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Mosfet??

mosfets = raw power .. maybe depending on design of the amp when they blow up they are quiet dramatic . that's my take on it . only because i blew my amp twice .. they don't like to be over driven .too much input is very bad or should i say bad input ? distortion .. i found they need controlling by electronics such as compressor limiters .mine is used in a p.a situation . with the correct stuff behind them no problem
 
ejman said:
I've tried a number of SS amps over the years and I recently realized that my favorite in the low power side of things is the Creek 4330 while my favorite in the higher power side is the Conrad Johnson MF 2300A. The one thing they have in common is output MOSFETS so I guess there must be something to that sound "character" that I find appealing. I guess it must be the lack of a "fatigue" factor.
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Interesting. I have the 2500, which uses mosfets in the gain stage but bipolars in the output stage. I'd be interested to hear the difference between the two.
 
As an output device I prefer the bipolar. I had a B&K ST-202 amp with mosfets in the output. It was a great amp! My Sansui AU-919 (restored) is one of the best amps I ever owned.:yes: Just my taste.:thmbsp:
 
There are good and bad on both sides.

Crown, for one, has done some amazing things in Safe Operating Area on their bipolar designs. Enough to say, "there is no inherent added protection with MOSFETs".
 
Jon_Logan said:
Crown, for one, has done some amazing things in Safe Operating Area on their bipolar designs.
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Have they what!! Take the Macrotech 5002VZ for example......

img0554ct.jpg
 
More to the OPs question I guess: IME amps using MOSFET outputs tend to be more on the 'audiophile' end of things.

BJT are much more common. If a manufacturer uses MOSFET outputs, they usually find a way to tell you that they do, as it's considered desirable. For example, Kyocera used MOSFETs in driver and output stages, and made sure they mentioned it in their ads.

I don't recall any ads for amps saying "Hey look at us, we use BJTs!" probably because most everybody does.

Just my impressions here...
 
Bob Cordell offers a very thoughtful discussion of this topic in his book: Designing Audio Power Amplifiers. One item that rings true for me is that class AB MOSFET amps make less trouble for the designer with regard to bias stability. Conventional class AB BJT (transistor) designs suffer from bias swings that can seriously alter crossover distortion performance when they're used hard. This problem doesn't exist in class A amps of either persuasion.
 
PickyEars81 said:
Interesting. I have the 2500, which uses mosfets in the gain stage but bipolars in the output stage. I'd be interested to hear the difference between the two.
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I would also love to hear the two side by side. It's damn difficult to do meaningful comparisons anymore. Nobody carries anything worth comparing anymore...
 
As I said, there's good and bad on both sides.

Parasound, for one, does tout their MOSFET driver/Bipolar output, for having better peak current output, or something. Some yahoo, John Curl, or something, claimed this.

An argument can be formulated for either side, at any time.
 
As far as I know, my Sansui 2000x and 4000 receivers both have mosfets in the power-section. Whatever the case, they run very-cool and sound extremely-smooth, musical, and non-fatiguing (although I tend to think a lot of that has to do with the overall design as well as the fact that they're fairly-low-powered receivers... IMO, low-powered amps and receivers as a whole are a bit warmer, but that's just a theory).

Don't the early '70's McIntoshes also use mosfets in the power-section?
 
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