Class A Solid State Sound

Would someone kindly describe the differences in class A sound of Pass XA.8 series, Accuphase A-70/75 series, and Gryphon class A amplifiers. Does much or any of the differences relate to mosfet (Pass and Accuphase) or bipolar (Gryphon)  output devices?  Thank you!


Showing 23 responses by georgehifi


High biased push/pull Class-A sound when all is correct, has an ease to it, almost like you need to turn it up.

Complementary output transistors like Bi-Polar’s generally will punch far more current than complementary Mosfets can.

If both are used in push/pull high biased Class-A like these amps you mentioned, you’ll find the Bi-Polar output amp able to drive far more taxing speaker loads, and therefore sound have a lot more punch when needed into those speakers.

Pass and Accuphase use Mosfets and a Gryphon uses Bi-Polar output transistors, on speakers like most all Wilsons ect ect, I would suggest watt for watt the Gryphon’s

Cheers George

BS Kosst, you can’t get complementary mosfets to do current like complimentary bi-polars can into low impedances! End of story!!

That’s why power amps  that are crowned  "amperage masters", are all bi-polar.

And "if" one owns say a pair of Wilson Alexia (0.9ohm EPDR), there you will see the advantage that bi-polars can give.
EG: Gryphon Anitllion Evo mono
175w Class-A into 8ohms
1400w into 1ohm
7500w peak into 1/4ohm
Sorry Kosst, there is no way complementary Mosfets can do these sort of figures.

Cheers George

Kosst, I thought you were smarter than that, you are making your self look like you have no idea.

Everyone knows given the best implementation for both, the complimentary BJT’s (Bi-Polars) will do current and low impedances far better than complementary Mosfets can. End of story.!!

Cheers George
You can waffle on all you like with your war and peace post, in our hifi world your wrong.

Cheers George
You have no idea, what constitutes current ability into low impedance loads with complementary Mosfets vs Bi-polars.

In term of drive, everything else being equal, BJT usually has more output current output so it should be able to drive better vs. FET. Therefore BJT sound tends to have more dynamic compared to FET.

Cheers George
same same, the bi-polar will do more current than mosfet, end of story.

My ME amp, 24 bi-polars (bjt's) per channel, (Nelson Parallel 24 bjt's per channel with one of the Thresholds.)
Lets see a Mosfet do 100amps continuous with 12 (six pairs) per side

Sorry, wrong!
If you really wanted to be a peacemaker, you should have just posted your first sentence and left it at that.

Cheers George
George is just a VERY sore looser when he’s proven wrong.

Your talking to yourself, and you have proved nothing, others have told you also, and you still don’t believe it.
You’ve built couple diy Pass amps kits, big deal, half the members here can also.
I also noticed you were outright rude to wolf_garcia, have another one sunshine.

To say it once again for the last time, complementary pair for complementary pair, you’ll get more amperage (current) from a BJT (bi-Polar) output stage than you will a mosfet output stage, end of story.
Nothing you say can change this, give up!.

NPN mosfets used by GamuT

N channel mosfets (not npn) can generate larger amounts of current, but it’s the "complimentary" P channel that has the problems.
To build a push/pull a/b amp that has just N channel top and bottom, the design has to be compromised to a degree, compared to when doing to same using N and P channel mosfets in class-A/B configuration.

MOSFET transistors used in industrial welding, using only one or two per rail. Eventually, GamuT sold these N-channel MOSFET amps to high-end devotees across Europe.
GamuT Di150 LE
 250Wpc into 8 ohms
400Wpc into 4 ohms
 As you can see in the Stereophile test, the Gamut even with the N channel mosfets top and bottom couldn't quite do a close to doubling act like a BJT could, and they didn't do a 2ohm test load for reasons you can only wonder about.

Cheers George
you’re moving the goal posts! I’m calling you on that fallacy.

Really!! Goal posts haven’t moved, still where they were, have another one.  

"To say it once again for the last time, complementary pair for complementary pair, you’ll get more amperage (current) from a BJT (bi-Polar) output stage than you will a mosfet output stage, end of story. Nothing you say can change this, give up!."
Your believing your own bull****!!!
"To say it once again for the last time, complementary pair for complementary pair, you’ll get more amperage (current) from a BJT (bi-Polar) output stage than you will a mosfet output stage, end of story. Nothing you say can change this, give up!."
George might not be right all the time, but he’s never wrong.

Thank you, and if so in other posts I’ve always admitted when I was wrong, and always started with the word "sorry".

"To say it once again for the last time, complementary pair for complementary pair, you’ll get more amperage (current) from a BJT (bi-Polar) output stage than you will a mosfet output stage, end of story."

This is why all the amps out there that are "known" to drive huge current into sub 2ohm loads, like the Wilson Alexia S1 0.9ohm, and keep almost doubling their wattage down to that, are all BJT’s (bi-polars) output stage poweramps.

Cheers George
Topology is by far the greatest determining factor in how a transistor delivers current to a load.
Given similar topologies it’s the final stage, "the output stage" that will determine how much current will flow into low impedance loads.
Complimentary class-A/B devices of the same pair numbers, the BJT will deliver far more current into low impedance loads than a Mosfet can.
Again end of story, your making yourself look ****** by saying anything else.
More false and irrelevant information. Keep trying...

I thought you had some knowledge Kosst, but you don't your clearly just a Pass Kit diy'er, that suddenly thinks he has some.

Seeing your always spruiking good Nelson Passes name.  
I challenge you to have Nelson come onto this thread and state that complimentary pairs of  P and N channel fets, can put out more current into low impedance loads than the same amount of complementary pairs but in NPN and PNP Bi-Polar (BJT). 
MOSFETs obviously drive plenty of current into very low ohm loads.
Don't try to twist it again in other direction to save face.

The argument here has always been, what can drive "more current" into "low impedance loads"? Mosfet or BJT output stage, for the same given amount of complementary pairs.

 And the answer once again is BJT commonly known as Bi-Polar.
Give up your making yourself look foolish.
This is the reason I put up with the downsides of Class A amps, namely, heat, weight, and cost, cost of the amp and the cost of additional electricity. I haven’t heard any other amp topology that gets me as engaged with the music as Class A.

Correct there’s an effortless ease to the way the music is presented with Class-A, big transients are not squeezed out at you and shot at you from the drivers, instead coming out and washing over you like a huge musical swell.
Yes Gryphon!! probably the best high bias Class-A amps one can buy in the retail market today, and can do enormous current down to that 1ohm courtesy of their Bi-Polar (BJT) output stage and power supply.

"Green Bias" though is another incarnation of Krells plateau (sliding) bias.
Which for those who would like to know, was invented in Australia by my boss Steven Deratz in 1980 and had a provisional patent on it, but nothing came of it, and he let it lapse.
I actually have always preferred the fixed (user adjustable amount) bias of the Gryphon Antillion Evo’s and my amps.

I have ME amps also bjt output, some of which can also be user adjusted fixed Class-A bias.

Cheers George
Is ME mainly confined to the Australian market? I have not heard of them.

They were much in the line of today’s Gryphon Antileon Evo’s, maybe that’s where they got the ideas from.

Believe it or not these were made back 1990’s by Peter Stein of ME Sound (ME stood for modular electronics), as the ultimate statement to hi-end solid state amplification, most went to the Chinese/Japanese market.
They were shown at a US show but were severely let down when every time they were pushed into the very inefficient speakers they caused the hotels circuit breakers shut down, so they weren’t received too well, as well as being from Australia (nothing good comes from Australia we all know that) I don't think you yanks ever forgave us for taking the America's Cup away from you for the first time ever!!! Then we send Paul Hogan (Crocodile Dundee) over there to sort you lot out.

Later Peter Stein’s 1st wife divorced him and he survived that divorce so did the ME Sound company. But yes the idiot got married again, and once again got divorced, and settlement caused ME Sound to go down, never to recover. (what’s that old saying once bitten twice shy) he didn’t listen.

These amps used "probably" the best BJT output transistor ever made, the now defunct boutique manufactured Hirel EB203,204 (PNP) and ED203,204 (NPN). Each was spec’ed at 20amp 200mhz 200w and super linear, the ME-1500 I posted above used 24 of them.
Here was a little talk on them at DiyAudio

Here is a token website he put up, where he still services them, maybe one day they will get going again.

Cheers George

Go away Koost, you are a pill, and have no idea really.
 I would never even look at a Gryphon.
Shame, but your entitled to that opinion.
A pill! I love that old expression, my mom used it a lot.
Yep, the shoe fits in his case.

Cheers George

That's it you need schooling end of story, go here to this Electronic lecture pay for the 8.1MB download, and learn something about BJT complementary pairs vs Mosfet complementary pairs and how BJT's (bi-polar's) can drive into lower impedances with more current output than Mosfets can.
As I've argued all along, (forget the vid it's an add).
This is the last I will recognize you, from now on your invisible.

Cheers George
no correction feedback at all
It would have had local not global feedback, just around the input/driver section not the output stage this is a very good feedback system first used/invented I believe by Matti Otala many years ago 70’s 80’s, just like the ME’s above.

Cheers George
but what’s the opinion of you guys on the capacitor-lifespan of a quality pure Class-A amp - 10, 15 years, or more?
If the interior of the amp is getting hot then yes the life of caps diminish considerably, they dry out and can leak. Not a bad idea to use a slow turning fan inside to push or pull the hot air out, this will stop the caps from drying out.

The ME amps I have  this in a way, they do this with their whole range, they also use the variable speed fan to cool the transistors to their ideal junction temperature regardless of which Class-A bias setting is used through the chimney heatsink while listening.
And when the amp is turned off the fans continue till the heatsink has cooled right down so there's no buildup of heat, the internal  heatsinking/fan also keeps all the stacks of over 300,000uf of capacitors cool.

Cheres George