Class A standby/warmup optimization?

This situation of being "fully stable" and the people that suggest such things are IMO just a long-running type of old wives tale passed around.
And as well, it likely stems from amps being unstable in the first place, a sign of poor design.

Agreed. Unless someone can post glaring differences in measurements. Slight changes to THD yeah I can see happening but are you going to be able to hear the difference in 0.02% THD? Now test equipment is a different story. You can be sure a 6.5 digit meter needs a warm up time to achieve its specified accuracy.
 
^ Can't quite tell with your winky. Are you agreeing with astouffer and showing further specific evidence that some test equipment needs a certain amount of time to "warm-up"?

Are you quibbling over the difference between "specified accuracy" and "uncertainty specs"?

If neither, I don't understand. Please expand.
 
No, as per an earlier post by me, I disagree (wholeheartedly) with audio kit needing a warm up , nor (absolutely) the need for audio kit to be on 24/7 **, I do agree higher end test kit does need a warm up time to be precisely precise (ie adhere to the stated specs )


** although it keeps me in a job picking up the pieces of such behaviour 😀
 
I finally went back to dig up some of my source material for this thread. The following is from the F5 Service Manual:

Papa said:
The amplifier requires about 1 hour of operation to reach normal operating temperature, and this warm-up time is appropriate for the most critical listening, but is not otherwise an issue. The amplifier’s final adjustments were made after a 2 hours, and the performance difference between that and cold operation is significant.

I read two slightly contradictory points in that paragraph. The first is that allowing the warm-up time is only a concern for really critical listening, and that in most cases you can simply turn it on and go. The second is that, in Nelson's opinion, the performance difference between two-hours of warmup and cold are "significant".

I'd be interested to see some quantification for that. Once I'm done building mine perhaps I'll do some tests myself.
 
That goes back to... "It depends on the amp" mentioned earlier. You've even seen tube amps mentioned. The FW F5 and its clones have a pretty neat mechanism for bias control.

My guess is that you still won't reliably hear the difference between 2 mins and 20 mins of turn-on time or even 2 mins and an hour with an F5, but you may. I fall into the category of that "older crowd", so it's highly likely I'd never hear a difference. If I did, It would likely not matter to me. I rarely listen for <20 mins. A few tracks to warm up would not make a difference to me.

IF you do hear a difference, AND
- that difference is meaningful to you, AND
- you can't wait for the amp to warm up to a satisfactory (to you) level each listening session, AND
- you're concerned about energy costs / component wear / room temperatures for that particular amp in your particular situation, THEN
- a standby circuit of some type may be beneficial to you.

Onto the paragraph from the F5 manual - Those sentences are not necessarily contradictory. If I were to put it into my voice... NP would be the only one that could say if I got it correct... It's an educated guess.

1. Relevant to you the listener / retail customer. Amp needs about an hour to get fully warm, but don't sweat the small stuff for the time in between turn-on and fully warm. It'll operate just fine. tl;dr - If you can hear a difference between 2 mins and one hour, awesome, you may have golden ears.

2a. Neat info, but not necessarily relevant to you the listener / retail customer. In order to make really, really sure that the amp had reached equilibrium before making the final tweaks - we let the amp sit for two hours. This is double the one hour time we think it normally takes to reach equilibrium. tl;dr - you should never have to worry about your amp not sounding its best after extended listening sessions. After 2 hours, it is measurably different than "cold", but may not be measurably different to "1 hour".

2b. Neat info and potentially relevant to you the builder. You may want to make your final bias and offset adjustments after the amp reaches a steady-state. If NP and team do it after about two hours, that's probably a pretty good starting point.

All posts of mine should be prefaced with... IMO and closed with YMMV.

Nice discussion you started. I'll look forward to your measurements and observations. It will be fascinating. Sorry for getting a bit OT earlier.
 
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I finally went back to dig up some of my source material for this thread. The following is from the F5 Service Manual:



I read two slightly contradictory points in that paragraph. The first is that allowing the warm-up time is only a concern for really critical listening, and that in most cases you can simply turn it on and go. The second is that, in Nelson's opinion, the performance difference between two-hours of warmup and cold are "significant".

I'd be interested to see some quantification for that. Once I'm done building mine perhaps I'll do some tests myself.


Yes, the "in Nelson's opinion" is typical of biased thinking.
Leading the reader to become more of a fanatic than necessary.


All my amps require 15 seconds for the tubes to heat up, maybe 2 or 3 minutes to reach a settled temperature.
After extended running, things like bias and other factors change a microscopic tiny bit, but none of that is detectable by the average human during listening.
This is the simple fact that always was a known and accepted behavior.
As for solid state amps, it's ready instantly.




Of course, the internet and its plethora of opinions and suggestions have made people into worry warts and paranoid zombies.
 
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Yes, the "in Nelson's opinion" is typical of biased thinking.

That's the problem with all of this, no one, Nelson, or us, are sharing quantifiable numbers. If we were, then we could identify if we are on the same page. EG, if at 1 minute the bias current is stable to +/-1% and after two hours it's stable to +/-0.1%, Nelson could reasonable consider that "significant" and you could reasonably consider that "microscopic". But at least we'd be able to agree on what was happening.
 
Nelson is, above all, teaching ya all this years - to use your own brain and to trust your own ears and judgment

everything else is sharing his personal experience and few facts of Physics

if anyone thinks different ........ well:

- this is his own delusion
- Nelson really doesn't care
 
That's the problem with all of this, no one, Nelson, or us, are sharing quantifiable numbers. If we were, then we could identify if we are on the same page. EG, if at 1 minute the bias current is stable to +/-1% and after two hours it's stable to +/-0.1%, Nelson could reasonable consider that "significant" and you could reasonably consider that "microscopic". But at least we'd be able to agree on what was happening.


Your example of bias, the +/-1% vs +/-0.1%...... IS a microscopic deviation indeed.
And yes, my reasonable opinion is that it's insignificant and nothing to even worry about or even discuss.
But if someone objects to that, it's also my opinion that they're suffering from obsessive disorder, a known illness.
Because something so trivial as those variations would only be justifiable if we're in some research lab designing steering trajectory of a manned spacecraft destined to visit another planet.
Only then would it be important.


But here, we're discussing a consumer-level audio amplifier.
And this amplifier is to be used for entertaining human ears, which have normal human deficiencies.


After 45+ years in the audio service business, and having experienced just about everything about it, I'd say my feet are firmly planted on the ground with what to worry about, and what not.
 
I have a (commercial) tube amp that needs maybe 5 to 10 minutes to be real warm but after a few minutes it already sounds very good, and my aca needs less (2-5 min to warm, about 1 min to sound good). After that there is no difference i can hear, so if there is, it's so little that it does not matter. But audiofools like to fuss about those things anyway...

And leaving power hungry amps like that on 24/7 is a waste of energy and will wear out your gear a lot faster. This myth came from old neve studio consoles that had a very long bootup time so the owners left them on. But it was not sound that mattered, it was saving time because they did not want to wait an hour to boot up the consoles in the studio. And after a time they noticed those that were always on needed a lot more maintenance as the heat did wear out the console much faster so they quit this practice soon...
 
My tube amps? Maybe 3 minutes (hey, built-in heaters and no cathode stripping).

My SS Class A? Maybe 30 minutes because my tin ears can't tell the difference.

My chip-amp? As soon as I can hit the Play button on the source because it is a chip-amp made mostly from the spare parts bin and a schematic from Make.

I am too scared (and not well heeled enough) to catch any of the audio nervosa that seems to be always going around.
 
My tube amps? Maybe 3 minutes (hey, built-in heaters and no cathode stripping).
My SS Class A? Maybe 30 minutes because my tin ears can't tell the difference.
My chip-amp? As soon as I can hit the Play button on the source because it is a chip-amp made mostly from the spare parts bin and a schematic from Make.
I am too scared (and not well heeled enough) to catch any of the audio nervosa that seems to be always going around.


I find it interesting that general society's focus on electronic devices has become so widespread and laden with its own set of problems, some even quite dangerous.

I think a lot of this trend is due to advertizing, peer pressures, and the need to fill boredom in their lives for whatever reasons.
While they think they're pursuing something wonderful and needed, in a lot of cases it's actually a crutch to remedy some other fault, an imbalance, that needs attention.
(Think cellphone mania for an example)



From an older issue of Stereophile magazine:
Audiophilia nervosa. It's a running gag with a mean streak. As audiophiles, we know its effects intimately. We know how it can turn what was once a source of pleasure and pride—listening to good music over a good sound system—into an irritating itch that can't be scratched. The UrbanDictionary.com defines audiophilia nervosa (AN) as "the anxiety resulting from the never-ending quest to obtain the ultimate performance from one's stereo system by means of employing state-of-the-art components, cables, and the use of certain 'tweaks.' Although the goal is supposedly to achieve maximum appreciation of the music, those afflicted with this condition are merely obsessed with their electronics."