Pass....Accuphase....or......

@southofdallas Here’s a little tip if you want the best sound for your investment $$$$.

The amp really should be loafing while doing its work. If your speaker is hard to drive the amp will make more distortion making it go. The result is the amp will sound less relaxed and less detailed because of the distortion increase which will be mostly higher ordered harmonics, to which the ear is keenly sensitive since it uses them to sense sound pressure.

On a speaker like yours if you push our amp too hard it will likely distort. The trick with any amplifier is simply make sure you have enough power so the amp is never working all that hard. Simply speaking you'd have to try it.

The problem is the more power you need for that, the harder it becomes to fine an amp that sounds like music rather than electronics.

if load is lower than nominal, one of devices indeed goes into cutoff!

@westcoastaudiophile That's true of a single-ended class A amp too.

@southofdallas Our amps have an over-current protection circuit that shuts the amp down if too much current shows up. Its got no problem driving 2 Ohms other than that. For example if there is a dip in impedance to 2 Ohms, if the speaker is an ESL that drops to 2 Ohms in the highs its no worries.

@southofdallas Class A means the output device or devices never go into cutoff.

There are class A push-pull amps and class A single-ended amps, which might be tube or solid state.

Class A is used to get more linearity out of the output section of the amp. If the amp is zero feedback this is pretty important. But depending on how much feedback is used it might be a lot less important, especially in modern designs where more feedback is possible.

Topping makes a line of class B amplifiers now that have exceedingly low distortion. From a designer's point of view, you use class A to reduce distortion, so in a way we can now see that the class of operation is far less important than it used to be. There are class D amps now that easily challenge any class A amp ever made.

If the amp is to be musical, IOW easy to listen to while being neutral, what is far more important is if the amp brings home the bacon in that regard rather than its class of operation! IOW there is far too much emphasis on the class of operation; probably that was important 30-40 years ago but no longer.

A48 is designed as class A amp for loads = or > than 8 Ohms. for loads < 8 Ohms it is a high-bias AB class amp. 

To be clear, 'high bias' class AB amp isn't a thing. Its either class A or its class AB. In this case, class AB. Any properly designed class AB amp will not have an audible 'transition' from A to the B region.

@southofdallas Where do you live? Our class D isn't the only you might consider, FWIW.

If I understand it correctly: the Accuphase class-A is a push-pull amp, the same as PASS LABS. Do they leave class-A at some level? How much class-A power does the A-48 deliver before drifting into AB?

@southofdallas This isn't a concern. If a class AB amp had an audible aspect where you could tell it was going into B mode, it literally would not be on your list.

If the amp is competent, the class of operation isn't important. The competence of the amp is! That is why there are class D amps that would do well on your list as well.

@southofdallas I've recorded stuff in the same halls I've played in. You get a sense of the hall and I wanted that in the recording. Each hall has a different sound to it so I describe that as the ambient signature. So yes, the ability to express that seems to fit with those terms (space, scale, spaciousness).

@southofdallas  Thanks!

I don't know that hall but I've played in a number of them here in Minnesota (bass in several orchestras so O'Shaughnessy, Orchestra Hall and the Ordway). I know what you're talking about but I'd never have thought to call that 'air'.

@southofdallas This is exactly why its a good idea to use speakers that are easy to drive. You don't have to sacrifice any resolution to have easy to drive speakers. Lower efficiency speakers tend to have something called 'thermal compression' which is caused by heating of the voice coils. The higher the efficiency of the speaker the less compression you get.

When a slightly lower power amp is driving higher efficiency/easy to drive speakers you find you can get the same effortless quality.

I always associated 'air' with ease and space in the highs. I've not heard of it used in the context that you do; probably a topic for another thread. 

It’s not so much high volume I’m after but dynamics.

@southofdallas Proper ’dynamics’ should arise from the signal and nothing else. Quite often amps can generate higher ordered harmonics which the uses to sense sound pressure, so just as often these harmonics are mistaken for ’dynamics’. So you can see that in many audiophile conversations you can replace the word ’dynamics’ with ’distortion’ and not change the meaning of the conversation.

I’ve found (using LPs and CDs I recorded personally) that the mark of the best systems is that of a relaxed, effortless presentation even at higher volume levels.

You don't need great power for that; just finesse.

@southofdallas Something to consider: In most rooms if you need more than 100 Watts to make the speaker fly, the speaker is likely impractical. This is for the simple fact that, to make the speaker sound twice as loud you'll need 10x more power; in this case 1000 Watts.

Its much easier to build a lower power amp that can sound like real music.

If you have a minute....I need ideas in that price range...+/- $$. Thanks!

@southofdallas There are class D amps out there now that are every bit as musical as the amps in your original post. Less heat too, and less cost as well.