International Rectifier IRFP240/9240 HEXFET vs. Hitachi 2SA1492/2SC3856 MOSFET for audio amplifier

[keilau]

I was in the market for a 100W/Ch MOSFET amplifier. The Adcom GFA-545II and the GFA-5400 are in this range and similar in price. In the Adcom GFA-545II, they used the Hitachi 2SA1492/2SC3856 MOSFET. But Adcom switched to HEXFET IRFP240/9240 for the Adcom GFA-5400. The result was much higher output for the GFA-5400, particularly at 4 ohms load. It is up to 200W/ch at 4 ohms. On the other hand, the Adcom GFA-5400 has much higher THD/TIM, almost 10 times that of Adcom GFA-545II.

I have the Adcom GFA-535 which also use the Hitachi 2SA1492/2SC3856 MOSFET and I like its sound a lot. But the Adcom GFA-545II and the GFA-5400 are at the same price range used which makes the GFA-5400 sound attractive for the higher output power.

In old time, it used to be said that HEXFET was not suitable for linear power amplifier for audio. But the thinking seemed to have changed. Any comment on the pros and cons of the sonic quality of Adcom GFA-545II vs. the GFA-5400?

 

[FootFungus]

The 2SA1492/2SC3856 are Sanken bipolars. The GFA-5X5 series only uses bi-polar outputs. The later GFA-5X00 series is Mosfet.

HEXFETs work fine for audio. You just have to crank the bias to get them happy, which creates heat.

 

[keilau]

The 2SA1492/2SC3856 are Sanken bipolars. The GFA-5X5 series only uses bi-polar outputs. The later GFA-5X00 series is Mosfet.

HEXFETs work fine for audio. You just have to crank the bias to get them happy, which creates heat.

Thank you for the correction. I should have known that the 2SA/2SC are bipolars. MOSFET should be 2SK/2SJ.

 

[keilau]

Any comment on the pros and cons of the sonic quality of Adcom GFA-545II vs. the GFA-5400?