NAGRA VPA

Pre owned. In excellent condition. Free from any obvious signs of wear. Supplied without original packaging.

Pair of monoblock tube power amplifiers designed for pure Class A operation with a push-pull triode configuration. Each monoblock delivers 50 W and features balanced and unbalanced inputs. The output stage operates without negative feedback, using a circuit design intended to maintain linear behaviour and minimise signal alterations.

Each VPA uses a pair of individually selected and matched 845 power tubes. Before matching, the tubes undergo a 24-hour burn-in process and numerous measurements, after which they are selected using a computer-assisted system to obtain pairs with the most consistent characteristics possible.

The circuitry is fully balanced from input to output, helping to reduce intermodulation distortion and phase shift while eliminating the need for internal feedback. The design also provides particularly fast rise times, high slew rate and low overshoot, maintaining consistent behaviour both at low power levels and when the amplifier reaches full output.

The VPA is designed to handle loudspeakers with demanding electrical loads. The absence of negative feedback facilitates matching with different types of loudspeakers, including electrostatic designs and low-impedance dynamic models. Dedicated outputs are provided for 4, 8 and 16 Ω loads, allowing the amplifier to be matched to the characteristics of the loudspeaker in use.

The output stage uses proprietary Nagra transformers designed to limit low-frequency saturation and high-frequency ringing commonly associated with transformer-coupled output stages. This configuration provides adequate extension in the low frequencies while maintaining precise delineation of the scale of the soundstage.

The chassis of each monoblock is constructed as a machined-aluminium tower. The construction follows an approach focused on the use of selected components and a design without compromises in the implementation of the amplifier's various stages.

Technical specifications:

• Amplification class: pure Class A
• Input impedance: >100 kΩ
• Output impedance: 4, 8 or 16 Ω
• Frequency response: 20 Hz–40 kHz +0/-3 dB
• Output power: 50 W RMS
• Signal-to-noise ratio: typically >100 dB, ASA A-weighted
• Input stage tubes: 2 × ECC83; 1 × E182CC
• Power stage tubes: 845 triodes
• Inputs: balanced XLR; gold-plated WBT Cinch unbalanced
• Speaker outputs: gold-plated WBT connectors; compatible with cables up to 4.2 mm; 4 mm banana connectors; 6.35 mm spade connectors
• Dimensions: 335 × 115 × 375 mm (W × H × D), without tubes
• Weight: 13.5 kg per monoblock