Recommended operating temperatures for Ncore / Class D in general?

[kemmler3D]

Recently managed to get a couple 4-year-old Nord NC500 monoblocks for $300 each. Lucky me! I think they were well cared for by the previous owner.

The problem is that due to strict WAF requirements in my application, all gear needs to live in a small IKEA cabinet, including the amps. No ventilation here, the cabinet has doors which remain closed.

After leaving the amps on for a few hours on a hot (~30C) day, the housings felt like they were around 60C, quite hot to the touch but not enough to burn your hand. Too hot for me to feel comfortable about it. IIRC idle power is around 12w each, which is low, but that will gradually add up if there is nowhere for the heat to go.

I've invested in some case fans to add to the back of the cabinet which will run while the amps are on.

Does anyone know what (case / ambient) temperature I should target to not harm the amps' longevity? I have an infrared thermometer to check with, basically wondering how fast I need to spin the fans to keep the amps happy.

Related: Is it OK to switch the amps on/off using the surge protector, or should I use the switches on the front of the case to be safe?

 

[Doodski]

Does anyone know what (case / ambient) temperature I should target to not harm the amps' longevity?

As low as you can possibly get the temp.

Related: Is it OK to switch the amps on/off using the surge protector, or should I use the switches on the front of the case to be safe?

The surge protector should suffice as a switching point.

Regarding temps, “The rule of thumb is that every 10°C increase in temperature reduces component life by half.”

 

[kemmler3D]

Good to know. I'll shoot for room temp. Maybe invest in a mini-fridge. Thanks!

e: I was joking but then decided to see if active cooling for amp cases was a reasonable idea. Turns out you can get thermoelectric coolers for like $40... this is plan B if the cabinet fans aren't very effective... if the 10°C lifetime halving thing is even half true, these things would pay for themselves many times over... https://www.adafruit.com/product/1335

 

[Doodski]

Good to know. I'll shoot for room temp. Maybe invest in a mini-fridge. Thanks!

I used to qualify hundreds of IC at a time in a calibrated test oven. We purchased the highest quality PICs (ICs) that we could get by the thousands at a time. After oven roasting them overnight in a dynamic powered test situation while still in the oven about 14% to 15% of them would survive to about 150C to 177C. The qualified PICs would then be used in downhole tools for measuring pressure to 20KPSI and max temp of 177C as the qualifying permitted. Then when the finished tool was actually used in a downhole where the temps are very high there is no actual guarantee of the life expectancy. It's a play and pray situation of put it downhole and if it lasted several seconds or two hours it's all good as long as a measurement was completed. So if you are at 40C or 50C you can imagine how that plays with the life expectancy. The components will take the heat but... but you are playing Russian Roulette with your gear.

 

[Doodski]

Good to know. I'll shoot for room temp. Maybe invest in a mini-fridge. Thanks!

e: I was joking but then decided to see if active cooling for amp cases was a reasonable idea. Turns out you can get thermoelectric coolers for like $40... this is plan B if the cabinet fans aren't very effective... if the 10°C lifetime halving thing is even half true, these things would pay for themselves many times over... https://www.adafruit.com/product/1335

Yes, Pelletier Coolers are cool (Literally and figuratively.) but they require a serious power source that creates more heat and are often found in some sort of refrigeration gear from what I know and have been seen on CPUs too. My best suggestion is to use a straight 5VDC or 12VDC fan that has variable speed so you can dial up the coolant level.

 

[kemmler3D]

Hmm, you're right. The one I linked to takes 60 watts (!) ... seems like overkill to dissipate 24w worth of heat... normal fans are obviously preferable if they work. But as long as the equipment case is cool (the cooler would be coupled to it), the IC is safe. What happens to the rest of the cabinet, who cares... some old DVDs? Meh...

I've already got some little 5V USB fans that should help a lot once I cut holes in the cabinet for them. But I am not sure if they will be enough... we'll see...

 

[DonH56]

What is the temperature rating of the capacitors? Their lifetime degrades rapidly with temperature even if not at max rated temp. That is likely to be the weak point. I would find a way to get some airflow, maybe an opening in the bottom or back and an exhaust fan.

 

[dlaloum]

Hmm, you're right. The one I linked to takes 60 watts (!) ... seems like overkill to dissipate 24w worth of heat... normal fans are obviously preferable if they work. But as long as the equipment case is cool (the cooler would be coupled to it), the IC is safe. What happens to the rest of the cabinet, who cares... some old DVDs? Meh...

I've already got some little 5V USB fans that should help a lot once I cut holes in the cabinet for them. But I am not sure if they will be enough... we'll see...

Or take a look at some of these:

Equipment Cooling - ELECTRONIC COMPONENTS - Page 1 - AC Infinity

acinfinity.com

 

[kemmler3D]

Update for anyone following this thrilling drama: added more ugly holes to the back of my cabinet last night and zip-tied some USB 120mm fans in place (had already bought some from AC Infinity). Conveniently, they are plugged into the same strip as the amps, dac, and pre, so will run only when those components are also on.

After about 2h of power-on-time, listening at very low levels, the amps were (to touch) only a hair above room temperature. Noise is negligible at MLP, you can hear it if you sit right next to the cabinet. I haven't opened the cases to check actual parts, but the cases themselves must be at least 25-30 degrees C cooler now.

I used these both blowing out the back of the cabinet on the medium speed setting: https://acinfinity.com/component-co...multifan-s7-quiet-usb-cooling-fan-dual-120mm/ seems adequate to remove ~25w of idle heat.

 

[Doodski]

I haven't opened the cases to check actual parts, but the cases themselves must be at least 25-30 degrees C cooler now.

The fans do make a big difference and will extend the life of your gear. Well done! I've been running extra fans in gaming PCs for decades and have never had a hard drive failure or any failure at all. My gear runs cool...

 

[Suffolkhifinut]

Thought electrical/electronic component ratings were for use at an ambient temperature of 20*C?

 

[Doodski]

Thought electrical/electronic component ratings were for use at an ambient temperature of 20*C?

Operating temperature ranges vary dependent on the type of component. Here is a IRF-Z44 with the Operating Junction rating in degrees Celsius.

 

[Vacceo]

The fans do make a big difference and will extend the life of your gear. Well done! I've been running extra fans in gaming PCs for decades and have never had a hard drive failure or any failure at all. My gear runs cool...

When I watercooled my PC i kind of wish I could do the same with an amp. After all, Sungularity computers produce a very nice detached case for two, four fan radiators.

Overkill? Sure, but think of all the RGB...

 

[NTK]

 

[Doodski]

When I watercooled my PC i kind of wish I could do the same with an amp. After all, Sungularity computers produce a very nice detached case for two, four fan radiators.

Overkill? Sure, but think of all the RGB...

Vapor tube cooling is effective for home audio amps. I've seen it used in several Technics amplifiers and one of them took a loaner week at a pub and the silver/gray paint was slightly brown after because the amp was so hot but still operating all through the week that it was on loan.

 

[Vacceo]

Vapor tube cooling is effective for home audio amps. I've seen it used in several Technics amplifiers and one of them took a loaner week at a pub and the silver/gray paint was slightly brown after because the amp was so hot but still operating all through the week that it was on loan.

Cooling an amp, at least in concept, should not be different from cooling a CPU.

 

[Doodski]

Cooling an amp, at least in concept, should not be different from cooling a CPU.

This video (That I have not seen in it's entirety.) shows a vapor tube in a Technics SU-V303 integrated amplifier.

 

[kemmler3D]

Cooling an amp, at least in concept, should not be different from cooling a CPU.

In terms of what types of coolers you'd use, agree. However, a CPU usually has a ton of heat (up to a few hundred watts) coming from a small area. A power amp needs to cool a larger area.

Luckily in this case seems like Nord has successfully coupled the amps to the case, so that blowing a bit of air around in the cabinet does the trick. That style of cooling is NOT recommended for CPUs

 

[Doodski]

Luckily in this case seems like Nord has successfully coupled the amps to the case, so that blowing a bit of air around in the cabinet does the trick. That style of cooling is NOT recommended for CPUs

I've never heat soaked a class D amp to see how it does at 1kHz and just backed off of clipping for awhile. Awhile being like a few minutes.

 

[dlaloum]

A number of the Class-D modules are clearly designed to be bolted to a case/heatsink for additional cooling... - but it seems as if merely bolting them to an aluminium chassis is ample for most situations.

I just look at those and think, hmm - how much cooler would they run if they were attached to a proper amp heatsink case... and low temperature = low life...

Just because a module is rated to run at a certain operating temperature, does not say anything about its long term life... drop it by 10C and its life is most likely doubled...