Class A amplifier

[SIY]

Too bad, I am highly suspicious of that curve being an accurate impedance magnitude plot.

 

[freemansteve]

Why only discuss A & A/B?
I'm sure these have been measured and subjectively reviewed as sounding fine with Hypex etc - they will drive anything, including a concrete wheel-barrow.

Nord Acoustics Hypex Purifi Class D Amplifiers

World Class Hypex NCore NC500 NCx500, NC1200, Purifi Audio 1ET400A 1ET7040SA and ICE Power 1200AS2 Class D Amplifiers from Nord Acoustics using discrete op amps and V regulators USA & World Delivery.

www.nordacoustics.co.uk

 

[RichB]

Why only discuss A & A/B?
I'm sure these have been measured and subjectively reviewed as sounding fine with Hypex etc - they will drive anything, including a concrete wheel-barrow.

Nord Acoustics Hypex Purifi Class D Amplifiers

World Class Hypex NCore NC500 NCx500, NC1200, Purifi Audio 1ET400A 1ET7040SA and ICE Power 1200AS2 Class D Amplifiers from Nord Acoustics using discrete op amps and V regulators USA & World Delivery.

www.nordacoustics.co.uk

These speakers have very impedance below 3 ohms below 60Hz and above 2kHz.


Some ASR amplifier reviews include power by frequency and some amps including Hypex Amps have reduced power into low and high frequencies, and other seem good.

Hypex:


Purify amps may be up to the task as well as beefy A/B amps.

Putify:

NAD M33 Streaming Amplifier Review

This is a review and detailed measurements of the NAD M33 Streaming Player with Purifi Eigentakt Amplification. It is kindly sent for testing from a member and has a retail cost of US $4,999. The NAD is part of their "Masters" series and has one of the best industrial designs of any audio...

www.audiosciencereview.com

I'd like to see all amplifier reviews include the power by frequencies measurements.
2 Ohms testing may be worthwhile for beefy amps.

- Rich

 

[SIY]

These speakers have very impedance below 3 ohms below 60Hz and above 2kHz.
View attachment 191394

Some ASR amplifier reviews include power by frequency and some amps including Hypex Amps have reduced power into low and high frequencies, and other seem good.

Hypex:
View attachment 191398

Purify amps may be up to the task as well as beefy A/B amps.

Putify:

NAD M33 Streaming Amplifier Review

This is a review and detailed measurements of the NAD M33 Streaming Player with Purifi Eigentakt Amplification. It is kindly sent for testing from a member and has a retail cost of US $4,999. The NAD is part of their "Masters" series and has one of the best industrial designs of any audio...

www.audiosciencereview.com

I'd like to see all amplifier reviews include the power by frequencies measurements.
2 Ohms testing may be worthwhile for beefy amps.

- Rich

I remember when Stereophile was accidentally inverting the impedance magnitude curves. At some point, they realized it and quietly fixed it. I wonder if that's what happened here? It would make more sense upside down.

 

[RichB]

I remember when Stereophile was accidentally inverting the impedance magnitude curves. At some point, they realized it and quietly fixed it. I wonder if that's what happened here? It would make more sense upside down.

Maybe, but my brother had pair of small Kappa and they were very hard to drive.

- Rich

 

[SIY]

Maybe, but my brother had pair of small Kappa and they were very hard to drive.

- Rich

Not mutually exclusive. Even upside down, there’s a lot of peak and dip, but it looks more normal. Ditto if it’s a phase curve, the integral will give a rugged magnitude.

 

[Dclone]

1ET400A - PURIFI

Single-channel, analog-input Class D amplifier module Negligible THD and IMD Extraordinary low noise Load-invariant response Exceptionally clean clipping Low losses & high efficiency Easy to integrate Designed in Denmark KEY SPECIFICATIONS

purifi-audio.com

View attachment 191377


JSmith

I’ve read through the information You linked to. Looks really interesting. I suppose those amps are used in subwoofers and active speakers normally. But two or four of those and someone who can build them together in a nice small box would be worth a try!

I solely use balanced interconnects (xlr) but that should hopefully not be a problem.

I will look further to see if Purifi has implemented their amp in a ready to use poweramp.
Thanks for the link!

Mikael

 

[Doodski]

2 Ohms testing may be worthwhile for beefy amps.

That goes against the prime directive to not damage gear when testing it. A 2 Ohm load is punishing for stuff and then poof the smoke is let out.

 

[pma]

Good amplifier MUST handle 2 Ohm load. And testing into 8 Ohm is pointless.

 

[sergeauckland]

That goes against the prime directive to not damage gear when testing it. A 2 Ohm load is punishing for stuff and then poof the smoke is let out.

One of the tests I've applied to amplifiers I've bought for my own use is to put a screwdriver across the 'speaker terminals at full power. If it doesn't survive, it goes back. Obviously, I wouldn't do that to an amp that wasn't advertised as short-circuit protected. but then I wouldn't buy one that wasn't, so I do test it.

S.

 

[Doodski]

Good amplifier MUST handle 2 Ohm load. And testing into 8 Ohm is pointless.

Where do we draw the line between expected to take 2 Ohms and the other stuff not req'd? Plus the gear is sometimes used and we don't know the condition of the circuitry. Maybe there is a fault just waiting to blow up. Then there must be a test time limit and 1KHz or 20-20KHz into 2 Ohms? Things will become hot.

EDIT:
Who will make this standard test?

 

[SIY]

Where do we draw the line between expected to take 2 Ohms and the other stuff not req'd? Plus the gear is sometimes used and we don't know the condition of the circuitry. Maybe there is a fault just waiting to blow up. Then there must be a test time limit and 1KHz or 20-20KHz into 2 Ohms? Things will become hot.

EDIT:
Who will make this standard test?

It is important that anyone having properly engineered speakers must pay significant extra expense for the 0.1% of badly designed speakers out there that they wisely avoided. Because reasons.

 

[Doodski]

It is important that anyone having properly engineered speakers must pay significant extra expense for the 0.1% of badly designed speakers out there that they wisely avoided. Because reasons.

The Kappa 9 is a very fun speaker to have about in the stable. I'd like to own one even with the low Z. They pound/thump pretty good when cranked up and the top end is decent too.

 

[RichB]

Good amplifier MUST handle 2 Ohm load. And testing into 8 Ohm is pointless.

Perhaps test for any amp that claims to be stable down to 2 Ohms.
For those, not a disclaimer by the owner and limited time testing.

- Rich

 

[Axo1989]

I have tried the 375 and they were nice but did not had enough power. Have not been able to test the 575 due to lack of distributors in Sweden. The 300 duo like the Evolution serie does not deliver current enough for the 9:s. Ok for the 8:s though. Epsilons design demands a minimum of two poweramps so maybe two Duos will work but it would be a step down from today. (I think…)

I was hoping for some lightweighted class D power amps. Maybe if I bi amp? Two, four or more of them?

Thanks all for taking time answering. And btw, as You can see above the Kappa 9 are really beautiful and sound fantastic. I am lucky enough to have my little Infinity collection in Santos wood.

If I find an alternative I let You know.

Cheers from Sweden

Interesting comment on new Krell. I wasn't aware they didn't specify 2Ω output post-Dan until I had a look at the specs re your question. I also read Stereophile review of the Epsilon, I have a better idea now. Great to read about nice older gear.

Did I read correctly that Evolution series didn't work for you? I'd have guessed any Evolution monobloc (400/600/900 watt models) would do ample current (Krell specified doubling output down to 2Ω and Stereophile verified) and they have monster power supplies. My speakers are less demanding, but I keep an eye out for used 302e which looks like the sweet spot (for me, probably not you). I didn't suggest them because they are just as heavy as your older models (no exposed heatsinks though).

I'll agree with @Doodski and others that more recent Hypex or Purifi may be worth a look: here's the new one (vendor is from my country, there are doubtless EU implementations of Purifi 1ET7040SA coming nearer you if not already). Note spec has it near enough to doubling all the way down (250/500/950 at 8/4/2Ω) which is new for class D (I think, certainly for Purifi).

 

[Dclone]

Interesting comment on new Krell. I wasn't aware they didn't specify 2Ω output post-Dan until I had a look at the specs re your question. I also read Stereophile review of the Epsilon, I have a better idea now. Great to read about nice older gear.

Did I read correctly that Evolution series didn't work for you? I'd have guessed any Evolution monobloc (400/600/900 watt models) would do ample current (Krell specified doubling output down to 2Ω and Stereophile verified) and they have monster power supplies. My speakers are less demanding, but I keep an eye out for used 302e which looks like the sweet spot (for me, probably not you). I didn't suggest them because they are just as heavy as your older models (no exposed heatsinks though).

I'll agree with @Doodski and others that more recent Hypex or Purifi may be worth a look: here's the new one (vendor is from my country, there are doubtless EU implementations of Purifi 1ET7040SA coming nearer you if not already). Note spec has it near enough to doubling all the way down (250/500/950 at 8/4/2Ω) which is new for class D (I think, certainly for Purifi).

Due to lack of distribution I have not been able to test the Evolution monoblocks. If i can get a chance to test them I will. The only Evolutions I tested are the integrated ones which did not have a chance driving the 9:s. I am only searching for poweramps because I have three Krell preamps and are very, very pleased with them.

Btw. (Off toppic) During recap of one of the preamps (KSP 7B) I used my Topping D90 MQA as preamp. Well it worked…. But sounded bad (thin and harsh). It also went very, very hot. I used xlr cables (with two Y splitters) to drive two KSA 150. The preamps ”colours” the sound or add distortion as some of You will put it. My ears prefer that ”distortion” and I certainly need all the in and outputs, especially the analogue ones (for Riaa to TT and R2R)

I will talk to my local Hifi dealer and see if he can arrange a home test with both Duo 575 and Evolution 600/900. Possibilty is low sadly enough. But I will not buy such relatively expensive gear without testing it in my home with my own gear, room layouts etc. (Main listening room is approx 64 m2)

I will dive in to the deep world of class D or H or any mixture of them (Hypex and Purifi comes first to test) and give them a really good testing!

Cheers to all You helpful people!