MOSFET vs Bipolar

[Defiant]

So, I know Mr. Pass seems to prefer MOSFETs, particularly vertical MOSFET's, in his designs. Now, granted, their lack of current crowding and resultant hot-spotting is a plus in a class A design, which may be a big factor in his use.

So, why do each of you prefer MOSFETs? I have built amps with both (as well as toooobs ), and while the MOSFETs have done the job I have always wished I could get devices with closer complementary specs. This is one area where I feel bipolars have an advantage...

[Zen Mod]

Tubes Rule !

[CBS240]

For vertical type mosfets there is no such thing as true complementary. Bipolars have an advantage here in keeping good symmetry without over complicating the circuit design and layout. It is my opinion that the 'complementary' operation of the mosfet output stage is achieved in the driving stage.

IMHO, mosfets are more complicated to use properly than BJTs, but for all the extra effort, I think they are more suited for driving reactive loads such as speakers. The effective Ft is much higher and they provide excellent current gain with no secondary breakdown and typically larger SOA for the same package........you just have to do something about the non-linear Gm at low currents.....or just use them in class A.

[qusp]

where are the power jfets? complimentary is overrated when circlotrons and cross-coupling exist. nothing more complimentary than using the same device for both phases

[markusA]

The clear winner is the well designed circuit.
They can all sound great or bad for that matter, it's up to the designer to work his/her magic.

Personally I like hollow state with it's simplicity and good looks. I would be hesitant to claim sonic dominance due solely to the tubes themselves. It might be easier in some ways to achieve a good sound than using other techs but they can all sound really good if designed right.

[jacco vermeulen]

Originally Posted by Defiant

Why prefer MOSFETs ?

They're cheap, as me.

[PMA]

Originally Posted by Defiant

So, why do each of you prefer MOSFETs?

I do NOT

[Jay]

Originally Posted by markusA

The clear winner is the well designed circuit.
They can all sound great or bad for that matter, it's up to the designer to work his/her magic.

I believe every transistor builds have their own sound character, as a result of combination of their technical parameters or characteristics, the possible circuit designs and the speaker. And I like the general sound character of a mosfet.

I don't like heat (because I have to pay for the bill, where I usually use my amp almost 24x24), so lateral is preferred over hexfet, as they have lower capacitance which is important in low bias application. Currently I'm hoping that the LazyCat's SSA amp will be the best place for some of my laterals. The Moskido was just too hot (it made my Aikido became useless).

For hexfets, my "best" transistor is the 100W 2SK1341 (Ci=980pF, Co=400pF) that I use for Aleph J.

Bipolars such as the thermaltrack (NJL) MIGHT be better (or not), but I don't have them, and I don't want to purchase them to find out how they "sound". The best bipolar I have (forgot the model number) currently goes to my AKSA-clone.

[Defiant]

I am mainly asking because it seems as though the vast majority of builds on the site, and of course ALL of Mr. Pass's builds, use MOSFETs.

Qusp, funny you mention the circlotron - I have my eyeball on some Semisouth depletion-mode power JFETs just for such a topology

[cyclecamper]

For many, originally the motivation was that the mosfest were less linear but faster, so despite more correction via feedback you get less time-related distortion due to the feedback and you come out ahead.

I just like that they don't blow out as easily.

Now the new v-fets, that looks like another reason, and I have no relevant experience.