Do they take time to fade when turned off is normally the easiest way of answering that on portables
Maybe he can check…? but my hunch from the glow being evenly dispersed, it looks like LEDs… hope it’s not
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hmm right will ask that.
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Thanks for coming back chap.
Shame
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I won’t bother with doing actual calculations, but I would assume you don’t want the tubes actually glowing in portable device.
For tube to glow in visible spectrum it needs to be couple of hundred degrees hot and therefore very inefficient as power would need to get dissipated on the tungsten wire instead of going down the signal patj. So while in large bulb glass it is isolated quite well and surface may be more or less warm to touch in smaller packages (like in such a device as M5 Ultra) it is impossible to achieve. Unless you want to actively loose your ability to procreate by boiling your testicles 
Plus it would drain your battery in phone as hell, so…
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This is definitely true, but then the question of why they even put this inside it arises and if it is even doing anything, is it just for pure marketing?? And if it isnt doing anything special, then you are just overpaying for it and also getting a less durable design since it has all those vent holes.
(I have asked vortex to graph an iem to see if the FR is any different with the tube on/off. Probably isnt a good way to check as the FR can change even with solid state amps…)
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I did not mean those tubes don’t do a thing, as if the signal passes through them they may definitely affect the fr. What I mean that tubey visible glow requires tons of power which is not achievable to my knowledge in such a small device
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hmm, the portable tube amps I got do indeed glow (for real) and some of them do get VERY hot.
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Which one do you have?
KAI Tap 2 mini
Little bear b4x
GAD AD3
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CS43198 chip instead of the ES9281AC. Not sure who this is for, considering the glowing reviews the original got for its sound. 
Looking at pics (of yours even) Kaei tap 2 looks like has LEDs soldered underneath, but the other 2 actually may be glowing because of the voltage going through them.
Those are having quite large bulbs though, so may be properly isolated. How is the battery life with them?
Yes the tap 2 mini has LEDs.
dont really remember tbh, but im pretty sure they are pretty bad.
Have enjoyed some of the xduoo tube gear.
Where is your commitment to audiophilia 
I have the GAD ADV - the balanced version of @Rikudou_Goku GAD AD3 - there are ones that do not use LEDs and do glow - but also takes a high voltage to power. Gets too hot for real portable use, but it’s too big for that anyway IMO. I agree I just am not sure how this all works significantly in a small form factor. Add potential for noise… 
The Cayin N3 Ultra uses the same tubes as the Muse M5 Ultra - I think they also use LEDs underneath. I wonder how that affects the mental health benefits of tube glow sunbathing
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Yeahhhh, being BT is definitely gonna make for a noisy environment for that tube…
LED = Next level snake oil. 
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all the portable tubes
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Or @CTOXmas
Do either of you happen to know what tubes it is using as I couldn’t see them listed…
Thanks
Even properly sized shit like xDuoo hybrid mt-60x series use LED backlight.
And while I agree it is gimmick, I would argue that having them on or off really affects the perception of how warm the music is playing in our brain in most of the people 
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Moondrop has released new bluetooth headphones for 80 dollars. With ANC, LDAC and 48 hours battery life it can be quite a bargain for that price provided that the tuning and build qualilty are not subpar.