CYBERFi - Review, 1996TECHNICAL DESIGN
The key to this amplifiers design is its simplicity. From the hard-wired input connections and the use of passive pre-amplification, to the absence of tone controls and filtering, this is about as minimalist an amplifier as you could conceive.
A 100kohm ceramic metal passive volume control is the main component in the passive pre-amplifier. A 10kohm metal film resistor is used with the pot to derive a near logarithmic attenuation logic. The almost total absence of filtering is very unusual. There's no output filer, only a 470pF input capacitor, and tone controls are omitted, on the grounds that NVA believes all these extraneous components and circuits are bound to compromise performance.
NVA's own phono stage can be added to the standard AP30 retrospectively. Alternatively NVA will fit the board during manufacture. As you'd expect, the phono equipped AP30 is slightly more expensive that the line only amp. All the necessary wiring changes and board fitting required to modify from line-only to phono-equipped AP30 are made at NVA's factory.
The amplifiers unusual glued case may not appear an inspired aspect of the design; don't be fooled. The case is an important element in the AP30. NVA discovered that the reason previous products sounded worse than preproduction, bread board equivalents was simply the addition of a production metal case. It turned out that the metal cases stored charge and electromagnetic fields which interacted with the signal-carrying circuits. Hence the use of wooden sides, an aluminum base and acrylic front panel.
The power amplifier is designed to deliver high current when required through conventional bipolar output devices. Mains power is fed to a 160VA toroidal transformer closely specified by NVA. Power supply regulation is achieved with the help of conventional 1950s wound paper capacitors.
Return to NVA AP30 Introduction