The Siegmund Amplifiers Doppler Stereo Amp is hand-wired and uses the company’s Asymmetrical Frequency Soundstage design, which it says divides high and low frequencies into the amp’s two rotating speakers, one 10″, the other 15″. The v-front cabinet helps it produce a pitch-shift vibrato with a rotating-speaker sound in stereo. It uses KT66 and EL34 power tubes, and the 15″ speaker rotates slower to provide background for the soundstage, while brighter frequencies from the faster 10″ speaker float in the foreground. Other features include a transformerless reverb, true-bypass Master Volume, variable-speed foot controller, adjustable bias, and custom transformers by Mercury Magnetics.