I ordered my Puffins with a optical output in one and SPDIF in the other. Own a ridiculous pile of ADCs - the Puffins are as transparent as anything I've tried. Run 'em thru a Benchmark DAC-3HGC into Meridian DSP-5000 24/96 speakers. Everything stays digital right thru to the speakers DSP crossovers. Puffins would be worth the price for the service/measurement applications alone - very nice bonus that exceptionally flexible phono preamp are part of the package too.