Can we kiss and make up now?
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@kosst_amojan, I meant no disrespect to Nelson Pass. I have a lot of respect for much his work, and am a happy long term user of a Nelson Pass pre and power amp. In my original attempt at my previous post, I tried to include links to all of the Stereophile's Pass labs amplifier measurements available on the web, but it seemed to overload Audiogon's capabilities, so I deleted them and summarized. ...And yes, I have read quite a bit of Nelson Pass's writings, which I enjoy on a number of levels. |
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". https://thumbs.dreamstime.com/z/delicious-cartoon-character-sign-isolated-white-background-vector-il... "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 |
How about PS Audio's BHK Signature 300 with a tubed input stage and MOSFET output stage using exclusively n-channel devices for both the positive and negative signals. Claimed power output is 300/600/1000 wpc into 8/4/2 ohms and according to JA's measurements those specs are mostly confirmed with 370/620/950W into 8/4/2 ohms, although like many manufacturers,
it appears
they sort of fudge the 8 ohm power rating (lower than actual) so they can claim that the amp "
doubles the output current with half the impedance." I appreciate that they provide a power rating at 2 ohms but cannot help wondering the reasons for JA's comment that the amp "was less comfortable at lower powers into this low an impedance" (i.e., a 2 ohm load), and Fremer's comment that, "there's still more weight, power, and physicality to be had in the very lowest octaves." Curious why an amplifier that provides 950 wpc into 2 ohms would be anything less than a powerhouse into low octaves. Does the MOSFET output stage have something to do with it or, how about the dual differential design? |
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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. |
@Kosst_amojan, I disagree with your take on the way Pass Labs specs their amps. The independent measurements aren't confusing, the labeling of Pass Lab's specs are. Nelson Pass's labeling of specs though still then confusing were at least less so with his previous Threshold branded amps. That Pass Labs declines (even upon request) to spec their amps into 2 Ohms quietly speaks volumes. |
@Mitch2, with traditional speakers as impedance drops so does sensitivity. The BHK mono's 950 Watts into 2 Ohms is the equivalent to what a 237.5 Watt into 8 ohms amp that could truly double down could provide into 2 Ohms. Even after what seems like PS Audio's underrating of their 8 Ohm power rating , where did the other 250 Watts go? |
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Getting back to the OP's original post. Class A circuits ( and we are specifically talking about amplifier output stages here ), just sound smoother, more homogenized, less artificial, more involving, with every attribute of recorded music reproduction, keeping one in his / her listening seat, longer. Granted, there are still audible differences, between designers and manufacturers products, but, Class A is still, imo, superior, at this particular time, in SQ. |
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). |
Lets not forget the difference feedback can make. IMHO it is nearly impossible to talk purely about the output stage class in isolation of the feedback method, if any. Also, with so many high bias AB amps, I venture to say you listen to them mostly in their A range anyway. 3 Amps I think you should listen to, are Luxman, Ayre and Pass. I can't see you loving all of them at once. Sorry, no experience with Accuphase, however if you are the US distributor and wish to provide me with a review sample, message me. :) Best, E |
What you will get running a Class A Pass amp into a 2 ohm load will be a very hot amp that will probably shut itself down or burn a hole through your floor. Into 4 ohms and up Pass class A amps will switch to AB at their rated power and continue on probably doubling that. God knows what the Xs 300 will do. IMHO there are very few speakers with impedance that drops below 2 ohms worth listening too. The amount of power any amp will put out is determined primarily by the size of the power supply. Whether or not the amp can safely transfer that power to the speakers depends on the capacity of the output stage and the size of the heat sinks. Power is power as far as I am concerned. I do not care about the type of output device used. It is all about topology and durability. I expect an amp like the $90,000 Xs 300 to run for a life time. If it can't I am not interested. |
Upgraded and former power supplies in my Class A monoblocks..... https://www.usaudiomart.com/details/649314340-clayton-audio-m300-class-a-monoblock-amplifiers-custom/images/1380838/ |
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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. |
“Getting back to the OP's original post. Class A circuits ( and we are specifically talking about amplifier output stages here ), just sound smoother, more homogenized, less artificial, more involving, with every attribute of recorded music reproduction, keeping one in his / her listening seat, longer. Granted, there are still audible differences, between designers and manufacturers products, but, Class A is still, imo, superior, at this particular time, in SQ. ” 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. I run a Gryphon Colosseum Stereo amp. It can generate 160w, Class A, at 8ohms, and 1250 watts at 1 ohm. It does not transition to Class B. On momentary transients, it can put out over 4000watts. The amp weighs 175lbs. I love the thing, it sings like no other amp I’ve ever owned. |
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. https://ibb.co/fr6SNVT https://ibb.co/D1h5nnF https://ibb.co/GcSfbCT Cheers George |
Thanks, George. The Gryphon Colosseum has three user selectable bias levels, Low, which is 30w Class A, Medium, which is 70w Class A, and High, which is 165w Class A. I can tell the difference and prefer running at High, but that’s hard to do in the summer. Still, I live in a northern city, so most of the year, I can run High without heating up my apartment too much. |
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 https://www.diyaudio.com/forums/parts/76846-whatever-hirel-transistors.html Here is a token website he put up, where he still services them, maybe one day they will get going again. http://www.me-au.com/ Cheers George |
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Why hasn't anybody spoken about Boulder amps. They are class A with sliding bias which for some unknown psychological reason I am uncomfortable with. Of course 250 large for a set of boat anchors is a bit steep even if your floor can support them. Next model down the 2150 at 100K is a direct competitor to the Pass Xs 300. Anybody ever hear a Boulder amp? Why would one buy it over the Pass?. |
Oh and George, a 200 watt class A amplifier conceptualized by a Danish Graphic Arts guy and designed by teams of worker bees resulting in......? I would prefer the work a dedicated electronics engineer who puts his reputation on the line with each amp preferably American. I would never even look at a Gryphon. Too much invested in flash resulting in rather silly looking stuff. Sound and durability are all I am interested in spending money on. |
Concerning Boulder, I would not say that it's a direct competitor to Pass Labs. I heard Boulder at RMAF and it is a pretty neutral amp with only a touch of that bipolar Class A lush/liquidy effect. The Pass Labs is a FET "warm and fuzzy" type of sound, but with high resolution that is very controlled. |
Oh, mijostyn, the Gryphon gear is durable and engineered to high standards. I expect to be running my class A amp for decades. It sounds great, too. The Gryphon Colosseum is one of the most beautiful amps I've ever seen and it does not take up a lot of floor space because it is laid out vertically. Believe it or not, the savings in floor space is what sold my wife on the unit. I live in a small apartment and don't have the room for the massive amps from Boulder. Plus, Boulder's prices are insane, as you pointed out. George, before the Gryphon I was running James Bongiorno's statement Class A amp from the 1970s, the Sumo Gold. I had it completely rebuilt. It was a 125w Class A amp and gave me eight years of trouble free service. The Gryphon sounds a lot better, as it should, with improvements in various technologies over that time. I sold the Gold for $1k to someone who was glad to get it. I've just never liked the sound of MOSFET amps. To each his own. |
Oh, I would never run anything but a class A amp but I am not sure there is a huge difference between Mosfets and Bipolars having had both. I also run ESLs which are a totally different animal when it comes to drive so my opinion really does not apply to dynamic speakers. The systems I set up are all Planars except for the sub woofers another specialized animal. |
I always prefer a multi-phase transfalgulator with floating ground ferbinators. There's medication to fight bi-polar, so it must not be ideal. But Seriously, thank you George and a couple others for shaking some of the cobwebs from my diminished memory of electronics. Thankfully I don't know enough on that level, to interfere with my love of music and my low-to-mid-fi equipment. Cheers! |
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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. https://www.lynda.com/Software-Development-tutorials/BJT-vs-MOSFET/502049/655701-4.html Cheers George |
George is right on this. Back to the OP’s question reguarging sound. I’ve had several pass amps over the years , if you like that voicing it’s pretty similiar in all their lineup. The gryphon ss amps asound more like symphonic line amps or boulder amps. If you do t have gryphon dealer nearby you might wanna listen to a boulder as they seem to be a little more popular in the USA |
"Getting back to the OP’s original post. Class A circuits ( and we are specifically talking about amplifier output stages here ), just sound smoother, more homogenized, less artificial, more involving, with every attribute of recorded music reproduction, keeping one in his / her listening seat, longer. Granted, there are still audible differences, between designers and manufacturers products, but, Class A is still, imo, superior, at this particular time, in SQ." Well put, @mrdecibel - certainly in agreement here. I’m using the MOSFET-based Belles SA-30, which outputs 30 watts pure Class-A. 30 watts mayn’t sound like much, but the number itself is not really indicative of its ability to successfully drive a variety of low to moderately sensitive speakers, some of them quite power hungry. My own speakers are very sensitive at 105dB’s, and being a fairly easy load on top of that suddenly converts the SA-30 into a small monster; approaching -20dB (I usually never go below -25dB, and typical listening is done in the -45dB to -50dB’s range) on the attenuator of my DAC/preamp things really start to become rather scary.. I bought the Belles new about 5 years ago, and I sometimes wonder how long I can expect it to perform "according to specs" - that is, before the caps begin to wear out to detrimental effect. The lifespan of amps vary somewhat for a variety of reasons, but of course pure Class-A amps are the ones most challenged in this regard due to the heat being produced (all things being equal; pure Class-A amps are typically very well build and being topologically more simple can use fewer and better components, in which case a quality pure Class-A amp may equal or even exceed the lifespan of a lot of the better Class-A/B offerings, or so I’m thinking). From what I’ve been able to assess Mr. Belles amps are quite durable, even the ones running in Class-A, but what’s the opinion of you guys on the capacitor-lifespan of a quality pure Class-A amp - 10, 15 years, or more? |
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. https://ibb.co/fr6SNVT https://ibb.co/D1h5nnF https://ibb.co/GcSfbCT Cheres George |