Abbingdon Music Research DP-777 Premier Class - Manual (Page 17)

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In the DP-777, to overcome this set of essentially analogue problems we devised a completely analogue solution.
AMR’s proprietary Valve Digital input technology (VDi) is a world’s first: it is the use of the 6N11 (high-speed
valve operating into the 100MHz region) in a zero feedback circuit derived from military radar technology to re-
establish the clean waveform of the original incoming signal from the two HD SPDIF Inputs.
Firstly, this ensures that even if the input SPDIF signal has an incorrect output level or poor waveform, the SPDIF
input receiver will have a clean and perfect SPDIF signal to lock onto.
Secondly, as all SPDIF receivers use Schmitt Trigger input circuitry, the receiver will create a glitch noise at the
trigger point, this noise travels back into the SPDIF cable, returning to the source component. It is this errant noise
that is at least in part responsible for the major differences between SPDIF cables and sources in the input system
of common DACs. As the HD-VDi isolates the SPDIF receiver from the outside world, HD-VDi eliminates the
detrimental effect caused by this noise once and for all.
The DP-777’s HD SPDIF inputs employ a NOS valve input circuit for everything all the way up to the 24/192 high-
definition standard. The result is clearly visible on an oscilloscope as the SPDIF signal is restored back to its perfect
wave form. This input ensures the “right note at the right time” to give the music the “life” that is missing from all
other DACs.
Therefore, we recommend that for the optimal signal transfer (i.e. highest sound quality), please use Inputs 1 or 2
(R1/R2) on either BNC or XLR. Even with an RCA connector, simply use the accompanying BNC > RCA adaptor.
Inputs 3 and 4 (R3) do not use the HD-VDi (as they are more for convenience/comparative purposes). The USB
input 5 (R4) is not required as the signal is not SPDIF.
...and HD-VDi, an
analogue solution, is a
world’s first
HD-VDi is on Inputs 1
and 2