I still notice all the outboard Dac's, good ones, I think
still have output transformers vs other methods
i also see the transformer guys; lyndall & Jensen advertise the output transformers as smoothing of digitis?
Some do some don't.
A good transformer will have bandwidth well past 20KHz which means its not going to do a whole lot of smoothing. In fact if not loaded correctly it can also ring (distort) which will make it sound brighter.
Lyndahl and Jensen both make excellent transformers. If used carefully they can be of some benefit, for example they can be used to go balanced even if the output of the DAC is single-ended. You **might** get some sonic advantage from doing that as if balanced line is executed correctly, the result is that the interconnect cable will cease to have an effect on the sound of the system. If it was contributing brightness prior, then this is an advantage. They can also isolate grounds; if you have a ground loop (which can allow noise in the ground to get amplified) then the ground isolation can be help out as well.