Tri-amplifying with Wotan

One of the VTL innovations is the use of extremely high power to better convey the power and emotion of large-scale music in large listening rooms. Recently we were able to demonstrate this point rather effectively to show goers at Hi Fi '98.

At Hi Fi '98 show in Los Angeles, VTL used 3 pairs of our most powerful amplifier, the Wotan MB-1250 Reference monoblock to drive the Martin Logan Statement evolution 2 CLS loudspeaker system in a 30' x 40' room: 1,250 watts of pure tube power per monoblock.

The primary reason for this amount of power requirement was because of the size of the room and the number of listeners: 1200 sq ft, with 40 people at a time. The loudspeaker requirement was for an average Sound Pressure Level of 110dB, with maximum peak SPL of 115dB, with as little distortion as possible, to match the ultra-low distortion characteristic of the Martin Logans. Using such high powered amplifiers meant that we could stay in class A operation for most of the program.

Taking advantage of the VTL Wotan's unique ability to switch between triode mode and tetrode mode, it was decided that for the demonstration material the triode (half power) mode was the preferred mode for the hf, mid and mid-bass.

The full power tetrode mode was chosen for the bass sub-woofers. Accurate gain matching between the triode mode and the tetrode mode was achieved by the Martin-Logan Exos active crossover.

The second decision to triamplify was made primarily due to the high SPL requirement of the demonstration: 600 watts in triode mode for the mid-bass (60 - 200 Hz) and another 600 watts for the electrostatic panels (200Hz - 20 kHz), added to the 1250 watts for the bass and sub (18 Hz to 60Hz) completed this most powerful presentation at a total of 2500 watts per channel.

The biggest reason for triamplifying a system like this is the unique ability of triamplification to separate out the different frequency requirements of the loudspeaker load. While the bass amplifier's power supply is being modulated by the bass notes, the effortlessness of the electrostatic's hf presentation can stay rock steady across the soundstage, and can build with its own power without being distorted by the demands of the bass requirement. This particular capability of this system's was most clearly demonstrated in the Rutter Requiem recording with the chorus and the underlying 32 Hz organ pedal. The bass rolled through the room in waves, while the chorus floated above the bass line, seemingly sublimely unaware of the (literally) room-shaking bass notes.

In driving loudspeaker loads down to 1.5 ohms in the panel and 2 ohms in the 16 x 12" sub-woofers, the VTL Wotans are the epitome of the power statement made by VTL, where it was clearly demonstrated that with modern approach to extremely stiff power supplies, tubes can be made to approach the reliability and loudspeaker control of the best solid state amplifiers, with the additional speed, musicality, tonality and headroom of the best tubed designs, allowing us to hear the beauty of the low-distortion combination of tubes and electrostats.