I see a frightening trend. MOSFET output amplifiers are becoming extinct! Can you guys help me make a list of current large manufacturers who still manufacture MOSFET amplifiers. I'll start:
1.) Spectral
2.) Naim
3.) Goldmund/JOB
4.) Pass Labs
5.) Holton Audio
6.) Monarchy Audio
7.) Nagra
8.) Constellation Audio
9.) Audio by Van Alstine
10.) Tenor Audio
11.) Perreaux
1.) Spectral
2.) Naim
3.) Goldmund/JOB
4.) Pass Labs
5.) Holton Audio
6.) Monarchy Audio
7.) Nagra
8.) Constellation Audio
9.) Audio by Van Alstine
10.) Tenor Audio
11.) Perreaux
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Don't worry, plenty of power Mosfets are used in industry for high frequency switching power supplies,
for a wide range of power levels. These devices are more popular than ever, and will continue to be.
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I, personally, don't see why it matters one iota whether audio power amplifier makers (at least not the Class D kind) use MOSFETs, Bipolar, silicon JFET or greased IGBJTs. Really.
Why?
Because they're all operating as cathode / emitter followers, dudes! Every last one of them.
And why are they being operated in that mode, typically with a bunch of identical devices connected in parallel, utilizing small value cathode 'current balancing' resistors?
BECAUSE everything from bipolar to FET to MOSFET to … are terribly nonlinear devices which just so happen to have large current sourcing capability when operated in their “follower” mode. CURRENT gain is the key. And this all of these devices do quite well.
Brilliantly, actually.
We really have to remember back when there were no power JFETS, no MOSFETs that weren't ridiculously limited in gate-voltage swing. No IGBJTs, no exotics. Just plain Jane bipolar transistors, hopefully in reasonably well matched complimentary-polarity parts. You know, IC max ≈ 20 amps, with 100 amp peaks tolerated on low duty cycles. VCEO of 100 or 150 volts. All the usual requirements. In both P and N polarity.
(don't jump to conclusions yet…)
Back then “the problem” was that the negative temperature coefficient of NPN and PNP bipolar transistors tended to leave power amplifiers exposed to thermal run-away on a per-piece basis. And that was like a zipper: once one transistor would blow, then quickly all of them could go. To spectacular sparks, smoke and stink. … usually during the middle of an important disco outing or live concert.
So… (again before FETS and kin), a lot of preventative engineering went into protecting the sand-state devices from their own run-away potential. Current limiters, short-circuit detection-and-quenching. All sorts of stuff.
THEN the FETS, power-JFETS and MOSFETs came along … that offered a delightful serendipitous solution to the thermal-run-away problem. They had “positive thermal coefficients”! BRAVO! So, much of all that preventative circuitry could be simplified. Which appealed hugely to people who neither fundamentally understood it, the need for it, or the LACK of impact that such circuitry would have on “the sound” of an amplifier.
AND it gave rise to “yet another generation or three” of amplifiers to replace the now-obsolete ones (in spec only). The industry didn't fall into the quicksand of terminal development.
_______
The above is why I'm obviously 'mildly outraged'. Because it really doesn't matter one iota what the final drivers are. If they're all just ganged together in endlessly creative “follower” circuits, their type hardly matters - except to the designers who pour over the details of protecting general-purpose, totally-consumer-friendly equipment.
GoatGuy
Why?
Because they're all operating as cathode / emitter followers, dudes! Every last one of them.
And why are they being operated in that mode, typically with a bunch of identical devices connected in parallel, utilizing small value cathode 'current balancing' resistors?
BECAUSE everything from bipolar to FET to MOSFET to … are terribly nonlinear devices which just so happen to have large current sourcing capability when operated in their “follower” mode. CURRENT gain is the key. And this all of these devices do quite well.
Brilliantly, actually.
We really have to remember back when there were no power JFETS, no MOSFETs that weren't ridiculously limited in gate-voltage swing. No IGBJTs, no exotics. Just plain Jane bipolar transistors, hopefully in reasonably well matched complimentary-polarity parts. You know, IC max ≈ 20 amps, with 100 amp peaks tolerated on low duty cycles. VCEO of 100 or 150 volts. All the usual requirements. In both P and N polarity.
(don't jump to conclusions yet…)
Back then “the problem” was that the negative temperature coefficient of NPN and PNP bipolar transistors tended to leave power amplifiers exposed to thermal run-away on a per-piece basis. And that was like a zipper: once one transistor would blow, then quickly all of them could go. To spectacular sparks, smoke and stink. … usually during the middle of an important disco outing or live concert.
So… (again before FETS and kin), a lot of preventative engineering went into protecting the sand-state devices from their own run-away potential. Current limiters, short-circuit detection-and-quenching. All sorts of stuff.
THEN the FETS, power-JFETS and MOSFETs came along … that offered a delightful serendipitous solution to the thermal-run-away problem. They had “positive thermal coefficients”! BRAVO! So, much of all that preventative circuitry could be simplified. Which appealed hugely to people who neither fundamentally understood it, the need for it, or the LACK of impact that such circuitry would have on “the sound” of an amplifier.
AND it gave rise to “yet another generation or three” of amplifiers to replace the now-obsolete ones (in spec only). The industry didn't fall into the quicksand of terminal development.
_______
The above is why I'm obviously 'mildly outraged'. Because it really doesn't matter one iota what the final drivers are. If they're all just ganged together in endlessly creative “follower” circuits, their type hardly matters - except to the designers who pour over the details of protecting general-purpose, totally-consumer-friendly equipment.
GoatGuy
With Lateral MOSFET from Exicon (like Goldmund/Job): the Audio by Van Alstine (aka AVA) in the ss (Synergy) and hybrids (Fet Valve) amplifiers.
Web: avahifi - avahifi
Forum: Audio by Van Alstine
Interesting reading: Fet Valve 200R, Why not, Frank?
Web: avahifi - avahifi
Forum: Audio by Van Alstine
Interesting reading: Fet Valve 200R, Why not, Frank?
As we get more and more and more class-D amplifiers, isn't our MOSFET-output amplifier trend going opposite your fears?
Also, who cares what architecture the output transistors are?! That is, given the designer(s) did their homework and used them appropriately. (This is GoatGuy's point in reduced form)
Also, who cares what architecture the output transistors are?! That is, given the designer(s) did their homework and used them appropriately. (This is GoatGuy's point in reduced form)
I think that in the next 10 years we will have some class D amplifier or similar concept that will be able to play like 1302-3281 or even better still ...i think that it will take more than 10 years to become available ....
In between we are going to loose even more listeners and expect posts from people that their first amplifier was a 3886 and sounds ...superb ...
In between we are going to loose even more listeners and expect posts from people that their first amplifier was a 3886 and sounds ...superb ...
I have story for you, not fictional. A guy recently bought brand new B&W802 D3, of course distributor lend him two shiny new big monos from Classé and guess what hehe, he order two of my amps instead. Maybe it's time for you to widen your perspective.
I will consider the suggestion Lazy Cat but you should expect results in the ....next life ...you see my ears do not help moving to this direction ....
Kindest regards ( and i think that thank you for your work is something i have to say as a minimum you have my respect ! )
Sakis
PS i have more than 10 similar stories from listeners that almost trussed respectable equipment like Goldmund for example for a well made P3A....I was asked to compose a thread with these stories no matter what you think obviously it will be fun to read since most of the times the actual conditions of "how it happened " was truly joyful ...Will do that some time ...
Kindest regards ( and i think that thank you for your work is something i have to say as a minimum you have my respect ! )
Sakis
PS i have more than 10 similar stories from listeners that almost trussed respectable equipment like Goldmund for example for a well made P3A....I was asked to compose a thread with these stories no matter what you think obviously it will be fun to read since most of the times the actual conditions of "how it happened " was truly joyful ...Will do that some time ...
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Lazy Cat's VSSA might have evolved from its 1.4 version or whatever it was which were marketed as CKDs. I've heard them, in my own setup. I didn't care to keep them hooked on for long - bass was loose, mids were more forward than desirable and the highs a bit too metallic; not a coherent sound. The stage was wide but lacked layers of depth. Forgettable at best. My subjective take.
MOSFET or Bipolar OPS. It is all in the design and implementation.
MOSFET or Bipolar OPS. It is all in the design and implementation.
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