The "18" denotes 18 watts from a pair of EL84 power tubes. But these are not your father’s EL84s. The Sets.33 specification runs the plates at a slightly lower voltage than the Vox AC15, forcing the tubes into saturation faster . This yields a harmonic-rich breakup that is simultaneously chimey (like a Vox) and throaty (like a Tweed).
The typical acquisition path is akin to finding a secret society: A Little Agency - Laney Model 18 Sets.33