150W MOSFET Amplifier with IRFP250x2

This circuit is upgrade on BUZAMP from Elektor. Use only N-mosfets, with +/-50V DC give 150W on 4R load.
 

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Is it a current dumping design?

Its just a bog standard classAB--- ltp, vas, bias and complimentary output transistors.

I just wind up the bias with a sine wave applied and a speaker connected until the crossover disotrtion goes on the scope.
It sounds good so the low bias must be fine.

I read somewhere Peavey do this as well, keeping the bias as low as possible.

It does make sense as all extra bias is doing is heating up the heatsinks.
 
Its just a bog standard classAB--- ltp, vas, bias and complimentary output transistors.

I just wind up the bias with a sine wave applied and a speaker connected until the crossover disotrtion goes on the scope.
It sounds good so the low bias must be fine.

I read somewhere Peavey do this as well, keeping the bias as low as possible.

It does make sense as all extra bias is doing is heating up the heatsinks.

Crossover and switching distortion that is audible may not be visible on a scope measurement you really need a distortion analyser of some sort. Switching and crossover distortion does not seem to affect some peoples enjoyment of music. For others, me included, it sounds like scratching glass which is why there is a valve and class A contingent in this conf :).


As far as I am aware Peavey amps are used for guitars so will not have much HF content and if they did the bass unit would not reproduce it anyway so there is no point in trying to reduce it.


As far as increasing the bias current it does make sense if you are one of the lucky or unlucky few, the cost of getting rid of those distortions is high!, that finds switching and crossover distortion annoying. As the bias current increases the switching and crossover point occurs at higher power levels and the louder the music the less sensitive the ear is to distortion.
 
Human ears cant hear THD<1%

As far as I am aware if its the second harmonic then you are right, as musical instruments produce large amounts of second harmonics the ear does not find it objectionable. In the case of higher order harmonics produced by switching distortion and to a lesser extent crossover distortion then the ear is sensitive at much lower levels.