[SteveFord]

This is kind of a touchy subject but I'll put in my two cents.
Many of the things that we build can be charted on a bell curve (an inverted "U"). 
As it breaks in it begins the upwards slope until it's at the top of it's performance capability and it should remain up there for quite some time.
Eventually things wear and degrade and it's all downhill from there. 
Take an engine, for instance.  As it breaks in horsepower rises and oil consumption lessens; as it wears, you have more blow-by, gasses are going past worn valves, parts get worn past tolerance and eventually it needs a rebuild.
I think that everyone here will agree that you can certainly hear the changes in speakers, headphones, tubes and cartridges as they break in and reach their optimum state.
On your own system it's only when things are really going downhill fast that you can detect when it's replacement time as the process is a gradual one.  You get used to the degredation in the sound quality because it's occuring so slowly.
Seemingly everything that we make changes over time and most things seem to improve when they're used on a regular basis - up to a point. 
If the performance (lifespan, if you will) of a speaker, tube, capacitor, etc. resemble a bell curve, it seems reasonable that most other things in your audio system would follow suit.
No scientific data but perhaps an EE could chime in as to whether or not my reasoning  is correct?

I just remembered something; somewhere in this thread there was mention of solid state and warm up.  I'm paraphrasing here but in the VTL Book, David Manley stated not to bother doing any critical listening until roughly 30 minutes had gone by. 
The tubes take only 10 minute to reach proper temperature but it was the wiring and everything else that would take another 20 minutes.
It's the strangest thing - when maybe 25, 30 minutes go by my systems just do a really abrupt snap into focus.  One second it's this sounds okay and then it's wow, this sounds great! 

[Steve]

I just remembered something; somewhere in this thread there was mention of solid state and warm up.  I'm paraphrasing here but in the VTL Book, David Manley stated not to bother doing any critical listening until roughly 30 minutes had gone by. 
The tubes take only 10 minute to reach proper temperature but it was the wiring and everything else that would take another 20 minutes.
It's the strangest thing - when maybe 25, 30 minutes go by my systems just do a really abrupt snap into focus. 

Nice points Steve. To expand further, warm up involves changes in capacitor and stray capacitance values (both tube and SS components), transformer winding capacitance/inductive reactance/leakage reactance changes (in tube equipment), and even resistor values, although normally minimal changes depending upon material used. Carbon is the most unstable resistance material that I know of in resistors.

Bipolar transistors change characteristics in dramatic fashion VS temperature changes and easily result in thermal runaway unless precautions are observed; but even then characteristics, resulting in different distortion products etc, can occur during warmup.

Test equipment almost always requires a period of warmup time to stablize, before measurments are taken.

Cheers.

[Letitroll98]

Ha!  Let's see, my guess is three major fights, two inferences of mental deficiencies, and one claim that your system (hearing) sucks right after a claim that that you'll say my system (hearing) sucks.  It will take two and 1/2 pages for the facilitator to post a warning and four posts after that to lock the thread.

Wadda ya think?   

Stay on topic please. 
This thread is getting personal and unfortunately isn't offering any particularly novel insights.

Darn!  I was a page and a half off.  Took him till page four for the warning.  I was pretty close with the insults and fights tho.

[Ethan Winer]

Ethan, you know very well, or you should,that a transistor based power amp will show a higher THD figure until the output devices reach their thermal equilibrium which is usually well above ambient room temperature.

But what is the actual amount of change? From 0.002 percent distortion to 0.001 percent? That's a good example of something that is measurable but not audibly important.

Tubes,being THERMIONIC devices also have a warm up period.

Sure, and tube amps (with their output transformers) tend to have higher distortion too. That's why I was specific and said solid state.

This thread is yet another example of people missing that their own hearing is not totally reliable. Someone earlier in this thread said a good system always sounds good. That is simply not true. A good system can sound not so good when you're tired, or hungry, or in a bad mood. Mood is probably the biggest factor. But even when in a good mood our hearing is highly variable. I honestly don't understand why this is so hard for some people to accept. It's not a flaw to hear things differently over time! It's simply how our hearing works. It's also the most logical explanation for why we perceive "break-in" or "warm-up" for a solid state device, or wires etc, when measurements show no change or very little change.

--Ethan

[jtwrace]

This thread is yet another example of people missing that their own hearing is not totally reliable. Someone earlier in this thread said a good system always sounds good. That is simply not true. A good system can sound not so good when you're tired, or hungry, or in a bad mood. Mood is probably the biggest factor. But even when in a good mood our hearing is highly variable. I honestly don't understand why this is so hard for some people to accept. It's not a flaw to hear things differently over time! It's simply how our hearing works. It's also the most logical explanation for why we perceive "break-in" or "warm-up" for a solid state device, or wires etc, when measurements show no change or very little change.

--Ethan

Thank You!  I thought I was the only one that thought this...guess we're the minority here.   

[SteveFord]

Your mood has a tremendous impact in how you think something sounds.
Sometimes you listen to an album or CD and can't wait for it to be over (too shrill, too muddy, hate the mix, hate the songs, whatever) and then you go back to it later on and you wonder why you shelved it for a couple of months.
It's been three decades but I'm still not willing to return to Side 2 of Live Peace In Toronto, though. 

[Steve]

Hi,

I am sure moods make some difference but does not explain what actually happens to a component during warm up. Since not much university scientific information has been presented, I thought I would expand on such for better understanding of heat related/warm-up concerns. Also check RCA Radiotron Designers Handbook, written by 26 engineers.

An audio component is actually quite dynamic during warm up, as we shall see. For ease in understanding, I am simplifying the discussion and not covering every issue. I am starting with parts, then negative feedback and comparing it to no feedback (open loop), as these have a major bearing on the discussion involved.

I think most understand that gainstage and passive parts conditions vary with temperature change, especially using bi-polar transistors, electrolytic capacitors, even transformers etc.

For example, under the most basic conditions, with no protection at all, bi-polar transistors are extremely heat sensitive and the hotter they become, the more collector current flows. "Thermal run-away" is the condition. This means that if enough power is available, "run-away" bi-polars will actually burn up (not including emitter followers). Of course such unstable conditions cannot be allowed to exist in any design but protection must be implemented. This information gives one at least an idea of what one has to deal with warm up issues with SS designs using bi-polar transistors. The problems are certainly no superficial. Tubes also require time to heat with the elements expanding and characteristics changing as well as passive parts changing characteristics.

Attempts to correct open loop variations (no feedback), such as harmonic distortion, frequency response, phase integrity etc, by applying some musical feedback voltage to correct the variations can help in certain respects, but also presents its own problems concerning warm up.

First, linear global feedback does not change the internal dynamics of a component per se. In theory it only samples the output of a signal, inverts it (180 degrees out of phase with the input signal), and feeds the inverted sample into the input, thus attempting to correct problems inherent in the open loop design. Global negative feedback can vary from little to very large amounts.

Linear global negative feedback reduces the higher gain portions of the audio band with respect to the lower gain portions of the audio band. Thus the bandwidth for a given -db is increased over the open loop design (no feedback applied). Imagine viewing a saucer bowl upside down on a table, viewing from the side. Now lower the top of the bowl (negative feedback applied). The bowl will appear flatter over a greater area, flatter frequency response over a greater range. Negative feedback "creates" a wider/higher frequency response as well as influencing other variables. (I hope the example helps one to understand.)
 
The actual effect of negative global feedback signal changes from cold to warm up conditions. Depending upon the open loop gain, bandwidth, phase response etc of the amplifier (which changes as it warms up) normal mid-band negative feedback (180 degrees out of phase with the input) actually becomes positive feedback at some high and low frequencies. Let's stick to the higher frequency example for ease.

Luckily protection measures are implimented to prevent oscillation from strong positive feedback at very high frequencies. However, just above mid-band  frequency, "A" the negative feedback signal becomes only 170 degrees out of phase with the input signal, a little higher frequency "B" 120 degrees, at higher frequency "C" zero degrees out of phase and into positive feedback territory (although not oscillation).
As the "warm-up" temperature rises, points "A", "B", and "C" shift/change (Using single points simplifies the explanation, but the phase shifts occur over many octaves in the audio frequency range.), with many variables changing as a result. So feedback is not just "static" by any stretch of the imagination. Neither are active and passive parts.

If steps are taken to limit each individual stage's warm up shifts/changes, such as using local current feedback, then gain is reduced which means more stages, more parts, and "more power supply", which are not sonically perfect by any stretch of the imagination. With more stages, more problems such as higher order harmonics, phase shift problems, feedback from stage to stage through the power supply, etc results. (And remember, linear negative feedback reduces all harmonics by the same proportion, not selectively. And the higher the harmonic, the greater the weight it has with relation to the second harmonic.).

If steps are presented to increase gain but limit DC changes, such as
bypassing cathode/emitter/source resistors with electrolytic capacitors (or even other parts), then we have added more DA and DF capacitor problems or other part problems which themselves are, or can be temperature sensitive problems. (Almost forgot, DA and DF problems include the huge power supply electrolytic capacitors as well as film capacitors, although to a lesser degree.)

So warm-up not only changes individual active and passive part characteristics, but varies the relationship between feedback, especially global feedback, and the variables in the open loop portion of the design itself.

As mentioned earlier, another problem that some may be encountering is system masking of inner detail, distortion, and spacial Qs. In such a case, musical changes may not be noticable with temperature rise but then the system is not resolving all the musical information either.

As one can appreciate, an in depth engineering analysis reveals that what is actually occurring as a component heats is quite complex involving many parameters, and secondly, a component is a vibrant, dynamic device, not "static" in any sense.

Cheers.

[KnowTalent]

Marketing Basis of Break In....

Customer: Hey, this doesn't sound better in fact I can't hear any difference.

Manufacturer: You need to give it more time to Break In...you'll be "amazed" at how the soundstage will suddenly blossom after 4000 hours!!!


 

[*Scotty*]

Ethan, you are just throwing numbers around with the change in distortion vs.the operating temperature of a SS amp, by the way the figures you cited represent a 100% change from .002 to .001. .
Lets suppose the SS amp starts at 0.1% THD and falls to 0.05% I would willing to bet this would be audible.
Plus in addition to this simplistic view of distortion the amplifiers IM distortion behavior when it is below its normal operating temperature has not been considered, nor has its behavior with regards to transient signals been examined. SS amplifiers are frequently not entirely stable before reaching their normal operating temperature. The amplifier might be ringing when reproducing transient music signals which would fail to be revealed if amp is only tested with a simple 1kHz sinewave. All of these factors must be considered when discussing SS amplifier performance cold vs warm. Of course the fact that all amplifiers are not identical designs must also be considered which pretty much rules out the applicability of any blanket statement about the cold vs normal operating temp. sound of SS amps.
Scotty

[srb]

Lets suppose the SS amp starts at 0.1% THD and falls to 0.05% I would willing to bet this would be audible.

I'll take that bet.
 
Steve

[KnowTalent]

Ethan, you are just throwing numbers around with the change in distortion vs.the operating temperature of a SS amp, by the way the figures you cited represent a 100% change from .002 to .001. .
Lets suppose the SS amp starts at 0.1% THD and falls to 0.05% I would willing to bet this would be audible.
Plus in addition to this simplistic view of distortion the amplifiers IM distortion behavior when it is below its normal operating temperature has not been considered, nor has its behavior with regards to transient signals been examined. SS amplifiers are frequently not entirely stable before reaching their normal operating temperature. The amplifier might be ringing when reproducing transient music signals which would fail to be revealed if amp is only tested with a simple 1kHz sinewave. All of these factors must be considered when discussing SS amplifier performance cold vs warm. Of course the fact that all amplifiers are not identical designs must also be considered which pretty much rules out the applicability of any blanket statement about the cold vs normal operating temp. sound of SS amps.
Scotty

When in standby mode....don't most manufacturers run a certain amount of current through thermally dependent components to avoid/reduce the cold/warm distortions you mention?

[Steve]

When in standby mode....don't most manufacturers run a certain amount of current through thermally dependent components to avoid/reduce the cold/warm distortions you mention?

Not really. Maybe a few but not many parts are covered, but then some are better than nothing.

Cheers.

[KnowTalent]

Not really. Maybe a few but not many parts are covered, but then some are better than nothing.

Cheers.

When you look at the standby power draw cited in specs of certain pieces...somethings getting heated! 

[werd]

Hi Steve

That explanation on warm up that i don't want to quote is excellent. It also gives a good feel of how some designers try and push the envelope in feedback to get as much out of their designs as possible especially in the higher freq neg global feedback that blow shit up.....lol

[jsaliga]

Marketing Basis of Break In....

Customer: Hey, this doesn't sound better in fact I can't hear any difference.

Manufacturer: You need to give it more time to Break In...you'll be "amazed" at how the soundstage will suddenly blossom after 4000 hours!!!

Customer: But I already have over 4,000 hours on it!

Manufacturer: Ok, 8,000 hours then.


Sorry, couldn't help myself. 

--Jerome

[*Scotty*]

KnowTalent,

When in standby mode....don't most manufacturers run a certain amount of current through thermally dependent components to avoid/reduce the cold/warm distortions you mention?
Posted on: Today at 07:53 PM
 

I agree with Steve on this one,I wouldn't count on it.
This complicates a design for a minor advantage in sonics, plus it uses up the designers budget and may cost you the benefits of what the designer could have built if he hadn't had to the spend the money on the standby circuitry.
If I had to chose between mute circuitry on a preamp or amp for protection against power interruptions and a standby mode,I will pick the former.
Scotty

[KnowTalent]

Customer: But I already have over 4,000 hours on it!

Manufacturer: Ok, 8,000 hours then.


Sorry, couldn't help myself. 

--Jerome

yes, I know it was juvenile of me but face it, if you've been in this hobby for long enough chances are you've had a similar conversation at least once

[Steve]

When you look at the standby power draw cited in specs of certain pieces...somethings getting heated! 

Read my previous post again. I think you misunderstood what I posted.

Cheers Know.

[Niteshade]

Hi Everyone-

I wanted to give you a heads up on how most soft-start power circuits operate.

When a TV, VCR, amp, pre, etc.. has a remote turn-on option there are two power supplies and usually twp power transformers involved.

When a unit is on standby, the main circuit has absolutely no power going to it. What receives power is the remote control circuit which is connected to the IR or RF input sensor. When the unit is powered on, a relay closes the circuit between the main power transformer and incoming power. This activates the rest of the amp/preamp/etc... When in sleep mode, everything except the remote circuitry is completely without power.

History: In the 60's, Motorola made a color tube TV which kept the filaments on when in "standby" mode. The result was a tube television which turned on instantly when the power button was pulled out. Yes, it did turn on faster than an 80's SS TV! 

[Letitroll98]

I am sure moods make some difference but does not explain what actually happens to a component during warm up. Since not much university scientific information has been presented, I thought I would expand on such for better understanding of heat related/warm-up concerns.....etc.

Thanks Steve, the only sensible thing posted so far.  This explains warm-up issues in SS components in a concisely worded fashion (re. simple enough for us dolts to understand).  And it explains why leaving my components always turned on results in a more stable audio presentation.  Now to the rub, how would one differentiate between warm up and break in, with break in being a permanent physical change to either a cable or component on the micro or macro level and warm up being the repeatable condition you describe?  For example, when we install a new cable or component we generally turn the system off for a period of time, cooling the system down.  When turned on are we hearing the system warm up, the component break in, or a combination of both?

As an addendum, how long can warm up last?  An hour, a day, a week, the mythical 4,000 hours noted previously?  When first turned on from a vacation period etc., my system sounds as harsh and brittle as a newly unboxed piece.  Of course it settles in after an hour or two, but if left on for 24 or 48 or 300 hours, it continues to smooth out.  And yes KT and turkey et al, it can certainly be my hearing that smooths out, but my question is there continued changes in thermal stability as the component ages over longer time periods?