Started modifying DACS in the 1980s. The first Wadia was good, but it could be easily upgraded. Then the high end units using Ultralink DACs became the standard. They were improved by replacing the op-amp current to voltage converters with precision resistors. Most high end DAC units had poor analog output stages and even the RCA jacks could be replaced with better Tiffany or WBTs. We tried different CD players as transports and found each had a unique sonic signature. So, not much has changed in 30 years. We still have poor analog output stages and there isn't anything made that can't be improved. It's just a matter of starting with something good.
