Depends. I will say that in general though, DACs after 2010 are MUCH better than those that came before them. (not including Oppos, Emotiva or Onkyo which manage to have the same crappy, thin sounding far east signature).
I wouldn’t try anything older.
There are some DACs specifically meant to be modded, with easily accessible op amps that can be replaced. There are also DAC’s with tube outputs, which usually have an output cap in series with the output. Those two sound like fun things to try.
In general, do this as a learning exercise. Not as a way to beat the market. If you can do that, then you'll find your money well spent.
Best,
E
I wouldn’t try anything older.
There are some DACs specifically meant to be modded, with easily accessible op amps that can be replaced. There are also DAC’s with tube outputs, which usually have an output cap in series with the output. Those two sound like fun things to try.
In general, do this as a learning exercise. Not as a way to beat the market. If you can do that, then you'll find your money well spent.
Best,
E