2stageEF high performance class AB power amp / 200W8R / 400W4R

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2stageEF 50W MOSFET - aka SA2015MT

... have had some spare time to start with some metal work ...

SA2015MT will be build using


  • a 2HE case,
  • has 4 audio Channels,
  • is powered by a Hypex SMPS 1200A180,
  • active cooled using ultra low noise fans

BR, Toni
 

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2stageEF 50W MOSFET - aka SA2015MT

Heat spreader mounted at heat sink using thermal compound.
In front you can see some raw parts from left to right:


  • heatsink "cooltec ct-1176" custom length 160mm
  • lasercutted fan holder, 1.5mm stainless steel
  • cnc machined head spreader aluminium 6mm
BR, Toni
 

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2stageEF 50W MOSFET - aka SA2015MT

Active cooling with lowest fan speed gives expected results.
Measured at room temp. 23 degree:

  • continuous output power 70W RMS / 8R over 20 minutes
    heat sink temperature < 50
  • continuous output power 140W RMS / 4R over 20 minutes
    heat sink temperature < 57
Cooling should have enough headroom if running at high room temperatures and higher fan speed ...

Pictures showing THD values during test 70W@8R

  • +/- 42V regulated power supply
  • VAS diode installed
  • over current protection installed
BR, Toni
 

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2stageEF 50W MOSFET - aka SA2015MT

Amplifier in action ...

Due to most resistors are vertical mounted the inserting orientation is important for some connections - at least for the mosfet gate resistors to suppress oscillations.
 

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2stageEF 50W MOSFET - aka SA2015MT - Final schematics

Updated schematic, gerber files and preliminary BOM for pcb rev. 1.3

Note: Schematic and BOM are free to use only for non commercial DIY projects.

WARNING: this circuit is using high DC voltages and is therefore dangerous. I am not responsible for any costs, damage and/or injury using these schematics and BOM. Do not use this schematics if you do not have the necessary experience and knowledge.

All BOM values have been carefully checked - if you detect errors please PM me.

Have fun!

BR, Toni
 

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2stageEF 50W MOSFET - aka SA2015MT

Updated schematic, gerber files and preliminary BOM for pcb rev. 1.3
...

Alternative BOM - using "opt." parts:

Instead of R49 / 30k use R49 / 47k and R57 / 82k
Instead of R54 / 30k use R54 / 47k and R60 / 82k
Instead of R55 / 1.3k use R55 / 1.8k and R51 / 4.7k
Instead of R62 / 780 use R62 / 2.2k and R63 / 1.2k
Instead of R65 / 780 use R65 / 2.2k and R64 / 1.2k

BR, Toni
 
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2stageEF 50W MOSFET - aka SA2015MT

Hint: do NOT populate C25 - C30 until MOSFET's and driver BJT's are (test-)mounted and soldered!

Have fun,
Toni
 

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2stageEF 50W MOSFET - aka SA2015MT

Before soldering the small heat sinks place pvc washers between pcb and heatsink solder legs to avoid short circuit with rail voltages. Do this even if your pcb has a very good stop paint...

Material used for mounting BJT's on small heatsinks:
1 x SK75-25 TO220 (Fischerelektronik)
2 x SK76-25 TO220 (Fischerelektronik)
6 x Isolation washer (PVC)
3 x M3/12mm + washer + spring lock washer + nut
3 x Keratherm 70/50 TO220, 0.25mm

Have Fun,

Toni
 

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2stageEF 50W MOSFET - aka SA2015MT

... ready for take off ...

4 channels finished.
3 channels where working out of the box, the 4th has had 1st CCS LED reversed - took me 15 minutes to repair... :)
THD quick test shows that all 4 channels have nearly same low values.:)
 

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