# Amps sound better when warm, huh?



## Hanatsu (Nov 9, 2010)

Heard this A LOT. Both in the home audio scene and on car audio competitions. Do amps actually sound "better" (or worse when cold) when they have heated up? Myth or not? If not, have anyone data to back it up or have any ABX blind tests been done?

(FYI, Never experienced any of this myself before... ^^)


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## Chaos (Oct 27, 2005)

I think I remember that being true of tube amps somewhere along the line, but never solid state.


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## jdsoldger (Feb 14, 2012)

Tubes take a minute or two for the heater fillements to come up to temperature. A lot of audiophiles claim it takes a lot longer for everything else to warm up as well and that it has to be warmed up to sound it's best. Honestly, our auditory memory is on the order of seconds, so I don't know how they make that comparison.

That said, almost all electronic components are temperature sensitive and their values will change with time, temperature and stress. Who is is to say that warm always sounds better? Maybe cold sounds better with some? Good designs are rather insensitive to this though.

My oppion on warm up ( and break in of non mechanical components) is to turn it on and enjoy the music.


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## minbari (Mar 3, 2011)

^^^ 


tube amps are the only ones I know of that need to warm up to work right. 

A pure Class A might have some argument for warming up first since the output transformer might change value slightly from cold to warm.

Most other solid state classes of amplifiers should work about the same cold or warm. Class A/B with BJT outputs might have some slight advantage once warm since BJTs conduct more one warm, but I dont know if you would hear it with all the feedback and gain control they have built in to those designs.


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## Jonathan (Oct 6, 2011)

I belive in the old theory:

In a class AB amp the biasing is very important for distortion. Not enough biasing and the dreaded crossover distortion starts. With production tolerances this can be a problem. You cant set the bias too high since some of the amps would overheat then.

BJT output devices need less base voltage as they get warmer. Usually some sort of bias current stabilization is involved (to avoid overheating), but often the biasing current is a bit higher with increased temp. With an amp that has a bit of crossover distortion when cold the increased bias can be enough to remove that distortion when hot.


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## Hanatsu (Nov 9, 2010)

Ok. All seem to have valid points here. It's good to know^^


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## steveholt (Feb 25, 2014)

interesting, i did not know this


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## FG79 (Jun 30, 2008)

It's like a car engine....you want to warm it up so it runs better, more fluidly. 

You don't turn on a car and immediately redline it in every gear. After it warms up a bit, it is in an ideal state for you to do whatever you want with it.

Audio gear is similar in a way although not as extreme. You don't have to wait 5 minutes before cranking the volume.

The sound quality is probably a little better warmed up, but not a huge difference.


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## NealfromNZ (Sep 3, 2013)

I've noticed a difference in my home hifi gear where the sound stage opens the most from cold in the first 20 mins and then will improve slighty more over the next day or so.
Used to leave my amps on 24/7 for that reason. (they've been hand built jobs with discreet mosfet and bipolar transistor designs in amps)

I get lesser a difference on my Yamaha HT rig.

Haven't noticed the difference in any car stereos I've owned due the clarity and environment of those systems , not withstanding the fact that you cant play vinyl through them.


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## mikelycka (Apr 4, 2008)

good read guys never thought about this


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## Rodek (Aug 19, 2006)

What about when the amp is nearing it's thermal shutdown point. It may or may not suffer from some sound degradation. I've seen some that do sound bad near thermal and some that keep pumping the power until the last possible point before shutting down to cool off.


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## CoLd_FuSiOn (Jun 25, 2012)

FG79 said:


> It's like a car engine....you want to warm it up so it runs better, more fluidly.
> 
> You don't turn on a car and immediately redline it in every gear. After it warms up a bit, it is in an ideal state for you to do whatever you want with it.
> 
> ...



+1 on that,i've definitely noticed a difference on my Mcintosh amps when I turn them on the first time in the morning and they sound better after 5 mins or so.


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## gijoe (Mar 25, 2008)

Since the intention of this sub-forum is to DISPROVE myths, I think that all of these subjective opinions are useless. At this point I call ******** on the sound changing an audible amount after anything more than a few seconds (if at all), however, being the open minded person that I am I can change my opinion if someone can provide some sort of evidence to support their claim.


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## miniSQ (Aug 4, 2009)

I'm sure its true to this day, but i remember back in my home stereo days, it was religion to leave your power amps on 24/7. This may have come from the tube days, but we are talking sold state here. i don't think i ever turned off my ARAGON 4004 monoblock for fear it wouldn't sound good if it ever cooled down.

There must have been some truth to it


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## BuickGN (May 29, 2009)

I don't think you can compare an amp to an engine. There are two main reasons we don't start a car up and make a full pass immediately and both have to do with longevity and reliability, not performance (assuming it's fuel injected). Piston/ring to cylinder clearance and thick oil. There are other clearances that change with temp but none that will matter. 

Cold thick oil can cause pump cavitation and when it's thick enough and rpm is high enough you're bypassing a good portion, recirculating it back into the pan. Some additives don't become effective until 160F. Cylinder walls are lubed by oil flung from the rod bearings that's squeezed out of the bearing. It's just not as effective when really cold. There are lots of reasons but I'll stop there. 

Cylinder to piston clearance, this changes more than any other clearance from cold to hot. The additional clearance when cold can cause piston rock in the cylinder and excessive ring wear. It can out a little extra wear on the thrust surface of the pistons. It's what most hear as piston slap. Usually harmless but not something you want to do every day when it's do easy to avoid by driving nice for a minute. 

Neither of these conditions cause a measurable loss in performance. In fact, a car will usually make more power during the warmup process as the denser charge air will more than make up for frictional losses. 

For a car, we drive it nice for a short while to increase it's life expectancy, not because performance sucks when cold. I've never heard anyone say you can hurt an amp by going full throttle right away , only the possibility of degraded performance. 

I'm convinced I hear an improvement from a 40 degree interior to a 110 degree interior but I've always suspected speakers. Anyone ever look into Class D amps and changes in performance related to temperature? I don't know enough about electronics to say anything but I can't imagine there being an audible difference hot to cold in a solid state amp. 

I know, useless info but I'm bored at work.


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## gijoe (Mar 25, 2008)

I agree with Buick that the engine/amplifier is a poor comparison. I also think that the trend of leaving an amplifier on is residual habit from the days of tube amplifiers. Comparing the sound of an amplifier from one day to the next with different temperatures is useless unless you are measuring real response, as mentioned, we do not have a very accurate memory with regard to hearing, unless the temperature change can be made drastically and instantly, using your own ears is not going to be reliable. I do not believe that an amplifier sounds any different when warm, but again, I'm open to being shown that I'm wrong.

Having said that, I do believe that the system as a whole can sound different in different temperatures, but I think this has much more to do with the speakers suspension and possibly the density of the air in the cabin.

Come on, somebody give us something scientific to work with.


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## CK1991 (Jul 13, 2013)

The only thing I can think of where there is an SQ difference from right when you turn it on is my home tape deck (Sony ES) when recording, and then it's only a couple seconds from when it turns on. With amps, I have never noticed a difference, especially in a car environment. Speakers when warm vs cold is a noticeable difference though.


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## 2010hummerguy (Oct 7, 2009)

Transistor performance is better when cold. In fact, transistor performance is extraordinary when super cooled as temp approaches zero degrees Kelvin. This is because you are not wasting any power to heat and you approach 100% efficiency. This is my non-electrical engineer understanding of supercooling theory 

The warmup myth only applies to tubes, not solid state.


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## NealfromNZ (Sep 3, 2013)

gijoe said:


> Since the intention of this sub-forum is to DISPROVE myths, I think that all of these subjective opinions are useless. At this point I call ******** on the sound changing an audible amount after anything more than a few seconds (if at all), however, being the open minded person that I am I can change my opinion if someone can provide some sort of evidence to support their claim.


Suggest you need to spend so time in a high end audio stores and train your ears to listen to the detail and report back. Its subtle, but you will be able to pick the difference. 

This is where I picked the difference when trying to find amps to match some kef speakers. Soon realised that the amps would change the depth and width of the soundstage with the position of instruments becoming more defined. The hot / cold thing didn't seem to change the dynamics however.

Being into electronics at the time I was at a loss to understand why this would occur in discrete solid state amps as most of the ones Id built I couldn't notice any real difference. Valves made sense, mosfet can exhibit similar behaviours thermally to valves but bipolar I was a at a loss with.


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## gijoe (Mar 25, 2008)

NealfromNZ said:


> Suggest you need to spend so time in a high end audio stores and train your ears to listen to the detail and report back. Its subtle, but you will be able to pick the difference.
> 
> This is where I picked the difference when trying to find amps to match some kef speakers. Soon realised that the amps would change the depth and width of the soundstage with the position of instruments becoming more defined. The hot / cold thing didn't seem to change the dynamics however.
> 
> Being into electronics at the time I was at a loss to understand why this would occur in discrete solid state amps as most of the ones Id built I couldn't notice any real difference. Valves made sense, mosfet can exhibit similar behaviours thermally to valves but bipolar I was a at a loss with.


Again, this is just another opinion. The purpose of this sub-forum is to disprove myths based on objective data. I agree that amps sound different, but I am not convinced that a solid state amplifier sounds different warm.


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## cajunner (Apr 13, 2007)

I've believed I have heard amp sonics change over a short time period, less than 30 minutes.

I remember something about this in Rockford Fosgate's explanation of their various circuits, that one of their circuits did a time-averaged setting of bias or feedback based on the amp's operating parameters, could be way off on this.

I think there is room for interpretation, and likely most amps are giving all they got from turn-on and will exhibit only the differences of temperature allowing more current to pass or crossover distortion to be blanked out, some of it may seem like it's trivial and some of it makes sense too.

As a myth, I'd say there's a problem reproducing the event of changing sonics when our auditory memory cannot extend through a full warm-up/cool down period for just about any amp.

Then we're relying on perception bias, and notorious as that sounds, is the bread and butter of audio sales people who can exploit our gullible natures as perpetual students of the human condition, led by our own desires to "have the best" or apply some non-logical bias of ownership that makes our amps, suddenly the winner that we knew them to be, back when we were wowed at the stereo store...

should you gain satisfaction by warming up your playback parts?

sure, why not? It's like giving a couple extra tugs on the ol' member before setting about inserting in some familiar place, nothing really wrong there if you get to the place you want to go, right?


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## Mapletech (Jun 20, 2014)

Not absolutely conclusive, but in the half-dozen studios I've been in, including CBC (=NPR), all gear is left on all the time.
Though I agree that solid state electronics work best when very cold, I believe the point of the studios is to have a consistent sound day-in, day-out, and therefore the global policy.

As for speakers...for some reason this thread reminded me of this - On outdoor winter gigs, especially multi-evening ones, we ran low level pink noise through the system when there was any long down-time such as dinner break, and especially overnight. Otherwise we were very careful to warm up the system carefully the next day.


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## ScaryfatkidGT (Mar 31, 2012)

jdsoldger said:


> Tubes take a minute or two for the heater fillements to come up to temperature. A lot of audiophiles claim it takes a lot longer for everything else to warm up as well and that it has to be warmed up to sound it's best. Honestly, our auditory memory is on the order of seconds, so I don't know how they make that comparison.
> 
> That said, almost all electronic components are temperature sensitive and their values will change with time, temperature and stress. Who is is to say that warm always sounds better? Maybe cold sounds better with some? Good designs are rather insensitive to this though.
> 
> My oppion on warm up ( and break in of non mechanical components) is to turn it on and enjoy the music.


Yeah I think they like making up fancy BS.

But that is another Myth, our auditory memory, for A/Bing 2 things we have never heard maybe but there are some things burned into our brains, voices et and we would know if they changed even if we hadn't talked to the person in 6 months. I got a new receiver and it made everything sound different even video games I hadn't played in months I could tell were off even after eqed similar to my old one.



FG79 said:


> It's like a car engine....you want to warm it up so it runs better, more fluidly.
> 
> You don't turn on a car and immediately redline it in every gear. After it warms up a bit, it is in an ideal state for you to do whatever you want with it.
> 
> ...


True, but I hate when people sit in there car and "warm it up" for a half our. Once you run it for 15 seconds to get the oil and stuff circulating wtf is the dfference between idling or running your car down the road but lets say not going over 2500rpm? I say nothing except it will warm up faster and you will stop freezing ur ass off sooner.



Mapletech said:


> Not absolutely conclusive, but in the half-dozen studios I've been in, including CBC (=NPR), all gear is left on all the time.
> Though I agree that solid state electronics work best when very cold, I believe the point of the studios is to have a consistent sound day-in, day-out, and therefore the global policy.
> 
> As for speakers...for some reason this thread reminded me of this - On outdoor winter gigs, especially multi-evening ones, we ran low level pink noise through the system when there was any long down-time such as dinner break, and especially overnight. Otherwise we were very careful to warm up the system carefully the next day.


I think thats mainly so the speaker surround and stuff doesn't crack isn't it?


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## Mapletech (Jun 20, 2014)

ScaryfatkidGT said:


> I think thats mainly so the speaker surround and stuff doesn't crack isn't it?


Yes - forgot to mention that.

Regarding the 'auditory memory' thing, I agree that it's relatively short, but I also think there are certain stages that listeners can generally agree on. Again I'm going to go from my experience outside of car audio, but when mixing soundcheck, I never really went much beyond a 'decent' mix, knowing how much the room would change once the waterbags (people) were in the room. For the first song, it would of course sound decent, but after that it's myriad small changes until the mix is finally 'in the groove'. Some nights that never really happens, at least not to my personal satisfaction, and other nights it just clicks. But when it makes it to that magic point, others around me sometimes give me a glance that says 'yep - it's there', including the lighting guys and so on. What I'm saying is that we can generally sense, in both measurable and immeasurable terms, and applicable to car EQ, my mix, and extending even to fine art, when something has reached a whole new level.


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## sirbOOm (Jan 24, 2013)

One of our demo cars at the shop with Pioneer Stage 4 gear "measures better" (according to electronics; I can't tell the difference) at a certain temperature (I forget what).


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## Hanatsu (Nov 9, 2010)

What exactly measures better? (just interested)


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## Ultimateherts (Nov 13, 2006)

I had an amp years ago (2000ish) catch on fire. Does that mean it would have measured better then not on fire?


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## Jepalan (Jun 27, 2013)

Ultimateherts said:


> I had an amp years ago (2000ish) catch on fire. Does that mean it would have measured better then not on fire?


Absolutely yes.


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