NVA's Specific Design Criteria
NVA has a unique design philosophy that would put many a high-end
manufacturer to shame:
The cases are made entirely of non-magnetic materials: anodized aluminum,
wood and smoked plexiglass.
The case sides are bonded together with structural adhesives to avoid the
magnetic contamination of steel screws.
The circuit boards are similarly bonded to wood strips, themselves bonded
to the thick anodized aluminum case bottom.
The output transistors, beefy 10 amp Darlingtons, are also bonded to the
case bottom, which acts as a superb heat-sink.
No surprise. The diode bridge is also bonded to the case bottom, as are
the power supply caps.
Internal high current wiring from the power supply is uncoated, stiff solid-core
coated copper of approximately 14 gauge. A real bus. No coating beats even
Teflon. The resulting girder-work makes any NVA kit amp a unique proposition
to look at with the lid off. However, pre-assembled amps are glued shut
to keep out the curious.
The input selector switch, where fitted, is wired to the input RCA jacks
with teflon-coated, plated copper wire, as is the connection from selector
switch to the volume control and thence to the input on the circuit boards.
A small compromise.
The volume control is of pure cermet type for minimal aural impact, even
if it may feel coarse to the touch. The pot's tracks are linear to achieve
close channel tracking, with a resistor added to simulate a log law.
No attempt is made to add output compensation networks, such as an inductor
or parallel capacitor network or even fusing. Therefore, the amplifier
is not unconditionally stable, and requires low capacitance speaker cable.
LS1 is a superb choice. It has a separate positive and negative cable
for each channel to minimize capacitance, about 7pF per foot, and
is made up of seven individual silver alloy solid core conductors per cable
in a black woven sheath terminated in the new safety-inspired European
Union banana plugs.
NVA assumes that you as the owner will read, understand and heed
the caveats regarding speaker wire and not short-circuiting the outputs,
in order to obtain truly high-end performance at a fraction of its normal
cost. Remember, the payoff is wonderful sound.
There are NO adjustments for DC balance or output bias current settings
-- nothing to go wrong or drift with age. Nevertheless, the amplifiers
are direct-coupled, no coupling capacitors to colour the sound. All circuit
board electrolytics are bypassed by large value polystyrene caps,
to filter the supply over a wide band.
All NVA amps are quiet -- extremely so.
The amplifiers are designed by Richard Dunn, who used to design bulletproof
pro amps for the road. But for hi-fi, he maintains simplicity and careful
design from a solid philosophical
base gets the job done best.
The NVA AP50 with MC module