As we see in the next photos taken in Nagra's listening room during my September 2014 visit when the HD monos were in R&D, two very large Verity Audio 4-ways serve as one of their design team's reference speakers. I was allowed to take photos of the big prototype amps whose circuitry then was pretty much locked in though still lacked various protection. What hadn't been decided yet were the final shape and associated mechanical engineering. For once, no considerations were given to fitting things into a case of predetermined legacy dimensions. Instead, the team were free to pursue whatever parts they wanted to obtain flagship sound. Only then would mechanical start sweating layout; and whether a taller narrower case à la VPA or Mark Levinson was best, or something wider and deeper like the temporary protos. The only thing crystal to everyone already back was that no matter what, these would be big.


With the first 50 watts in pure class A and from a linear supply, the in-house wound power transformers of the HD monos had to become seriously ironic chunks. Here they were concealed beneath the internal hoods. Their size then approximated a 2-litre cooking pot. The power-supply caps were of Coke-can diameter. Again, what became the progenitor of the Classic Amp was a balls-out project. It finalized before number crunching had its bill of materials to determine what the big boys had to go for. Without even an approximate target price—and with precedents of competing Swiss amps commanding well in excess of €100'000—marketing manager Matthieu Latour himself didn't have the faintest. He did however know that the Classic would come in at about twice the coin of the MSA. After all, for every sky's-the-limit customer, there are 100s if not 1'000s willing to likewise indulge their hifi passions but who are constrained by less opulent means. Spinning that theme downward and seeing how the MSA would be discontinued... might Nagra follow the Goldmund/Job precedent? Why not repackage the MSA as a poor man's Nagra and sell it direct? Sans trademark case, modulometer and designer heat sink, wouldn't a plain Jane 60-watter with bona fide Swiss-made Nagra sonics enjoy a very appreciative audience? Consider this our informal petition.


Here now is Matthieu with more on the Classic.


"The MSA had always enjoyed a very fine reputation for its great transparency and finesse. It came with amazing measurements, an extremely low noise floor, negligible distortion and so forth. Really the only request we ever received about it from customers was, could we make it more powerful. Though it might seem a trivial matter, in Nagra terms it isn't. When the HD DAC created a new chassis paradigm for us with its increased depth, we dared push that envelope further to now grow vertically. Whilst the Classic Amp remains reasonably compact, it provides far more interior space to accommodate larger parts and scale up thermal dissipation. This allowed our engineers to go after a much larger power supply. Just like in the MSA, that's an SMPS with PFC (power factor correction) to increase its dynamic headroom. As a consequence, the amp behaves far more powerful than its specs would suggest. The larger casing also supports more and larger capacitors and higher voltage rails. Then the Classic benefits from a completely new input stage with RCA and XLR balanced inputs. As our extensive R&D on the HD Amps showed us, this stage is an essential contributor to the final sound. Applying advanced computer simulation software, we also optimized heat dissipation. This allowed for a dramatic increase in class A bias. The result is a very smooth transparent amplifier with more power and greater reserves than the MSA and a tighter grip over your speakers. It behaves rather more powerful than its measurements indicate. As any short audition demonstrates very quickly, this new amplifier is really a smaller HD Amp, not a bigger MSA."

Matthieu Latour with Martin Gateley during a Jazz/Classic Amp demo of the new soundkaos SK16 speakers in our digs which led to a joint show exhibit in Munich.

Re-reading a 2010 paper on the MSA, I found this: "With a PFC-driven power supply, the electrical current is always in phase with the voltage in a perfect sinusoidal curve. There are no interference peaks or distortion. From the power grid’s perspective, this type of power supply is seen as a pure resistance. That avoids polluting the grid. In a way such a supply behaves as though it were electrically decoupled from the wall AC. Another obvious advantage is the very clean current propagated downstream to other circuits. By precisely superimposing current and voltage, the PFC power supply generates little losses. It guarantees very efficient energy transfer and doesn’t collapse with load increases. It is therefore capable of reacting extremely rapidly to on-demand stress situations from the output stages. The MSA power supply is built in ways which fundamentally distinguish it from more conventional switch-mode power supplies. In particular, it has no fly-back transformer or snubber circuit which can lead to hot spots on the PCB. Instead a sizeable 200VA toroidal transformer reduces the rail voltage to ±35V to suit the output stage and derive all other supply voltages from. This transformer runs at the power grid’s frequency to avoid generating any residual HF noise."


On further specs, the MSA had 10Hz-75kHz response at +0/-3dB, an A-weighted SN/R of 109dB, >100kΩ input impedance and <0.08% THD at full power. Its 115/230V acceptance windows of 90-132V and 180-264V demonstrated further SMPS benefits. For the Classic, the rail voltage became ±48V (up from ±35V) with a 50% increase of class A bias and 141'000µF filter capacitance per channel (up from 84'000µF). The input board grew its own dedicated ultra low-noise linear supply. The already low noise floor of the MSA was pushed down by another 10dB. Bandwidth became <10Hz-80kHz +0/-3dB, THD at full power <0.05%. Max power draw is 400 watts which implodes to below 1 watt in standby and auto modes. Output impedance is 60mΩ in stereo, half that in bridged mono mode. Net weight is 15kg, size is 27.7 x 39.5 x 17.4cm WxDxH.