Do Solid State stereo amps needs "warm up" time to sound good?

[john_k_antony]

Friends,

Do Solid State stereo amps need a good warm up every time you "cold" start it? Meaning you switch it on after they have been kept off for a while (more than 8 hours) and you have to play it for 30-45 minutes before it sounds good?

I have an Acoustic Portrait SS power amp and it needs a good 30-45 minutes of playing to start sounding good. When I do a "cold" start , it sounds very thin and bright. The bass and mid range shows up after 30-45 minutes .

I also noticed that I can hear a feeble humming sound from the speakers when no signal is fed, like a tube amp. The humming/distortion sound is heard from both the speakers.

Does the above symptoms sound like there might be a leaking / weak Cap in the amp that needs replacement?

Thanks,
John.

 

[hydrovac]

While it is true that solid state circuits have a warm up period, the aural effect is negligible, as all of the components have stabilized at their nominal operating parameters within about a minute of being turned on. However, unless the circuit is being used in a lab to take measurements that are of microscopic magnitude, the time between when the circuit is charged, to when it reaches full equilibration, is not important. The changes just cannot be heard by most people. Furthermore, if there is a very noticeable change in the quality or magnitude of the sound during warm up, then it's likely there may be a problem with that circuit to begin with.

So, are there measurable differences in the output of a solid state amp from the time it's turned on, to the time it has thermally stabilized? What is the engineering basis for this if there is?

Caps values and ESR shifts when it heats up??? And this is because of capacitors charging and transistors coming up to temp? As for the warm-up time, most transistors are likely to be operating well within their margins, so they will probably heat up slowly to the steady state operating temperature.

So leaving it on all the time is a good practice. Amps also take time to break in - may be months! Leaving it on also stabilizes the operating point. So when you want to listen, it is ready. The only negative thing about this is that in countries where the power fluctuation is very bad it might kill the amp if you get spikes or high voltage often. So you will have to do this judiciously.

My contribution to this thread is that I suspect that a "cool" amp is less sensitive compared to a "hot" one. So, experiment for yourself. If you hear a difference in the sound after the amp has "warmed up," then go with what you hear, and not with what I say. Your ears are the final arbiter in this discussion.

Cheers.

 

[john_k_antony]

Thanks for the excellent explanation. I do hear a significant difference. But I have to make sure if its my ears getting used to the original sound after 30-45 minutes or there is a difference. I will have another pair of ears access the same. I would attribute the difference in the quality. I feel the sound is getting more 'beefier' after the first 30-45 minutes. When it starts, it plays pretty 'thin' and 'bright'. The magnitude / volume level is not changed when the amp is warmed up. And the speakers are also old and they have properly run in. I felt the same issue with multiple sources. Initially I thought it was my new Oppo 105 taking time to warm up. I tried it with my 3 yr old Project TT -> Denon and Denon Pre outs -> AP Amp and felt the same behavior.

Also I hear a humming / distortion sound from the speakers when there is no signal. I think I should talk to Shiva from AP and find out whats going on.


BTW, the amp is quite old and has been properly run-in. I bought it used from a FM and I think i am the 3rd or 4th owner .

Thanks,
John.

 

[jagdish_p]

Amps also take time to break in - may be months! Leaving it on also stabilizes the operating point. So when you want to listen, it is ready. The only negative thing about this is that in countries where the power fluctuation is very bad it might kill the amp if you get spikes or high voltage often. So you will have to do this judiciously.

My contribution to this thread is that I suspect that a "cool" amp is less sensitive compared to a "hot" one. So, experiment for yourself. If you hear a difference in the sound after the amp has "warmed up," then go with what you hear, and not with what I say. Your ears are the final arbiter in this discussion.

Cheers.

While I could understand the heating up concept I can not reconcile to the fact that a number of people recommend breaking in of solid state Amps!

What could be the technical reason - there are no moving parts?

 

[asliarun]

While I could understand the heating up concept I can not reconcile to the fact that a number of people recommend breaking in of solid state Amps!

What could be the technical reason - there are no moving parts?

I mean this as a genuine question and not a "comment". I've tried to understand the rationale and basis of "breaking in" and in many cases, it makes sense. Mechanical and electrical components can have changes in their specifications and characteristics as they are used.

However, my question is, if the specifications change with usage, why is it that almost universally, the change happens for the better. In other words, why does the process of break-in almost always end improves the sound and never ends up distorting or worsening the sound?

Conversely, why do manufacturers sell us products that are out of spec? We spend a ton of money buying expensive audio components with the assumption that they will be well engineered. And a well engineered product should be "in spec" when you buy it. Other electronics that are far cheaper are manufactured with much better tolerances and QC.

Imagine if your refrigerator needed to run for 500hrs before it properly cooled and froze your food. It has more mechanical components than your amp (and is probably cheaper too).

 

[rikhav]

I dont have any technical explanation but my odyssey stratos amps sounds totally different after being kept on for about 1. 1.5 hours

Everything in sound changes for good. Infact the manufacturer recomends to never switch off the amp. But its not possible for me to do that

What i have read that its something to do with power caps being completely charged snd then the true sound of amp is heard

 

[manoj.p]

While I could understand the heating up concept I can not reconcile to the fact that a number of people recommend breaking in of solid state Amps!

What could be the technical reason - there are no moving parts?

Well, its the people who recommend breaking in of amps, not the manufacturers. If it was required, they would have stated so in the manuals. Sometimes, you would see this breaking in for few days recommended by dealers. You are most likely out of the return window by then.

John: Most of the time, its psycho accoustic playing the tricks. Same way as the car feels smooth after oil change. The only way for you to know if the frequency response is different is measure it - when its cold started and then after the warm-up. So far, nobody has proven it scientifically how it affects. Indeed, if warmup was needed, manufacturers would have mentioned it in the manual.

 

[asliarun]

I dont have any technical explanation but my odyssey stratos amps sounds totally different after being kept on for about 1. 1.5 hours

Everything in sound changes for good. Infact the manufacturer recomends to never switch off the amp. But its not possible for me to do that

What i have read that its something to do with power caps being completely charged snd then the true sound of amp is heard

You may be right - I don't know. But a cursory google search indicates that capacitor charging and discharging times are in the order of micro and milli seconds. So I'm not sure.

Maybe the circuit operates better at higher temperatures??

It still mystifies me why the sound always changes for the better.

Psychoacoustics cannot be that consistent and that strong a factor, right? I mean, take other examples. Do you feel that the sound in a movie theater or a music concert significantly improves after a period of time?

No, right?

 

[rikhav]

You may be right - I don't know. But a cursory google search indicates that capacitor charging and discharging times are in the order of micro and milli seconds. So I'm not sure.

Maybe the circuit operates better at higher temperatures??

It still mystifies me why the sound always changes for the better.

Psychoacoustics cannot be that consistent and that strong a factor, right? I mean, take other examples. Do you feel that the sound in a movie theater or a music concert significantly improves after a period of time?

No, right?

I am not at all sure, but with a movie theatre or a concert all the concerned equipment is kept on long before the actual show starts.

Maybe that's why one does not experience any improvement as the show goes on as it has already reached optimum levels

As I said earlier I don't have any scientific backing to prove my point.

But with my regards to my setup, I have experienced it several times in the last almost three years of owning the amp that sound reaches another level after a warm up around two hours

 

[jagdish_p]

I dont have any technical explanation but my odyssey stratos amps sounds totally different after being kept on for about 1. 1.5 hours

Everything in sound changes for good. Infact the manufacturer recomends to never switch off the amp. But its not possible for me to do that

What i have read that its something to do with power caps being completely charged snd then the true sound of amp is heard

There are two aspects being discussed here - the improvement in SQ after a warm up period of around 1 hour has been explained by FM Hdrovac in this thread. To me it sounds logical as its a known fact that the characteristics of the circuits change with temperature and the manufacturers design their circuits for steady state operating temperatures.

My skepticism is about the need to break in a new Amp over a period of time for a few hundred hours. I can understand this requirement for speakers as they have a moving coil with very close tolerances but the same should not be applicable to Amps and some people even recommend this for Cables!

 

[hydrovac]

While I could understand the heating up concept I can not reconcile to the fact that a number of people recommend breaking in of solid state Amps!

What could be the technical reason - there are no moving parts?

Possible theoretical (and probably not audible) is that some of the electrolytic capacitors that are overrated for breakdown voltage may gradually reform the insulating film at a smaller thickness and end up having a slightly increased capacitance.

One possible explanation is that the output devices /heat sink interface becomes more efficient after a while. So I could see an argument that its cooling efficiency improves slightly with burn in. Another possibility is that the heat in the unit bakes out residual moisture and solvents with a resulting slight increase in isolation resistance on the printed circuit board. This type of "burn-in" should be done at the manufacturer during final test.

The design of some low priced digital amps involves some kind of AC-based variable gain device to drive the speaker output. I don't know a lot about it other than it's comprised of transformer coils. Transformers like this are made of very long copper windings and known to be heat sensitive components that settle in when they are first put into service. I could be butchering this explanation but that's my short version of a plausible explanation seen somewhere.

Oh, here's a quote from a man who has designed some of the most incredible amps ever made. Nelson Pass, and this quote is from the owners manual of his latest amp the X series.

"People are interested in how long it takes for these amplifiers to break in. It takes about an hour for them to warm up, and this is where we adjust them first. Then we adjust them again and again over a couple of days, keeping the bias and offset in the sweet spot."

Sounds like he not only breaks the amps in for 48 hours for you, but adjusts them after break-in. Perhaps he's just wasting his time? I think not.
Would that change the sound of the amplifier? It's a long shot in my opinion, but there are aspects of the amplifier performance (e.g. heat sinking efficiency and possibly others) that can be changing over time so it's not impossible.

Cheers

 

[rikhav]

There are two aspects being discussed here - the improvement in SQ after a warm up period of around 1 hour has been explained by FM Hdrovac in this thread. To me it sounds logical as its a known fact that the characteristics of the circuits change with temperature and the manufacturers design their circuits for steady state operating temperatures.

My skepticism is about the need to break in a new Amp over a period of time for a few hundred hours. I can understand this requirement for speakers as they have a moving coil with very close tolerances but the same should not be applicable to Amps and some people even recommend this for Cables!

Hi
I was discussing about improvement in SQ after warm up

About break in of amps, I have no personal experience since I purchased my amp used

 

[asliarun]

Hydrovac, the snippet from nelson pass is different as he is talking about changing the amp parameters after running them them. I submit that this is part of any good engineering or manufacturing process. Heck even your car mechanic will take a test drive of your car and will then make some fine tuning before finally giving it to you.

But here you have some manufacturers that will not do it for you?? That is a strange notion, in my opinion, especially when the premium you pay for HiFi gear is precisely for the superior engineering. Companies boast about the brand of capacitors and resistors they use in their circuits and people ask for such upgrades by name, and yet we are willing to put up with a burn in process?

Jagadish - then why is the optimum operational temperature not specified in the manual? Most manuals don't even say that you need a warm up process. Again, considering the minutae and nitpicky specifications that companies reveal about their amps, something so fundamental should be written in bold and upfront. Right?

 

[jagdish_p]

Jagadish - then why is the optimum operational temperature not specified in the manual? Most manuals don't even say that you need a warm up process. Again, considering the minutae and nitpicky specifications that companies reveal about their amps, something so fundamental should be written in bold and upfront. Right?

Any Amp will heat up in the first hour of operation - and the manufacturer has to design assuming an ambient room temp between 25 to 30 deg centigrade . The Amps internal temp will be fairly constant - based on the load, cooling provided etc. So the temp armature effect may not be significant after the initial warm up and hence not specified. - just my guess

 

[kanwar]

Temperature plays an important role in Solid State devices.
What you call Break-in is nothing but setting of a thermal equilibrium of the circuit and its components. It happens every time you switch on the amplifier, it takes time to reach a certain gradient. 30 mins is good approach if some serious listening has to be enjoyed.

Yes , it has its effects on Sonics as well. There are technical reasons behind it.

A well designed circuit will be immune to it and will take much less time to reach that equilibrium than a poorly designed one with uncontrolled thermal stability.

 

[denom]

Friends,

Do Solid State stereo amps need a good warm up every time you "cold" start it? Meaning you switch it on after they have been kept off for a while (more than 8 hours) and you have to play it for 30-45 minutes before it sounds good?

I have an Acoustic Portrait SS power amp and it needs a good 30-45 minutes of playing to start sounding good. When I do a "cold" start , it sounds very thin and bright. The bass and mid range shows up after 30-45 minutes .

I also noticed that I can hear a feeble humming sound from the speakers when no signal is fed, like a tube amp. The humming/distortion sound is heard from both the speakers.

Does the above symptoms sound like there might be a leaking / weak Cap in the amp that needs replacement?

Thanks,
John.

Hi John,

Hum is not a good thing to have! Does the hum increase with the volume raised? Is it audible when music is being played? Does the hum go away after a while post warm up period? Does the amp have a 3 pin mains power cord?

Take the amp to Mr. Siva ASAP as he will be right person to diagnose best since the amp is made by him.

BTW, what pre amp have you paired the AP power amp with???

 

[denom]

Temperature plays an important role in Solid State devices.
What you call Break-in is nothing but setting of a thermal equilibrium of the circuit and its components. It happens every time you switch on the amplifier, it takes time to reach a certain gradient. 30 mins is good approach if some serious listening has to be enjoyed.

Yes , it has its effects on Sonics as well. There are technical reasons behind it.

A well designed circuit will be immune to it and will take much less time to reach that equilibrium than a poorly designed one with uncontrolled thermal stability.

So, time & again it boils down to technical knowledge, know how & ability of the designer/company for making a good product, that is less or not affected at all by external parameters that one has no control of.

 

[arj]

regarding Warm up..as the name suggests the equipment has been designed to work optimally with all components at a certain temperature and thats the time it takes to get there. The "standby" option means just that..ie the min current needed to keep the components at the right temperature.

Equipment breaking in...well it has extreme views like saying it is absolutely needed for 100* hours to that it is bogus and it is the ears which break-in. I guess the truth is somewhere in between ... and frankly why should it matter other than for theoretical discussions

 

[kanwar]

Let me put this way:

By Manufacturar:

Burn-in involves weeding out any instabilities in components, by pushing the amplifier into extremes of temperature handling and seeing for any failures, if not then its said as Tested OK.[In context with thermal stability concern]

By Consumers:

Break-in involves letting the amplifier reach its optimal thermal point with respect to surrounding environment i.e. ambient temperature.

If the thermal point is not tuned properly by the designer you have variation in break-in period and after effects as well. For example the Biasing of quiescent point of amplifier needs some expertise , if not set optimally will result in cross-over distortion which is inversely proportional to temperature rise and its audible.

 

[Robert Bose]

I have a 20 + Year Old well Broken in Power Amp and Preamp

I notice very significant change in sound quality for the better

after 15-20 minutes of moderate playing, It might be the speakers

sound is changing or the CD player who knows , but after 15 minutes

there is a very significant change in quality, I have not checked if

same thing happens with headphones or not

if you try turning the Vol up from cold the base is blurred and

dominating , the CD player is on Standby always so is the preamp

Its either power amp or speaker, we can check with headphone to

isolate power amp or speaker

Robert Bose