Aleph 2 build questions

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Hello everybody. I intend to build Aleph 2 amp. The amp has benn chosen due to tube-like sound (based on the feedback from this forum). So by now i've encountered couple of questions while designing the amp in CAD.
1. What is the matching criteria for MOSFETS and BJTs?
2. What is the proper area of radiator to be used?
3. If i replace original IRF244 by IRFP240 -the amount of output stages should be the same (X6)? The question is due to different capacities.
4. By replacing of original IRF244 by IRFP240 - what are the sonic diffences?
 
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Official Court Jester
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1.mosfets - matched input pair , matched upper group , matched lower group

bjt - no matching

2. what is dissipation per channel and what case/set of heatsinks you have on disposal/easy acquired list?

3.same number of mosfets ;

4. no difference in sonics , nor in any other area
 
There are several threads on here regarding MOS-FET matching.

As Zen Mod said, you only need to match the 6 x devices in the upper half of the circuit to each other, and the 6 x devices in the lower half together (NOT all 12).

Devices from one batch will not necessarily match (and probably wont), you just need a bucket full of them and pick out sets of 6 that are a close match to each other.

You are matching for Vgs / Ids. ie at a set Vgs all 6 x devices should be within a few mA of each other for Ids.

How close you want to match them is up to you, 1mA max discrepancy will be fine.

The upper six and the lower six can be wildly different as can the other channel. It is only important to get each set of 6 closely matched.
 
Sadly Dad's Aleph 4 is dead at the moment and I don't have the £400 to replace the suspect caps.

These beasts generate some serious heat, 400-500W in the case of the Aleph 4. It shares the same 24 x MOS-FETs as the Aleph 2.

This one has cooked its PSU capacitors.
 

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There is no way, forget it.
There is no free lunch, as Papa said.
Aleph-like sound quality needs thermal dissipation.
My Aleph beast dissipate about 1200-1300W.
It is very nice feature in winter season.

If you need less power, you can build Aleph 4 or Aleph 3.
 
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