I do believe that only a 110$ dac would not bring out the full potential of the amp however the whole reason I bought the THX 789 was because of its price. If there is any dac that you would recommend I would like to see and maybe save as maybe an upgrade for the future. I am still having trouble with the connecting the dac and hearing sounds from the THX 789 I might have some gist of what I did wrong. #1 I pugged the double xlr to 1/4 adapter in the front of the dac instead of the ones in the back? #2 I bough a double xlr to a single 1/4 instead of getting 2 two pairs of xlr to 1/4 adapters. #3 When I'm in the Focusrite software I see the microphone settings which are in the input settings. But In the Output Routing settings it states "output routing is not supported on this device" which makes me think that maybe my focusrite scarlett solo (3rd gen) isn't compatible with the THX 789? #4 my Headphone is an 3.5mm cable not an 1/4 inch which means I need to get an 3.5mm to 1/4 adapter Going back to the idea that I'm trying to save some money I would try all these other options but I can't simply afford them so can you confirm that if any of these might be a problem and a solution to fixing my problem before I waste moneys on more items that are irrelevant to the problem.

Did you make sure to download and install the latest focusrite drivers and select the focusrite interface as the audio output? If you wanted to be able to monitor your microphone input in real time and get your desktop audio output simultaneously, you would have to run a cable from the headphone monitor output on the front to an input on this amp. I believe the cable you linked should would work when you plug the 1/4 inch TRS end to the headphone output on the interface and then plug the XLR ends into the amp. As the scarlett interface has both a DAC and an amp, please gain stage properly between the two so you send a properly leveled audio signal to your amp from the interface and actually get the benefit of using this amp. You can also use the two line outputs on the back of the interface and route those to your amp, but you wont get real time audio monitoring of your microphone input (which may be what you want if you are using speakers as well as headphones so as to not get feedback). However, I feel like pairing this interface with this amp is not a great idea if you are trying to achieve the great sound quality this amp provides. The focusrite scarlett interfaces all have DACs and amps built into them, as that is what is needed for a standalone interface. The amp on the scarlett interfaces is not very good. The DAC and ADC are both good for the price, but I can't help but feel like using a $300 amp with a ~$110 DAC/amp is not utilizing the THX 789 to its full potential. But you can use it however you want, just giving my 2 cents :)

set up question: I want to connect my turntable directly to this amp just to power headphones. Can I also run RCA from passthrough to an AVR to power and control volume of speakers?