And more importantly, can our ears even hear the difference?

If you are worried about fatigue, you probably should have returned the Axioms, as they are known as being a little bright. Also, you may want to check out the September 2004 Stereophile magazine where Sam Tellig describes the sound of the Cambridge 640c as "a tad hard". Not to say the Cambridge is a bad player, because it certainly is not. Perhaps, you are putting equipment with the Outlaw pieces that are just a tad bright for your listening preferences. As a 950/755 owner, I can say that the Outlaw combo is very neutral and will generally only pass along what it is fed. Good luck with your hunt for audiophile nirvana!

S.

Exactly! Interesting word SirA uses to describe the Axiom, "revealing". I would have used bright. I had a pair of Axiom M80's and returned them during the 30 day trial period, they were just to bright. I went with the polk LSI series.

Solid state amplifiers do have a warm up period in which time the bias current in the output stage stabilizes. Usually this is controlled by a thermal feedback loop, and until the heatsinks reach a stable temperature, the bias may not be optimum. In some cases, this could lead to a lean bias situation which could cause more crossover distortion than the amp would otherwise exhibit. The effect would be much more audible with extremely sensitive speakers, like my 106dB/Watt horns than speakers with medium to low efficiency.

Tube amps reach operating temperature more rapidly because of the much higher bias current flowing though the output stage in comparison to a solid state amp, and the fact that tube amps do not have heatsinks which slow the warmup process.

i usually keep my b & k amp on all the time, will this cause problems down the road?will it shorten the life?

Not really, as long as it is in a well ventillated area. It is standard practice in professional studios to keep equipment powered up continuously, and I've never experienced any unusual wear.

i kinda figured it would be ok, but better to ask and be sure.
thanks SH

I've got racks full of solid state power amps that have seen all forms of "duty": everything from left on most of the time to being switched off and on once a day. Two of them date from the 70's - others from the 80's and 90's. I've never noticed a correlation between "mostly on" and "off and on" with respect to failure rates. In fact only one amp has ever failed. But after a $100 repair it's been back in service ever since. One other amp had two lights in each power meter that, one by one, eventually failed. When the last one went, I took the amp in to the shop to replace all four. At the time the tech identified a handful of parts (caps, resistors and transistors) than were out of tolerance. Again after a $100 bill everything was back up to spec. But you know I never did hear a difference in that 30 year old beast - and it's still powering my centre channel speakers (where I'd be most likely to notice.)

So as to turning 'em off and on or leaving them powered? I now turn mine off and on simply because eight stereo power amps tend to consume a bit too much power, even at idle, to be left on all of the time. Except for outright major failure, with the occasional bit of maintenance every decade or two, I expect my solid state amps to potentially outlive me.

And that leads me back to the original post for this thread, and the very cogent argument put forth by SH. If my amps actually "broke in" during their first few hours, or days, or even weeks, after being first turned on, then that process surely must have continued until, by now, decades later, they'd be producing nothing but pathetic bleeps and chirps. But since that's not the case, my conclusion is that break in is a myth in the case of such solid state devices.

I'd also consider that my speakers broke themselves in the first time they travelled a cycle or two. And my phono cartridge? Once around a groove would have been about it. After that they're all very slowly wearing out - not breaking in! But luckily for me I can't hear a difference. (Then again I've got audiograms of my hearing response going back to 1981 and it certainly has changed over the years. So even if I were to postulate that my speakers sound different now than when I got them in 1979, given the fairly significant change in my hearing, I doubt that any change attributable to the speakers over their lifetime would come within an order of magnitude within what's happened to my hearing.)

Jeff Mackwood

Not necessarily. If your amps actually broke in, they'd follow the 3 rules of break-in:

1) Break-in always results in a change in sound (always for the better, never for the worse).

2) Break-in automatically stops (but it does so only when the sound is optimal to your ears).

3) Break-in never goes too far (e.g., an amp will never go from too harsh to just right to too mellow). See #2.

As you can see, the very nature of break-in wouldn't allow your amps to reach a point where they produce "pathetic bleeps and chirps".

who's rules are these?