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Post by garbulky on Jan 3, 2018 14:00:39 GMT -5
So an interesting question came up on another forum.
Schiit had hinted that they would be producing a 25 watt class A stereo amp which would produce *ahem* 200 watts @ 4 ohms in mono.
So naturally I mentioned the XPA-1 gen 2 which produces 60 watts of class A as a high bias class A.
An aside Jason quickly deleted most of my posts regarding the XPa1 for some tenuous reasons.
A poster took exception to me daring to call this a class A amp because of something Jason had mentioned (he was not calling out emotiva). I think it was because this was a high bias unit and apparently that disqualified it from being a proper class A amp.
Anyway any light as to why it couldnt be called a class A amp? Because it all seems a little silly to me.
This quote was by Jason but it was not directed at this discussion and was written previously many days ago having little to do with it.
So to be clear Jason was not picking a fight with Emotiva.
The poster quoted Jason's quote and said
.
Jason's post (which had nothing to do with this discussion):
“
Because, the final word on "Class A" is this: about 98% of "Class A" claims are for amps that are not true Class A designs.
To see what I mean, let's see what Schiit calls "Class A." Exactly ONE product is tagged as Class A: Asgard 2. Asgard 2 is, by any definition, Class A. It cannot ever leave Class A. Its single-MOSFET output stage is always 100% on. It's not handing off to an opposite polarity device, it's not sliding the bias around, it's not "biased into Class A a lot of the time," it is Class A. Period. End of statement.
"Buh, buh, buh, other guys say that their complementary-output amps are Class A, and other guys say their bias slides around to keep it in Class A, and other guys say their preamp circuitry is Class A, and other guys say they bias op-amps into Class A," you might be saying.
And that's fine. They can say that. They can always find a way to make some tenuous connection to Class A, just like McNuggets are "Made with white meat." (Perhaps the single greatest marketing phrase of all time, as it says absolutely nothing. Think about it.)
Here's the reality: unless the circuit is a single output transistor biased to its highest operating point, it will not provide all the benefits of real Class A. And that's what Schiit defines as Class A.
Why? Let's look a bit deeper:
Complementary output stages, with both N-channel and P-channel devices, can be biased such that they are running all the current they're ever expected to source, and called "Class A." However, these output stages CAN go out of Class A, so they are more properly called "high bias Class AB." They also have problems with transconductance doubling past the turn-on region and are hobbled by the fact that N and P devices are never really "complementary." Magni and Jotunheim use complementary output stages.
Sliding bias can keep the output stage nominally in Class A, but it cannot predict the demands of the music, so their sonics are dependent on their control system, and how finely it is tuned. Lyr uses a sliding bias output stage, we spent a lot of time tuning it. It does not sound like Class A.
Preamp circuitry being Class A? Well, I'd certainly hope so. There's no reason that it needs to be anything else.
Biasing op-amps into Class A? Yeah, you can do that. Sometimes it can make them sound better. Sometimes not. But again, it's a complementary output stage, with the limitations of that approach.
As a bonus, consider Mjolnir 2 and Ragnarok. They use a circlotron output stage. Circlotrons use same-type devices (all N-channel, for example), so they sidestep the "complement mismatch" problem. They are not inherently Class A, however. Both Mjolnir 2 and Ragnarok run high bias Class AB. Do we call it Class A? No. Because it's not.
And there you have it. Bottom line, the best thing to do, when comparing marketing claims, is simply to not do it at all.”
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Post by qdtjni on Jan 3, 2018 14:14:03 GMT -5
You'd better ask Jason what he meant rather than some random forum member. As for the 200 W at 4 Ohm, was that "true" Class A then?  EDIT: Was that a quote of what Jason wrote? |
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Post by Soup on Jan 3, 2018 14:18:33 GMT -5
+1 agree!
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Post by garbulky on Jan 3, 2018 14:44:55 GMT -5
You'd better ask Jason what he meant rather than some random forum member. As for the 200 W at 4 Ohm, was that "true" Class A then? EDIT: Was that a quote of what Jason wrote? I’d be impressed if they made it 200 wattclass A ampin Vidar chassis. But yeah I very much doubt that’s what it will be due to heat and size constraints. I know how hot 60 W of class a get in a chassis the size of my amp which is a whole lot bigger. I am guessing it’s also going to use a high bias design. That quote was by Jason but it was not directed at this discussion and was written previously many days ago. So to be clear Jason was not picking a fight with Emotiva. I actually thinks he likes them quite a lot. The random for a member told me that calling my Amp class a was a misnomer and referred to that quote by Jason. I posted it here because I don’t actually fully understand what would make his description of the class a any better than what the XPa1 does. |
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Post by qdtjni on Jan 3, 2018 14:52:18 GMT -5
I’d be impressed if they made it 200 watt class A amp in Vidar chassis. That quote was by Jason but it was not directed at this discussion and was written previously many days ago. So to be clear Jason was not picking a fight with Emotiva. The random for a member told me that calling my Amp class a was a misnomer and preferred that quote by Jason . I posted it here because I don’t actually fully understand what would make his description of the class a.m. any better than what the XPa1 does. So the Schiit amp "true" class A to 25 W in stereo but class AB 200 W when bridged to mono and that without biasing?  If Jason truly meant that the XPA-1 G2 is not "true class A" in any sense he' might be biased (pun intended) and/or suffer from "not invented here syndrome". Still think it's best to ask him to clarify than reading to much into it. |
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Post by brubacca on Jan 3, 2018 15:02:28 GMT -5
You'd better ask Jason what he meant rather than some random forum member. As for the 200 W at 4 Ohm, was that "true" Class A then? EDIT: Was that a quote of what Jason wrote? I am a regular over on that forum. The amp in question is a 25W Class A stereo amp. I believe that the 200w was running the same amp Mono in the way that they do in Vidar. It a bit complicated for me, but I think it broke down as - 25W 2 Channel 8 Ohm 50W 2 Channel 4 Ohm 100W Bridged Mono 8 Ohm 200W Bridged Mono 4 Ohm It's not an available product, just an idea he is toying with and everyone is excited about. As far as Class A, I think that Jason feels that amps that are only Class A should be called Class A. This is from what I can see from the posts, as I jump in and out because I have other real things to do. |
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Post by garbulky on Jan 3, 2018 15:55:37 GMT -5
You'd better ask Jason what he meant rather than some random forum member. As for the 200 W at 4 Ohm, was that "true" Class A then? EDIT: Was that a quote of what Jason wrote? I am a regular over on that forum. The amp in question is a 25W Class A stereo amp. I believe that the 200w was running the same amp Mono in the way that they do in Vidar. It a bit complicated for me, but I think it broke down as - 25W 2 Channel 8 Ohm 50W 2 Channel 4 Ohm 100W Bridged Mono 8 Ohm 200W Bridged Mono 4 Ohm It's not an available product, just an idea he is toying with and everyone is excited about. As far as Class A, I think that Jason feels that amps that are only Class A should be called Class A. This is from what I can see from the posts, as I jump in and out because I have other real things to do. 200 watts class A in a vidar chassis would produce huge amounts of heat. So I wonder how realistic that would be. You'd have to have a way to get a lot of that heat out. |
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Post by monkumonku on Jan 3, 2018 16:09:34 GMT -5
Jason explained what he meant in the quote you posted. He said Class A is Class A. If it goes out of Class A (such as into AB) then it isn't a true Class A amp. It has to remain strictly Class A throughout its entire usage.
I suppose it depends on how you define a Class A amp. Perhaps it is like an AVR that someone decides to call a processor. You can say that isn't a processor per se because it has an amp section, but on the other hand it does have a processor, it just happens to have an amp as well. An amp that starts out class A then switches to AB can be said to be class A but it just happens to also use AB, too.
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Post by garbulky on Jan 3, 2018 16:28:02 GMT -5
Jason explained what he meant in the quote you posted. He said Class A is Class A. If it goes out of Class A (such as into AB) then it isn't a true Class A amp. It has to remain strictly Class A throughout its entire usage. I suppose it depends on how you define a Class A amp. Perhaps it is like an AVR that someone decides to call a processor. You can say that isn't a processor per se because it has an amp section, but on the other hand it does have a processor, it just happens to have an amp as well. An amp that starts out class A then switches to AB can be said to be class A but it just happens to also use AB, too. My question is - how is that better from a high bias class A? For me, it sounds like it gives you the benefit of class A (60 watts) and then transitions out of it for loud transients. Now I can understand if the high bias was 5 watts. Because then yes you go out of it pretty often. So I would understand saying that's not a true class A amp. But at 60 watts, you are going to have class A amps that can't put out that level of power like the pass labs xa30.8 30 watt class A amp or the First Watt amps. So in that case wouldn't it be fair to say this is a class A amp or at least bringing all the benefits of class A if it's output is in class A? Well, unless you are cranking it. I mean I don't see the real world difference here. It sounds like they are saying if the amp does ONLY class A there is a sound difference versus a high bias class A that can switch to AB. In this case we were discussing a 25 watt class A amp, so that was why I was wondering why it being pure class A would be any better than a high bias design that puts out 60 watts class A? |
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Post by monkumonku on Jan 3, 2018 16:36:58 GMT -5
Jason explained what he meant in the quote you posted. He said Class A is Class A. If it goes out of Class A (such as into AB) then it isn't a true Class A amp. It has to remain strictly Class A throughout its entire usage. I suppose it depends on how you define a Class A amp. Perhaps it is like an AVR that someone decides to call a processor. You can say that isn't a processor per se because it has an amp section, but on the other hand it does have a processor, it just happens to have an amp as well. An amp that starts out class A then switches to AB can be said to be class A but it just happens to also use AB, too. My question is - how is that better from a high bias class A? For me, it sounds like it gives you the benefit of class A (60 watts) and then transitions out of it for loud transients. Now I can understand if the high bias was 5 watts. Because then yes you go out of it pretty often. So I would understand saying that's not a true class A amp. But at 60 watts, you are going to have class A amps that can't put out that level of power like the pass labs xa30.8 30 watt class A amp or the First Watt amps. So in that case wouldn't it be fair to say this is a class A amp or at least bringing all the benefits of class A if it's output is in class A? Well, unless you are cranking it. I mean I don't see the real world difference here. It sounds like they are saying if the amp does ONLY class A there is a sound difference versus a high bias class A that can switch to AB. In this case we were discussing a 25 watt class A amp, so that was why I was wondering why it being pure class A would be any better than a high bias design that puts out 60 watts class A? Seems like you need to talk to Jason about that. Until you do, you're going to have a hanging thread. |
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Post by garbulky on Jan 3, 2018 16:41:47 GMT -5
My question is - how is that better from a high bias class A? For me, it sounds like it gives you the benefit of class A (60 watts) and then transitions out of it for loud transients. Now I can understand if the high bias was 5 watts. Because then yes you go out of it pretty often. So I would understand saying that's not a true class A amp. But at 60 watts, you are going to have class A amps that can't put out that level of power like the pass labs xa30.8 30 watt class A amp or the First Watt amps. So in that case wouldn't it be fair to say this is a class A amp or at least bringing all the benefits of class A if it's output is in class A? Well, unless you are cranking it. I mean I don't see the real world difference here. It sounds like they are saying if the amp does ONLY class A there is a sound difference versus a high bias class A that can switch to AB. In this case we were discussing a 25 watt class A amp, so that was why I was wondering why it being pure class A would be any better than a high bias design that puts out 60 watts class A? Seems like you need to talk to Jason about that. Until you do, you're going to have a hanging thread. Jason doesn't usually talk about other products. Which is probably good sense. When I introduced the XPA-1 gen 2 he (or somebody) quickly deleted most of my posts and asked that I go to PM with another person. So he is presumbaly not interested in talking about the XPA-1 gen 2 compared to his version of class A. I was interested in KeithL 's viewpoint. Specifically this: And So my question is what is the benefit would a comparable 60 watt class A amp would have over an XPA-2 gen 2 amp with its class A 60 watt switch turned on? Or is it essentially the same thing - as long as you stay in class A? |
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Post by Gary Cook on Jan 3, 2018 17:20:42 GMT -5
Technically a Class A amp always runs in Class A and has no ability (circuitry) to run in Class AB. Using that technical limitation then a Class AB amp should always run in Class AB. But a lot don't, they run for some period (time/watts) in Class A, how much is dependant on the design. Technically then an XPA-1 (and an XPA-1L) are somewhat of a hybrid Class A / AB, with high ('ish) transfer from Class A to Class AB. But then so are most Class AB amplifiers "hybrids" as they run for some time/watts in Class A, but we call them Class AB amplifiers because they have Class AB circuitry and the amount (time/watts) of Class A amplification is very small.
In summary if Jason were applying the strict technical definition to an XPA-1 (or an XPA-1L) (which I understand he wasn't) then it's a Class AB amplifier, full stop. But that doesn't mean that it can't run in Class A and be useful, have some sound benefits, in doing so.
It's like arguing over whether Richie's suites are cream, bone, white, off-white, ivory or beige (another Aussie will understand).
Cheers
Gary
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Post by garbulky on Jan 3, 2018 17:25:51 GMT -5
Technically a Class A amp always runs in Class A and has no ability (circuitry) to run in Class AB. Using that technical limitation then a Class AB amp should always run in Class AB. But a lot don't, they run for some period (time/watts) in Class A, how much is dependant on the design. Technically then an XPA-1 (and an XPA-1L) are somewhat of a hybrid Class A / AB, with high ('ish) transfer from Class A to Class AB. But then so are most Class AB amplifiers "hybrids" as they run for some time/watts in Class A, but we call them Class AB amplifiers because they have Class AB circuitry and the amount (time/watts) of Class A amplification is very small. In summary if Jason were applying the strict technical definition to an XPA-1 (or an XPA-1L) (which I understand he wasn't) then it's a Class AB amplifier, full stop. But that doesn't mean that it can't run in Class A and be useful, have some sound benefits, in doing so. It's like arguing over whether Richie's suites are cream, bone, white, off-white, ivory or beige (another Aussie will understand). Cheers Gary Yes what I was getting at is....if it can do 60 watts of class A the nyou experience the full benefit of the 60 watts of class A power as long as you are doing at or below 60 watts @ 8 ohms. As in if you had a pure 60 watt class A amp (of similar design except where applicable) then you would get the same sound quality. Since it's 60 watts - which is quite a lot, imo this is a class A amp as long as you are not doing party levels. |
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Post by Gary Cook on Jan 3, 2018 17:38:47 GMT -5
Technically a Class A amp always runs in Class A and has no ability (circuitry) to run in Class AB. Using that technical limitation then a Class AB amp should always run in Class AB. But a lot don't, they run for some period (time/watts) in Class A, how much is dependant on the design. Technically then an XPA-1 (and an XPA-1L) are somewhat of a hybrid Class A / AB, with high ('ish) transfer from Class A to Class AB. But then so are most Class AB amplifiers "hybrids" as they run for some time/watts in Class A, but we call them Class AB amplifiers because they have Class AB circuitry and the amount (time/watts) of Class A amplification is very small. In summary if Jason were applying the strict technical definition to an XPA-1 (or an XPA-1L) (which I understand he wasn't) then it's a Class AB amplifier, full stop. But that doesn't mean that it can't run in Class A and be useful, have some sound benefits, in doing so. It's like arguing over whether Richie's suites are cream, bone, white, off-white, ivory or beige (another Aussie will understand). Yes what I was getting at is....if it can do 60 watts of class A then you experience the full benefit of the 60 watts of class A power as long as you are doing at or below 60 watts @ 8 ohms. As in if you had a pure 60 watt class A amp (of similar design except where applicable) then you would get the same sound quality. Since it's 60 watts - which is quite a lot, imo this is a class A amp as long as you are not doing party levels. My view is that Jason is deliberately splitting hairs, in stating that to be technically classified as a "Class A amp" it is only allowed to have Class A circuity. That the only test is to compare the amp to a circuit diagram for a Class A amp and if the amp has any Class AB circuitry then it's not a "Class A amp". That's his test. Whereas your test is if it runs in Class A then it's a Class A amp, that it doesn't matter what other circuitry it has. My view is that I would never claim that my XPA-1L's are Class A amps, but that doesn't mean I can't claim that I am listening to my music via Class A amplification. As I said, splitting hairs. Cheers Gary |
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Post by brubacca on Jan 3, 2018 17:40:12 GMT -5
Technically a Class A amp always runs in Class A and has no ability (circuitry) to run in Class AB. Using that technical limitation then a Class AB amp should always run in Class AB. But a lot don't, they run for some period (time/watts) in Class A, how much is dependant on the design. Technically then an XPA-1 (and an XPA-1L) are somewhat of a hybrid Class A / AB, with high ('ish) transfer from Class A to Class AB. But then so are most Class AB amplifiers "hybrids" as they run for some time/watts in Class A, but we call them Class AB amplifiers because they have Class AB circuitry and the amount (time/watts) of Class A amplification is very small. In summary if Jason were applying the strict technical definition to an XPA-1 (or an XPA-1L) (which I understand he wasn't) then it's a Class AB amplifier, full stop. But that doesn't mean that it can't run in Class A and be useful, have some sound benefits, in doing so. It's like arguing over whether Richie's suites are cream, bone, white, off-white, ivory or beige (another Aussie will understand). Cheers Gary Yes what I was getting at is....if it can do 60 watts of class A the nyou experience the full benefit of the 60 watts of class A power as long as you are doing at or below 60 watts @ 8 ohms. As in if you had a pure 60 watt class A amp (of similar design except where applicable) then you would get the same sound quality. Since it's 60 watts - which is quite a lot, imo this is a class A amp as long as you are not doing party levels. Please understand that when I say what I am about to say, I don't care. You like the XPA-1 and it's ability to run in class A and that is great. I think that it is a class AB amp that is biased high. If you are running under 60W you are running in Class A and A only (thus being equivalent to a 60W Class A amp sonically), but that doesn't change the fact that it is a class AB design. We are doing a bit of a Tomato vs TomAto here. All that matters in the end is that it sounds good. Am I making any sense here? |
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Post by qdtjni on Jan 3, 2018 17:52:21 GMT -5
It's like arguing over whether Richie's suites are cream, bone, white, off-white, ivory or beige (another Aussie will understand). They're neither   |
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Post by garbulky on Jan 3, 2018 18:01:52 GMT -5
Yes what I was getting at is....if it can do 60 watts of class A then you experience the full benefit of the 60 watts of class A power as long as you are doing at or below 60 watts @ 8 ohms. As in if you had a pure 60 watt class A amp (of similar design except where applicable) then you would get the same sound quality. Since it's 60 watts - which is quite a lot, imo this is a class A amp as long as you are not doing party levels. My view is that Jason is deliberately splitting hairs, in stating that to be technically classified as a "Class A amp" it is only allowed to have Class A circuity. That the only test is to compare the amp to a circuit diagram for a Class A amp and if the amp has any Class AB circuitry then it's not a "Class A amp". That's his test. Whereas your test is if it runs in Class A then it's a Class A amp, that it doesn't matter what other circuitry it has. My view is that I would never claim that my XPA-1L's are Class A amps, but that doesn't mean I can't claim that I am listening to my music via Class A amplification. As I said, splitting hairs. Cheers Gary I would describe it similarly. Yes what I was getting at is....if it can do 60 watts of class A the nyou experience the full benefit of the 60 watts of class A power as long as you are doing at or below 60 watts @ 8 ohms. As in if you had a pure 60 watt class A amp (of similar design except where applicable) then you would get the same sound quality. Since it's 60 watts - which is quite a lot, imo this is a class A amp as long as you are not doing party levels. Please understand that when I say what I am about to say, I don't care. You like the XPA-1 and it's ability to run in class A and that is great. I think that it is a class AB amp that is biased high. If you are running under 60W you are running in Class A and A only (thus being equivalent to a 60W Class A amp sonically), but that doesn't change the fact that it is a class AB design. We are doing a bit of a Tomato vs TomAto here. All that matters in the end is that it sounds good. Am I making any sense here? Absolutely. I would agree with you. Imo it has an advantage over pure class A designs in its headroom. I was wondering if there was something I was missing. Like not having class AB circuitry and only doing class A period makes the sound quality better or something. Or introducing a bias prevents the transistors from delivering the full benefit of class A sound vs a class A amp. I was wondering if Keith could chime in here. |
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Post by rbk123 on Jan 3, 2018 21:11:32 GMT -5
He's just trying to redefine terms that make his gear better in comparison. No different than when Dan uses the phrase "receiver watts" vs. Emo watts (in which I would agree with Dan).
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Post by teaman on Jan 3, 2018 21:24:24 GMT -5
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Post by mgbpuff on Jan 3, 2018 21:25:58 GMT -5
In a true class A amplifier (sometimes called a single ended amplifier) current flows thru one power device (or a parallel set of devices to get more current). In a class A push-pull circuit current flows through two complementary power devices. Each power device in the push-pull, due to ever so slightly differing characteristics, adds a slightly differing harmonic component. This causes slightly more harmonic distortion in the push-pull class A than in the pure or single ended class A.
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