What Class D amps will drive a 2 ohm load


Just asking.

I see specs into 4 ohms but nothing into difficult speaker loads (like Thiel CS5's).

Thanks for listening, 

Dsper


dsper
@atmasphere Although we just got news this week that the USPTO is granting our class D patent with all 20 claims supported
Congrats Ralph, finally 



This statement is false. The ability to double power as load impedance is halved has nothing to do with how well the amp will play bass

Of course it does when it demands current into low impedance to do it, get over it.!

Ralph you’re so transparent.
Stick to what your good at, super efficient easy to drive horns that you heavily promote and your OTL’s, that can’t drive these kind of sub 2ohm inefficient speakers that you have no love for. But then yet in the same breath, promote the use of your OTL’s with them, with expensive Zero autoformers, saying that their great and the perfect answer for your OTL amps to use on these hard to drive speakers, just to make some more dollars from the gullible.

All your doing here, is to branch out into the Class-D gravy train $$$’s (so transparent) without any loyalty to where you came from, OTL’s and horns. But then they are both a dying breed.
Not at all in your wheelhouse, just an FYI option I overlooked mentioning in my earlier response.

https://www.bobcarvercorp.com/crimson-raven-features-specs

I drive a pair of 3.6 ohm Avalon Acoustics Eidolons off the 4 ohm tap with the earlier less powerful 180s with aplomb. Compared to an MFA D75 which would run out of steam and the Hypex nCore 400s described in my previous response.
Point-to-point wiring, low heat, group biasing, switchable feedback, and untypical low maintenance. Again, just an FYI.
just if they don’t try to double from 8 to 4 to 2ohm, you won’t get the very best out of them, they will be compromised in the bass, if you don’t mind that that go ahead.
This statement is false. The ability to double power as load impedance is halved has nothing to do with how well the amp will play bass- even if the bass is where the load impedance is lowest. Quite simply, it doesn't work that way; a lot more has to do with the output impedance of the amp which is independent of its ability to double power.
dsper OP
I emailed, to both Nord and Appollon, the Stereophile measurements for the Thiel CS5’s and both suppliers said that their amps would drive them.

(Without seeing any independent tests)
Of course they did, they want a sale.
No one disputes that they can’t drive the Thiel CS5’s to a point, just if they don’t try to double from 8 to 4 to 2ohm, you won’t get the very best out of them, they will be compromised in the bass, if you don’t mind that that go ahead.

But not if you drove them with amps like the ones I have described, that can come close to doubling wattage all the way, from 8, 4, and 2ohms, I believe the Thiel’s are worth the right amp to make them sing top to bottom, don’t you?? it’s up to you.

Cheers George
So what am I not being told?
:)  Apparently you're *not* being told that the amp won't work...
And FWIW, if the amplifier has a low enough output impedance, it will act as a voltage source even with a 2 ohm load. It **does not** have to double power to do that.
This just gets more interesting.

I emailed, to both Nord and Appollon, the Stereophile measurements for the Thiel CS5's and both suppliers said that their amps would drive them.

For example, Appollon replied that their NC1200SL HYPEX NC1200 BASED AMPLIFIER "...is a perfect choice for your speakers and probably the only class d amplifier that will drive your speakers with ease at 2 ohm loads. The NC1200 module is specially designed for such low impedance loads. Any other class d amplifier will fall apart sound wise with your speakers but the NC1200 shines @ 2 ohms."

So what am I not being told?

Thanks for listening,

Dsper



Sorry but what you get is a good PA amp.
Hypex suck in, they purposely put things backwards to confuse at glance. Look again, and that’s peak watts and amps, also the wattage go backwards as the impedance goes down, it gets severly current starved.

Nowhere in this universe can this thing come close to doubling into 2ohms The NC400 of theirs is a far better module as far as current delivery into low impedances it actually goes up in watts instead of down. Data sheet download here
  https://www.stereo.net.au/forums/applications/core/interface/file/attachment.php?id=480207

Cheers George
Holy crap - 49 amps. Didn't know this one existed

https://www.hypex.nl/product/nc2k-oem/79

Here's Apollon's version:  https://www.apollonaudio.com/hypex-nc2k-monoblock-amplifier-apollon-audio-nc2kslm/

Yes, 2,000W in 2 ohms. Tell that to some who believe that say a 100W/200W/400W in 8/4/2 ohms amplifier would be more suited to drive 2 ohms speakers just because they double power as impedance halves...
I've mentioned before, we're not using anyone's modules.

It seems that what you aren't getting is that comparitors (a kind of chip or circuit used in many class D amps) can be unstable if used with high input impedances. To prevent oscillation, lower impedances are used at their inputs.
Whatever Ralph.
Seems like this could be the module your using, as you've turned up the force shields a notch higher on this one, if so just go with the buffer by-pass switch. 
Here is the comments from a manufacturer of these Purifi’s Class-D amps when I queried him on the unnecessary low 2.2k input impedance. I think it could be because of the use of bjt input stage instead of fet, I’ve yet to suss that one out.
Yes you are absolutely correct that you can use a high output DAC directly into this module. "That would be the ultimate solution"
And I am considering a buffer bypass mode. However most power amps will have gain in the region of 26dB to account for sources down to 2 Vrms. A typical DAC straight in is a good solution with digital volume
I explained why already. This is a common issue and why you see many Class D amps with some sort of buffer input. Many opamps can drive lower impedances like 600 ohms no worries and since so much feedback (+30dB) is being used, the assumption is that the distortion added by the feedback on the opamp will be quite minimal. But there are some class D amps where the designer opted to simply have a low impedance input for the very simple reason of having less circuitry- a purist approach. But you have to have a source that can drive it. Its nothing to do with FETs or BJTs.

Our preamps can drive such low input impedances-

Of course it can, how did I know that was coming, stick with tubes, your good at it, and built your rep on them.


The fact is this amp without buffer it has around 15db of gain around the same as the Nelson Pass First Watt F5 and with today’s high output sources and preamps, in most cases you don’t need another soul destroying opamp buffer in the signal path with or without gain.

Here is the comments from a manufacturer of these Purifi’s Class-D amps when I queried him on the unnecessary low 2.2k input impedance. I think it could be because of the use of bjt input stage instead of fet, I’ve yet to suss that one out.
Yes you are absolutely correct that you can use a high output DAC directly into this module. "That would be the ultimate solution"
And I am considering a buffer bypass mode. However most power amps will have gain in the region of 26dB to account for sources down to 2 Vrms. A typical DAC straight in is a good solution with digital volume

Most digital sources today have far more than 2v and owners preamps can certainly have enough for the Purifi without another buffer.
As Nelson Pass with his F5 said " If you need to turn the gain up on your preamp, then do so."

Cheers George

WHY!! they keep making low input impedance amps these days is beyond me, go back to 48k (the once recognized industry standard) or even 100k like it used to be with tubes, makes for a whole better range of preamps ,tubes SS or passive able to drive them properly.
The reason you see this has to do with the fact that a filter often has to be installed between the audio input and the encoder (comparitor or the like). The filter is there to remove high frequency noise that might otherwise get amplified and add to the noise floor of the amp. But good high speed comparitora have issues of their own and can be unstable with a high impedance inputs. Hence low input impedances if there is no input buffering.
There’s no need for it in many cases, as sources and preamp have enough gain these days. It’s just "another opamp in the signal path" that’s not needed in many cases if the input was high enough instead of 2.2k, who wants that in hi-end if it can be taken out and one less opamp yay!!! gotta be good for the sound, and the business.
This statement is incorrect. Of course there is a need for an input buffer in many cases- a lot depends on the encoding scheme of course (for example with PWM the gain is based on the difference between the amplitude of the triangle wave in the circuit and the input signal). Things might not work out in the design that you have enough gain- particularly if feedback is employed. So an opamp or instrumentation amplifier might be used to make up the needed gain. Quite often this isn't a lot of gain, maybe a gain of 2 to 10. You could do it with an input transformer which has certain advantages, but it should be obvious that an input transformer adds a whole set of problems of its own.


Our preamps can drive such low input impedances- any preamp that supports the balanced standard can, but in high end audio such preamps are quite rare.


Custom buffer adds gain and increases impedance to 47k ohms.
There’s no need for it in many cases, as sources and preamp have enough gain these days. It’s just "another opamp in the signal path" that’s not needed in many cases if the input was high enough instead of 2.2k, who wants that in hi-end if it can be taken out and one less opamp yay!!! gotta be good for the sound, and the business.
I think that’s a very legit observation or "complaint" as you would put it..
Custom buffer adds gain and increases impedance to 47k ohms. As seen on current NC500 based amps such as Nord or Apollon. Just Google it before complaining... These modules are NOT finished products yet, manufacturer is supposed to add their buffers.
For all in one, buffer+power section+power supply, see Hypex nCore MP series or ICEpower. The bufferless modules are for manufacturers wanting to differentiate their implementations.
Purifi 1ET400A has no buffer, so it is expected to a manufacturer to add a custom buffer, and add more gain as needed.

It also has a disappointedly low 2.2k input impedance, so the use of most capacitor coupled (unless >10uf) preamps, tubes, or solid state or passive preamps direct in are out of the question if no extra gain is needed, which with today’s sources giving so much higher output, no extra gain is needed, so then neither would be an opamp buffer.

And if more gain is needed then a direct coupled opamp smd buffer is the only obvious option, again not capacitor coupled, solid state or tube buffer otherwise a massive 10uf coupling cap will be needed into that 2.2k input impedance.

WHY!! they keep making low input impedance amps these days is beyond me, go back to 48k (the once recognized industry standard) or even 100k like it used to be with tubes, makes for a whole better range of preamps ,tubes SS or passive able to drive them properly.

Cheers George
All we have here are a few manufacturers spruiking their new or yet to be released Class-D amps without any shame, saying they "can handle" the 2ohm load, making out they can drive this speaker to it’s best in the bass. Without presenting any measured proof of their claims, that they can almost double their clipping wattage from 8 to 4 to 2ohms.
With GaNFETs having 'on' resistances of only a few milliohms, its obvious that a class D amp using such devices will easily double power into 2 ohms (not that such is important for proper audio reproduction) as long as heatsinks and the associated power supplies can support the current. This has been stated before, its really not an issue of debate to one learned in the art.

  What I've learned lately on this thread is to avoid using speakers that present loads to the amp of less than 2 ohms. I believe if speaker designers and manufacturers decide to rule out the use of the majority of amps working well with their speakers, then we can certainly decide to rule out the purchase and use of their speakers.  
@noble100 +1 on this comment and post. This is exactly the issue- IMO/IME its irresponsible to create such low impedances where serious power is required for the simple reason that distortion will be higher, and increased distortion will make the presentation less musical.
why can't discussions of audio stuff, hifi stuff and music listening stuff, be non confrontational ?
really you have to ask this?? Because there's way too much BS and Voodoo in hi-end audio Mr D

Its not so much voodoo (although that is a problem); on this thread it really comes down to the posts of exactly one person.
Good quality sound? into hard speaker loads it’s all about current.
This statement is misleading. Its really all about distortion.
Spectron amplifiers can deliver peak currents of 65 amps, with a staggering peak power of 3500 watts per channel for over 500 msec (!), which allows the amplifier to deliver the full transient (burst of music) without current or voltage “clipping”. "
this statement is also misleading- here's why:


Current cannot exist without voltage. When the two are together you have Power, and the relationship is thus: 1 Watt = 1 Volt times 1 Amp.


If you don't know the voltage, you can use algebra to sort out the power anyway, using Ohm's Law. That relationship is used here:


Doing the math and giving the amp the benefit of the doubt, lets assume that the speaker load is 1 ohm. You'll see why in a second. Power equals Resistance times Current squared. So if we have 65 amps, the square of that is 4,225 watts into 1 ohm (just multiply that number by the impedance of the load if you want to know what 65 amps into higher impedances is). You can see right away that 65amps has nothing to do with the output of the amp. It likely represents how much current flows when the power supply of the amp is shorted for 10 milliseconds. IOW its really a measure of the capacitance in the power supply. FWIW, our MA-2 power amplifier (Vacuum tube class A triode OTL) has about the same current by this measure.


FWIW this sort of current number being bandied about is a common myth with solid state amps.



Purifi 1ET400A has no buffer, so it is expected to a manufacturer to add a custom buffer, and add more gain as needed.
The only caveat I'd have about the Purify 1ET400A as a separate power amp in the gain spec of 12.8dB.  I'm sure that doesn't hurt the distortion specs but may not be good for many people depending on their associated equipment.
dsper,
All amplifiers running 2 ohms continuously will get hot, independent of class. But I have seen that class D modules (Icepower, hypex, purifi) have current limit to protect the module from overcurrent.

As for thermal dissipation, musical signal has peaks, it never has the same power requirements as a full signal sine wave. So the manufacturers add dissipation to the modules in a coherent way for music listening.

If an amp was to be built to run full power sine wave at 2 ohms just for long term measurements, just add a lot of heat sinks and even a fan or two. It would do great on the benchmarks, but would make no sense for customers to pay and lift the extra weight.

As for distortion is simple: along with the Benchmark AHB2, the Purifi module is the lower distortion amplifier in the market, as far as we know (most manufacturers don't publish THD x power graphs, just single number specs).
I did see this:
Output Power, Short Term
8ohm, 1% distortion = 227 watts
4ohm, 1% distortion = 450 watts
2ohm, 1% distortion = 450 watts with a footnote stating "Power is limited by overcurrent protection system (OCP) and highly dependent on thermal conditions."

Not sure what the footnote means.

Amps goes self into destruct mode if current limiting doesn’t work, no other reason for it to be limited, unless purposely done to sound bad into those low loads?

Cheers George
FWIW,

I went to the Purifi Audio website and found many charts and specifications for their 1ET400A, most of which I did not understand so I could have very well missed something important about relationships between the stats they quoted.

I did see this:
Output Power, Short Term
8ohm, 1% distortion = 227 watts
4ohm, 1% distortion = 450 watts
2ohm, 1% distortion = 450 watts with a footnote stating "Power is limited by overcurrent protection system (OCP) and highly dependent on thermal conditions."

Not sure what the footnote means. 

I went to the Spectron website for the Musician III Mk2 and they tell us "The current headroom is primarily limited by the amplifier’s ability to deliver high currents into low impedance loads. There are many well regarded speakers whose impedance dips down, some even lower than 1 ohm. When a musical note is played at frequencies where the impedance dips, the current demands skyrocket. When this happens with amplifiers that do not have large output current capability, they “current clip”. These transients will be both attenuated and quite distorted. Moreover, most other amplifiers only deliver their rated peak current for sometimes a fraction of the time called for by the music. Spectron amplifiers can deliver peak currents of 65 amps, with a staggering peak power of 3500 watts per channel for over 500 msec (!), which allows the amplifier to deliver the full transient (burst of music) without current or voltage “clipping”. ".

Their stats also state 0.3% THD up to 600 watts in 8 ohms. Could not find anything about distortion at 4 or 2 ohms.

Not sure what that does or does not tell us.

It appears the old adage about trying it in your listening room will tell the real story.

In the meantime, quit bashing my low impedance speakers as they sound wonderful to me in my listening room 😍!

Thanks for listening,

Dsper

I’m by no means an expert and cannot speak to class d amps, but old school heavy duty class a amps are made for this sort of load. I drive my Apogees with a Balanced Audio Technology VK-600 with bat pack and couldn’t be happier. Yes, they run hotter than class d (and aren’t nearly as efficient), but everything is a compromise in one way or another. At the end of the day, the quality of the sound and the experience are most important to me.

Cascadesphil, thanks for taking the time and sharing your experience. Especially pertanent to me was your description of the amounts of heat being emitted. Well done. 
I would (and actually did) choose to buy amplifier B.


Good quality sound? into hard speaker loads it’s all about current.

If you wanted the "best sound (not volume)" into speakers that dip to below 2ohm for most of the bass, then you chose poorly, A would be better sounding overhaul "to a given volume level".
http://3844s14.tracigardner.com/wp-content/uploads/2014/03/youchosewisely.jpg

But if your a head banger and needed volume level, then you chose right in B.

But if the volume of B was as the "same volume" as A, it would not be as good so you chose poorly
https://waserpa.com/wp-content/uploads/2016/05/He-chose-poorly-2-1.jpg

Cheers George
Rhetorical question: which hypothetical amplifier has more power to drive 2 ohms speakers?

Amplifier A:
100W at 8 ohms
200W at 4 ohms
400W at 2 ohms

Amplifier B:
400W at 8 ohms
700W at 4 ohms
550W at 2 ohms

Amplifier A doubles power for each half impedance.
Amplifier B has more power at 2 ohms.

Just because A is voltage limited at higher impedances, does not mean it supplies more current at 2 ohms than amplifier B.

I would (and actually did) choose to buy amplifier B.
" With these sorts of speakers like the CS5 ect it’s no wonder, these tested figures show it was definitely no current master into low impedances
8ohm load 690w
4ohm load a reasonable 1000w
2ohm load it barely got off the 8ohm mark at 720w, very sad."

That probably was the beginning of what turned me off to mainstream dealer sold companies (not that Bryston is anything but a good company).  Before I bought the 14BSST, I was using a 6BSST on the front (3) channels.  As noted the room in my old house was huge.  I had a 4BST at one point and it was clear that was at its limit driving the (Thiel) 7.2s.  I corresponded back and forth many times with Bryston about the 15 vs. 20 amp version of the 14BSST.  When I had the old house built (basically in mostly in the first half of 1997), I specified I wanted an extra receptacle on its own circuit in addition to what would be behind the audio system.  I found later they used a 20 amp breaker but just used 14 ga. wire.

Anyway, the purpose of many communications (with lots of detail) going back and forth is I wanted an upgrade to the 6BSST (and in my old room was probably around barely above its limit based on my old 4BST where I had situations where it would almost go into protection mode) and then just use the 6BSST on the center and surrounds.  I guess they just didn't want to admit that the 15 amp version of the 14BBST wouldn't drive my 7.2s.  Before I sold the 14BSST, I sent it back to Bryston to have a check-up to make sure it was OK and it tested fine.  When I spoke to the technician and went into detail over the phone and told him my Modwright KWA150 SE drove the 7.2s better, he just told me that was (literally) impossible.  I may not be a technician but can feel heat and the protection circuits certainly confirmed the heat felt.  The guy I sold the 14BSST to had B&Ws so I didn't think he'll have an issue with it (and he didn't).

So that was the beginning (and in combination with the fact that there are fewer brick and mortar 2-channel dealers than there used to be vs. stuff like custom installers who don't have showrooms) about a dozen years back of what pushed me more in the direction to look at things that are sold consumer direct.  When one considers the cost of materials/quality that one gets at the price point, it is just off the charts compared to what gets from going to a brick and mortar dealer.  One may not be able to go to such a route for all purchases for various preferences and purposes but it is a strong consideration for me personally.  I have multiple systems (including one with a Hegel H190 and one with another with a Class D amp using the IcePower AS1200 stereo module) in different rooms and I'm quite satisfied that if I were to walk into a store the EVS 1200 would compete favorably to amps between $10-15000 (my Modwright was $9k list and the Bryston 14BSST was not a cheapie either) and if I went to buy either the Modwright or Bryston today used, I'd likely be paying almost double what my EVS 1200 costs new and I already know which amp is easily much better in my system.  
the Bryston 14BSST would go into protection mode from overheating due to the impedance.


With these sorts of speakers like the CS5 ect it’s no wonder, these tested figures show it was definitely no current master into low impedances
8ohm load 690w
4ohm load a reasonable 1000w
2ohm load it barely got off the 8ohm mark at 720w, very sad.

Cheers George
I'm the guy Ric was referring to who previously had a Bryston 14BSST (15 amp version as that's all I could get with my circuit in the old house) and a Modwright KWA 150SE amp to drive my Thiel 3.7s  Before the 3.7s I had Thiel 7.2s.  The room in my old house was huge (19 foot ceiling and over 6,000 cu. ft. that opened into other spaces) and on certain things (both music and movies as I have an integrated system with a Modwright LS 36.5DM preamp) the Bryston 14BSST would go into protection mode from overheating due to the impedance.  I had to build a custom amp stand with fans inside.  The Modwright (amp) drove the 7.2s better but still would get so hot (and the heatsinks are inside the case).  I ended up selling the 7.2s and getting the Thiel 3.7s (when they came out), which, although not as bad as the 7.2s are not an easy load (https://www.stereophile.com/content/thiel-cs37-loudspeaker-measurements).

Anyway the EVS 1200 dual mono amp not only sounds better than the Modwright  KWA 150SE (which was better than the Bryston) in my system, it doesn't even get warm to the touch when I crank it loud.  My current room is not as huge as my old one but it is still a big room (over 3,000 cu. ft.) that opens up into other spaces that are probably a bit bigger than the room itself (system is in the living room which is completing open to the foyer, dining room and most of the kitchen).

The CS5 impedance (https://www.stereophile.com/content/thiel-cs5-loudspeaker-measurements-0) is tougher below around 70Hz but probably not quite as tough as the 3.7s over the rest of the band.  After the EVS 1200 (which I've had for just over a month), I have no desire for anything else.  I'm still tweaking things and had a friend over (he has a Pass Labs amp, XA25, but his room is smaller and his speakers are more efficient and an easier load, Reference 3A Taxims) and he was quite impressed with the sound he heard from my system.
We all know George will be first in line.

Having a dig are we? well at least you’ve got that one right sunshine. I’ve never been against Class-D, just it’s two Achilles Heels I have a big problem with, switching frequency and dead time. Which gives it that " Plate glass transparency" that you call it, I call it "sterility" and missing harmonic decay.
I’ve always said, ever since I started the the debate about the new GaN technology here way back, that when the GaN Class-D amp becomes affordable to me, with what Technics has done with the SE-R1 with using 1.5mhz switching speed, I’ll be the first in line to get one, and ditch my inefficient hot boat anchors, door stops if you don’t live by the sea.

he’s able to make them reasonably priced since I get the feeling I’m going to be a future customer.
Judging by his offsider Tweak1 by another maker here, that’s going to cost you far bigger than it should.
https://forum.audiogon.com/discussions/which-class-d-amplifier-ps-audio-ghent-nord-merrill-or-other/...
m-db:
"I’m a class D fan but I’m not fooling myself either. Their plate glass transparency along with switching amplifiers general lack of congestion make them a tool in my studio. In the living room they’re simply no match for the relaxed musicality of my tube amps. All the best with that Ralph, you’ve got the ears for it. "

Hello m-db,

     ’Plate glass transparency and a general lack of congestion’ is a very good description of good class D sound characteristics. I’m a big class D fan, too, using a pair of D-Sonic M3-600-M monos for my main speakers for music and two additional stereo class D amps for HT, one in bridged mono for the center and one in stereo for the rear surrounds. They all function and sound great and they draw so little juice at idle, I’ve just left them on virtually 24/7 for the past 5 years.
     I usually describe their sound as very detailed, accurate, dynamic, smooth without ever sounding harsh or bright and so neutral they’re like ’the audio ideal of a straight wire with gain’. But ’plate glass transparency’ is very descriptive and really paints an accurate picture. I hope you don’t mind if I steal that phrase.
      I'm also really looking forward to auditioning the class D amp or amps Ralph is creating.  He definitely does have the ears for what good amps should sound like.  Hopefully, he's able to make them reasonably priced since I get the feeling I'm going to be a future customer.

     We all know George will be first in line.

Thanks,
Tim

georgehifi5,679 posts08-27-2019 10:43pm
 And you maybe happy with that, because you don't know better.

Cheers George

   This is an unfortunate reality from those of us attempting to make a helpful suggestion with very little actual in home comparative experience. 

   After owning four makes and in home auditions of three other switching amplifiers I've been using a pair of Hypex nCore 400s to drive my studios monitors that dip down to 3.6 ohms, an Acoustic Image Focus 2R driving a menu of Bass cabinets, and various Velodyne subwoofers. My only suggestion is to listen for yourself.

   I'm a class D fan but I'm not fooling myself either. Their plate glass transparency along with switching amplifiers general lack of congestion make them a tool in my studio. In the living room they're simply no match for the relaxed musicality of my tube amps. All the best with that Ralph, you've got the ears for it. 

At 10Hz it is approximately .6 ohms.
That when the vinyl warp frequency will tax an amp, or even a bit of dc servo flutter when the mains chucks a slight wobbly.

It's been reported that Jim Thiel ended up using Krell 600 Watt'ers.
Correct type of amp, that will almost double down to 2ohms without breaking a sweat, though the 250 or even 150 watt'ers would do, they all can do the Krell doubling act.
There are many other brands that do the Krell doubling act also, all use Bi-Polar (bjt) output transistors, just like the Krells.    

Cheers George
The impedance of the CS5 at 20Hz is 2 ohms and not .5 ohms as stated. At 10Hz it is approximately .6 ohms.
maplegrovemusic1,030 posts09-01-2019 9:05amhttps://www.crutchfield.com/p_859XLS2502/Crown-XLS-2502.html?awcr=77584293537695&awdv=c&awkw...


Amazing for $599.00!!!
"says" again not by an independent tester.

  • 440 watts x 2 at 8 ohms
  • 775 watts x 2 at 4 ohms
  • 1200 watts x 2 at 2 ohms
Why get any of the others?? When you have this for $599

Cheers George
A Carver Signature Sunfire 600 should do the trick.  That amp is so powerful it’ll get good sound from a cinder block.

If you get one Bill Flannery has up-kept there will be no heterodyning. 
Theta Digital Prometheus -

8 ohm - 250 W
4 ohm - 500 W
2 ohm - 850 W


Yes another one beside the Spectron (which is yet to be independently tested) that "can" get the watts up into 2ohms, but this is at a cost.

JA’s Note: " However, the distortion rises considerably into 2 ohms"

BTW: Note! Both use Linear power supplies that’s why they’re big/heavy for a Class-D >20kg. No smp power supplies here, that’s a good thing.

Cheers George

I have driven my 1 ohm Scintilla’s with the NC400 mono blocks from hypex.I use them sometimes in the summer months when it gets to warm for my Krell KRS100 mono blocks

My friend also has the Scintilla’s, what a great speaker when driven right.
With this
https://ibb.co/mSV04BP
https://ibb.co/m6LhhPc

1st post, bet you can’t wait for winter, otherwise you wouldn’t still own the Krells. It must be because they sound and drive the Apogee’s better by quite a margin, otherwise you would get rid of them?
Also there are cooler running Krells, that would sound almost as good as the 100 mono’s, and still blow away the NC’s on these great speakers..

Cheers George

Theta Digital Prometheus  -

8 ohm - 250 W
4 ohm - 500 W
2 ohm - 850 W  (measured by Stereophile at 980 W)
I have driven my 1 ohm Scintilla's with the NC400 mono blocks from hypex.I use them sometimes in the summer months when it gets to warm for my Krell KRS100 mono blocks consuming 700watts each.

Link: https://www.diyclassd.com/product/nc400/11
it does not double the power when halving the impedance - but it is apparently stable at 2 ohm
No it’s "not bad" for a class-D, nowhere near doubling still, at least it goes up as the impedance goes down, too many either don’t go up at all at 2ohms or go backwards. "Could" be ok for the OP’s speakers if it's to be believed, and "may" get the best out of the low impedance bass they have.
600 Watts at 8 Ohms
800 Watts at 4 Ohms
1400 Watts at 2 Ohms

It will be interesting to see with independent tests if they give it to someone like Stereophile, if they have "underquoted the 8ohm and 4ohm" to make the 2ohm look as good as it is. As many manufacturers are doing that now, that you can see that on Stereophiles bench tests, it one way of making the amp look to be doubling, and it’s wrong (lying) and should be stamped out.

Sorry - the specs above are for stereo single amp - the power is considerably more in mono block configuration

If these are bridged stereo’s into mono’s? (probably as they give no specs) if so they won’t even do as good as the stereo amp in doubling down.

Cheers George
Sorry - the specs above are for stereo single amp - the power is considerably more in mono block configuration 

http://www.spectronaudio.com/musicianIII.htm

600 at 8ohms.  800 at 4 and 1300 at 2 ohms - it does not double the power when halving the impedance - but it is apparently stable at 2 ohm   

I’m not an electronics engineer - but the specs are in the link - I just know that these sounded great - but I never cranked the volume - as the room is too small -  they deliver lots of current 
Spectron Musician III mk2 mono blocks - I believe they will provide around 300 watts at 1 ohm - or it might be at 0.5 ohm -

Once again this means nothing, give us the clipped wattage at 8ohm 4ohm and 2ohm and 1ohm, only then will you know if it's being current starved (sagging).

Cheers George