HPPA
I've built this amplifier about 4 years ago. A friend of mine still uses this amp. It's sounds pretty good, but I haven't compared it to my new amps.
The amplifier is called HPPA (High Performance Power Amplifier) and it's designed by Bert Molenkamp in the Netherlands.
One thing I do remember about this amp was that it was pretty hard to get the bias stable. You MUST use a 5mm or thicker U- profile to mount the six output transistors and use a large heatsink. A temperature controlled fan is also recommended.
Bert also recommended the MJ3281A/MJ1302A instead of MJ1500x transistor. And MJH6284/6287 instead of the TIP142/147 darlingtons. But I used the transistors in specified in the schematic.
The BD791/792 might be hard to get, but you can use BD139/BD140 instead. Those four transistors must be placed on the same heatsink.
/Freddie
I've built this amplifier about 4 years ago. A friend of mine still uses this amp. It's sounds pretty good, but I haven't compared it to my new amps.
The amplifier is called HPPA (High Performance Power Amplifier) and it's designed by Bert Molenkamp in the Netherlands.
One thing I do remember about this amp was that it was pretty hard to get the bias stable. You MUST use a 5mm or thicker U- profile to mount the six output transistors and use a large heatsink. A temperature controlled fan is also recommended.
Bert also recommended the MJ3281A/MJ1302A instead of MJ1500x transistor. And MJH6284/6287 instead of the TIP142/147 darlingtons. But I used the transistors in specified in the schematic.
The BD791/792 might be hard to get, but you can use BD139/BD140 instead. Those four transistors must be placed on the same heatsink.
/Freddie
I noticed in the design the long-tailed pair uses an adjustable current mirror instead of a simple adjustable current source - what is the advantage in doing so??
Ford_V6 said:
I made a couple of these amps some years ago and I must say they were quite good indeed.
I have a PCB layout in BMP format (200 dpi) only, components placement has to be "hand-made".
Driver transistors are mounted on the main heatsink as well as the BD139 which sets the bias current.
Cheers
Andrea
Ford_V6 said:
Question... why have 2 BD792? It seems the first one is to be saturated so why the other?
try using 2 rectifier diodes instead of the 39Ohm resistor. It would be safer.
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