Thank you for all the feedbacks, need some time to digest all the information. But using a passive preamp, or go direct from the DAC to the MC275 is something I will look into. I actually, I don’t know what determines if a preamp is needed. I definitely don’t need more volume. My 18w Almarro usually set between 9-11 o’clock, and the colume in my computer is 1/3 - 1/2. If I play from computer, then yes, I can control volume from in the computer. I am using a audio-gd NFB3 and still waiting for a Topping dx7 pro. Below is the product page of the DX7, towards the bottom has RCA output specification, but it doesn’t mentioned anything in ohms or V. Can I connect it directly to Mc275?
https://shenzhenaudio.com/products/topping-dx7-pro-es9038pro-dac-headphone-amp-bluetooth-5-0-32bit-7...
https://shenzhenaudio.com/products/topping-dx7-pro-es9038pro-dac-headphone-amp-bluetooth-5-0-32bit-7...