Dyad S400 is the worldâ€™s first true fully balanced hybrid power amplifier in which voltage amplification is done by all vacuum tubes. It employs the patented Dual Balanced Feedback Topology (DBFT) and proprietary high current buffer amplifier (HCBA). S400 is a stereo power amplifier that delivers over 200W to a 8-ohm load and 400W to a 4-ohm load per each channel. Since voltage amplification is done by all vacuum tubes, and the HCBAs have unity voltage gain, the mids and highs of the audio spectrum have retained very much to a tube power amplifier. But S400 has much better bass performance over tube power amplifiers by means of tremendous current drive provided by solid-state transistors.