1 Topic by Manuel (edited by Manuel 2023-08-24 23:20:49)

  • Manuel
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Topic: Why does my UCX II generate so much heat even whilst idling?

My room's temperature right now is 32 °C (I have no air conditioning) and my Fluke 28II multimeter's temperature probe, which has an accuracy of ±2 °C, says the underside of my UCX II chassis temperature is 48.7 °C. For reference and context, the temperature of the underside of my gaming laptop with an Intel Core i7-6700K CPU is 45.6 °C in the same room. I've just checked the user manual and it says the operating temperature range of the UCX II is +5 °C to +50 °C, does this refer to ambient temperature or the device's temperature?

The component that generates most of this heat are the 4580 dual audio op amp ICs. Is there any way to selectively disable these op amps when they are not needed? It would be nice if, for example, muting an output would also turn off its corresponding op-amp.

Right now I'm only using the AES/EBU I/O (I'm not using any of the onboard FX, mic pres or anything else) so basically those op amps are wasting a lot of electrical power. The user manual says the UCX II typically draws 13 W but, judging by the chassis temperature, I think that might be an understatement and this is is something want to confirm empirically.

If there is no way to turn off the op amps, is this functionality something that could be added in the future via a firmware update? I suspect the answer is "no" because the ICs are probably connected directly to the power rails.

If the temps I'm seeing are considered normal, I don't have a problem with that because this is something RME will have already tested. The problem for me is that 1) my UCX II adds a lot of heat to my already hot room which is uncomfortable during the summer and 2) it wastes electrical power.

It would be interesting if RME could comment on this. Thanks!

2 Reply by MC

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Re: Why does my UCX II generate so much heat even whilst idling?

Please do the power consumption test before speculating. I am pretty sure all you see is normal and not changeable, especially not by firmware. Other than your computer the unit does not have a fan, and other than your computer it does not contribute significantly to the heating of your room.

The tech specs refer to ambient temperature. The UCX II could be 70° Celsius on housing and still would work normally.

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Matthias Carstens
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Re: Why does my UCX II generate so much heat even whilst idling?

4. floor south facing apartment with big windows here. No aircon either. Room temps approaching 40° - I bought a 120mm USB fan at that big online retailer and placed it behind my rack. It's inaudible at low speed but brought down temps significantly.

4 Reply by Manuel (edited by Manuel 2023-08-25 12:26:20)

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Re: Why does my UCX II generate so much heat even whilst idling?

MC wrote:

Please do the power consumption test before speculating.

Thanks for replying, @MC. I just measured ac current using my Fluke DMM and it reads ~102 mA. Input voltage is 230 V, therefore P = V*A = 230*102/1000 ≈ 23.5 W. There is no way the typical power draw is 13 W like the user manual claims because I am using the bare minimum of features: just the AES/EBU output —no FX, no phantom power, all gains set to minimum in case that matters, and running the interface at 44.1 kHz sample rate.

Is it possible there is something wrong with my interface? My BabyFace Pro doesn't get hot at all (just barely warm), what's different? The UFX II specs claims 22-25 W typical power consumption, but it has considerably more I/O than the UCX II. It would be interesting if someone at RME could measure the current and confirm the power draw values.

MC wrote:

not changeable, especially not by firmware.

I imagined this would be the case, because the op amps are almost definitely hard-wired to the power rails. Maybe the ability to selectively turn off hardware features would be an interesting feature for future products.

MC wrote:

the unit does not have a fan, and other than your computer it does not contribute significantly to the heating of your room

Definitely my computer contributes the most but the second hottest piece of gear in my room is the UCX II, and my Genelec subwoofers come in a distant third.

MC wrote:

The tech specs refer to ambient temperature. The UCX II could be 70° Celsius on housing and still would work normally.

That's good to know!

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Re: Why does my UCX II generate so much heat even whilst idling?

Manuel wrote:

I just measured ac current using my Fluke DMM and it reads ~102 mA. Input voltage is 230 V, therefore P = V*A = 230*102/1000 ≈ 23.5 W. There is no way the typical power draw is 13 W like the user manual claims because I am using the bare minimum of features:

But that equation is valid for DC, not for max value of AC . P that comes from your measurements is cca. 12 W (half of the value you have calculated), which is on par with the sheet value.
https://study.com/learn/lesson/ac-power … ation.html

6 Reply by Manuel (edited by Manuel 2023-08-25 12:36:42)

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Re: Why does my UCX II generate so much heat even whilst idling?

Kubrak wrote:
Manuel wrote:

I just measured ac current using my Fluke DMM and it reads ~102 mA. Input voltage is 230 V, therefore P = V*A = 230*102/1000 ≈ 23.5 W. There is no way the typical power draw is 13 W like the user manual claims because I am using the bare minimum of features:

But that equation is valid for DC, not for max value of AC . P that comes from your measurements is cca. 12 W (half of the value you have calculated), which is on par with the sheet value.
https://study.com/learn/lesson/ac-power … ation.html

Yep, but my meter reports RMS ac voltage and current, so my calculations should be correct.

Off-topic but are you this Kubrak? If so, I quite like some of your tracks!

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Re: Why does my UCX II generate so much heat even whilst idling?

You are right.... :-( Till now I thought that 230 V is the max value, but it is RMS.

No, it is not me, I am different Kubrak.

8 Reply by MC

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Re: Why does my UCX II generate so much heat even whilst idling?

You have to measure the current at the DC side or you will end up with bogus numbers. The effficiency of the SMPS is all over the place.

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Matthias Carstens
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9 Reply by Manuel (edited by Manuel 2023-08-25 13:27:06)

  • Manuel
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Re: Why does my UCX II generate so much heat even whilst idling?

MC wrote:

You have to measure the current at the DC side or you will end up with bogus numbers. The efficiency of the SMPS is all over the place.

That is a good point and that was my initial plan but I couldn't find any DC barrel connectors so, as a preliminary test, I measured at the AC side. I will measure at the DC side as soon as I can and report my findings here. BTW the power supply is actually running only slightly warm so it would seem its efficiency is good, and most of the energy being dissipated as heat appears to come from the audio interface.

10 Reply by MC

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Re: Why does my UCX II generate so much heat even whilst idling?

Just measured: UCX II newest firmware, USB connected, no sound playing, 0.807 mA @ 12 V = 9.6 Watts.

Here is the measurement on the AC side: you measured 102 mA which I can reproduce, but doing a DC style calculation of power won't work here. You see measured power is about 11 Watts.

https://www.archiv.rme-audio.de/images/ats024ucx2.png


https://www.archiv.rme-audio.de/images/ats024ucx2dso.png

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11 Reply by Manuel (edited by Manuel 2024-02-25 22:20:16)

  • Manuel
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Re: Why does my UCX II generate so much heat even whilst idling?

MC wrote:

Just measured: UCX II newest firmware, USB connected, no sound playing, 0.807 mA @ 12 V = 9.6 Watts.

Here is the measurement on the AC side: you measured 102 mA which I can reproduce, but doing a DC style calculation of power won't work here. You see measured power is about 11 Watts.

Hi MC, I think I must have missed the topic reply email notification because I missed your reply entirely. Honestly thank you for taking the time to test this—It's all clear now.

I also understand from your earlier reply that the heat is normal and perfectly within specs, and I'm happy that's the case; that said, for future RME interfaces, I really would like the ability to power off unused sections of the hardware so, for example, if I'm only using the AES/EBU out, I would like the ability to turn off all the analogue outs. This would not only save a little power (admittedly not much but hey...) and more importantly generate less heat. Perhaps there could even be an "Eco mode" setting which, once enabled, would automatically turn off any "power-hungry" sections of the hardware that have not had an audio signal for longer than 1 minute—maybe something like that. Even if that only shaves a measly 5 watts off the total power consumption, I would think this feature would be appealing to users because... who doesn't love gear that runs cool?