We have brought back our hybrid phase inverter bridge completely modernized to Ultra standards with a new multi-stage regulated power supply, new audio circuits, and an astonishing level of performance -- it simply is so transparent it is not there at all.
We did it because the Ultimate 70 vacuum tube amplifier is soooo good, only lacking in absolute power, and we wanted to see just how useful it would be to run two Ultimate 70 amplifiers bridged, with an absolutely pure bridge - phase inverter circuit.
We did it. It works. The results are pretty magnificant. A dual mono reasonably high powered vacuum tube power set that sounds nothing at all like a big vacuum tube amplifier. Attacks and dynamics and range are oh wow startling, but no rough edges, no grain, no glare at all, just all of music, all of the emotions but no mud!
The connection is from your preamp to the left and right inputs of the Ultra Inverter, and from the left and right inverting and non-inverting outputs of the Ultra Inverter to the inputs of two stereo power amplifiers. Then the speaker wires are connect from the hot terminals of each channels (ground side terminals not used) and on to your speakers. The inverter sums the voltage swing of both channels, and since power is essentially voltage squared, the result is close to four times normal single channel power, subject to real world inefficiences of course.
Disadvantages, none except that you need two stereo power amplifiers and the Ultra bridge to make it work. The configuration is not advised for low impedance speakers as the bridge connection causes your amplifier to look at a speaker load as being one half of normal, so this is not useful with 4 ohm speakers or less.
The Ultra Bridge is available right now, at $899 plus $15 shipping.
Thanks for listening.
Frank Van Alstine
