NMOS350 / 500

This amplifier was created from my ideas and also from the ideas by members of DIY Audio.  It intended as a high quality and powerful amplifier for domestic use.

pdf's schematic layout & tracks construction guide
sprint layout files Nmos350 with DC detect Nmos500 with DC detect
Gallery

Power selection guide.  

This table should be used as a power configuration guide.  Powers shown are approximate and probably maximum depending on the size and quality of the power supply. Power have been estimated to real world applications using a reasonable power supply.

Definition of Reasonable:

Transfomer VA = total output power x 1.5.  DC smoothing section = 80uF capacitance per DC rail per watt of output power.

Example: A stereo amplifier running 60 volt rails capable of 165 watts into 8 ohms per channel will require a 500va transformer and a capacitor bank of 13,200uF per rail or 26,400uF per amp module or 52,800uF for a stereo set-up.

AC volts
(Vac 0 Vac)		 DC rail volts (+/-) Value R6 (Kohm) Value R17 (Kohm) Pwr
8 ohms		 FETs
req.		 Fuses (A) Pwr 
4 ohms 		FETs
req.		 Fuses (A) Pwr 
2 ohms 		FETs
req.		 Fuses (A)
30 40 2.7 22 64 2 2.0 115 2 3.0 210 4 6.0
33 45 6.8 22 82 2 2.0 146 4 4.0 265 6 7.0
37 50 6.8 27 107 2 2.5 192 4 4.5 346 6 8.0
40 55 6.8 27 128 2 2.5 230 4 5.0 415 8 9.0
44 60 12 27 160 2 3.0 290 4 6.0 515 8 10
47 65 12 33 185 4 3.5 335 6 6.0 610 10 11
51 70 18 33 223 4 3.5 405 6 7.0 NO NO NO
54 75 18 33 253 4 4.0 460 8 7.0 NO NO NO
58 80 18 33 297 4 4.0 540 8 7.5 NO NO NO
61 85 18 39 330 6 4.5 600 10 8.0 NO NO NO

Notes:

The guide is configured for power mosfets similar to International Rectifier IRFP450, and is generally applicable for FETs with a Pd of 180 to 200 watts (Tc = 25 degC).  The number of FETs shown is per module.

R6 determines the voltage remaining across T4 the constant current source for the first stage.  R17 sets the gain of the amplifier.

Fuses are fast blow types.