I am close to finalizing the new tube circuit design and I will install it in the DAC and test next. This is a much more sophisticated fully balanced circuit than we have used in the past and I expect it to be better in every way! I finalized the analog filtering yesterday. The analog stage by itself is flat from 20Hz - 150Khz. Obviously there needs to be analog filtering to deal with the ultra-high frequency noise from DSD recordings. The use of signal transformers accomplishes some of this for us, by nature of their limiting ultra-high frequency signals by nature. I now have the analog filter installed to have a sharp cut-off at the 100Khz range and an appropriately less steep rolloff at 60Khz.
This same circuit, once perfected, will also be applied to the UHD-205!