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

Kijanki -- Really excellent post!

As you undoubtedly recall, we discussed (and somewhat disagreed about) these matters a while back in the following thread, which discussed whether or not it is best to leave a system on all the time (although it was not addressing Class A specifically):

http://forum.audiogon.com/cgi-bin/fr.pl?htech&1228170308

For those who may be interested, in the last of my posts dated 12-3-08 in that thread I addressed the statistical aspects of this question.

Re your post above, I agree 100%, with the slight qualification that the phrase "last forever" be taken to mean "very unlikely to fail within a reasonable period of ownership."

Near the end of the other thread, in which a lot of people threw in a lot of conflicting opinions, one person asked if a consensus could be stated. I was the only one who responded, and I said:

I'm hesitant to declare that we have a general consensus. But in terms of reliability I would say the diversity of opinion we have seen is consistent with the opinion I expressed that, considering your frequent but not extreme usage patterns, you won't be going too far wrong either way.

In terms of sound quality, optimal warmup time is going to be system dependent, and probably listener dependent as well, so if you choose to have your system off during the day see if you notice continued improvement in sound quality following whatever warmup period you choose to use initially.

Perhaps this is a bit of an anticlimactic conclusion in view of all that has been said, but I think that any conclusions beyond these simple ones are unprovable, are probably not universal, and in terms of longevity probably don't make a lot of difference anyway.

Musicnoise --

Nor does an amplifier that is on but not driving a load use a great deal of energy so it shouldn't change your utility bill anymore than leaving a porch lite on 24-7.

That is not even close to being true in the case of a Class A amp.

It takes about 1 second of on time for a solid state amp to sound its best.

I don't think too many Audiogoner's would agree with you, based on their own listening experience. Although I am an electrical engineer, and I tend to be among the first here to recognize that perceptions about equipment performance that derive from listening experience can often be distorted by expectations, failure to control extraneous variables, etc., I would agree with them that you are incorrect about this. Notwithstanding the fact that to my knowledge a solid technical explanation of warmup effects has not been offered in the context of audio.

Regards,
-- Al

It seems I have to continue putting up with listen to music late at night after giving the system most of the evening to warm up. I didn't have the time yet to read carefully the thread on whether to power on/off (thanks, Almarg) just yet. But from what gathered, it seems like a hot debate. Also water evaporation on the electrolytic capacitor is a time-dependent thing. The longer it stays hot, the more time for water to evaporate. Yet regardless of where the truth lies, leaving expensive equipment on and unattended at the risk of power outage and surge is asking for trouble. Does anybody have positive experience using a constant power source to drive your equipment. I once tried a hefty computer battery. It sure kept the equipment on regardless, but the sound is awful.

Class A is the opposite of what A-B and Class D type equipment needs.. So Class A and Tubes need "LITTLE" time to warm up and sound there best... My Class A gear gets to good hot and excellent sounding idle in less than a Half hour.. Same with most tubes.

Class A-B and Class D designs do benefit from being turned on for hours or even a Day before critical listening, but that process can even be sped up by playing a music signal thru it and leaving the room.

In general I have tested several times and found that Class A gear and most tubes 40 minuets after start are pretty much 99% the same sounding as if you come back leaving them on for a day or three... Thats why many think Tubes and Class A sound better than some standard solid state gear which is the hidden potential, its simply Class A and tubes do in fact warm up and sound musically enhanced faster. This is from my experience, and some A-B stuff does sound nearly as good after a few more hours of music signal and warm up.

Class A turn it on a half hour prior, and turn it off when your done. A-B will take some experimentation to see if you find differences leaving them on all week.

"It seems I have to continue putting up with listen to music late at night after giving the system most of the evening to warm up."

Spatine - Can you hear it improving over time. Would you know if amplifier was ON for one or three hours? If you cannot tell then don't listen to somebody's recommendations.

You made excellent point about power outage and surge. I use surge protector but still turn off the switch while not at home and unplug my gear during thunderstorm or long absence. Surge protector works for small spikes but is useless for direct lightning hit. My insurance agent told me that stereo equipment is always insured independently of value (One doesn't need special insurance) but it's a little hard to believe.

My amp is class D and uses about 10W idling but I still turn it OFF - I don't see (should I say "hear") reason not to. In case of class A amps electric bills should be one more argument - unless one can really hear big difference over time and is willing to pay for it.

How about blind test - you come home from work and find your gear ON. You have to guess how many hours it was ON. This would perhaps tell us what is real and what is placebo effect.

Kirjanki, during that 4-5 hour warm up, sound quality fluctuation is serious. It can sound pretty good almost at start up, then sound hemped in again a few minutes later. Of course it still sounds better than the previous amp. despite the fact; however, that's not the point here. As to placebo effect, my hearing capability definitely changes from moment to moment. But this 4-5 hour waiting period has been going on for some time now. This definitely isn't so before I got the XA60.5, and behaves as such immediately right after I start using the XA60.5.