Is low cost DAC worth it?

Is the Modius new? If so, you need to give it at least 100 hours of play time to break in before it can begin to perform to its potential. Also, using a laptop as a source and the Airport Express as a streamer with an optical connection are also big drags on performance. A dedicated streamer is a very good idea and should help a great deal. Stick with it — you’re on the right track and good things should follow.

According to Ken, the internal Dac of Airport Express (AE) seems decent if what you have is the newer 2014 model. I am not an expert on measurement. Just to compare several key parameters such as (1) SNR on AE 103 dBA vs 120-130 dBA on the most of entry-level DACs that Topping / Smsl has; and (2) jitter level, it seems AE’s digital out thru Toslink is not as impressive. I do not wish to get into the debate whether we should place the judgement solely on measurements. Since decent entry-level DACs are so affordable nowadays, you might want to just grab one and take a home audition to see if you like them better.

If you want to limit the budget under $500, consider two DACs: Topping E70 Velvet and Smsl Su9 Pro. Very good performers for their price point, good dynamics, soundstage dimensions, bass slams and airy trebles. Detailed but not analytical. The soundstage on almost all Topping/Smsl Chinese Dacs prior to these two DACs in this price point sounds flat.  If you like Schiit housesound / tembre, pick a Modius ($200). At these already lower price point, I do not recommend used products because you never know how previous owners treat their gears.

https://www.kenrockwell.com/apple/airport-express-audio-quality-2014.htm#:~:text=The%20AirPort%20Express%20has%20its,the%203.5mm%20analog%20connector.

I’m sorry, but the DAC in the Airport Express is not decent.  It was a $100 multipurpose “lifestyle” device from Apple, which is not known as an audiophile-level company by any stretch.  If a device is $100 how much of that went into the DAC section?  How much went into the power supply?  How much went into shielding and noise reduction?  You gotta be kidding me.  The “DAC” in the AE is a relative joke and a toy.  Period.  Stop trying to promote it as “decent” because it is not, and if you think it is you’ve absolutely no idea what you’re talking about. 

"The “DAC” in the AE is a relative joke and a toy.  Period.  Stop trying to promote it as “decent” because it is not, and if you think it is you’ve absolutely no idea what you’re talking about.".................

Okay.... I'm not an expert.  And you might be right.....and Ken Rockwall and a few other that measured the output can be wrong.  And remember we are comparing low end equipment.   Anyone can have a great sounding system for thousands of dollars.  

Bottom line...... we still couldn't hear a difference.    

But there is good wisdom here and I'm going to keep plugging forward... especially with giving this DAC time to "burn in".

It’s simple economics. You cannot build a “decent” DAC into a $100 multipurpose device. The parts quality and overall implementation from power supply to output stage are just not there. It can’t be. I will say this though — differences in DACs are more nuanced and subtle than those of, say, speakers that are far more immediately apparent. But, the subtle nuances can make all the difference in the ultimate quality of music reproduction, and details missed at the source can never be recovered. You’re on a very worthwhile path and goodonya for daring to take it, so keep an open mind and open ears and you’ll ultimately be rewarded.