High end Vintage SS amp vs the best Class D amps

[ex audiophile]

The biggest criticism of Benchmark's $3000 class AB is the lack of power, and the answer to that is a Purifi class D stereo build at half the price (+/-) for the cheapest option and almost double the power at similarly low distortion. This is going to be the best option for probably 99%+ of people when looking at the purchase holistically. If for whatever reason you need more than ~400+ WPC then you can opt to give up some specs for Hypex NC1200 or NC2k with not much change in price, maybe a couple hundred more. When you are comparing these to class A amplifiers that have comparable specs, or cost many thousands or tens of thousands and may in fact have inferior specs at worse, the answer is fairly clear if you care minimally about aesthetics or ease of future serviceability. If a module dies outside of warranty you can just replace it easily or even upgrade it with whatever is the best in the future. I feel like with these options available most big class A amps are for the ostentatious, or those in need of a space heater in winter.

I've come to the same conclusion. Over the past couple years I have purchased the STR power amp, a McIntosh MC312, multiple AHB2s, a pair of P701 March monoblocs and several other less costly amps. I've mixed the amps amongst 3 systems, all with nice Revel speakers (226be and 228be) always using an STR preamp. I have never been able to hear a difference between the amps; I personally liken the situation to comparing DACs i.e. very difficult to hear differences and if there are any, they're damn subtle. I will fully admit to loving the look of the McIntosh, but put a cover over it and I could not differentiate it from an amp costing magnitudes less. And then there's the 100+ pound weight of the damn thing!
So in my case any further amp purchases will be Class D because of the power, small footprint/weight and very reasonable cost. Amir has said that the most frequent "problem" with amps is not enough power. Just my opinion but I think all the discussion about topologies is far less important than having plenty of clean power and a decent SINAD. IMHO the D class amps do that the best.

 

[Angsty]

I've come to the same conclusion. Over the past couple years I have purchased the STR power amp, a McIntosh MC312, multiple AHB2s, a pair of P701 March monoblocs and several other less costly amps. I've mixed the amps amongst 3 systems, all with nice Revel speakers (226be and 228be) always using an STR preamp. I have never been able to hear a difference between the amps; I personally liken the situation to comparing DACs i.e. very difficult to hear differences and if there are any, they're damn subtle. I will fully admit to loving the look of the McIntosh, but put a cover over it and I could not differentiate it from an amp costing magnitudes less. And then there's the 100+ pound weight of the damn thing!
So in my case any further amp purchases will be Class D because of the power, small footprint/weight and very reasonable cost. Amir has said that the most frequent "problem" with amps is not enough power. Just my opinion but I think all the discussion about topologies is far less important than having plenty of clean power and a decent SINAD. IMHO the D class amps do that the best.

This posting from another thread gives additional credence to the idea that well-performing amps can be very difficult to tell apart in blind testing. Chasing SINAD can yield diminishing returns in the real world.

We did some real world blind audition amp testing on Sunday with this amp and a few others. Here's a link for anyone interested.
https://www.avsforum.com/threads/ka...e-night-events.1496367/page-450#post-60198218
post 8989.

 

[MaxBuck]

[Blah blah yadda yadda.] Others will emphasize that "you actually need more power than you assume" (e.g. for big peaks/transients). What's a poor audiophile to do?

Buy a bigger amp.

Duh.

 

[Rottmannash]

@AdamG247 This where use-case is really important. What is perfect for one person, makes no sense to another.

...Say someone living on the North Pole? Class A all the way for them!

 

[Rottmannash]

The Benchmark is actualy on top of my list to test (listen=

The Benchmark AHB-2 is actualy on top of my wishlist to try, however it is not a powerful amp so you probably need 2 at €3650 each! Some of the old Gurus are still alive and kicking, Bob Carver please come in!

How much power do you need?!

 

[Angsty]

That's interesting and seemingly part of the conundrum. On one hand I hear in many cases with average speakers that our amps are usually barely taxed, e.g. if playing below 80 or 75 db. Others will emphasize that "you actually need more power than you assume" (e.g. for big peaks/transients). What's a poor audiophile to do?

Buy an amplifier with a lot of dynamic headroom, like the NAD C298 that I mentioned earlier.

Stereo Dynamic Power 260/490/570W @ 8/4/2 Ohms - https://nadelectronics.com/product/c298-stereo-power-amplifier/

"The C 298 is one of the lowest-distortion amplifiers I have measured, rivaling the less powerful Benchmark AHB2."

https://www.stereophile.com/content/nad-c-298-power-amplifier-measurements

 

[restorer-john]

...Say someone living on the North Pole? Class A all the way for them!

Powered by Huskies!

 

[JSmith]

Class A is dead

Agree and due to the wasted power they should probably be banned... do they even comply with new device energy requirements?

Had someone on another forum try to tell everyone that class A was an absolute must, especially for a couple of specific speaker types. Poster was rather taken aback when I found an article where the very speakers he mentioned had been compared on both class a mono's and class D Purifi, where the Purifi had no issue matching the output of the class A mono's.



JSmith

 

[rdenney]

John makes a good point about power specs, but I don’t know if it was ever really better. The NC502MP is rated at 350 wpc into 8 ohms. But that is measured at 1% THD, using test signal at 3 frequencies—100 Hz, 1 KHz, and 6 KHz. At the point where distortion and noise turn steeply northward, it’s more like 220 watts into 8 ohms, which is nothing to sneeze at. So, if it puts out 350 watts at 1% THD and 220 watts at 0.003% THD, might we rate it at 220 wpc and then state it has 2 dB headroom before it clips at greater than 1% THD? This assumes the implementation can keep it cool and shielded from noise. Most keep it cool enough for playing music at that level, but maybe not for playing full-power test signals indefinitely.

My B&K Reference 125.2 is rated at 125 wpc into 8 ohms, but over the audible spectrum and 0.09% THD. And they rate it for 1.2 dB dynamic headroom—165 wpc—but don’t specify the performance at that peak overage. But it is supposed to play a 125-watt test signal all day, with a S/N of -95 dB.

So, the NC502MP is cleaner and more powerful, but by the usual power doubling before it is “noticeable”? It doesn’t seem that easy to tell, but the older specs are less illuminating than those for the Class D amp.

Rick “waiting for the test of Adam’s new amp” Denney

 

[restorer-john]

At the point where distortion and noise turn steeply northward, it’s more like 220 watts into 8 ohms, which is nothing to sneeze at. So, if it puts out 350 watts at 1% THD and 220 watts at 0.003% THD, might we rate it at 220 wpc and then state it has 2 dB headroom before it clips at greater than 1% THD

That's the way amplifiers were rated, back in the honest days. A rated power where the low THD number at rated power was a major selling point and a decent amount of clipping headroom was desirable. (1-3dB)

The Hypex at [email protected]% is excellent performance and aligns with plenty of vintage high performance power amplifiers. Certainly nothing to be ashamed of.

Example:

 

[MakeMineVinyl]

Agree and due to the wasted power they should probably be banned...

Puleese!

 

[JSmith]

Puleese!

LoL you must like a heater in the room I gather?

Class-A amplifiers are inefficient. A maximum theoretical efficiency of 25% is obtainable using usual configurations, but 50% is the maximum for a transformer or inductively coupled configuration.

Class AB speaker amps offer high signal-to-noise (SNR), low THD+N, and typically up to 65% efficiency

Theoretical power efficiency of class-D amplifiers is 100%. That is to say, all of the power supplied to it is delivered to the load, none is turned to heat. This is because an ideal switch in its “on” state would conduct all the current but have no voltage loss across it, hence no heat would be dissipated.

Performance vs energy usage... class D wins every time. I also have vintage AB amps and a new class D amp... class A is just silly in 2021.



JSmith

 

[restorer-john]

Puleese!

And ban all V8s, ban leaving your lights on when you go out, ban houses without double glazing, ban burning a pile of dead leaves and ban billionaires taking rocket trips for a few seconds of weightlessness.

 

[restorer-john]

class A is just silly in 2021.

Nope. They do a nice job playing music and heating the room in winter.

 

[JSmith]

ban burning a pile of dead leaves

Well I'd like to see chimney's and open fires also banned... don't see why as an asthma sufferer I should need to struggle to breathe because some wanker wants to burn some wood.

heating the room in winter

Well better than an open fireplace anyway.



JSmith

 

[MakeMineVinyl]

Nope. They do a nice job playing music and heating the room in winter.

Mine with only two and a half watts of available output does a rather poor job of heating the room.

 

[Mart68]

Nope. They do a nice job playing music and heating the room in winter.

Yes this is very true, as I don't have central heat the KSA100 is very useful 650 watt fan heater in the winter months.
Although my daily driver is a KSA50S and that barely gets warm even after several hours of blasting it out.

I don't think there is anything necessarily 'magical' about class A, I just use these amps because they don't wimp out into low impedance load.
Maybe a big class D would also cope (the little TPA3116 certainly couldn't) but I stick with what I know works.

They can ban them if they like, I'll just ignore the ban

 

[Mart68]

. I feel like with these options available most big class A amps are for the ostentatious, or those in need of a space heater in winter.

Technical question - I have four big class A amps. Am I reaching the theoretical limits of ostentation?

 

[restorer-john]

Technical question - I have four big class A amps. Am I reaching the theoretical limits of ostentation?

Not even close. Relax, you have a long way to go. Buy a few more.

 

[tomtoo]

Technical question - I have four big class A amps. Am I reaching the theoretical limits of ostentation?

Ah come on, thats not even enough to do a stereo 3-way active system with them.