GRAAFITI VENTICINQUE

Pre owned. In good condition. Shows minor signs of wear on the top panel, slightly visible in the photos. Not supplied with the original packaging.

Tube stereo integrated amplifier with a pure Class A push-pull output stage, designed to deliver 25 watts RMS per channel into a 4-ohm load and 20 watts into 8 ohms. The configuration combines preamplification and power amplification in a single unit, reducing the number of connections required within the system.

The power stage uses a total of four 5881 tubes, two per channel, configured in push-pull and coupled to output transformers specifically designed by GRAAF. The same platform can also use 6L6 tubes, while maintaining the circuit configuration specified by the design. The power supply employs a toroidal transformer built to GRAAF specifications, integrated into a structure designed to provide the different stages with the required operating conditions.

The bias circuit for the output tubes is automatic. This particular bias system maintains a stable operating point even as the tubes age and allows the power tubes to be replaced without requiring manual adjustment of the amplifier.

The driver stage uses two 6922 dual triodes, which precede the output stage and complete the all-tube amplification path. The amplifier stage and output transformers are designed to maintain the signal in an entirely tube-based configuration, from the preamplifier section through to the speaker outputs.

The integrated preamplifier allows various analog sources to be connected. It provides four line inputs, a Tape Monitor input/output and an additional line input prepared for the installation of an MM/MC phono board. The phono board can be requested with the amplifier or supplied later as a GRAAF optional accessory, allowing a turntable to be integrated directly into the system.

A separate stereo output is also provided, allowing the signal to be sent to an additional power amplifier. This configuration allows the Venticinque to be used in systems where a second set of speakers needs to be driven, for example in a multi-room system, or as part of a home theatre configuration.

The design therefore combines a preamplifier, tube power stage and the possibility of connecting a phono source within a single chassis, while retaining the option of expanding the system through the dedicated stereo output. The construction follows the GRAAF design approach of the period, with particular attention to circuit implementation, tube operating stability and the integration of the different amplifier sections.

Technical specifications:

• Output power: 25 W + 25 W RMS
• Output impedance: 4 – 8 Ω
• Input sensitivity: 140 mV
• Input impedance: 47 kΩ
• Preamplifier output: 1.4 V at 25 W
• Frequency response: 5 Hz – 100 kHz (-3 dB at 1 W)
• Power response: 11 Hz – 80 kHz
• Total harmonic distortion (THD): 0.2% at 1 W
• Signal-to-noise ratio: 86 dBA
• Damping factor: 1.5
• Negative feedback: 6 dB
• Power tubes: 4 × 5881; compatible with 6L6
• Driver tubes: 2 × 6922
• Output stage configuration: pure Class A push-pull
• Bias: automatic bias
• Inputs: 4 × line; 1 × Tape Monitor; 1 × line input prepared for MM/MC phono board
• Stereo output: 1 × preamplifier output for connection to an additional amplifier
• Mains voltage: 105 – 120 V / 210 – 240 V; 50 – 60 Hz
• Dimensions: 410 × 145 × 385 mm (W × H × D)
• Weight: 20 kg