Check the manual @ p 28-29 for frequency response, image suppression and impulse response for the 2 digital filters available, DF1 & DF2, and LIANOTEC...
What I conclude from my reading of the Trinity DAC manual is, that their sound quality is not primarily due to linear interpolation - at least, not for source sample rates less than 176KHz. The impulse response graphs clearly depict that linear phase brick wall type digital filters are utilized, one featuring a sharp transition and the other a slow, both apparently in a hybrid reconstruction filter scheme utilized in tandem with LIANOTEC. Linear interpolation cannot remove the pre-ringing or post ringing produced by these digital filter functions. I now suspect that much of the Trinity sound character is largely due to other design factors, such as the massive paralleling of D/A converter unit outputs.
Probably the filtering is more critical with DS DACs due to out of band noise which the R2R DACs don't have (correct me if I'm wrong) and this may be a reason for which Trinity selected the 1704 chip.
While delta-sigma conversion generates out-of-band quantization noise, full resolution R-2R type converters (such as in the PCM1704 chip) will still produce strong ultrasonic image bands which must be effectively filtered for correct signal reconstruction.
If the oversampling pushes the first image bands way beyond the amplifier bandwidth would it still matter? That's what Trinity claims with its 8x digital + 8x analog oversamplig (manual p 16)...
It may still matter. At high oversampling ratios, the image bands are essentially feeding RF to the next amplification stage. Unfiltered, this may or may not cause inter-modulation, junction rectification, or common-mode signal coupling problems, depending on how resistant that stage is to RF input.