Do Pre-pros & AVRs have lower output when too cold?

[AcuDefTechGuy]

When I placed four 120mm cooling fans atop my Denon AVP-A1HDCI and Denon x3100, the speaker channel levels (volume) are about 6dB lower than if I only have 1 fan or no fans at all.

Yes, that's a 6dB volume difference!

Because of this, I removed all fans atop my AVP-A1HDCI and used only 1 fan atop my X3100.

I have verified 3 different times using a SPL meter. Each time, the ATI amps, AVP-A1HDCI, and X3100 have been on for 1 hour.

So the only thing that changes is the number of fans atop the AVP-A1HDCi and X3100.

Why does this happen?

Do Pre-pros/AVRs have lower volume output when they are "too cold"?

Is this the reason why some people say that amps sound better when they are "warm" and why some people even leave your amps and preamps on 24 hrs a day?

I won't be recommending to people to place more than one fan atop their amps and preamps anymore, unless it's a class-A amp or an Onkyo.

 

[slipperybidness]

When I placed four 120mm cooling fans atop my Denon AVP-A1HDCI and Denon x3100, the speaker channel levels (volume) are about 6dB lower than if I only have 1 fan or no fans at all.

Yes, that's a 6dB volume difference!

Because of this, I removed all fans atop my AVP-A1HDCI and used only 1 fan atop my X3100.

I have verified 3 different times using a SPL meter. Each time, the ATI amps, AVP-A1HDCI, and X3100 have been on for 1 hour.

So the only thing that changes is the number of fans atop the AVP-A1HDCi and X3100.

Why does this happen?

Do Pre-pros/AVRs have lower volume output when they are "too cold"?

Is this the reason why some people say that amps sound better when they are "warm" and why some people even leave your amps and preamps on 24 hrs a day?

I won't be recommending to people to place more than one fan atop their amps and preamps anymore, unless it's a class-A amp or an Onkyo.

For SS gear, this seems odd to me (suspect). For tubes, this is a given.

@TLS Guy should be able to enlighten us.

 

[TLS Guy]

For SS gear, this seems odd to me (suspect). For tubes, this is a given.

@TLS Guy should be able to enlighten us.

Well I had never thought about this before. What an interesting observation.

Now IC and transistors are basically triodes. They are a sandwich, with the base between emitter and collector. The low impedance emitter base junction is generally the low impedance junction and the input. The base collector junction high impedance and the output. As current flows through the base emitter junction electrons are sneaked across the base collector junction and amplification occurs. The gain is called the beta of that device. Well it turns out that beta is temperature dependent and decreases with temperature, so gain will decrease with temperature.

Optimal temperature for most devices is 55 to 85 C.

This is of interest to me as I recently got into something of an argument about the temperature of my Intel i7 seventh generation processor in my new DAW. The temp spec for this device is higher than I am used to and the also what the computer experts on this forum are used to.

Anyhow I put in expensive quiet cooling fans. Now this dual fan is controlled by the board from a signal form the temperature sensing device in the chip. Now the fans in use run slowly. The temperature of the device is running right in the midrange specified by Intel. Even under max stress it does not exceed max temp. However the experts here advised more cooling as they thought it was running too hot despite the spec. I resisted, reasoning that the fans could speed up if they got a signal via the board from the chip temp sensor.

So I think Intel know about this and the chip is choosing the optimal performance temperature.

The problem that ADTG has uncovered is very interesting as we are talking measurement here and collected data with exclusion of variables.

From what I have discovered for most devices then the optimal temp at the devices, and I stress at the devices is 55 to 85 degrees C.

So yes, ADTG has drawn our attention to the fact you can over cool. I had previously not considered the problem of beta being temperature dependent, only catastrophic thermal runaway at very cold temperatures.

This can be a problem in our winters here in severe cold snaps. It was a big problem in the early day of ECMs, but you hear much less about it now. So the devices car manufacturers use must have a lower thermal runaway point than they used to.

 

[KEW]

Wow! 6dB is a lot of power increase.
So that leads to a question of how to decide if you are better off running cooler and increasing the volume to compensate?
Ideas?

 

[AcuDefTechGuy]

Wow! 6dB is a lot of power increase.
So that leads to a question of how to decide if you are better off running cooler and increasing the volume to compensate?
Ideas?

Absolutely significant difference in volume! Not just 1dB, but 6dB!

It's a balancing act.

The Denon X3000 and lower series get really hot, so I think at least 1 or 2 fans is a must. This will decrease the temperature just enough, but not too much. When it gets too hot, these Denon AVRs will shut down in protection mode.

But the AVP-A1HDCI, AVR-5308CI, X7000, X6000, X5000, and maybe X4000 series don't seem to get that hot. So I think adding cooling fans here probably doesn't add any benefits.

Don't fix something that's not broken.

 

[slipperybidness]

I had previously not considered the problem of beta being temperature dependent

Yes, that is quite interesting! I don't recall ever seeing mention of Beta being temp dependent in any of my school books. I could have missed it, we typically would not be looking at that in the labs, unless we are looking to utilize that phenomenon for some reason.

 

[slipperybidness]

It's a balancing act.

Having to increase 6dB volume means having to increase a lot more power than usual, which can be detrimental for the speakers since we know too much thermal energy will fry the drivers, especially tweeters!!!

The Denon X3000 and lower series get really hot, so I think at least 1 or 2 fans is a must. This will decrease the temperature just enough, but not too much. When it gets too hot, these Denon AVRs will shut down in protection mode.

But the AVP-A1HDCI, AVR-5308CI, X7000, X6000, X5000, and maybe X4000 series don't seem to get that hot. So I think adding cooling fans here probably doesn't add any benefits and may just be detrimental for some speakers.

I don't think the goal should be so much "cooling the devices", but rather "moving away the hot air so the devices are more efficient at self-regulation."

 

[Pogre]

How very interesting. It's funny, when I started up some music this morning I thought "man, that sounded a lot better last night" and just brushed it off as my brain being fickle. Well now my music seems to sound "better" after a couple of hours of warmup. Again, I brushed it off as acclimation.

Now it appears possibly I'm not imagining and there could be something to it? One of these days I'm gonna check spl when I first fire my system up, then again after its good and warmed up. My curiosity is definitely piqued.

 

[TLS Guy]

Yes, that is quite interesting! I don't recall ever seeing mention of Beta being temp dependent in any of my school books. I could have missed it, we typically would not be looking at that in the labs, unless we are looking to utilize that phenomenon for some reason.

I had not either. But from our nuclear physics education it should not surprise. The motion of all atomic and molecular particles is temperature dependent. If you don't believe that, then consider boiling liquids.

As you heat the liquid the molecules dash about faster and faster, until more and more get to escape trajectory speed, and eventually not just at the surface but deep in the liquid until you have a rolling boil.

So the electrons in the semiconductor will be more agitated and ready to move as they speed up.

If you think about it, when you touch and object to see how hot is is, your brain is actually measuring the speed of molecular activity!

 

[MrBoat]

So none of this could be caused by a voltage drop adding 4 more fans to the current draw? Is all of this from the same outlet. Just seems there would be a noticeable difference when first starting the system and say, a minute or two in. If nothing else, it seems the load vs. the circuit capability should be mentioned. I know a lot of home systems are near or at their limit more often than not, with crowded power strips and whatnot. My home is limited with outlets and I have considered adding other breakers and outlets just for the amount of power strips employed here for my meager setup.

 

[AcuDefTechGuy]

So none of this could be caused by a voltage drop adding 4 more fans to the current draw? Is all of this from the same outlet. Just seems there would be a noticeable difference when first starting the system and say, a minute or two in. If nothing else, it seems the load vs. the circuit capability should be mentioned. I know a lot of home systems are near or at their limit more often than not, with crowded power strips and whatnot. My home is limited with outlets and I have considered adding other breakers and outlets just for the amount of power strips employed here for my meager setup.

I have 2 dedicated 20-Amp circuits in my HT closet. The 3 ATI amps are on 1 dedicated 20-Amp circuit. The Denon AVP-A1HDCI is on another 20-Amp circuit. The 4 small USB fans are on the same circuit as the Denon AVP. The 4 fans were not plugged into the outlets of the Denon.

In the living room, the Denon X3100 and 4 small SUB fans are on the same 20-Amp circuit. The 4 fans were not plugged into the outlets of the Denon.

From what I've read, each 120mm USB fan is about 5 watts. So 4 fans = 20 watts total.

 

[PENG]

When I placed four 120mm cooling fans atop my Denon AVP-A1HDCI and Denon x3100, the speaker channel levels (volume) are about 6dB lower than if I only have 1 fan or no fans at all.

Yes, that's a 6dB volume difference!

Because of this, I removed all fans atop my AVP-A1HDCI and used only 1 fan atop my X3100.

I have verified 3 different times using a SPL meter. Each time, the ATI amps, AVP-A1HDCI, and X3100 have been on for 1 hour.

So the only thing that changes is the number of fans atop the AVP-A1HDCi and X3100.

Why does this happen?

Do Pre-pros/AVRs have lower volume output when they are "too cold"?

Is this the reason why some people say that amps sound better when they are "warm" and why some people even leave your amps and preamps on 24 hrs a day?

I won't be recommending to people to place more than one fan atop their amps and preamps anymore, unless it's a class-A amp or an Onkyo.

I have not noticed such difference based on running REW for s few hours, with and without the fans blowing to my prepro and amp. Next time I will pay more attention in case I missed something, though I am quite confident it did not make any significant difference based on the graphs. In my case the difference in temperature would have been between 37 to 47 degrees C., on the top of the enclosure.

 

[M Code]

Before drawing any final conclusions...
Measure the unit's temperature with (1) fan vs. (4) fans. Post back what the measurements are.

Just my $0.02...

 

[KEW]

It would be good if someone else could repeat this cause-and-effect. The Magnitude of it is Rather astounding! I have no doubt that ADTG is honestly reporting his observations, however there is always a possibility of a unknown variable unique to his situation confounding the relationship of temp vs SPL.

A sample of one should always be looked at with skepticism until confirmed.

 

[KEW]

Before drawing any final conclusions...
Measure the unit's temperature with (1) fan vs. (4) fans. Post back what the measurements are.

Just my $0.02...

Where would that measurement best be taken?
Top of case?
Cooling fins?

 

[AcuDefTechGuy]

I should have measured the temp before and after, which would have been easy to do with my laser temp.

I will add this.

After removing the 4 fans from my Denon AVP-A1, I turned off the Denon & ATI amps for 2 hrs and allowed them to cool down.

Then after 2 hrs, I powered everything up and checked the SPL. Call this the "cold" SPL.

Then 2 hr later, I rechecked the SPL. Call this the "hot" SPL. There was still a difference of about 1.0 - 2.0 dB. It seems the left front speaker increased the least amount, but still 1dB. The other speakers increased more - about 2dB.

I am also certain my 60kW Generator was not on.

And I have noticed and measured the SPL of this 3 different times. Definitely not a fluke. Whatever caused this significant SPL change definitely happened.

I should have measured the before and after temp, though. Can't believe I didn't think of that.

Next time I'm off work during the week, I'll have to investigate this some more.

 

[AcuDefTechGuy]

It would be good if someone else could repeat this cause-and-effect.

Yes, someone please grab four 120mm fans and put them atop your pre-pro. Make sure the fans are pulling the heat up and set to High speed, not Low speed. Also make sure the room temp is nice and comfy cool around 78F degrees, not freezing cold.

Please confirm I'm not crazy.

 

[Irvrobinson]

Andy, are the fans literally sitting on top of the AVR chassis, or are they mounted to a cabinet position?

If the fans are literally on top of the devices, are they pushing or pulling air, from the device perspective?

 

[AcuDefTechGuy]

Andy, are the fans literally sitting on top of the AVR chassis, or are they mounted to a cabinet position?

If the fans are literally on top of the devices, are they pushing or pulling air, from the device perspective?

The fans are literally sitting on top of the Pre-pro and AVR chassis, and they are blowing air upward.

 

[slipperybidness]

It would be good if someone else could repeat this cause-and-effect. The Magnitude of it is Rather astounding! I have no doubt that ADTG is honestly reporting his observations, however there is always a possibility of a unknown variable unique to his situation confounding the relationship of temp vs SPL.

A sample of one should always be looked at with skepticism until confirmed.

In industry, we typically say "1 data point is no data point".

Just another way of saying "be skeptical".