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Do you lose fidelity when an amp is hot?

NH-MAN

NH-MAN

Addicted Member
From my knowledge in a basic way electricity and components like the cooler side.

Now I do not mean abnormally hot just normal hot for what ever is being used.

I am wondering if I turn my amp up to 8 (1-10) does it sound better "initially" than when everything inside gets hot 20 min or so later?

Electrical things from my understanding become less efficient with heat which is the basis of my question
 
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NH-MAN said:
From my knowledge in a basic way electricity and components like the cooler side.

Now I do not mean abnormally hot just normal hot for what ever is being used.

I am wondering if I turn my amp up to 8 (1-10) does it sound better "initially" than when everything inside gets hot 20 min or so later?

Electrical things from my understanding become less efficient with heat which is the basis of my question
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If an amplifier becomes abnormally hot due to some fault, that may cause sound degradation.

Amplifier bias is normally set once the amplifier has reached operating temperature. If the heat sinks are doing their job, the temperature and bias will remain relatively constant at the lowest distortion point of the amplifier.

In other words, it will sound best at its normal operating temperature.

Running cooler improves longevity and reliability, but isn't necessarily where an amplifier operates most linearly and thus with least distortion.
 
DaveVoorhis said:
If an amplifier becomes abnormally hot due to some fault, that may cause sound degradation.

Amplifier bias is normally set once the amplifier has reached operating temperature. If the heat sinks are doing their job, the temperature and bias will remain relatively constant at the lowest distortion point of the amplifier.

In other words, it will sound best at its normal operating temperature.

Running cooler improves longevity and reliability, but isn't necessarily where an amplifier operates most linearly and thus with least distortion.
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I understand what you are saying but warm isn't cranked up some changes must be happening? No?
 
NH-MAN said:
I understand what you are saying but warm isn't cranked up some changes must be happening? No?
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Certain electronic components change value depending on temperature, but all components have a normal operating temperature range and any good amplifier will be designed so that all components operate within their acceptable temperature range. The overall circuit will be designed to assume a normal operating temperature range, i.e. "warm", and will produce least distortion within that temperature range.
 
DaveVoorhis said:
Certain electronic components change value depending on temperature, but all components have a normal operating temperature range and any good amplifier will be designed so that all components operate within their acceptable temperature range. The overall circuit will be designed to assume a normal operating temperature range, i.e. "warm", and will produce least distortion within that temperature range.
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So you are saying as long as the components stay within the advertised temp range they dont change much. what i mean is x resister has a temp rating of X or a capacitor has a temp rating of X
 
NH-MAN said:
So you are saying as long as the components stay within the advertised temp range they dont change much. what i mean is x resister has a temp rating of X or a capacitor has a temp rating of X
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Temperature ratings printed on the capacitor body indicate a maximum temperature, above which the life of the cap will be rapidly shortened.

Components do change value as temperature changes, but amplifiers have their bias manually adjusted within a nominal temperature range (i.e., "warmed up") and/or maintained by temperature-sensitive devices (typically diodes, or temperature-sensitive resistors called thermistors) that regulate circuit behaviour as temperature changes. This means changes in component value due to temperature changes are compensated by other components intended to react to temperature changes.

So when an amplifier is running within its intended operating temperature range, it is sounding its best.
 
Audio gear is not hard on electronic components. Some Class A amplifiers do run hot but by design. If that design does not include adequate heat sinks to keep temps under control then the amp dies and they don't stay in business. So most amplifiers operated normally will not sound worse at the higher temps operating conditions that might exist when you run them very, very hard.
 
NH-MAN said:
From my knowledge in a basic way electricity and components like the cooler side.

Now I do not mean abnormally hot just normal hot for what ever is being used.

I am wondering if I turn my amp up to 8 (1-10) does it sound better "initially" than when everything inside gets hot 20 min or so later?

Electrical things from my understanding become less efficient with heat which is the basis of my question
Click to expand...

No.
If class A/B, it might even sound better with a teeny tiny bit more bias :)
 
I run a Pass F5 amp of my own making and that thing idles at around 58C at the sinks: very hot for an amp. I usually let it idle until it's fully heated up before I do any listening because it definitely sounds better when hot. Transistors tend to be more linear the more current you pump through them, and that means heat, which also contributes linearity. The amount of heat a transistor can take depends on the type. BJT's are minority carrier devices very prone to thermal run away so you need to be very diligent about the heat they emit. MOSFETs are majority carrier devices with more benign heat vs. conductivity characteristics so heat isn't quite the problem. I personally have no qualms running a MOSFET upwards of 85C if the devices specs allow it.
 
NH-MAN said:
Thanks all of you I was just wondering as I like loud often.
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Tube equipment runs hot. Tubes "like to see the sky". Tube amps do need some space around them as they run hot. They sound best after about 20 minutes or so when everything has heated up and stabilized. Some power transformers run so hot its uncomfortable to keep your hand on. Power tubes can reach 300+ degrees! And they can keep chugging along like that for many years. A space heater that plays music, what's not to love!?
 
Modern amp designs take into account temperature changes to control parameters that other wise might compromise the sound. Now weather the manufacturer choose to use the knowledge is a choice. If on a tight budget or building to reach a desired cost plateau all sorts of compromises might be made. Most of the time we don't get what we think we are paying for.
 
I have a rule of thumb. If I can't hold my thumb on an output transistor without being burned, it is running too hot. That means either a bad design, or bad component somewhere. Likely the bias or output zero dc is off. Good amplifiers class A, AB, and B generally have more transistors on the output than necessary. So, at normal high volume operation these transistors will just run warm, not spit fry hot. I realize that to improve profit margin there are a lot of amplifiers out there that have too few transistors on the output and insufficient heat sinking.
 
Not sure about effect(s), if any, of heat on the sound quality, but y'all might lose yer amp. Try keeping it (well) ventilated.
 
tomlinmgt said:
I have an F5 clone, as well...this is good to know. Thanks for sharing that.
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Well, to be honest, I'm not recommending people build amps that run that hot. Each channel will get its own chassis at some point, but I'll still crank enough current through it to get it idling at 53C. I'm guessing 1.6 amp of bias.
 
I have a First Watt F5(built by the man himself). Does it run hot? You bet! Not so hot that you can't touch it,but hot none the less. Like stated already, I let mine idle for a while before any real listening. It sounds a bit thin when it's cold.
 
Technically, if the amp's RMS rating is accurate, it should be fine during "normal" operation. For me, that's pretty much cranked. And worth mentioning, hot is pretty much what tube equipment does, eh. My only rule of thumb is to make sure my amps can handle my listening requirements at around 80% of their rated output - that seems to be the sweet spot whre they hit their max output/min distortion for the most part and still leave clean reserve for major excursions.

** Only solid state heat issues I'm aware of is transformers - they can lose some drive as they heat, especially older iron. For solid state, I'd say paired "complimentary" transistors are about the only other component that will have issues if they don't heat evenly - You'll recognize those as their cases are normally bridged to facilitate that.

Short version ... if your equipment matches your usual needs, and is in decent shape electronically ... wango de tango!
 
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One factor not yet mentioned here is that amplifiers (largely all!), have negative feedback which generally 'equalises' matters. Still general, main amplifiers would have to be rather - er - compromisedly designed if an audible difference is apparent, even at the ends of its design 'spread'. In that sense I would frown on an amplifier if the sound changes audibly over the operating temperature range. Then I would imagine 'normal operating region' temperature-wise would differ substantially between say Iceland and the tropics (the amplifier would stabilise at different temperatures depending on the region). Having had the advantage of a climate chamber at some time of my life, I could not really say that ambient temperature variations were my greatest worry with any design, provided the basics were taken proper care of.
 
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