I was searching for something else and I saw this.
170$US
Possible op-amp rolling
Claimed 2.2 watts
Claimed 123dB SNR
1/4 inch + 3.5mm + 2.5mm balanced out.
Non-balanced: 1.1w @ 32 ohms / 160mw @ 300 ohms.
Balanced: 2.2w @ 64 ohms / 640mw @ 300 ohms.
You can found topping A50 on hifigo, shenzhenaduio, apos and aliexpress now
Yup, it’s everywhere now… finally. 
Too bad, I already bought a JDS Labs Atom last month.
Waiting for Amir/ASR’s measurements now, heh.
Now on massdrop
Can some one tell me why 2.5mm is balanced while 3.5 isn’t , also why the need for 2.5mm ?
There can be 3.5 mm balanced (as used on ifi products and other stuff too), but 3.5 mm trs is not balanced because it uses a shared ground. 2.5mm trrs is balanced because there are separate grounds for each channel. 2.5mm is used so people don’t go plugging an unbalanced connector in there and causing damage to the headphones or the amp
130$ instead of 170$ on (mass)drop if bought with the D50S for 185$ (instead of 240$).
So 315$ for both.
Edit: You have to choose “D50S and A50 combo” in the list, otherwise just buying the D50S and adding another item (A50) will cost 335$. Huh, okay. 
