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?
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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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
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.
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.
You can see here my early attempt, it is working even now, but it only get the opportunity to work at winter season:
My good old-new Aleph
this is I built sometime around the turn of the last millennium.
My good old-new Aleph
this is I built sometime around the turn of the last millennium.
if you go at Forum's fave case manufacturer site , appropriate page is Frontale 10mm
look at 5U/500 case
that one will be approximately enough for one monoblock , dissipating 300W of heat
look at 5U/500 case
that one will be approximately enough for one monoblock , dissipating 300W of heat
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.
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.
Attachments
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.
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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yup
search forum for Aleph reloaded thread ......... here
for few more tricks and tips (easier to build) , read this thread
search forum for Aleph reloaded thread ......... here
for few more tricks and tips (easier to build) , read this thread
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