I thought this thread is supposed to be all about ath M40x. 

Whatever works for you.  Enjoy!

First, the C5 is a big unit with lots of power.  I would use it from headphone out jack on your cell phone to the in on the C5.  Then try your setting Gain on Low.  Like I said, I don't believe Cayin designed this unit to be used with a cell phone.  Therefore, overkill.

Excellent explanation, and on point.

To my ears, overkill with a cell phone.  Best suited to a seperate DAP.

Yes, several.  X5 with Cayin C5, C3 with BH2, DX 50 with E12, among others.  Flat response is very close, unlike the M50x

Go back and read some of the other posts from people who had problems.  I cancelled and got my pay pal refund.

For those waiting for a refund from TOMTOP, I can only speak to my experience. Got a response from them after I cancelled, and it took 5 days to hear from PAYPAL.  Got me refund through Amex and all is well.  Good Luck! 

I got into the habit of never playing anything while charging.  It just seems to work out better that way.

Yes, run S5 headphone line out to C5 line in.  Headphone out from C5 to your hd600.  Set Galaxy volume at 3/4 to start and after turning on C5 raise its volume only slightly so as not to ruin your hearing. There could be a problem with using your S5 but you wont know until you try this. ...

I agree, no more TOMTOP.  I just received my notice this date from Pay Pal that I got a full and complete refund.

I agree, no more TOMTOP.  I just received my notice this date from Pay Pal that I got a full and complete refund.

As I remember the impedance of HD600 is 300ohm.  The NX1 will mot pair well with this fine headphone.  for portable use I would say the Fiio e12 series is or will be discontinued in favor of the A5.  the other unit I know will power your 600's is the Cayin C5 amp.  Hope this helps.

Its not about money or patience.  Its about doing business the right way, not on the come. Now, you know I would not insult your intelligence by suggesting you really believe what you just said. Enjoy!

It is a big deal when you do business.  I buy a product that your Company does not have but yet advertises they do.  I even pay an extra amount of money for expedited shipping. It's called less than honest at any price.