What could I expect to hear from a Class A amp?

I am familiar with Nelson Pass's very best current products. I have the pleasure of knowing a dealer who employs Pass components powering the towering Apogee Full Range speakers.

There are 600.5 amps handling the huge bass panels. The XA.5 100 finesses the mid and tweeter ribbons.

Through all types of music, and loudness, I never saw the power needles ever move on any of the amps. That would mean they are all running class A.

So, do both the 600.5 and the XA amps sound the same? The answer is no. I don't know why they sound different, but they do. The class A amps are clear, and easy listening amps. The 600.5 is forceful, and less open.

The question here is what is the difference between a wholly class A amp, and a powerful Class AB biased towards running in class A for around a fourth it's power rating?

Hi Almarg, I anticipated the questions you forwarded. The story of my visits to this dealer, to be honest, encompasses several visits. On one visit, I heard the 600.5 amps driving Apogee Scintillas, actually an even more ravenous ampere pig.

I use to own the Pass X 600 monos which I used driving my Scintillas. The ribbon array of the Full Range is very similar to the Scintillas. I was comparing the sound from the Scintilla powered by the 600.5 and the sound of the Full Range powered by the XA 100.

These Full Range speakers are not stock. They have been structurally reinforced, and the transformer loaded crossover has been chucked for a much simpler one. Ridding the speakers of it's transformer makes the speaker an even more torturous load for any amp. It was simply awe inspiring how a 100 watt amp can push the FRs to shocking loud levels, without any whimper.

Saying all that, I have to confess, the Pass sound from either amp does not approach the performance I enjoy with my class D system. Whereas the Pass 600 bloats the Scintilla's bass, my amps fully rule the Scintilla.

Next time I am there, we will replace the XA with my amps, the Pass XP -20 preanp for my Fire, the SCs for my ribbons, and even swap the sources. This should be fun, and instructive.

Ferrari, that would be calling me a fibber. Like I wrote, I used other conventional amps, including Pass Labs fair. Nothing ever came close, including the latest class A ware that approaches the fierce speed of resolution to the faintest nuances offered by my amps and preamp by the same maker.

I hope you don't mind me offering just few pointers when auditioning class D amps. First of all, don't be sure your system is conducive to class D amps. Secondly, there is a quality hierarchy applicable to class D amps as you found out.

On the first point, I have had the same monos and preamp for years of listening. During that time, the resultant sound moved through a series of personalities. At one time, it was airy and whimsical. Another time it sounded warm but focused.

After eschewing commercial speaker cables, and employed the short ribbons I use now, the sound took a revolutionized step. I upgraded my non oversampling DAC which I sent to Henry Ho of H2O to work his genius on. The stage stretched fore and aft, bass grew in heft and musicality, highs perfection, mids as natural as it gets. The last amazing surge in fidelity occurred when

I could go on and on. If I thought any of the class A amps could do me more, I would be happy to buy them. The knowledge Henry makes class D amps and class A preamps to be as squeaky clean as can be, I knew there was a way to harness the best possibilities.

The dealer I am referring to told me, "I am not an audiophile." He has a huge collection of discs. He sells monitors of his own design to recording studios where he knows recording stars by first name. Of course his amps and preamp are on all the time.

They sound wonderful, and to virtually all ears the music is as good as it gets. His Full Range speakers are spooky good, much better than stock. I have watched his gear and speakers improve steadily over the year.

I have a couple tell tale discs I took with me on one of my visits. One is a cathedral pipe organ recording. I told him you can hear the organist pull and push stops between pipe changes. It is something I take for granted.

Remember, he is using Nelson Pass's best 2 part preamp, XA 100 monos, and 600.5 monos. Even on listening for those wooden pegs, I could not hear them. On another disc, a brass quintet. The tuba and trumpet were recognizable, but the other three horns just became a background blend.

Where the XA amps excelled was on simple fair, such as voice and guitar.

You know these arguments can go on and on. SET/single driver adherents think we are both idiots.

Ahhh the wonders of ribbons. It's like running a space heater in a cold breezy outdoors.

Hey, I already said, the XA-100.5 monos did 115 dB without ever choking up on
any dynamic swing, and the X-600.5 never gassed out on heavy bass runs. The
needle never moved, staying class A. It blows your hair back, and to think they
are working a 1 ohm load throughout. The long ribbons never get warm.