And here is some more detail on the differences, as well as compare and contrast with the other models: "To expand on the comment about discrete stages: 1. The discrete stage in the Yggdrasil and GMB are both just buffers. The DACs used there have voltage output. So, they are very simple stages, just four active devices per channel. However, as measurements clearly show, this simplicity does not compromise distortion performance (this is usually the penalty paid...simple discrete amps typically have high THD.) That's why when you see some "2-PPM wonder amp" it usually has about 80 active devices per channel. We can argue till the cows come home which sounds better. 2. The discrete stage in the standard Bifrost and Gungnir is actually a small amp stage—not exactly a discrete op-amp, due to its very specific gain structure and open-loop bandwidth beyond the audio band--but it also takes a voltage output of the DAC, amplifies it a bit, and passes it on. No I/V necessary. 3. Bifrost Multibit is totally different. Its DAC has current output, so it doesn't just need a buffer--it needs an actual I/V stage, or current-to-voltage converter stage. There are many ways to do this, from op-amps to discrete. If you're going discrete, it's best not to use a typical voltage-in amp topology, but to design specifically for current input (into, say, the emitters, with overall feedback to bring the input impedance down--you want very LOW input impedance in an I/V stage, unlike a voltage amp.) However, Bifrost Multibit doesn't have a lot of real estate on the analog board, so we had to choose: discrete I/V OR burrito filter. Both wouldn't fit. I believe Mike and Dave made the best choice, which was to retain the burrito and lose the discrete I/V. Consider this: the discrete I/V I did for Theta's Gen V had 250-ish through-hole parts...on a 4 x 6" teflon board...per balanced channel. The complete Bifrost analog output stage--which includes digital filter, DAC, glue logic, local power supplies, voltage references, and the I/V stage is 4 x 5". Surface mount gets us only so far."