aleph 4 stands, each MOSFET would operate at approximately 75 Degrees which would not engender long term reliability.

Would the design be compromised by increasing the MOSFET count to 16 per channel? This would result in each device dissipating 36Watts with +/-48V supply rails. If Iq is 3A each MOSFET would then run at approx 60 Degrees.


8 times 1.1 k/W is equivalent to 6 times 0.825 k/W, not 0.72 k/W.

Output devices of a production Aleph-4 run at 80-85C idle, a standard value.
Provided your heatsinks are really 1.1 k/W, 12 of them would be sufficient for 288 watts dissipation (48 x 3 x2)
If you stack them in a row, Japanese power amp style, chimney effect would lower the temperature of the heatsinks a few points more.
Why are heatsinks so damn expensive? Does anyone know of a cheaper UK supplier at DIY quantities. The cheapest I have found so far is RS Components. 0.7(ish) K/W heatsinks are about the £10 to £15 mark. Not too bad if you only need ONE, I need sixteen of them - I could always sell the wife's car, or even the wife if anyone wants her.
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