What Class D amps will drive a 2 ohm load

+1 George

"I know someone using the Icepower IceEdge modules on his Thiel CS3.7's and he can blast it all he wants. I have tested the IceEdge module to do 1000 watts at 2 ohms."

It was posts like this that sucked me into thinking these amps (Icepower 1200AS1/2) practically had no limit. Hopefully, anyone with speakers lower than 4ohm minimum won't get burnt by the hype.

@ricevs  - "I know someone using the Icepower IceEdge modules on his Thiel CS3.7's and he can blast it all he wants."

CS3.7 impedance has been measured at 2.4 - 2.8 ohms through most of the frequency range by Stereophile.

Icepower 1200AS1/2 has an minimum impedance of 2.7ohms.

I doubt very much the person you know using the $300 Icepower modules is getting anywhere near full potential on his speakers.

Back in the day (before internet sales), any experienced audio dealer wouldn't have sold an amp so badly unrated for this type of speaker. There's a reason both online reviews I've read suggest serious amps are required because these speakers are 'Pigs'.

I wouldn't be selling these modules to anyone using speakers with anything less than 4 ohms minimum.

OP is asking about Class D amps rated for 2ohms. One of the suggested amps (1200AS1/2) is rated at 2.7ohms. This module also has a clipping indicator built into the controller. It would make sense to me that the clipping indicator was active to see how well the amp is doing. I doubt B&O had something like the CS3.7's in mind when developing this module.

Based on OP's last post,  it seem the question is if there's a Class D amp that drops down to 2ohms without any issues, while maximizing the speaker to it's full potential. Not a Class D amp that only allows a speaker system 40-50% of it potential. Is there a Class D amp that will do this, if so which ones. According to OP, the 2 that were mentioned failed.

@mcreyn - "George, still waiting for you to demonstrate how an amp putting out 200 watts at 2 ohms is flowing more current than one putting out 400 watts at 2 ohms."

I'm pretty sure this is George's point. This is from the Pass Labs website - https://www.passlabs.com/press/power-supplies-commentary-consumers:

"If the stereo amplifier is rated 200  watts per channel pure Class A, it will draw about 1000 watts all the time, meaning that about 3000 watts of power transformer is called for, no less."

Also from the same article on Switching Power Supplies: "This can be a deep subject, but suffice it to say that I believe that some of the same caveats apply to switching supplies as linear regulators. Again, they should be rated far beyond the nominal current requirements of the amplifier circuit, particularly as the switchers I have seen usually degrade badly beyond their ratings. Also, it helps if the power supply capacitors before and after the switcher are very substantial. This is typically not the case, since one of the primary motivations to use switchers is to save money."

And here's an example from Stereophile for the Mytek Brooklyn Class-D amp that viper6 owns: Defining clipping as when the THD+noise in the output reaches 1%, Mytek specifies the Brooklyn Amp as clipping at 250Wpc into 8 ohms (24dBW), at 300Wpc into 4 ohms (21.7dBW), and at 400Wpc into 2 ohms (20dBW). I measured clipping powers of 245W into 8 ohms (23.9dBW, fig.4) and 315Wpc into 4 ohms (22dBW, fig.5), both with both channels driven. However, when I tried to measure the clipping power into 2 ohms, the Mytek went into protection mode at 310W (18.9dBW), with any further increase in the input voltage not resulting in a higher output power - https://www.stereophile.com/content/mytek-brooklyn-amp-power-amplifier-measurements

I believe all George is saying is that regardless of manufactures specs, it's probably in the best interest of a potential buyer for any amp to have measurements done independently to support the specs.

It seems to be more often than not that when Stereophile measures Class-D amps, there's a comment about careful matching to low impedance speakers.

@viber6 - no need to get defensive about your Mytek Brooklyn amp. No where did I mention anything about quality of sound from any amp. My comments were specific to mcreyn's question to George.

I would also like to add, my post has everything to do with the question asked about Class-D amps for 2 ohm speakers (from the OP), as the Manufacture specs do not align with the measurements from Stereophile. And I'll repeat it again, 'this is George's point about Class-D amps not being suitable for low impedance speakers - make sure they measure as the specs suggest because more often than not, Stereophile mentions the amp will have a hard time with low impedance speakers."

Please don't twist my words around again and make this into something it isn't.

@erik_squires 

I've never seen you pass an opportunity to tell some one who says they like class D why they should not. If there is anything you are passionate about here it seems to be correcting people who like Class D.

D’Agostino, Luxman, Ayre are my top favorites right now.

I find their sound in sharp contrast with Pass, which is really not for me.

Spectral is a line I wanted to be impressed with, like Pass, and I just haven’t. They do not bring me joy.

On the opposite end of the spectrum is Pass. A sound I really don’t like.

First two posts were what amps do you like, not which ones you don’t like.

Third post was one of his trolling threads, which was created after another one didn’t bring any posts.

Anyway, there's others, but this should be enough to explain myself.

@gdnrbob - I was commenting on a question made by noble100

I also don't believe there's any validity to golfnutz claim that Erik has criticized Pass Labs or Spectral amps.

Anyway, I didn't answer Erik previously about this because sure enough it would turn into a pissing match, and you didn't wait too long to make that happen. I've made my point, so yes, I'll give it up as you wish.

Sorry Erik, I won't be engaging in any more of this discussion. You can find the quotes yourself if you need to see them.

I’ve kind of been looking at your threads. I’m going to give you advice I’m sure you won’t take.

I guess you're the only person that's allowed to look at other members threads/posts.

Thanks George.

This thread should have been finished after the 5th post. I think your response nailed it perfectly. Class-D and speakers < 2ohms just don't work, with maybe the exception of some of the latest offerings that cost just as much as a good quality Class A amp.

@rambo21

I believe PS Audio Stellar M700 monoblocks
are rated to be stable down to 2 ohms.
Class D 350 watts at 8 ohms, 700 watts at 4 ohms

Spec sheet for Icepower 700ASC specifies 2.5ohms minimum.

That was my point George, someone mentioned the Stellar M700 goes down to 2ohms, and the specs are only 2.50ohms.

It's also interesting that Stereophile didn't bother reporting specified power rating at 2ohms, but did mention THD rises into 2ohms at higher frequencies.

Like everything else, you get what you pay for and there is no free ride with Class-D amps (with reference to low impedance speakers).

We define clipping as when the percentage of THD+noise in the amplifier's output reaches 1%, and fig.5 indicates that the M700 slightly exceeds its specified power of 350W into 8 ohms (25.44dBW). Into 4 ohms (fig.6), the M700 clips at precisely the specified 700W (25.44dBW). Fig.7 plots the THD+N percentage against frequency at a level at which I could be sure I was looking at distortion rather than noise: 20V, which is equivalent to 50W into 8 ohms, 100W into 4 ohms, and 200W into 2 ohms. The THD is very low at low and middle frequencies into 8 and 4 ohms, but does rise into 2 ohms and at high frequencies.

Read more at https://www.stereophile.com/content/ps-audio-stellar-m700-monoblock-power-amplifier-measurements#rLo...

Can I make the same comment that higher impedance is receptive to noise, in the same context that lower impedance adds distortion.

Seems like most of the Class-D amps Stereophile measured included power ratings at 2ohms. It just thought it was weird they didn't include those measurements for the M700 amps.

Yep, WFS SX-1000 uses those same modules.

Spec sheet specifies 2.0 ohm minimum load, as well as 40 amp current (peak). Unlike the Icepower 1200AS1/2 being rated at 2.7 ohms.

Also included in the specs:

Overload Protection - In case of high-amplitude continuous low frequency signals in loads lower than 4 ohms the power supply may not be able to deliver the required amount of power to the amplifier and the supply voltage will drop. The overload protection circuit will then lower the threshold of the input soft clipping circuit until the output power has been reduced to an acceptable level. As a result the amplifier will not shut down because of under voltage and the music will still be playing but with a softly shaped audio signal.
 

It had trouble with Thiel CS3.6's and was a joke with the CS5's.

So the Icepower 1000ASP had trouble with Thiel CS3.6. Well, they are a tough load through most of the frequency range.

The 1000ASP should have an easier time with the Thiel CS3.6 than the 1200AS1/2 since the ratings are 2.0 ohm minimum load and 40 amps peak, vs 2.7 ohm and 38 amps peak for the 1200AS1/2.

The 1200AS2 didn't pair that well with my Wilson Watt/Puppy's. If you compared the 1200AS2 to my Class A amps, it was no contest really.

To be honest, I'm not sold on what @cascadesphil is saying about his EVS1200 amp being suitable for his Thiel CS3.6 speakers(based on Icepower 1200AS1 modules). I suspect he is using subwoofer's and this is masking the issues. It's too bad he never had a decent amp as a reference point to compare. Both his previous amps weren't sufficient for those speakers either. He should have paid attention to the Stereophile reviews for those amps as they were only mediocre. This is just my opinion. I'm sure the Icepower 1200AS1/2 do well with higher impedance speakers.

Overload Protection - In case of high-amplitude continuous low frequency signals in loads lower than 4 ohms the power supply may not be able to deliver the required amount of power to the amplifier and the supply voltage will drop. The overload protection circuit will then lower the threshold of the input soft clipping circuit until the output power has been reduced to an acceptable level. As a result the amplifier will not shut down because of under voltage and the music will still be playing but with a softly shaped audio signal.