Class A and B differences?

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.

Jim

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.

Big,

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!