[sendler2112]

The sonic difference between 50ma and 100ma bias current is actually very slight And probably most noticeable with inefficient headphones at high levels that are drawing more than 50ma of current in their drivers

 

[Marlowe]

Class A amps are by their very nature hot-running but I don't know hot the S17 gets compared to others. I may well add an extra heat-sink when mine arrives.

According to reviews, the Burson Soloist, another popular Class A amp, puts out a whole lot of heat and virtually the entire surface of that amp's case is literally a heat sink. (They also sell a stand that allows vertical placement to dissipate even more heat, though it is rather outrageously priced at $100 USD.) In contrast, the venting on the S17 seems fairly minimal, just on the back, and below average even for a non-Class A audiophile level amp. This, like the inadequate stock feet, seems to be a bad design choice, possibly for budgetary reasons. Though I hasten that I am no engineer, audio or otherwise (just an old history major who took a couple of soft science survey courses to fulfill my science requirement), so I may be out of line on that. Aune does emphasize the internal cooling structure, including the rear vents, of the S17 on its web site.

 

[Hooster]

That's what strikes me as odd and troubling--different users seem to have very different experiences with heat and the S17. It's winter now for me (and probably most S17 users) and outside daytime temperatures (I rarely use the S17 at night when I am usually at the TV) here have probably mainly been 40-50°F (5-10°C; sorry, I'm a dumb American and while I can roughly convert metric distances in my head, I'm just lost in Celsius and need a conversion table). I like it cool and often have a window cracked even at those temperatures, so I'd guess the temperature in my apartment is around 70°F (21°C) or even a little less. I have the S17 raised about 22.5mm above my DAC and even after 3-4 hours operation at 100mA, it stays around 63-64°. It's never gone above 65°. Though I guess at worst, a fairly inexpensive quiet fan (like the one linked in a recent post) should keep it below 69° in summer.

You may as well find it "odd and troubling" that different users have different room temperatures, stack their equipment or not, have well ventilated or poorly ventilated spaces, etc. As far as I am concerned there is nothing odd or troubling about that.
Having a class A amplifier so close to your DAC is probably not a good idea.

 

[Dimitry188]

The sonic difference between 50ma and 100ma bias current is actually very slight

In Hifiman Arya and DC Ether С Flow, I hear this difference very well. And it's pretty noticeable.

 

[MiguelP]

I think that is just for the volume issues.

Isn't it that older models had these problems and the volume issue, at least, was rectified during the production run? Aune recently posted here offering an update to fix it but I've been talking to them about it and they're not at all helpful.

Class A amps are by their very nature hot-running but I don't know hot the S17 gets compared to others. I may well add an extra heat-sink when mine arrives.

Mine is a new model. Volume works perfectly fine - each two steps it raises the volume by the same amount. The temperature does raise to 69 C even with tall aluminium feet. After reaching 69° C it switches to 50ma and the temperature drops very, very slowly (much slower than it raises). Room temperature 25C. I don't use the amp near the DAC. I guess that the difference in temperature between different units is due to different room temperatures.

 

[Marlowe]

You may as well find it "odd and troubling" that different users have different room temperatures, stack their equipment or not, have well ventilated or poorly ventilated spaces, etc. As far as I am concerned there is nothing odd or troubling about that.
Having a class A amplifier so close to your DAC is probably not a good idea.

That's why my post risked being boring and repetitive by stating in detail (much of it repeated from my prior posts) the conditions under which I am operating the S17. And without going back over this thread and quoting posts, I am pretty sure that some posters have reported their S17 to overheat very quickly despite using it in conditions that do not appear very different from mine: the S17 is elevated higher than the stock feet in a well ventilated space in a room that is not particularly warm. As for stacking the S17 on my Denafrips Ares 12th-1, it is not really feasible for me to place them any other way, which is why I ordered tall legs (almost an inch) even before I received the S17. The DAC seems to be roughly the same temperature by touch (admittedly not the most accurate measurement) as it was when the Liquid Platinum was stacked only about a quarter inch above it and remains significantly cooler than the S17.

 

[MiguelP]

It took exactly 1 hour to get from 28 °C after turning the unit on to 69 °C. The heating behaviour is very consistent in my unit.

 

[labeelen]

In Hifiman Arya and DC Ether С Flow, I hear this difference very well. And it's pretty noticeable.

Agreed, with my HE6se v2 (@100mA) sound becomes more spacious (increased depth) and softens a little. Temperature is a non issue for me, S17 is stacked on top of R26 DAC and tops at 58 Celsius (room temperature of 21 degrees)

Just received the confirmation that my S17 volume is reprogrammed by the distributor and is on its way back to me. Excellent service.

 

[fededige]

Guys, I’m sorry but here we’re making doubt of math and science: we’re not talking of ppl living in countries or have house temperatures 20º C hotter or colder. The difference could be 2-3, maybe 4º C, but this can’t justify ppl stating their units won’t exceed 55º and ppl who can use this amp in class A for no more than 30 mins. Clearly there are some faulty units or QC is a big deal here. I think I’m gonna order mine when I come back home from holiday. i’m in Italy and I hope they will have a good batch of units. But if heating will be an issue for me now that we’re in winter, I don’t think I could keep it: I’m a mixing engineer and I love working with headphones, which means my amp is on 10 hrs a day. In this case I will pull the trigger on the audio gd master 19 which heats as any other clsss A amp, but doesn’t degradate its sound quality to avoid melting.

 

[sendler2112]

There is a very slight difference between 50ma and 100 into my Ananda Nanos. 50ma will still be class A up until the point where you surpass the level of bias in the output where it will transition to class AB. There is a much bigger difference between low gain and high gain with low gain sounding much better.

I was surprised by a couple other obvious differences such as the big differences in the sound of various USB cables into the upstream Aune X8 with Sparkos dual Pro amps I am using for my source. Digital filter choices in the DAC are also audible with 16/44 files where I prefer the minimum phase filters. These become less relevant when playing 24/ 192 hires files it seems.

The Douk Audio USB to SPDIF convertor sounds better than the USB straight into the DAC even though this involves a 20cm RCA digital cable. Which I even made two of with different connectors and found that the generic Nickle RCA added quite a glare compared to the Cardas. Same wire.

And there is a huge difference between the balanced 4pin XLR headphone output and the single ended 6.35 jack with versions of the exact same brand of wire. Both jacks are active simultaneously so it is easy to switch back and forth at the headphones with a quick level match and scroll back to the same passage. The XLR is more spacious and a bit distant with better retrieval of reverb fine detail. The single ended output is narrower with a bit less fine detail but more solid in body. I prefer the detail of the balanced.

 

[Shane D]

Mine is a new model. Volume works perfectly fine - each two steps it raises the volume by the same amount. The temperature does raise to 69 C even with tall aluminium feet. After reaching 69° C it switches to 50ma and the temperature drops very, very slowly (much slower than it raises). Room temperature 25C. I don't use the amp near the DAC. I guess that the difference in temperature between different units is due to different room temperatures.

How long does it take to max out at 69C?
Does it essentially render 100 amp operation a temporary function that times out?

 

[Shane D]

It took exactly 1 hour to get from 28 °C after turning the unit on to 69 °C. The heating behaviour is very consistent in my unit.

So you can only use the 100 amp feature for one hour?

 

[Shane D]

Guys, I’m sorry but here we’re making doubt of math and science: we’re not talking of ppl living in countries or have house temperatures 20º C hotter or colder. The difference could be 2-3, maybe 4º C, but this can’t justify ppl stating their units won’t exceed 55º and ppl who can use this amp in class A for no more than 30 mins. Clearly there are some faulty units or QC is a big deal here. I think I’m gonna order mine when I come back home from holiday. i’m in Italy and I hope they will have a good batch of units. But if heating will be an issue for me now that we’re in winter, I don’t think I could keep it: I’m a mixing engineer and I love working with headphones, which means my amp is on 10 hrs a day. In this case I will pull the trigger on the audio gd master 19 which heats as any other clsss A amp, but doesn’t degradate its sound quality to avoid melting.

If you go for the Master 19, Please let me know your thoughts and experiences. Maybe what thread you use?

Thank you.

 

[MiguelP]

So you can only use the 100 amp feature for one hour?

Yes. From turning it on until it switches to 50ma takes exactly 60 minutes. When I turn it on the temperature indicated is 28 °C. The unit gets really hot - you cannot hold it. Even the volume knob gets uncomfortably hot.

 

[Giangi]

Yes. From turning it on until it switches to 50ma takes exactly 60 minutes. When I turn it on the temperature indicated is 28 °C. The unit gets really hot - you cannot hold it. Even the volume knob gets uncomfortably hot.

On mine, volume knob is cold however and I can normally hold it even if at 68 C. So, it's strange. Which headphones and which cable do you use?