Topping A90 - Just bought and connected.....Daft questions

[DavidNesbitt]

Guys

I have just received my Topping A90 and connected to my RME ASI-2 FS.
They are connected via balanced XLR
I am sure these are daft questions.....? But what settings do I need on the...

1) RME to output and just use it's DAC
2) The settings on the A90 - I have so far used HPA, XLR and low gain

Also - My headphones are Massdrop Sennheiser 6XX - For the way these 2 boxes are connected do I need to use 4.4mm balanced headphone jack plug or an XLR balanced headphone output jack plug?

Because at the moment I only have the standard 6.3mm jack plug and the standard IEM jack plug on my 6XX's - so what's the best way of adapting these headphones or do I need to buy a new cable to listen to them balanced / unbalanced through the A90?
At the moment I dont think I can listen through the A90 through the 6.3mm headphone output jack when it has XLR inputs from the DAC.

 

[CTRLM]

To keep it simple:

1) RME to output and just use it's DAC
Settings on the RME:
Reference level +7dB
Volume level 0.0 dB
Auto Ref Level: Off
Lock Volume: On
Should be fine for low & medium gain with 3.47 Vrms going to to the A90. If you are going to use high gain on the A90, make the volume level on the RME -2.0 dB

2) The settings on the A90 - I have so far used HPA, XLR and low gain
Yep on the A90:
HPA (head phone amp) for using headphones
Input: XLR
Gain: Low & Medium are fine. I think medium should be good enough for the 6XX unless you are listening at ear bleeding levels. I use medium gain with my HD600 & 650s with a balanced connection from my DAC

Also - My headphones are Massdrop Sennheiser 6XX - For the way these 2 boxes are connected do I need to use 4.4mm balanced headphone jack plug or an XLR balanced headphone output jack plug?
You don't need either but you can always try a balanced cable from places like:
https://www.audiophileninja.com/product/sennheiser-hd6xx/
https://periaptcables.com/products/4-type-4-dual-2-pin-sen-hd-series
https://hartaudiocables.com/collections/headphone-cables/products/hc-5-dual-senn

Because at the moment I only have the standard 6.3mm jack plug and the standard IEM jack plug on my 6XX's - so what's the best way of adapting these headphones or do I need to buy a new cable to listen to them balanced / unbalanced through the A90?
Buy a balanced cable if you want to as above, it will give you more volume but you don't need to, you can enjoy the setup as is

At the moment I dont think I can listen through the A90 through the 6.3mm headphone output jack when it has XLR inputs from the DAC.
Yes you can

 

[DavidNesbitt]

Thanks very much for your advice and time - I have used your settings and it is all singing so I am delighted!
You are spot on medium gain is perfect with 6XX.