Source of heat while at "idle"?

[PENG]

I seriously doubt the outputs are more efficient- electronics is nothing if not always trying to get more from less. The output devices need different bias voltage and current. The normal operating temperature is determined by the device, how much power is developed for output and how much is wasted and dissipated as heat. If it was Class A, you'd know it. 110 degrees would be when it's heating up or cooling down, but definitely not when it was cranking along. A Class A amp runs a lot hotter than this one. I can't think of a single purely Class B amp, either.

I never said the outputs are more efficient, I said the components but I was not thinking about the output devices. I could have meant the power supplies and the heat sinks combined with a big less crowded enclosure. I never said it was class A either. In fact I said it was definitely not class A, but could have been a class A/B with higher bias so it may be closer to A in terms of efficiency (meaning actually generate more heat compared to a lower bias A/B) but still an A/B. If you want to nitpick, closer could mean 1% closer. Basically I am saying that the Sansui has huge heat sink and the box is way bigger relative to the fact that it is a 2X85W integrated amp vs the Marantz 7X100W receiver with much more than just amps and preamps in it. It is possible that the Sansui in fact produces more heat on a per watt output rating basis but much less overall, and with much better cooling. Now if you want to continuing your nitpick practice then go ahead but I am done with it.

 

[PENG]

Update

With an infra red thermometer I was able to get the temperature of the inside. It actually reached a maximum temperature of almost 140 deg.F. under load and only a few degrees lower when idling. That's a little too close to the typical rated temperature of solid state components. My little CPU cooling fan is going to stay for sure as I want the receiver to last forever.

 

[Lordoftherings]

Some receivers runs hotter than others when just iddling.
It's perfectly normal; some different configurations in the circuitry from the power amp and preamp sections, transistors, plus video processing, DSPs, heat sinks adequacy, fan(s), etc., by different manufacturers.

If the OP (KEW) is bothered by his receiver running too hot when idling,
I simply suggest to turn it OFF, when not using it.

* But during winter time, that might be a benefit.

** Also, the use of an external fan can help greatly, as mentioned by PENG on the above post.

 

[M Code]

The reason some AVRs run hotter @ idle is the way the output devices are biased. Essentially the factory sets the bias higher so that output devices are partially turned on, think about it like a Class A operation.

Primary reason this is done is that the audio sonic output will be smoother from start-up, as the crossover distortion is lower...

Just my $0.015...

 

[PENG]

Some receivers runs hotter than others when just iddling.
It's perfectly normal; some different configurations in the circuitry from the power amp and preamp sections, transistors, plus video processing, DSPs, heat sinks adequacy, fan(s), etc., by different manufacturers.

No, that would not be normal, at least not for class A, B, & A/B amps. Normally they all should run warmer when actually doing its full duty of amplifying and powering speakers. When idling the heat mainly comes from the bias current and a little bit from the power supply transformer. If it is a full blown AVR then the video section should also produce some heat.

When loaded, it still produces the heat that it does during idling, plus the heat resulted from losses when powering the speakers. Since most of the time our amplifiers don't output much more than a few watts on average at normal listening level in an average sized room, the additonal heat produced when loaded is only going to be a few watts, that is negligible.

For example, let's say something like an Onkyo 875 consumes 120W when idling. And let's further assume it's average output is 10W when driving a 5.1 system. Given that class A/B amp efficency under lightly loaded condition is around 40% (i.e.60% losses/heat), the additonal heat will be 10WX0.6= 6W. That is only 5% more heat, you can hardly feel the difference. Now if you push the AVR to its limit so it is running continuously at rated output of say 100X7=700W (No one would ever do this unless he/she wants to go deaf instantly or risk blowing his speakers and the AVR). The efficiency at rated load would be higher, say 60%, the additional heat will then be 700WX0.4=280W. That is, 60% of the power is consumed to produce sound while 40% of it will be losses in the form of heat. So in this case, the total heat that has to be dissipated =120+280=400W, more than 300% of the heat produced during idling.

None of the above calculations are anywhere near accurate, obviously I over simplified the whole thing, pick some fictitious numbers and do the minimum math, just to illustrate the effect of load on the heat produced. Feel free to attack..., but be nice!

 

[highfigh]

No, that would not be normal, at least not for class A, B, & A/B amps. Normally they all should run warmer when actually doing its full duty of amplifying and powering speakers. When idling the heat mainly comes from the bias current and a little bit from the power supply transformer. If it is a full blown AVR then the video section should also produce some heat.

When loaded, it still produces the heat that it does during idling, plus the heat resulted from losses when powering the speakers. Since most of the time our amplifiers don't output much more than a few watts on average at normal listening level in an average sized room, the additonal heat produced when loaded is only going to be a few watts, that is negligible.

For example, let's say something like an Onkyo 875 consumes 120W when idling. And let's further assume it's average output is 10W when driving a 5.1 system. Given that class A/B amp efficency under lightly loaded condition is around 40% (i.e.60% losses/heat), the additonal heat will be 10WX0.6= 6W. That is only 5% more heat, you can hardly feel the difference. Now if you push the AVR to its limit so it is running continuously at rated output of say 100X7=700W (No one would ever do this unless he/she wants to go deaf instantly or risk blowing his speakers and the AVR). The efficiency at rated load would be higher, say 60%, the additional heat will then be 700WX0.4=280W. That is, 60% of the power is consumed to produce sound while 40% of it will be losses in the form of heat. So in this case, the total heat that has to be dissipated =120+280=400W, more than 300% of the heat produced during idling.

None of the above calculations are anywhere near accurate, obviously I over simplified the whole thing, pick some fictitious numbers and do the minimum math, just to illustrate the effect of load on the heat produced. Feel free to attack..., but be nice!

Would it be worth calling the manufacturer about this? Someone had to decide what heat sink would be adequate and they would have had to measure the temperature, so....

 

[Lordoftherings]

PENG, maybe you should design power amps and receivers.

* Anyway, I found the ideal solution; during winter time, I'll use my Onkyo TX-SR805.
And during the summer months, I'll get a Pioneer Elite receiver with ICE power.

 

[MidnightSensi]

PENG, maybe you should design power amps and receivers.

* Anyway, I found the ideal solution; during winter time, I'll use my Onkyo TX-SR805.
And during the summer months, I'll get a Pioneer Elite receiver with ICE power.

The ICE power amps I have seen seem to run hotter at idle than while being run hard, perhaps because their efficiency is less at lower output levels.

 

[PENG]

PENG, maybe you should design power amps and receivers.

* Anyway, I found the ideal solution; during winter time, I'll use my Onkyo TX-SR805.
And during the summer months, I'll get a Pioneer Elite receiver with ICE power.

No I won't do it because my company would go broke due to my over designed heat sinks. I absolutely hate fans! I installed one purely for peace of mind thinking that cooler means "extra" longer life, i.e. longer than what the manufacturer might have projected in their design.

By the way, I just took some voltage/current measurements. My 86 dB/W/M speaker drew 1 to 5A peak and most of the time less than 1A RMS at a voltage of 1.3 to 2.5 V rms and 12V peak when averaging 87 dB at 10 ft and 92 dB at around 2.5 ft.

When playing around with the measurements I had my ear plugs on because it was too loud for me. I did this little experiment first with the 4308 and then the 4B SST. Both yielded about the same current and voltages. I can now tell you for sure even when the amp was putting out 1 to 2W average with peaks up to 60W per channel, I had to wear hearing protection. Obviously to calculate heat losses we have stick to rms values, not peaks. So for most home applications, amps/receivers will not run noticeably warmer loaded than idling.

 

[Lordoftherings]

^ That is a very interesting analysis. Thanks for sharing with us, PENG.

 

[M Code]

Would it be worth calling the manufacturer about this? Someone had to decide what heat sink would be adequate and they would have had to measure the temperature, so....

Are you aware that UL and CSA have specific maximum temperature specifications that an AVR must meet before being certified.. The majority of heat issues raised with AVRs are usually due to one of the below factors..

1. Air Vents for the AVR
Often these are blocked by stacking components or installing in a compact shelf or wall unit without adequate air circulation around the sides, top and rear panel.

2. AVR Amplifier is Overdriven
Amplifier is driven beyond its design limits constantly at extremely high volume levels. And/or an inefficient, low sensitivity or low impedance loudspeaker is connected.

3. Listening Room is Large, and the power output capabilty of the AVR is too low.

4. High Dynamic Source Material is being played, and the entire system chain is being pushed beyond its design limits.

Just my $0.015..

 

[Lordoftherings]

So, about our Onkyo Receivers being UL certified (while running hot at idling)?
But then, some excellent power amps run quite hot too when just idling.

* And as mentioned by MidnightSensi; the Pioneer receivers with ICE power seems to run hotter when idling then full normal operation!
Anyone else noticed that?

Is heat a good sign or a bad sign?
According to some, it's bad.

And what about those high-end tube amps?
And those expensive transistor power amps running in Class A?

Are we just rewriting the books?

 

[PENG]

So, about our Onkyo Receivers being UL certified (while running hot at idling)?
But then, some excellent power amps run quite hot too when just idling.

UL/CSA/OSHA/NRTL etc., are less concerned about equipment longivity or performance than they are about safety (e.g. fire hazards). AVRs that are UL certified are safe to use as long as they are used properly, such as providing adequate ventilation. When people say Onkyo receivers run hot they don't necessarily mean there is anythiing wrong. If you follow the manufacturer's recommendations you should be fine but if you want it to run cooler than you can go beyond those recommendations by providing addtional ventilation or forced air cooling, use speakers that are easy to drive etc. If you can live with it running hot (again, only in relative term) then just sit back and enjoy.

* And as mentioned by MidnightSensi; the Pioneer receivers with ICE power seems to run hotter when idling then full normal operation!
Anyone else noticed that?

Those are class D amps so they do run cooler but when idling or lightly loaded they still produce heat, just not as much.

Is heat a good sign or a bad sign?
According to some, it's bad.

Electronics actually perform better when "warmed" up, but excessive heat is always bad. It is not a matter of opinion, it is a fact. Even if an amp is operating within the temperature limit designed by the manufacturer, many of the internal components such as the transformers and transistors will likely last longer if you let them operate at temperatures lower than their high limits.

And what about those high-end tube amps?
And those expensive transistor power amps running in Class A?

You already know class A amps run hot, but let's be more specific here. If you consider the internal components such as the transistors that are mounted on heat sinks, they will likely operate at similar temperatures whether they are inside a class A or class A/B amp. The only difference is, the ones in a class A amp, every else being equal, will produce more heat but it will also have heat sinks that are capable of dissipating the heat quick enough to keep the temperature of the PN junctions within the safe operating temperature range they are designed for.

Conversely, the same transistors uesd in a class A/B amp would likely be mounted on less (relatively speaking) capable heat sinks because there will naturally be less heat to dissipate. In other words, the owners of the amps will find their class A amps hotter because of all that heat produced by the power transistors, dissipated by the heat sinks and escaped through the top and side vents and then felt by the owner's hands. The power transistor themselves are not necessarily any hotter than their counterparts in the class A/B amps because they are sitting on heat sinks that are capable of removing the heat quickly by conduction; and then dissipate the heat by conduction to the chassis, radiation and convection through the space and finally out the vents.

Are we just rewriting the books?

Pretty much, if you prefer books you can always visit your local libraries.