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Packing density. Appreciating the challenges of stuffing this circuitry inside a standard Nagra box of admittedly extra depth kicks in once we look at the innards and compare those to the bread-boarded horizontal prototype. Most of it ended up as tightly stacked vertical modules which just clear the cover. To deconstruct the original circuit into this many sub assemblies, then fitting them together for the shortest circuit path and no proximity interference effects clearly was quite the task. Obviously this was a self-inflicted challenge to continue the link of Nagra's iconic identity with their legacy casing. Should the company embrace standard widths one day, they'd simply scale up height to whatever a given circuit demands. This should net less taxing and costly builds. Remaining iconic whilst manufacturing in Switzerland come at a price!


The D/A module on its ceramic board is fully shielded from EMI/RF and prying eyes. It also covers up the lower input board with the custom Amanero USB transceiver and its upgraded clocks. Nagra's mu-metal ensconced interstage/step-up transformers bracket the heat-sleeved twin triode followed by the two skinny upright 'Kraft-paper-wrapped' bee's wax customized coupling caps from the US whence the signal hits the two huge output capacitors which like all the other black power supply caps are custom Nagra issue manufactured by SCR in France.


The empty space between the output caps and gleaming DAC module is for the optional true balancing transformers which aren't linked to the single-ended volume control, hence can only be used in fixed-out mode. In stock trim, the analogue XLR outputs are pseudo balanced, paralleled to the RCAs and usable in fixed or variable mode.

On the belly of the HD DAC close to the front panel is a micro SD port for future firmware updates (the first of which will add various digital filter options). Owners will download such code from Nagra's website, save it to micro SD card and insert it to prompt an auto update of the machine. Hello future proofiness. The vertical board on the right cheek is the headphone amplifier. Its gain can be adjusted via internal jumpers. The factory setting is no attenuation. This can be diminished by 6dB; and there's a limited power option which acts like a rev limiter. The trademark modulometer's back lighting can be adjusted over 7 steps including off. The included remote wand—identical to the Jazz remote but in a slightly different colour—controls volume and mute, toggles through inputs sequentially or selects them directly with buttons A-F as they've been assigned in the menu. The remote's current stand-by button will become an absolute polarity switch in a future firmware revision to make that function accessible from the listening chair too.
Note the shiny shielded high-quality ribbon cable for the signal transfer between DAC module and driver stage.
The push/rotate controller knob inverts absolute polarity when pushed briefly; and enters menu when held longer. Rotating the knob shuttles through the inputs as confirmed in the display; or scrolls through menu items. Pushing the knob inside the menu validates a selection. Selectable menu items include: language (during review period English, French, German, Spanish and Italian, with more planned by demand); input names; input assignment to specific buttons on the remote including disabling unused inputs; lo/hi gain; variable/direct output; USB mode always on or only active upon selection. Display items include software version; no-reset operating time in hours and minutes like a car odometer, perfect to document actual usage vs. ownership age to protect your investment; tube time to track valve aging which is resettable to restart after a tube swap; a software-based serial number to secure unit identification even with a defaced external serial number; and DAC info which includes the internal software version and the actual operating temperature which will show ~51°C.


All HD DACs undergo a 200-hour factory pre-conditioning before their final individualized measurement documentation. My review loaner showed channel gain of 1.3/1.3V for low gain and 2.04/2.04V for high gain, i.e. perfectly matched. Nagra's pass window is 1.3/2.0V ±0.1V. THD+N was 0.033/0.034 and 0.053/0.054 for the L/R channels in lo/hi gain. Cross talk was -99.7/99.5dB for both channels, with Nagra's minimum tolerance better than 95dB. Things got freakier yet with inter-channel phase. At 20kHz it showed a deviation of +0.01°. Nagra's minimum spec here is better than 0.3°. Remember, that's with two complex interstage transformers which also act as step-ups for passive voltage gain. Their relative phase plot in fact showed a perfectly straight line from 10Hz to 50kHz. That's true Swiss precision!

Upon delivery, Matthieu told me that the SNR of their analog circuit actually measures around 145dB! That the entire circuit would measure lower is due to the DSD front end. That hovers around 128dB. This unexpected offset between digital and analog is testament to Nagra's chops in the analog domain; and their pursuit of costly custom parts to push their engineers' envelope.