First of all, thank you Marco for sharing your experiences with this 'one-off' piece!
It is the original 3D Audio DAC board, with USB 1.0, integrated into our LS 36.5 'DM', which has also been redesigned with a different and higher gain tube stage - more in common with LS 100 circuit, but still using 6H30 tubes. This particular piece was rendered single-ended, but could be build fully balanced with full dual-differential circuitry, instead of output transformers.
USB 1.0 limits sample rate to 48Khz I believe. May 96Khz, but I a not sure. Obviously this is a critical design point for hi-rez files. We found that SPDIF inputs sounded BETTER(!) than USB, so we have debated the value of even adding USB. I do understand however, that SPDIF IS limited to sample rates below the best hi-rez.
TVAD is RIGHT. Tech is changing VERY fast and it is a slippery slope in many ways. We have the ability to produce an EXCEPTIONAL hi-rez input, but the necessary capital investment for programming, etc., is NON-TRIVIAL. Given the fast pace of digital, it is a tough decision as to how and WHEN to act, and insure that your will receive the ROI that you anticipate and aren't beaten to the punch by someone else!
Most significantly, Alex has a BRILLIANT DAC design and once the input formats are sorted, the sky IS the limit. As it is, we could right now, produce a BRILLIANT DAC with SPDIF input that would blow you away. Obviously the market wants USB or other hi-rez inputs and this is something that we are still working out.
What I really look for and value, is WHAT YOU GUYS WANT! Specifically, inputs, formats, etc. We will first offer digital inputs to our modified players and then a simpler integral DAC for our LS 100. A DAC of the scale that Marco is describing WILL be a higher priced product and WILL perform beyond its price-point!
Thank you all!
Dan W.