Audio Research CA 50 Needs to be re-tubed. This unit brought me many hours of enjoyment. See reviews below. The unit comes with 4 Sovtek 6550. You will need to buy new matched 6922 driver tubes. The design is quite particular about the matched drivers for optimal performance and reliability. Best to use the matched sets from Audio Research as they are matched according to the AR specs. The output section is more forgiving. Please keep this in mind. I opened up the unit for photos. It comes with the top and bottom covers and feet. Tube Compliment: Sovtek 6550 output x 46922 driver tubes x 4 Power output: 45 watts per channel into 8? (stereo) Frequency response: 2Hz to 50kHz Total harmonic distortion: 2% Damping factor: 13 Input sensitivity: 300mV (line) Signal to noise ratio: 85dB (line) Speaker load impedance: 4? to 8? Valve complement: 2 x 6550C, 4 x 6922 Dimensions: 483 x 178 x 381mm Weight: 19.5kg https://www.whathifi.com/features/was-then-audio-research-ca50-review Terms & Conditions: Sold As-Is. All Sales Final