[Simon Patten]

I have a slight suspicion that maybe it is the cable I'm using with my kph40s, that's why I ordered today a hart audio cables that works with the Y-split connection of the koss utility series to rule that out, if after getting that cable on my koss on the S17 I'm still having issue with temps rising up really quickly then I think this will confirm that really efficient dynamic drivers are creating issues with this amp.

I don't think it's cable related, the temperature was more or less the same with my XS's NA cable and old Faaeal cable, although the NA cable runs c.1 degree cooler.

 

[Simon Patten]

Class A amps are very inefficient. They draw the same amount of power regardless of load. When you have a larger load, there is less excess power that gets converted into heat, leading to lower temperatures than with a smaller load.

That said, I'm surprised the difference is that big between the XS and IE600.

Indeed, if we were comparing the XS with, say, 6XX's I would expect to see a difference but not with these two.

 

[Zaemon]

The buzz could have caused by your ac outlet/extension/other items that are plugged in. I plugged my S17 into an extension with other power adapters and there was buzzing noise out of the headphones. Plugged the S17 into another extension with no other stuff and no interference noise.

No. Its an internal problem.
Buzzing is only on the left chanel. Never changed the setup or cables. Even if. That still would be not ok.

 

[Erick Muller]

I don't think it's cable related, the temperature was more or less the same with my XS's NA cable and old Faaeal cable, although the NA cable runs c.1 degree cooler.

I'm just saying that maybe it's the cable because of the experience that I had changing from the long xlr cable that came with my clear's and then moving to the shorter one, temps also climbed really fast with that long cable but once I change to the shorter one, both my radiance and clear's never reached pass 65 on my amp on 100ma mode, so I also don't think the cable is the problem with my kph40's, I just want to rule it out as a possibility.

 

[Erick Muller]

Indeed, if we were comparing the XS with, say, 6XX's I would expect to see a difference but not with these two.

I have a 650 which is basically a 6XX(or the other way around, depending on your perspective) and I don't have problems with temps also on those cans and I run them really hard, 100ma mode, high gain, volume max out on the amp, controlling it through my DAC, so the issue seems to be of another kind, maybe like @dl95 said in his response to you.

 

[AuneAudio]

No. Its an internal problem.
Buzzing is only on the left chanel. Never changed the setup or cables. Even if. That still would be not ok.

Hi, if there is constant noise, then it is likely a problem with the S17 Pro;

If there is intermittent noise, we suspect it may be caused by fluctuating power grid voltage or noise introduced by the front-end equipment.

 

[Zaemon]

Hi, if there is constant noise, then it is likely a problem with the S17 Pro;

If there is intermittent noise, we suspect it may be caused by fluctuating power grid voltage or noise introduced by the front-end equipment.

But then it would be on both channels. It was only on the left channel. Frontend was disconnected Here in germany we dont have high fluctuating grid voltage. Never had a problem like this with other amps. Same grid...

Also, intermittend noise can be caused by bad solderjoints expanding when warming up and or a transitor wich fails under load/heat. Even a bad decoupling capacitor can cause noise. Or it can be dc voltage leaking through. Impossible to diagnose without at least an oscilloscope and a multimeter. You could probe with the scope where noise enters the signalpath e.g. Schematics are handy too.

 

[sianofabio]

i wonder if anyone here could hear a difference in sound (bass, stage) going from SE out to Balanced out? would it make a difference if i invest in a balanced cable for my headphone. I'm on high gain and 100MA and listen with the volume at 52 ?

some amps like the violectric v226 does benefit a lot by going to balanced out..

Also concerning impedance:
my dac output impedance is 1250 ohms going to this amp that's 10K, Is it good enough? as my dac say 2.3V @ 47kohms, so im probably just sending 1V to the amp.
Maybe i could add a Loki eq , that's 47k in and 100ohms out, in between?

 

[Erick Muller]

i wonder if anyone here could hear a difference in sound (bass, stage) going from SE out to Balanced out? would it make a difference if i invest in a balanced cable for my headphone. I'm on high gain and 100MA and listen with the volume at 52 ?

some amps like the violectric v226 does benefit a lot by going to balanced out..

Also concerning impedance:
my dac output impedance is 1250 ohms going to this amp that's 10K, Is it good enough? as my dac say 2.3V @ 47kohms, so im probably just sending 1V to the amp.
Maybe i could add a Loki eq , that's 47k in and 100ohms out, in between?

Haven't tested that much the single ended vs balanced hp connections in the S17 tbh, but concerning going between 100ma and 50ma sound difference, they become more apparent with higher impedance cans like a SEN 650, but it is even noticeable on more efficient headphones. The sound gets warmer and lusher and when listening to heavy metal, trash and that kind of music, the sound coming from 100ma has like a weight to it that's kinda hard to describe, it works in most cases but sometimes I noticed that I prefer the 50ma depending the headphones and the music I'm listening too.

 

[Musiccc]

Could you suggest some working cables above 2.5 meters which are not making the noise ? Because I have got the problem with mine.

What headphones were you using and was it stock cable? My stock cable worked ok, it was the aftermarket pure copper cable that has issues.
I have a new silver plated copper cables coming. Will see.

 

[anonbert]

Here are the internals of the S17 Pro on YouTube:

Some improvements that may lower temperatures would be:
1. Swap the stock thermal pads between the MOSFETs and black heatsinks with thermal paste (such as CX-H1300 or Upsiren U6 Pro)
2. Add small copper heatsinks to the top of each voltage regulator (16 total) (instructional video: )
2. Add thermal paste (such as CX-H1300 or Upsiren U6 Pro) to the bottom larger aluminum heatsinks (plate and bar)

 

[Simon Patten]

Thanks. I was going to open mine to see what can be done but there's a seal over one of the screws and I didn't want to damage it as I'm hoping to get the volume control issue fixed.

I had similar ideas, there isn't room for a fan but those mods ought to help lower the temperature a bit, not too much though as of course it needs to run hot.

Have you tried any of them?

 

[Zaemon]

Here are the internals of the S17 Pro on YouTube:

Some improvements that may lower temperatures would be:
1. Swap the stock thermal pads between the MOSFETs and black heatsinks with thermal paste (such as CX-H1300 or Upsiren U6 Pro)
2. Add small copper heatsinks to the top of each voltage regulator (16 total) (instructional video: )
2. Add thermal paste (such as CX-H1300 or Upsiren U6 Pro) to the bottom larger aluminum heatsinks (plate and bar)

Very interessting. Nice find. The heatsink is cool.

As a warning. If you use thermal paste for the voltage regulators LM337 and LM317BT, Vout is then connected to the heatsink. So if the heatsink is ground that wouldnt be such a good idea Even if it isnt ground it would be a bad idea. There are special heatconducting mica sheets for use with thermal compount. But i strongly doubt that it would make a big difference since the thermalpads are pretty ok.

Those 2SC4027 BJTs ( 16 ) are rated -55 to 150°C btw.

 

[anonbert]

I think there would be a risk if the thermal paste was electrically conductive, but both CX-H1300 and Upsiren U6 Pro and similar products are specifically designed to be non-conductive. I haven't tried these mods yet, but I may do so in the future. The thermal pads used on the MOSFETs look somewhat thin.

 

[moonbst1]

After two hours in a room with AC turned on (room temperature 18 C). Before, with room temperature around 28C, in 1 hour it would switch to 50ma. Like I've said many times before, most users will only notice in their summer and hotter months.

Having a exac same issue.
My room temp is 20C, my unit is rised up on the spike, During the testing, it was powered on without headphone, without any audio input, with zero volume.
Tempurature reached out maximum 69C degree at 100ma mode VERY quickly, then switched to 50ma mode.
I feel S17 (general class A amp) makes good sounds when it is warmed up abourd 50C degree.
The temp changing speed from 50C to 69C, only takes 15 mins, ramps up fast.
Basically, I only can listen the music for 15 mins at 100ma mode, 50ma mode stays at 62C.

Definitely this is not normal, therefore I reached out the seller to return or get replacement, A seller refused my return request, and said unit is VERY normal.
If anyone consider to order any audio equipment from AliExpress, "All buyers worldwide, beware of the seller below. Despite clear heating issues and provided test results with pictures and videos, this seller has refused return & refund."

AliExpress seller: AKHiFi Audio Store