Class A and B differences?

I have been auditioning the Pass Labs X-250 amp along with the Spectron Digital amp versus my Kinergetics KBA-75 power amp. My system consists of a Sony SCD-777ES, BAT VK-30SE preamp, B&W 803 matrix series II speakers, Acoustic Zen silver ref. ICs, Hologram speaker cables, JPS digital AC and power AC cords along with an Audience power AC cord. I hear the differences between the amps but I was expecting to hear larger differences, like a WOW what have I been missing. The Pass has more detail and seperation but maybe 10% max 15%. Is that the difference between a class A rated amp and a class B rated amp? Or is my Sony CD player or B&W speakers not up to the Pass amp capabilities?

Your comments are appreciated.
Have you been leaving the Pass amp fired up 24 / 7 ? If not, try doing that and see what you think of it. Give it three days of "steady AC burn" before really giving it a good listen. Things may settle even more after that point, but they will be very gradual and take an extended period of time. The 72 hour "settling period" will give you a good idea of what the amp sounds like with the rest of your system. Sean
Personally, I think that 10%-15% is a pretty good increase in performance, when you are getting up into the higher levels. Remember, you get into that "diminishing returns" area at some point, where you have to pay alot more for each little increase in performance. At the top of the scale, a 15% improvement would be astonishing, and costly.

As far as Class A and Class B are concerned, the quality of implementation is the key, and not always just the A or B classes that may make the difference. A real good Class B design may sound better than an inferior Class A amp. It is generally accepted, though, that well done Class A amps will give the most sonic purity.

I can't comment on your exact comparison, as I have no experience with those amps personally.

And yes, the quality of the speakers and source will have a direct bearing on the sound that you get out of the amp.
I've owned amps that were rated class A up to a certain output and then transitions over to class AB. I can't say I've have heard much of a difference. Basically, class A amps have their output devices on all the time, where as class B devices are on only 1/2 the time. One device handles the positive waveform and another handles the negative. The crossover point is where distortions can occur. Whether it's audible or not depends on the resolution of your entire system. Not to nitpick, but when you mention class B I believe you are refrring to class A/B. Class B amps are very efficient but would not really make a good audio amp.

"but when you mention class B I believe you are refrring to class A/B."

No, I think he's right. "Class" A/B (althought there are plenty on the market) really isn't a class: its an amplifier that goes from class A mode into class B mode when the power demands reach a certain level. Randy Slone and Douglas Self among others cover it pretty well (saying exactly that) and many of their designs are Class B. I've seen other artcles on the internet that'll even state "Class B amps aren't used in Audio" and I don't think they know what they're talking about entirely. Incidentally, he does have a Spectron which is a Class D circuit and "even worse" than class A or B--loosely speaking. As TWL put it "the quality of implementation is the key."

I believe there have been a few previous threads on the subject in the archives now to help answer the original thread/question--can't vouch for the content though, but....
I retract partially--you may be right on the Class AB. But they both seem to be of the impression that to quote "Class AB is less linear than either A or B" and "is not really a seperate class of its own..." Or "Class B is by far the most popular mode of operation...." and many of there designs are just Class B. Parasound, Adcom, and Magnum Dynalab all claim Class a/b in many models. And Perraeux has that weird Class a/ab, which got me thinking more about what you said cause that would make sense for ab to be real, just a little weird.
The differences between various classes of amps can be very confusing, to say the least.

My take is this: For an amp to be rated class A, it's output devices (tube or transister) must be turned on all the time. Class B output devices are on 1/2 the time. Fact is, most amps are class A/B which is not, I supose, a separate class, but rather a combination, and their output devices are on more than 1/2 but less than always on.

Then to cloud the issue even more is the class G and H amps. Of course these are not really classes by themselves. Instaead, they use some sort of sliding bias or other means to make their power ratings appear higher than they really are. This is not necessarily a bad thing, I've owned such amps. Soundcraftsmen and Parasound are two such amps and I am sure there are many others. What about amps with switching power supplies? I think these are called class D and I am sure these are not normaly used in audio.

Thanks for the responses but in general I was referring to amp ratings by reviewer ratings and not the class A or A/B. My question still remians, if my Kinergetics amp was rated by Stereophile 10 years ago as a B rated component and the Pass X-250 probably an A rated amp, why is the Pass only providing a 10-15% improvement, I was hoping for more since the Kinergetics amp is a 12 year old design. Or is this what I should be happy with. I did not get goose bumps with the Pass like I thought I would.

Any help is appreciated.
Ooops! Big, if you ain't getting the bumps with the Pass, look elsewhere for now. UNLESS it's a matter of electrically matching yr pre to the Pass. OR we have to reconsider the set-up, as you imply in yr last sentence.

In this last instance, & if we leave the speakers out of the discussion for now & look at the chain upward, the ONLY excuse for the Pass is that it's amplifying ALL that it's getting from the preceding Sony & BAT combo (do follow Sean's advice & leave the Pass on for 72 hrs, however).

In which case, you may want to test the Sony direct into the Pass (using volume attenuation, of course). There are numerous mods for the Sony that, reportedly, help a lot & don't break the bank account.

As Twl implies, however, you may wish to reconsider the component to upgrade... perhaps a newer B&W? I think the "Wow" factor is hidden s/where between speaker & pre -- THEN power amp. But that's just me.
When I read your thread I was almost sure that you were refering to "Stereophile rating". This is always confusing, although the previous comments were still very interesting.

From my experience having a Pass X-350 and since I experimented with few other speakers and many other amplifiers, in my opinion I think the following:

1- Sean is right. Pass amplifiers need a very good break in period. After a week of using it you should notice another 5-10 % improvement.

2- I would not blame the Sony SCD-777, but the B&W 803. Your speakers are limiting the overall system performance.

First of all, I'd suggest that you consider the source for the class "A" or class "B" rating. These are just as you state, "reviewer ratings". Just trust your ears.

Secondly, some people prefer the "classic" sounding devices to the newer designs. Maybe that is a factor here.

I can tell you from my own personal experience that an audio component doesn't necessarily live up to it's price tag. For example, I've owned a Krell FPB600 ($12.5K) and a Plinius SA-250 MK IV ($8.5K) and yes, they sound quite different in my system. Both sound very good in there own respect. But, my preference has been with the Plinius. Is there a $4K difference? Not in my system. So here you have what TWL calls "diminishing returns". I also agree with TWL, that a 10-15% improvement is actually quite good, especially at the high end of audio gear.

Another factor to consider is how much difference will you hear in your current system by changing one component. Some times a very good component just won't shine in the wrong system. Could also be a factor.

Now, I've never heard the Kinergetics amp or the Spectron (yet), but I do have an opinion on the Pass amp. Pass! Some of Nelson's earlier designs sounded very good. IMHO, the new series of amps do not. I considered (auditioned) several Pass amps about a year ago.

One last word of advice, shop around. Listen to as many different amps (in your system) as possible before settling on one. Otherwise, you may wind up with a “for sale” post here sooner than you expected to.

Good Luck!
Listener is the first person I've heard to have the opinion Nelson Pass made better sounding amps in the past, meaning, I guess, the Aleph series. I own a Pass X-150 powering large ribbon speakers. The Pass X amps will faithfully pass along whatever you feed it. I don't like Sony, and wouldn't have one for my front end. I feel they sound too clinical. The B&W 803, a good rock speaker, does not have the resolving ability of an electrostat, panel, or ribbon speaker. I've been through a number of amps, and the Pass X amp proved to be a relevation. It doesn't sound like anything, really. It is substantially more dynamic than other designs I've tried. It's greatest achievment has been it's limitless sweet highs.

I just heard a Plinius 250 class A amp. I didn't learn anything about it because it was running some ancient speakers that colored everything. On the other hand, with my system's being ruthlessly transparent, any small change shouts out, wheher it be a tube switch or an amp switch. Most resently a visiting Llano failed to win my heart, to say the least.
I am not saying that the Pass does not sound good and maybe I should not expect more than a 10-15% improvement. I just WANTED to be so blown away that I had no other option but to buck up the $$$. I am hearing a very refined amp with the Pass, very musical, natural sounding, but I guess that I was thinking of 30-50% improvement from a $6K amp versus the $2200 ten year old Kinergetics. I asked the question awhile ago to upgrade speakers or amp and got a very mixed review. It was easier to audition amps in my home since many dealers are willing to let me try them out versus sending speakers. I also have the Linar Audio amp coming this week and possibly a BAT VK-500 or 6200. Any others? Most of the amps can be bought for $3500 or less new or demo so that would be my price range.

Thanks for all the repsonses.

I sort of misunderstood your original question about classes of amps. I personally take with a very large grain of salt the Stereophile class ratings. I understand their attempt to rate components, but to think that a class A versus class B component will have a quantifiable difference in sound quality is, in my opinion, not going to happen.

Of course, if I could afford some of the A rated components I would probably own them if for no other reason than pride of ownership.

I'm selling matched Mullards. These are being gobbled up by a lot of people. On my super transparent system, I found the Mullards to be objectionally colored. Why are they so popular?. On other less resolving systems, be it the fault of speakers, amps, pre amps, or front ends, the Mullards will assume a most pleasing lush sound. The point is, Bigkidz, if you move to more revealing speakers, you may find your older amp wanting. The Pass then, will have a much larger impact on your sound.

I found the speaker I wanted, and from then on I had to be very careful about my choices of component matches. Watching the used market carefully, I bought the X150, Aleph P, and Jolida NOS tubed 100 to feed my ribbons. The total outlay, including speakers, was about $6000.

What size room do you have Bigkidz?