Modern Class D amplifier recommendation for ML electostats?

[Sammy135]

I need some recommendations for a class D amp for my Martin Logan EFX electrostatic speakers. I found impedence charts of the ML electrostats, and they begin to dip starting at 1kHz. At 3kHz, they are at 4 ohm, and at 10kHz, they are ~1.8 ohm, and at 20kHz they are less than 1 ohm.

ML manufacturer recommends: ...it is important that the amplifier be stable operating into varying impedance loads: an ideally stable amplifier will typically be able to deliver nearly twice its rated 8 Ohm wattage into 4 Ohms and should again increase into 2 Ohms.

From the Hypex based offerings, I found amplifiers based on: NC52MP, NC122MP, NC252MP, NC502MP.

NC252MP = • 2 x 150Wrms 8 Ohms , • 2 x 250Wrms 4 Ohms, • 2 x 180Wrms 2 Ohms. I don't think this will work, 4 ohm does NOT double from 8 ohm power, and 2 ohm power decreases, going against ML recommendations.

NC502MP = • 2 x 350Wrms 8 Ohms, • 2 x 500Wrms 4 Ohms, • 2 x 450Wrms 2 Ohms. Looks to me like this would suffice, but not be the best pick, because of power not doubling, and 2 ohm power still going down. High power numbers but doesn't seem like it's the best pairing...

NCx500 = 380W 8ohm, 700W 4ohm, 700W 2ohm

NC1200 = 400W 8ohm, 700W 4ohm, 1200W 2ohm

Purifi

1ET400A = 227W 8ohm, 425W 4ohm, 450W 2ohm
1ET700A = 250W 8ohm, 500W 4ohm, 950W 2ohm

Icepower

Ice1200AS2 = • 2 X 600W 8Ohms 700W 4Ohms


Looks like the best amp would be a 1ET700A based board from Purifi.



I want to choose Icepower, because it is the cheapest/channel. But, I don't know its sub 2 ohm power performance (manufacturer recommends min 2.4 ohm loads on icepower website)... Most of hypex offerings 2 ohm performance looks to be same as 4 ohm performance, so would this not be the best amp, and would I even hear the sideeffects of this if I were to choose a hypex amp? Looks like the purifi 1et700A amp would check all the boxes and have infinite power with rated 2 ohm performance from the manufacturer.

Which class D should I choose?

Thanks..

 

[pogo]

1ET9040BA is the best choice

 

[Doodski]

ASR list of known class D home audio amplifiers.

Any suggestions are welcome. Post suggestions here. I will gather the details and add them. Thanks. :D This will be organized as results come in. So give me brand names and model numbers of class D amps and I'll create the list just like the EQ/PEQ webpage @ ASR is done. 3E Audio 260-2-29A PFFB...

www.audiosciencereview.com

 

[Sammy135]

1ET9040BA is the best choice

I saw that too, didn't bother adding it because I feel like those would be what someone with the ML Renaissance 15A would need. Crazy crazy performance.

 

[Sammy135]

ASR list of known class D home audio amplifiers.

Any suggestions are welcome. Post suggestions here. I will gather the details and add them. Thanks. :D This will be organized as results come in. So give me brand names and model numbers of class D amps and I'll create the list just like the EQ/PEQ webpage @ ASR is done. 3E Audio 260-2-29A PFFB...

www.audiosciencereview.com

Very good exhaustive list for me to choose from, thank you. Has stuff I am missing too.

Should I be filtering that list down to amps that double twice in power compared to their 8 ohm performance?

 

[Doodski]

Very good exhaustive list for me to choose from, thank you. Has stuff I am missing too.

Should I be filtering that list down to amps that double twice in power compared to their 8 ohm performance?

The list started yesterday morning. After 14 hours this is what I have... plus maybe a dozen more in que to be added to the list.

 

[Doodski]

Should I be filtering that list down to amps that double twice in power compared to their 8 ohm performance?

Take a look @ Buckey Amps... good prices and nothing too fancy.

 

[DVDdoug]

You don't (usually) need high power at the highest frequencies. In normal program material it's just weak harmonics & overtones. So you aren't over-stressing the amp as much as low impedance at low frequencies.

But you're still taking some risk running an amplifier outside of its specifications.

 

[Doodski]

@Sammy135 Where do you hail from? If we or I recommend stuff sometimes we need to know the purchasing/destination country.

 

[tmtomh]

That kind of crazy low impedance load is not necessarily as much of a problem as it might initially seem since it occurs at 10kHz and above, where there's generally much less energy in music and therefore less current (or voltage) required of the amp than if that low impedance occurred in the bass region. (EDIT: looks like someone else said the same thing above while I was typing this!)

That said, the speaker still presents a challenging load, and for $4400 a pair I don't think it's out of line to spend another $1k-$1500 on amplification.

I don't think you need the Purifi 9040 series. But the Purifi 7040 series, or the roughly equivalent Hypex NCX series, would be an ideal choice and you could rest easy that they could drive your MLs with all kinds of music at all kinds of volume.

That said, if you want to economize a little bit and still have first-rate amplification, I drove a pair of Infinity Kappa 9s with a stereo amp based on the older and lower-power Purifi 400 series modules. The Kappas not only go below 2 ohms around 10kHz but are also notorious for going below 2 ohms somewhere in the lowest 1-2 octaves of the bass region. Even switched into their "less bass" mode they are, I believe, a slightly sub-4 ohm load in much of the bass region. The Purifi 400-based amp drove them with zero problems. I don't listen insanely loud, but I did drive them to abut 92dB SPL at 3 meters, which is roughly equivalent to an official 1M SPL of 100dB, and the amp didn't even get warm.

 

[EdW]

I need some recommendations for a class D amp for my Martin Logan EFX electrostatic speakers. I found impedence charts of the ML electrostats, and they begin to dip starting at 1kHz. At 3kHz, they are at 4 ohm, and at 10kHz, they are ~1.8 ohm, and at 20kHz they are less than 1 ohm.

ML manufacturer recommends: ...it is important that the amplifier be stable operating into varying impedance loads: an ideally stable amplifier will typically be able to deliver nearly twice its rated 8 Ohm wattage into 4 Ohms and should again increase into 2 Ohms.

From the Hypex based offerings, I found amplifiers based on: NC52MP, NC122MP, NC252MP, NC502MP.

NC252MP = • 2 x 150Wrms 8 Ohms , • 2 x 250Wrms 4 Ohms, • 2 x 180Wrms 2 Ohms. I don't think this will work, 4 ohm does NOT double from 8 ohm power, and 2 ohm power decreases, going against ML recommendations.

NC502MP = • 2 x 350Wrms 8 Ohms, • 2 x 500Wrms 4 Ohms, • 2 x 450Wrms 2 Ohms. Looks to me like this would suffice, but not be the best pick, because of power not doubling, and 2 ohm power still going down. High power numbers but doesn't seem like it's the best pairing...

NCx500 = 380W 8ohm, 700W 4ohm, 700W 2ohm

NC1200 = 400W 8ohm, 700W 4ohm, 1200W 2ohm

Purifi

1ET400A = 227W 8ohm, 425W 4ohm, 450W 2ohm
1ET700A = 250W 8ohm, 500W 4ohm, 950W 2ohm

Icepower

Ice1200AS2 = • 2 X 600W 8Ohms 700W 4Ohms


Looks like the best amp would be a 1ET700A based board from Purifi.



I want to choose Icepower, because it is the cheapest/channel. But, I don't know its sub 2 ohm power performance (manufacturer recommends min 2.4 ohm loads on icepower website)... Most of hypex offerings 2 ohm performance looks to be same as 4 ohm performance, so would this not be the best amp, and would I even hear the sideeffects of this if I were to choose a hypex amp? Looks like the purifi 1et700A amp would check all the boxes and have infinite power with rated 2 ohm performance from the manufacturer.

Which class D should I choose?

Thanks..

A thread started by @pma

PURIFI EVAL2 Eigentakt Mono Amplifier Kit

PURIFI EVAL2 Eigentakt Mono Amplifier Kit I bought this kit from Soundimports https://www.soundimports.eu/en/purifi-eval2.html I had some troubles with the first kit, it would not start switching. However, Soundimports customer support were very helpful and they sent me after return a...

www.audiosciencereview.com

Has some discussions about driving difficult capacitive speaker loads with Purifi amps and a series of measurements made by @pma . Worth a read

 

[Sammy135]

That kind of crazy low impedance load is not necessarily as much of a problem as it might initially seem since it occurs at 10kHz and above, where there's generally much less energy in music and therefore less current (or voltage) required of the amp than if that low impedance occurred in the bass region. (EDIT: looks like someone else said the same thing above while I was typing this!)

That said, the speaker still presents a challenging load, and for $4400 a pair I don't think it's out of line to spend another $1k-$1500 on amplification.

I don't think you need the Purifi 9040 series. But the Purifi 7040 series, or the roughly equivalent Hypex NCX series, would be an ideal choice and you could rest easy that they could drive your MLs with all kinds of music at all kinds of volume.

That said, if you want to economize a little bit and still have first-rate amplification, I drove a pair of Infinity Kappa 9s with a stereo amp based on the older and lower-power Purifi 400 series modules. The Kappas not only go below 2 ohms around 10kHz but are also notorious for going below 2 ohms somewhere in the lowest 1-2 octaves of the bass region. Even switched into their "less bass" mode they are, I believe, a slightly sub-4 ohm load in much of the bass region. The Purifi 400-based amp drove them with zero problems. I don't listen insanely loud, but I did drive them to abut 92dB SPL at 3 meters, which is roughly equivalent to an official 1M SPL of 100dB, and the amp didn't even get warm.

Noted, thank you.

@Sammy135 Where do you hail from? If we or I recommend stuff sometimes we need to know the purchasing/destination country.

Canada

 

[DonH56]

With almost zero research I would pick an NCx or Purifi from your list simply because they seem more likely to handle the low impedance of the EFX. It is a hybrid system but not powered (no bass amp) so the woofers may dip down a bit as well (I did not see an impedance plot but did not look hard for it). My choice would be the Purifi 1ET400A as it has more than sufficient power and is a top-measuring (and reviewed) amplifier. As others have said, for ESL's the lowest impedance is at very high frequencies, where power is low. Despite the panels being big capacitors, the impedance of most ESL's is actually inductive at HF due to the transformer used to couple amp (and DC supply) to the panels, so a very low but not hideous load.

FWIWFM - Don

 

[Doodski]

That kind of crazy low impedance load is not necessarily as much of a problem as it might initially seem since it occurs at 10kHz and above, where there's generally much less energy in music and therefore less current (or voltage) required of the amp than if that low impedance occurred in the bass region. (EDIT: looks like someone else said the same thing above while I was typing this!)

That said, the speaker still presents a challenging load, and for $4400 a pair I don't think it's out of line to spend another $1k-$1500 on amplification.

I don't think you need the Purifi 9040 series. But the Purifi 7040 series, or the roughly equivalent Hypex NCX series, would be an ideal choice and you could rest easy that they could drive your MLs with all kinds of music at all kinds of volume.

That said, if you want to economize a little bit and still have first-rate amplification, I drove a pair of Infinity Kappa 9s with a stereo amp based on the older and lower-power Purifi 400 series modules. The Kappas not only go below 2 ohms around 10kHz but are also notorious for going below 2 ohms somewhere in the lowest 1-2 octaves of the bass region. Even switched into their "less bass" mode they are, I believe, a slightly sub-4 ohm load in much of the bass region. The Purifi 400-based amp drove them with zero problems. I don't listen insanely loud, but I did drive them to abut 92dB SPL at 3 meters, which is roughly equivalent to an official 1M SPL of 100dB, and the amp didn't even get warm.

That's pretty good. I too have muchO experience with the Kappa 9 and found even 200 and 260 Watt/ch class AB amps struggled if not up to the task.

 

[SIY]

Why did you exclude Nilai? That's been the best I've tested to far with unreasonably capacitive loads.

 

[DonH56]

Why did you exclude Nilai? That's been the best I've tested to far with unreasonably capacitive loads.

Link? My half-second search points to Malaysia...

Edit: Duh! https://www.audiosciencereview.com/forum/index.php?threads/hypex-nilai500diy-amplifier-review.41669/

 

[SIY]

Link? My half-second search points to Malaysia...

Edit: Duh! https://www.audiosciencereview.com/forum/index.php?threads/hypex-nilai500diy-amplifier-review.41669/

I was thinking more of this.

Fresh From the Bench: Hypex Nilai500DIY 500W Mono Power Amplifier Kit - A New DIY Benchmark

The Hypex Nilai500DIY 500W Mono Power Amplifier Kit is new DIY benchmark from the company's dedicated DIYClassD brand. The kit is specified to deliver 500W with 1% THD at 4 ohms, improves output noise and idle losses significantly, and comes with a discrete buffer stage and voltage regulators...

audioxpress.com

 

[DonH56]

I was thinking more of this.

Fresh From the Bench: Hypex Nilai500DIY 500W Mono Power Amplifier Kit - A New DIY Benchmark

The Hypex Nilai500DIY 500W Mono Power Amplifier Kit is new DIY benchmark from the company's dedicated DIYClassD brand. The kit is specified to deliver 500W with 1% THD at 4 ohms, improves output noise and idle losses significantly, and comes with a discrete buffer stage and voltage regulators...

audioxpress.com

OK, I read "I've" and should have checked your site, sorry!

Nice performance, though still has the weird steps in the HF distortion. At a level orders of magnitude below what we can hear, and that speakers will create, of course.

 

[restorer-john]

Nice performance, though still has the weird steps in the HF distortion.

In @SIY 's review, he mentions/notes the SR (sample rate) of the AP's A/D in various tests, but not the actual measurement bandwidth he selected. So who knows what's going on with the HF THD. I reckon the steps are just the harmonics falling off the top of the measurement bandwidth. And why 12.5kHz? So the first harmonic is outside the measurement BW?

 

[SIY]

though still has the weird steps in the HF distortion.

Yes, Pavel remarked to me that our measurements lined up pretty well on this- which they should.

but not the actual measurement bandwidth he selected.

96K SR, so about 45-46kHz bandwidth.