[labeelen]

Ok, so it seems like there shouldn't be anything above the Aune at all

I think it is best to have some free space around and above and not place it directly on top of a heat generating device like another amp.
(so me putting it directly on top of the Gustard R26 is also not a best practice

 

[Musiccc]

Maybe because is´nt an issue, except for you.

As an example, my S17 has a bigger jump in volume from 40-42 with my AKG 712 Pro, but not with my other HP´s - this
does´nt bother me and this no reason for debating.

The S17 Pro is an stellar amp for his price and it has best sound i´ve heard from HPA´s under 2K.

the debate is over - now enjoy the music

A friendly reminder: Helpful post from Hengstenberg. Think about the synergies of your other equipment/headphones with S17 Pro when talking about volume "issues".

 

[nobela]

What evidence do you have to support this? It does not make any sense to me either. Are you confusing gain and bias? What has class A got to do with high and low gain?

This thing is happening in front of me. THAT is the evidence. Just reached 68 degrees and automatically switched from 100 mW to 50mW mode. It only does this in high gain mode, and not in low gain. And yes, true class A mode should not be affected by gain settings or output power.

So I consider this amp a scam, it's not true class A. Sounds quite good anyway.

 

[Giangi]

This thing is happening in front of me. THAT is the evidence. Just reached 68 degrees and automatically switched from 100 mW to 50mW mode. It only does this in high gain mode, and not in low gain. And yes, true class A mode should not be affected by gain settings or output power.

So I consider this amp a scam, it's not true class A. Sounds quite good anyway.

I'm in low gain and, however, it became too hot 69C. Switch from 100bias to 50bias

 

[labeelen]

This thing is happening in front of me. THAT is the evidence. Just reached 68 degrees and automatically switched from 100 mW to 50mW mode. It only does this in high gain mode, and not in low gain. And yes, true class A mode should not be affected by gain settings or output power.

So I consider this amp a scam, it's not true class A. Sounds quite good anyway.

To my understanding the protective circuitry kicks in when the unit gets too hot and will then reduce the bias current from 100mA (class A) to 50mA (class AB) in order to cool down (and prevent damage).
So it is a true class A amplifier as long as it does not overheat … which for most of us will never happen, unless you use it 24x7 at tropical room temperatures (or there is something else that prevents it from dissipating its heat)

 

[Musiccc]

 

[Musiccc]

So many whiners here with phantom issues.

 

[Dimitry188]

I have met in discussions that if the radiator is incorrectly fixed inside, the heating turns out to be too strong.
It may be a defective unit.

 

[Giangi]

So, in your opinion, is it normal?

 

[bogi]

Thermal limit for my notebook CPUs, where throtling starts, is near 100 °C, and for my nVidia laprop GPUs it is near 70 °C.
So limit set to 69 °C looks to me as nothing unusual in electronics.

 

[sendler2112]

I wrote to Aune headquarters contact person on Saturday (today it is Tuesday) about my issues of the volume staying exactly the same for 4 clicks at a time and then jumping to a new level on the 5th click, And the more serious concern that the sound quality is completely muffled and veiled at all volume settings up to 55 and below, and then suddenly makes a big jump in level (7db) and sound quality at 56 at which point the sound is suddenly pristine. And the other minor question of why am I listening at such a high indicated level with the moderately efficient Ananda Nanos?

I haven't heard back yet. I'm hoping to get a clarification from them that they know what the problem is, which serial numbers might be affected, and have fixed it going forward. There are several of us here that are having the more or less same problems and probably dozens more that don't know about forums and just sent their amps back.
It seems there is something wrong with the volume resistor chip shorted across ladder tracks, the relays, or the controller holding too many relays at once.

I want to like this amp and recommend it over the equally unreliable Topping A90D that are being price reduced everywhere, but don't have confidence that exchanging it will get me a good one. And for how long?

 

[Dimitry188]

So, in your opinion, is it normal?

I think this is quite normal. I see about the same thing on my device.

 

[Giangi]

Thermal limit my notebook CPUs, where throtling starts, is near 100 °C, and for my nVidia laprop GPUs it is near 70 °C.
So limit set to 69 °C looks to me as nothing unusual in electronics.

Ok, but the "problem", if we want to call it that, is not this. The "problem" is because in less than an hour, with the DAC connected in balanced fixed volume, with the headphones connected in balanced, at low gain, volume at 35-40, with an external temperature of 19 Celsius, it reaches 69 Celsius and scale at 50mA while keeping the temperature constant at 65-66 Celsius? Maybe you need some cleats underneath to lift it up and put it on a surface with holes?

 

[bogi]

I haven't heard back yet. I'm hoping to get a clarification from them that they know what the problem is, which serial numbers might be affected, and have fixed it going forward. There are several of us here that are having the more or less same problems and probably dozens more that don't know about forums and just sent their amps back.
It seems there is something wrong with the volume resistor chip shorted across ladder tracks, the relays, or the controller holding too many relays at once.

I was thinking about ordering one from hifigo till prices are lower, but now it looks to be too risky - shipping from Europe to China and back is slow, it may take weeks or few months to resolve an issue. Ordering from EU shop costs about 100 EUR more. I will watch this thread ...

It's clear they are not testing the volume control functionality sufficiently after production - that's not good indication.

 

[bogi]

Ok, but the "problem", if we want to call it that, is not this. The "problem" is because in less than an hour, with the DAC connected in balanced fixed volume, with the headphones connected in balanced, at low gain, volume at 35-40, with an external temperature of 19 Celsius, it reaches 69 Celsius and scale at 50mA while keeping the temperature constant at 65-66 Celsius? Maybe you need some cleats underneath to lift it up and put it on a surface with holes?

I think that's about your piece and correct behavior should not be of that type. We need more user reports about temperature and switching to 50mA to clear the extent of this issue - if it is rare issue of some units, if it happens often but not with all units or if it is systematic behavior (reviewers did not mention that).