I would be hesitant to buy another Teac DAC
I have the 501 and it has an issue with its clock. It has difficulty locking into a setting, and it will often go from DSD to white noise randomly.
I have seen posts on other sites that others have this issue and the suggestion that firmware would likely fix this.
However, Teac has never issued any firmware updates.
Yeah I might be hesitant replace defective items too... if I didn't understand nothing is ever perfect. That if it's made by man, it can break or be defective. Sometimes defective items slip by QC. It happens, and NO ONE is immune... even those not branded Teac
That said, there are many of us here who doesn't/haven't had issues, and the unit works perfectly fine. Perhaps we're the exception?
Anyway if the unit is bad, simply have it replaced. Period. Yeah, it's a pain in the @ss when you get a defective unit, but it's not like you're likely to get a second defective unit. And who's the say the unit wasn't damaged during shipping??? That happens as well.
My two cents.