Hybrid Bi-Amping

People like tube amplifiers because of their softer tones at higher frequencies. At lower frequencies this effect is less pronounced. More importantly, due to audio transformers used on tube amps, the lower frequencies are less amplified. The high-end Hi-Fi speakers usually support bi-amping. Therefore, high frequency section of the speaker can be driven independent of the mid to lower frequency section of the speaker. I would like to propose a hybrid bi-amp to create the lovely soft tones of a tube amp with a much efficient and economical way.

My design solves three major problems. First, the low frequencies would be better amplified using transistor amplifiers compared to tube counterparts which are less affected by the tube’s tonality. Second, high frequencies do not need high power amplifiers. Therefore, the tube amplifier can be designed with much less power output which reduces the cost. Third, output audio transformers of the tube amplifier can be optimized for a narrower frequency range to lower cost and improve tonality.

The input signal would be pre-amplified using tube amplifiers. Then the amplified signal would be split into high and low frequencies using a cross-over network. The lower frequencies would be power amplified by efficient push pull amplifiers without coupling capacitors or transformers to output even the lowest frequencies, 20 Hz. The highs would be power amplified using a single ended tube amplifier, e.g. by KT-88, to create the beautiful tones of a single ended amplifier. Coupled with highly efficient horn speakers, e.g. Klipsch horns, they would produce really powerful highs with minimal input.