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Post by rbk123 on Oct 8, 2020 7:23:07 GMT -5
It's an odd conversation, for sure. Boom - discussing Class H power supplies, for both A/B and H topologies Keith - clarifying A/B and H topologies, for both linear and SMPS power supplies They're not on the same page. Read the description for the HC-1. In that document, it is made fairly clear that 'H' is a power supply scheme and A/B is the output bias of the amplifier section. 2 different things. Read my post again. I'm very aware of the difference between an H power supply and an A/B amp topology. |
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Post by leonski on Oct 8, 2020 15:37:19 GMT -5
Yes, you ARE. But Keith a few posts back muddied the waters......
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Post by rbk123 on Oct 8, 2020 21:17:01 GMT -5
Agree. I was just pointing out how Boom also gets it but Keith wasn't on the same page.
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Post by Boomzilla on Oct 8, 2020 21:29:20 GMT -5
...HC-1...power looks adequate for even the lowest sensitivity speakers at higher levels and in larger spaces. Simply not needed for 90db+ speakers, in general. And certainly NEVER if the speaker is a real 96db or higher..... The exception would be if the amp were incapable of driving highly reactive loads.......Some B&W, maybe, or even some Thiel speakers. One would tend to THINK so, based on conventional wisdom, but I've recently reviewed some speakers ( the Alta Audio Alecs) that, despite high sensitivity, responded to more power very positively. I know nothing of their crossovers, so it's possible that they're just "high-sensitivity Thiels." Boom |
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Post by KeithL on Oct 8, 2020 23:42:42 GMT -5
The difference between Class A/B, Class G, and Class H is not a difference in the output stage itself... It is also not a difference in the power supply itself... The difference is in how the output stage is connected to the power supply... You can draw the schematic so as to group that switching section with the power supply or the output stage...
However we believe those details are important enough to be considered as a separate circuit feature... That's what we call our "soft switch Class H topology".
In a "regular" Class A/B amplifier the output stage is run from a single pair of + and - power supply rails. This includes the XPA Gen1 and XPA Gen2 amps.
In a Class H amplifier the same Class A/B output stage is run from two or more sets of power supply rails. This offers you the option of running the output stage from a lower set of voltage rails when you don't need full power...
This, in turn, allows the output stage to dissipate less heat, so it's a bit more efficient, and runs slightly cooler... The cost is the added complexity of the circuitry that controls the power supply rails. The details of exactly how the output stage switches between the rails vary...
And not all designers agree about which ones are properly called Class G or Class H. Our XPA-DR and XPR amps use what we call "soft switch Class H topology"... They have two sets of power supply rails and a Class A/B output stage that "soft switches" between them...
And, incidentally, since someone mentioned them... The PA-1's have a pure Class D output stage... The PA-1's ALSO have a Switch Mode Power Supply... This makes them "a pure Class D amp"...
And, yes, you CAN mix and match any combination of: - linear power supply or SMPS - Class A, Class A/B, Class B, or Class D output stage
- Class G, Class H, or "regular connected" power supply topology (It's just that certain combinations make more sense than others.)
Just for the record... SMPS and Class H have nothing specifically to do with each other. You can have either a linear or SMPS power supply with either a Class A/B or Class H topology...
A linear power supply is one with a 60 Hz power transformer that runs directly off the line... By their nature SMPS type power supplies are regulated. Linear power supplies can be regulated, and the smaller ones found in devices like DACs and preamps almost always are... However, a regulated linear power supply big enough to run a power amp would be PROHIBITIVELY large, heavy, and expensive. The term "toroidal" refers to the shape of the core used in the transformer (a donut shape)... and there are several other types. The toroidal type has become popular because it has several benefits in audio applications...
Those benefits include a low output impedance, low magnetic flux leakage, and a convenient low-profile shape.
Our XPR amps used linear power supplies and a Class H topology (Class H is a specific variation of Class A/B)... The Gen1 and Gen2 XPA amps used linear power supplies and an ordinary Class A/B topology... The XPA Gen3 amps use a fully regulated SMPS and a Class H topology...
And, yes, each design does sound a tiny bit different... Although we find the differences in sonic signature, other than those due to the obvious differences in power, to be quite subtle...
And, also, just for the record... Along with the other benefits of SMPS and Class H topology... We do actually think that the new XPA Gen3 amps sound a tiny bit better than the previous generations... Although we do agree that the XPA-1, which was also fully balanced and fully differential, was quite nice. The current equivalent of that is the XPA-DR1, which we also think sounds quite nice.
(Although, obviously, we are all entitled to our opinions.)
Keith? Why do you and otherss contintue to conflate 'H' and 'A/B'? |
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Post by KeithL on Oct 8, 2020 23:58:48 GMT -5
Errrr... the "high current" imprimatur isn't actually fishy at all...
The HC-1 is the monoblock of the XPA Gen3 series...
It's not a fully differential monoblock like the XPA-DR1 but it's still a full-fledged monoblock...
The HC-1 has a single channel module being powered by its own full-sized power supply... That means that it does have access to lots of instantaneous current if it should need it to drive an especially difficult load. I'm not going to try and convince you that you'll hear a major difference there... but the idea is still comforting.  (We just put it in a smaller chassis to make it easier to find room for a set of them.)
It's an odd conversation, for sure. Boom - discussing Class H power supplies, for both A/B and H topologies Keith - clarifying A/B and H topologies, for both linear and SMPS power supplies They're not on the same page. Read the description for the HC-1. In that document, it is made fairly clear that 'H' is a power supply scheme and A/B is the output bias of the amplifier section. 2 different things. People tend to conflate the 2. As it turns out? The specs of the HC-1 look good, even if 'High Current' is a certain red herring. But the power looks adequate for even the lowest sensitivity speakers at higher levels and in larger spaces. Simply not needed for 90db+ speakers, in general. And certainly NEVER if the speaker is a real 96db or higher..... The exception would be if the amp were incapable of driving highly reactive loads.......Some B&W, maybe, or even some Thiel speakers. For me? If I had a pair of TRIO of these? I'd make certain that I had a DEDICATED 20 amp line for JUST the amps......The PS willcertainly ide at very low power, but the A/B output won't ever be more than maybe 50% efficient and with speaker efficienty not greater than maybe 4% or so? Do the math and see that 98% of your 'power' goes to heat. Good in winter, not so good in Summer! |
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Post by leonski on Oct 9, 2020 1:59:20 GMT -5
...HC-1...power looks adequate for even the lowest sensitivity speakers at higher levels and in larger spaces. Simply not needed for 90db+ speakers, in general. And certainly NEVER if the speaker is a real 96db or higher..... The exception would be if the amp were incapable of driving highly reactive loads.......Some B&W, maybe, or even some Thiel speakers. One would tend to THINK so, based on conventional wisdom, but I've recently reviewed some speakers ( the Alta Audio Alecs) that, despite high sensitivity, responded to more power very positively. I know nothing of their crossovers, so it's possible that they're just "high-sensitivity Thiels." Boom Too much unknown, boom. Size of room? Peak to continuous power ratio? (crest factor, maybe?) Any idea of the speakers measured reactance? I see Alta calls the sensitvitiy 93db. But cheats, feeding the speaker 2 watts. So real sensitivity may be 90db...... Power handling and sensitivity are 2 different things, of course. But still and all the Thermal coefficient of copper tells me that as it warms, the driver will change and NOT for the better. How will the Neo magnet react to high temp? |
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Post by Boomzilla on Oct 9, 2020 3:44:40 GMT -5
Hi leonski - Having answers to only SOME of your questions is worse than having answers to none. Without all the answers, there's just no predicting any answer to the question (which, if we're of one mind on this is "what makes the Alta Audio Alec speaker so hard to drive?"). I don't know that answer, but I can say from experience that the speakers ARE more difficult than most to drive. |
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Post by audiobill on Oct 9, 2020 6:07:22 GMT -5
But what do they sound like?
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Post by klinemj on Oct 9, 2020 14:33:57 GMT -5
But what do they sound like? They sound like HABBAHHABBAH's to me. Mark |
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Post by teaman on Oct 9, 2020 14:51:49 GMT -5
...HC-1...power looks adequate for even the lowest sensitivity speakers at higher levels and in larger spaces. Simply not needed for 90db+ speakers, in general. And certainly NEVER if the speaker is a real 96db or higher..... The exception would be if the amp were incapable of driving highly reactive loads.......Some B&W, maybe, or even some Thiel speakers. One would tend to THINK so, based on conventional wisdom, but I've recently reviewed some speakers ( the Alta Audio Alecs) that, despite high sensitivity, responded to more power very positively. I know nothing of their crossovers, so it's possible that they're just "high-sensitivity Thiels." Boom I agree totally Boom. My 102db efficient Klipsch KLF-30 respond much better to big power than they do to average power. Each step up the chain as far as amp power resulted directly in better driver control. My XPA-1 monoblocks bring out the very best of my speakers. To me, any tower speaker with twin twelve inch woofers need to be driven accordingly. Tim |
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Post by leonski on Oct 9, 2020 15:03:35 GMT -5
Hi leonski - Having answers to only SOME of your questions is worse than having answers to none. Without all the answers, there's just no predicting any answer to the question (which, if we're of one mind on this is "what makes the Alta Audio Alec speaker so hard to drive?"). I don't know that answer, but I can say from experience that the speakers ARE more difficult than most to drive. An Impedance / Phase plot MIGHT help clear the air? Speaker manufacturers generally don't want that kind of data getting out. A speaker pair for 2 grand? Good and VERY competitive price point. But what if you need some wacky amp (like a lot of $$$$) to make it work? Once again? Sensitivity and power handling are maybe related but generally don't constrain the other. |
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Post by Boomzilla on Oct 9, 2020 15:37:17 GMT -5
...But what if you need some wacky amp (like a lot of $$$$) to make it work?... Hi leonski - Good news, amigo! Not that long ago, "super amps" cost super $$$. But I've been enjoying some excellent amplifiers (at ALL price ranges) that match the performance of amps that used to cost an arm and a leg. The latest amp I've gotten in for review is blowing my mind! The 4-channel, Starke Sound AD4.320 sports 320 Watts per channel @ 4 Ohms, and can be bridged into two channels of 430 Watts @ 4 Ohms (or 650 Watts @ 2 Ohms!) for about a thousand bucks. What's more interesting is that the voicing does not change when the amp is bridged! This amp makes my Emotiva T2 speakers sound better than I've ever heard them before. In the past, only "super amps" for prices of $2K to $10K and up could provide this level of performance. And this amp is Class-D! Got speakers that don't need a lot of Watts or a lot of iron-fisted woofer control? Check out the $400 Emotiva TA-100. Its 90 Watts per channel are seriously stout! My only disappointment about the TA-100 is that its volume-controlled pre-out jacks are mono (for subwoofers) rather than stereo. This prevents you from using the preamp section as a stand-alone. My impression is that really, really good-sounding amplifiers are dropping precipitously in price. That's a solid win for the consumer! Boomzilla |
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