A strange phenomenon

when i turn on my system the sound is good. dynamic,punch,transparent...
after a few hours the sound begin to be lazy. overall the sound is less good. like i need more power.

A few months back a very similar thread was started here by a poster with PSB speakers and a Musical Fidelity integrated. Going by memory alone, I believe he posted under the moniker "fishing716". Over 500 responses came in. See if you can dig it up in the archives. Tony (his name), are you out there?

Incidentally, the sanest response he got IMO came from an audio dealer in the NJ area who had dealt with a similar problem for a client and determined that there was a connection arcing over in the system owner's service panel which they discovered by darkening the room where the panel was and observing the periodic flashes as they occurred in the panel.

Again, going by memeory, it seems that fishing716 finally determined that the speaker wires were hooked up icorrectly but that never satisfied me because his system (like yours) would play fine for an hour or so and then suddenly go lifeless.
Perhaps it is an electrical supply problem to that outlet or the panel.
There is a surge and then a lag and the amp cannot compete with the irregularity. Personally I would be concerned with a "short" or some other
safety/fire hazard issue and bring an electrician. Last question, is there a periodic large power draw, like a well pump etc. Not an electrician but have
experienced dimming lights for no reasons etc. Lastly, I wonder if the
voltage regulators, capacitors or similar devices within the amp are functioning correctly.
Maybe after a few hours of listening you just get tired or bored. Your mental state could definetly affect your perception of the sound
If there is no technical problem such as something with your ac or one of your components, then it could simply mean that you have a poorly matched system that once warmed up just doesn't sound good. A system's sound will change when it goes from being turned off and cold to being on for a while and warm. Some never turn off a system because of the warm up process unless they have a system with a tube amplifier. You do not provide any information on your system. It could be the basic issue of amp-speaker matching (the foundation of any good system, imo). Putting together a good-sounding audio system with a separate amp, preamp, sources and speakers can be a real challenge. It requires research, auditioning, listening, trial and error, as well as simple luck sometimes. You can hit and you can miss.
Yes, Mr. Fishing's thread was entertaining with 500 comments, yet very frustrating. I also recall he had a wire incorrectly hooked up.
The most likely cause of his system sounding dynamic, then sounding anemic after warmup was a mismatch between amp and spkrs. His speakers had an impedance curve which went as low as 2 Ohms and he did not have an amp with enough current to drive them. I know he is still auditioning new amps with higher current.

Musicland1, what amp and spkrs are you using?
I tend to agree with what Arh said. Systems that have that initial "wow" factor tend to wear on the listener in the long run. You may be mistaking what you hear for listener fatigue. Symptoms can be as you described, the desire to do something else besides listen to music.

Turn the system on and let it play for 2 hours and leave the room. How does the system sound when you return? If it sounds anemic at first listen, then it could be an equipment problem. If the system sounds great and then falls off within 2 hours, it is more than likely listening fatigue.
"Turn the system on and let it play for 2 hours and leave the room. How does the system sound when you return? If it sounds anemic at first listen, then it could be an equipment problem. If the system sounds great and then falls off within 2 hours, it is more than likely listening fatigue."

Good idea!

Definitely assess how much your "mental state" and how it changes over time during listening might be a factor. Listening fatigue over time is not uncommon, and could be the cause with what you are noticing just the symptom.

VEry good idea to leave the room and come back. THat allows your ears to "reset" and make a second unbiased assessment of what you are hearing.

Then also make sure everything is set up correctly and in good operating condition, though this is often easier said than done. When a component system does not sound "right", the only way to determine the cause is via a series of regression tests, where you change one thing at a time and notice any differences, until finally you identify a prime culprit or suspect and then take corrective action. I always keep spare components around that I can substitute one by one to help identify where an issue may exist, but many may not have that option.

If everything appears to be in order, then next it is time to try easy no cost tweaks, like tweaking speaker placement, toe-in, listening position. etc.

THen once all else fails, you are in a better position at this point to really assess what kind of upgrades, if any, might help.

It all takes time and patience. ITs easy to try to throw money at the problem, but what is really needed first is knowledge and understanding of why something is either working or not.

IF changes are needed, buying used and not overpaying is a good strategy to enable experimentation without paying an unnecessary premium along the way.
Just a wild guess, faulty caps somewhere?