If this is true then the fault lies in the DVD-A reproduction and not with the amp. If the amp were at fault then CD reproduction would be bad as well. I have used several Class A amps but not DVD-A, which I didn't know was still around. Barring some incompatibility between the amp and whatever you are using for DVD-A playback there would seem to be no logical way for the amp to be at fault, just how did you propose that it could be?
It is hard to generalize among class A amps. There are class A amps that are still flat, strident, and dull.
Moving from a class AB to a class A topology, you might experience:
Increase in dynamics. Music is more energetic, punchy, rounded.
Less compression of the soundstage width and depth.
Better delineation of details with less strain or harshness.
I know this because I had an amp that could switch between A and A/B. The difference is not even close. It is like going from mono to stereo. I would not say that class A resulted in an artifically smooth sound, but there was more ease and less strain.
As said, there are great Class A amps, and inconsequential Class A amps. But keeping everything else constant except the A and A/B designation, the A should have a more satisfying sound.
The Pass XA.5 has a warmer midrange with more textural and harmonic richness compared with many SS amps. I would say that is more by design throughout, than due purely to class A.
Perhaps, it's more likely that Class AB amplifier(s) artificially roughen sound.
I am trying to come across neutral, that people would be more comfortable voicing either positive or negative comments about class A amplifiers. Personally I don't think it's an artificial compensation by Class A to make the sound more pleasant as some of us tend to suspect. I wrote because I want to see more people benefited from such healing effect of music; and I was so glad to have stumbled into Class A amplifier design that allows the sustained listening without having the headache and the disappointment I have had for years beforehand. What use is music if you cannot listen to it for so long. So I raised a case-and-point contrasting between DVA-A and CD reproduction both by Pass XA60.5. Nor do I think there is something wrong with the disc player which is Meridian 808. We all know that Meridian has spent a lot of effort to polish their DVD-A technology, and they receive nothing but compliments for their work. Personally I think the XA60.5 monoblocks transmit whatever they receive. If the source is good, then it's good. If the source is not ideal, then I am going to pay for it with a headache. Yet all of this is just my personal view. Any difference in opinion is more than appreciated.
No matter what the topology, all amps have artificial artifacts. Some are simply more true to the source than others. I think Rtn1 is correct in that specific design is what ultimately dictates the result. I own 3 class A Bedinis, a 25/25, 100/100, and a 250/250MKII. It's well known that the Bedinis are the SS amp that's trying to be a tube amp. They all have an upper mid-range "hump". The 25/25 is fabulous with extremely fine transients and upper detail. The 100/100 sounds similar as all Bedinis do, however it"s fatiguing with just too much upper-mid. The 250/250 is the best all-round balance with great bottom-end and flat response and I think that's the key. I have a couple of A/B amps as well which are extremely flat and sound very similar to the 250/250, only faster with better bass extension. Flat response is what reveals the source material. If all your source material has the same sonic characteristics, then I would say your amp is leaving something to be desired. Also, in my opinion, an amp with a slew rate of less than something close to 50 is not going to be satisfying and fatiguing. The 100/100 is just that, too slow. My Meridian Super Class-A is very fast, detailed and flat. Definately not fatiguing. However I do all my listening through my Leach Superamp mono A/Bs, which have a slew rate of 80. Even though their soundstage characteristics are not as good as the Class A's, their linearity and speed make them more pleasing.
We've made class A amps for a long time and one thing that has always been an issue is the revealing nature that class A can bring to an amplifier. If your digital gear does not have its ducks in a row, it can give you a headache. So I'm with Stanwal on this one.
Its hard to use digital as a reference. IOW if it gives you a headache with analog too I would be a lot more suspicious of the amplifier, although if you are suggesting that its the Pass, I don't buy it- they make some of the best transistor amps made.
I'm not sure music was meant to be listened to "for so long". I think even live unamplified music can become fatiguing if listened to too long.
If you get a headache after 20 minutes, that is not going to work, at least not for me. I like to be able to listen fatigue free all evening long.
No, other classes artificially harden sound...;)
Class A amplifiers don't exhibit switching distortion.
A Pure Class A amplifier is running 'full out' all the time--AB amplifiers run (about) 5 Watts of output all the time, and when the volume needs exceed that output the B transistors switch 'on' and that's where the so called switching distortion can be heard.
Put it this way. Let's say you own a speaker that's 88db 1W1M which is to say that a steady tone with at 88decibels will create a need for 1 watt of output from the amp. At 91db, you're using 2 watts, then at 94db 4 watts of power.
So, depending on room size listening tastes and program material, right at the edge of the sound exceeding 94 db, the B transistors 'cut in' and therein comes the 'switching distortion'. That distortion is more noticible in some amps than others, depending on too many factors to tend to in this short space.
The Class A isn't necessarily smoothening anything, it just doesn't have the issue of the swich from one bank of transistors to the secondary ones.
I hope this makes sense.
I am not the leading expert on this but know a little about it. If I can answer any questions on this just let me know.
What DVD-A offers, at least in my system, is more detail. Positioning of instruments is more distinct as well. It's good in the precision area, and not so good in harmonizing and flowing instruments and voices together. In live performance everything is obviously more precise, but these sound sources propagate together toward you. It's nice to precisely know where the individual sources are in DVD-A. But if they approach you in a disjointed fashion, your brain would naturally do extra work to subliminally help you think that you actually listen to somebody singing in natural setting. That extra work is part of causing the headache. It's also interesting to note that the extra detail does not apply to the entire frequency range. Detail in the midrange,particularly voices, is actually reduced with DVD-A. Thirdly, the extra force and intensity of DVD-A sound is also unnatural. That extra pounding does not help the headache either.
My point is this sort of observation, with such descriptive words, occurs a lot in posting involving Class A vs other amplifiers, or tube versus SS. Well, this contrast between DVD-A and CD listening, at least with my system, appears not to support categorizing amplifiers as such.
Spatine, no arguments about the increased resolution of DVD-As! From your comments though, it sounds as if your DAC is creating HF noise which is making it painful. I doubt its the DVD-As myself. Its this comment:
In one case (redbook CD), I can listen to music for hours. In the other case using the same amp. and disc player, I got tired rather quickly (within 30 minutes).
that makes me think the amp has nothing to do with it in this case.
Atmasphere, I am using the analog out of the Meridian 808, thus its own DAC. Yet with such contrast between CD and DVD-A, this has nothing to do with the Pass XA60.5. Comments thus far seem to support my original thought that what you put in (meaning the source disc) is what you get out. Comments that Class A amplifiers are too relaxing, too sweet, or too pleasant might not be as definitive as some people think. In fact it's the same comments that many people think of all tube amplifiers. I don't think so either, but that is a different subject from the focus here.
I don't understand how a DVD-A can give you a headache. I don't listen to DVD-A's but I do listen to SACD's and I can't ever remember a situation where my SACD's sounded worse than my SACD's. There may be some artistic license with mixes and multichannel that does not sound "right" but more fatigue from a superior software doesn't make sense to me. Atmashpere's may be on to something. Perhaps there something going on with the DAC.
Bjbcab, I hear you. Don't ask. What I heard is what I tell everybody. I used to prefer DVD-A over CD back in the days of using Class AB amplifier however. My reasons then were probably about the same as yours.
Perhaps the OP should stop by the Pass Labs website and read a few of the articles Nelson has written. Especially the one titled "Leaving Class A".