Svetlana Winged =C= 6550C represents high quality audio output tubes intended for hi‑fi power amplifiers. Known for their stability and linearity, these 6550Cs are valued in serious lighting systems and studio applications.
Technical characteristics
Type: Beam-tetrode (6550C), base: octal (8-pin), standard 6550 pinout
Heater: 6.3 V / 1.6 A
Max. anode voltage (Va): 600 V
Max. grid voltage (Vs): 400 V
Max. anode dissipation: 35 W; screen: 6 W
Transconductance (gm): ≈ 11 mA/V (typical)
Gain factor (µ): not applicable for beam-tetrodes; GM is relevant
Typical power (push‑pull AB1, 6550 pair): ~60–100 W with proper voltage and bias
Bias: according to construction; often 35–45 mA/tube at fixed bias (approximate)
Compatibility: 6550/6550A/6550C; often a replacement for KT88 with a check of operating points
Sound characteristics
Neutral to slightly warm balance, very controlled and deep bass, clear and unmatched high zone, open and stable midrange. They feature good microdynamics, a wide stereo stage and mature headroom, with low microphonics and noise when properly paired and tuned.
Compatibility and application
Ideal for push‑pull amplifiers from hi‑fi manufacturers such as Audio Research, McIntosh, VTL, Cary and similar, as well as for instrument amplifiers designed for the 6550. They can operate in ultralinear or triode mode (depending on the design of the amplifier). Paired quartet is suitable for stereo amplifiers with two outputs per channel or monoblocks; precise bias adjustment after installation is recommended.
Condition and maintenance
Second-hand, perfectly preserved. The quartet is matched (matched quiescent current conditions and gm) and tested for leakage and emission; visually clean with no signs of overheating. There is no visible damage to the plinth or glass. Recommendation: after transport, check the bias and allow several hours of stabilization in operation. Measurement data available on request.
