With this Bel Canto e1X, even the 8ohm to 4ohm is a tell to what the 2ohm wouldn’t/couldn’t do grunt wise.
That wasn’t even considered to be measured as it would have fallen flat on it’s face like all Class-D’s do that I’ve seen, but at least it's stable into 2ohms and won't blow up. (so is a Nad 3020)
340Wpc into 8 ohms
530Wpc into 4 ohms |
Hi Dsper, While I am hesitant to chime in here, for fear of attack, this is what I think I know: I replaced my Classe CA-2300 (an amp I Ioved) with Mola Mola Class D Kalugas. They drive my Revel Ultimate 2 Salon 2's, a speaker not super easy to drive. The Kalugas are more dynamic, better bass control, faster, as well as more resolved on the high end. I honestly heard sounds I had not heard before, with no compromises to me. I compared back and forth several times before absolutely deciding the Mola Mola's were better to my ears. I previously had rejected Class D amps (PS Audio). Here are their 8, 4 and 2 ohm specs:
PERFORMANCE 400W/8 ohm, 700W/4 ohm, 1200W/2 ohm
Gain: 28dB
Unweighted Signal/Noise Ratio: 128dB
Distortion (THD, IMD): <0.003 % (all frequencies and power levels)
Input Impedance: 100kohm
Output Impedance: <0.003 ohm (DF>4000), all frequencies
Bandwidth: >50kHz
I have since added the Mola Mola Makua with onboard DAC and all I can say is wow and the WAF is off the charts. These are not inexpensive Class D amps by a long shot, but are both aesthetically and sonically stunning. If you are near to Maryland, stop by for a listen! Ken |
...falling flat on my face now...but at least I can still listen from this position! |
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The Mola Mola amps are using the Hypex NC1200 module. You can buy mono block amps from $1700 a pair using these same modules. VTV Amplifier have $1700 mono blocks using the built in stock input stage and $3000 the pair with expensive Weiss discrete input stages using Sparko labs regulators. Even more high end is the mono blocks from Apollon that add better sexier, stunning looking chassis, wire, jacks, and separate linear power supply for the Weiss input op amps....these are $6000 the pair delivered to the US......the Mola Mola's are $17K! I doubt the Mola's would be as good as the Apollon. Check them out! These amp modules are rated at 1200 watts into 2 ohms (hence the name...NC1200). When the Mola Mola amps first came out the only way a manufacturer could sell an amp using these modules was to agree to sell mono blocks for at least $9K. This was to protect the Mola Mola brand. A couple of years ago Hypex finally stopped this restriction so now amps using these modules can be sold for way, way less. The Acoustic Imagery (now out of business) Astah amps ($9K the pair) were reviewed in link below. These amps used the built in op amp (equivalent now sells for $1700!!!).
http://www.10audio.com/acoustic-imagery_atsah.htm
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Yes, I had seen that test. I would guess that the module only? (he he) does a little under 1100 watts into 2 ohms at 1% distortion. Plenty of grunt for 98% of listeners on 95% of the speakers in the world. I have never read a post that said any amp using these modules would not drive a particular speaker.......Can you find one? A powerhouse, for sure. |
I wouldn’t believe any manufactures, specs only independent ones.
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I have no idea how they sound but according to Anthem their M1 Class D Monoblocks if connected by 240 volt will drive into an open circuit or short circuit. - Flat frequency response into any load, without having to resort to digital conversion or equalization to compensate.
- Stable into all loads including open circuit and short circuit.
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This is the OP again...it sounds like I am hearing Class D might not be the best for tough, low impedance load speakers.
If that is indeed the case, why is this and what has to change in Class D design to achieve it? The Mosfet output transistors themselves as well as the output filter, which both have not changed much since it’s inception. The GaN output transistors are maybe going to change that with optional far higher optional switching speed available, so then output filter can also be far higher up, then there’s also no phase shift down into the audio band. But this also needs small heat sinks to be used, as you can see below. But only one amp so far has utilized that combo this the unobtainable Technics $30K SE-R1 power amp. https://i.pinimg.com/originals/15/3c/fd/153cfd69d01a6ce16656dedab64f1519.jpg
https://www.technics.com/us/products/r1/se-r1.html
Cheers George |
George, You are not even addressing his statement. Class D can already drive low impedances.......1100 watts from the NC1200 and 1000 watts from the mono 1200AS1 (all at 2 ohms). Tons of high end manufacturers use class d in their subs and in their powered speakers. Certainly, there are those very very few super low impedance speakers that need a welding amp to drive them. The switching speed of an amp and the type of output devices have little to do with power (so why are you bringing it up?). The Technics does not have super low impedance driving capability (300 watts a channel into 4 ohms and no mention of lower impedance capabilities). That amp converts all analog signals to 24/192 and then fools around with the signal in the digital domain before it changes PCM to PWM.....really a digital amp. I was talking to someone at IcePower some time ago about them using GaN transistors. They said the engineers were looking at them because they are so efficient they can be used in serious high power amps with less heatsinking. The IceEdge chipset is capable of producing up to 7000 Watts. Imagine what that amp could drive! There is no reason class D cannot drive even super low impedances....but why? Since the number of amps that need drive below 2 ohms is super limited....they why would a manufacture bother? You need higher voltage rails, more capacitors, more output devices, larger circuit boards, more cost, etc. Also......all amps create more distortion as the impedance lowers......I have never seen a measurement of an amp that did not measure worse at 4 ohms compared to 8......and then 2 ohms is even worse. Why would you want to listen to more distortion? High efficiency speakers and reasonable impedances make sense. BTW, this (link below) has been available for years. No one has made a serious version, that I know of.....2000 watts into 2 ohms.....is that enough power?! It has built in op amp, somewhat low gain and low input impedance.....so probably would never sound as good as the NC1200 tweaked to the max........but, shows what can be done. Look at the size of that 3000 watt switching supply you use with it Much more can be done with GaNs as they are so efficient. https://www.hypex.nl/product/nc2k-oem/79 |
The Mosfet output transistors themselves as well as the output filter, which both have not changed much since it’s inception.
The
GaN output transistors are maybe going to change that with optional far
higher optional switching speed available, so then output filter can
also be far higher up, then there’s also no phase shift down into the
audio band. But this also needs small heat sinks to be used, as you can
see below. This statement is 100% and certifiably false. George, I suggest you read the white papers of Bruno Putzeys. Advisory: its is helpful to know a bit of calculus to follow along. Your statement about the filter is incorrect if the amplifier is self-oscillating; even if the filter frequency is fairly low (80KHz for example) the feedback used in almost any self-oscillating class D amp allows it to correct the phase shift from the filter from affecting the audio passband. You don't use GaN devices to increase the switching speed- it appears that Technics did it purely for bragging rights, not sonic merit. You use GaN Devices for their properties such as fast switching speeds, gate input capacitance, output capacitance and possibly lower deadtime. 600KHz is a very practical upper limit for switching with them, not because they can't go faster but because creating a low noise layout gets exponentially harder as frequency is increased. But you should be advised that MOSFET devices have been fast enough for a while that Technics could be easily using them at the same switching speed; Bruno is using MOSFETs rather than GaN devices in his Purefi circuits- think about that for a moment will you? Bruno is arguably the acknowledged master in the world of class D and he's not using GaNFETs. This is not to say that he doesn't acknowledge their benefits. Quite simply it just isn't as you've portrayed it above. |
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Title to this thread
What Class D amps will drive a 2 ohm load
Simple fact is: Class-D cannot drive a 2ohm load and double it's wattage down to that 2ohms, load like a good linear bi-polar amps, end of story!
That is why with the many speakers similar to the Alexia, B&W etc loading, Class-D's are not a good match, even complimentary push pull N and P channel Mosfets are not, except amps that use only N channel Mosfets only.
To others here. Both the above posters have financial interests in selling their own Class-D current or yet to be released, this is why they have their backs up.
Cheers George |
Simple fact, very few amps.....including class A or A/B doubles its power down to 2 ohms. For instance, the Parasound JC1+ was measured at 1200 watts into 2 ohms (if it doubled all the way down to 2 ohms then it would put out 2000 watts).....which, by the way is exactly what the NC2000 does (2000 watts)....sorry, Parasound loses. By the way, the Merrill 118 class D mono blocks double all they way down to 2 ohms (1600 watts into 2 ohms)....much better than Parasound.
Doubling power does not matter. The only thing that matters is whether the amp has enough power at 2 ohms to drive the speaker at the listening level you want. George can rant on and on about this but this is the truth. 1000 watts into 2 ohms is 1000 watts into 2 ohms. Practically no one who has a 2 ohm dip speaker will ever use this much power unless you are in a huge room and play super, super loud.....this is the actual fact.....not anything to do with doubling power. George has never listened to any of these class D amps so what does he know about how they drive these speakers? You know the answer. |
Parasound JC1+ was measured at 1200 watts into 2 ohms (if it doubled all the way down to 2 ohms then it would put out 2000 watts).....which, by the way is exactly what the NC2000 does (2000 watts)....sorry, Parasound loses. "Dreamer" I would back any time the Parasound Halo JC1+’s sound and drive-ability up against ANY Class-D into the loads the likes of the Alexia’s, B&W’s etc etc You and Ralph are both just in product protection mode, it's so obvious |
Its so obvious you are in ego protection mode. Ralph is not even talking about power......in fact, you are the one that brought up (for no apparent reason)....your thoughts on bandwidth and GaNs here. They have nothing to do with power and you know it. I sold 12 class D amps LAST YEAR and am making no more.....so what product am I protecting? You keep saying the same silly things over and over again. I really feel sorry for you.
BTW, I have said all that I know on this subject so I will bow out unless I see some info that needs help. I like to be helpful. I want people to be happy and buy the best and least expensive thing for their stereo or whatever. |
whatever!
Like i said
"I would back any time the Parasound Halo JC1+’s sound and drive-ability up against ANY Class-D into the loads the likes of the Alexia’s, B&W’s etc etc"
And that's what this thread is all about!!
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You and Ralph are both just in product protection mode, it's so obvious Actually, no. Again, I suggest you read the white papers of Bruno Putzeys and perhaps some of his interviews. Quite plainly, you have mistaken impressions about how class D amps work. This is probably a forlorn hope to explain this in common terms as in the past you've proven highly reticent to taking on new information that might be different from what you think. But I can tell you that all class D amps are not the same. Some do have phase shift and those are likely to be one of two types. If they run feedback, the filter isn't in the loop. Or else they just don't run feedback. For either of these then you do have to keep the switching speed as high as possible so the filter frequency can also be high. But what you don't seem to have any idea about is self-oscillating class D amps. Self oscillating amps have so much feedback that as soon as you turn them on they go into oscillation. The oscillation is the switching frequency. As a result they can have a lot of feedback and in excess of 35dB is common. I think some of the Purefi amps have a total of 75dB of loop gain, which is an impressive feat. With this kind of feedback, the amp is then able to do two things. First, the feedback allows the amp to compensate for phase shift caused by the filter. Second, there is so much feedback that it actually allows the amp to compensate for distortion caused by the feedback itself. I think the only other amp that can do this that is not class D is made by Benchmark. So this means that self-oscillating amps can have extremely low distortion, and output impedances so low that they are difficult to measure; 0.001th of an ohm being entirely possible. Such an amp will easily behave as a voltage source with a 2 ohm load. The only thing stopping them is the current capacity in the output section, the power supply and the heatsinks. |
