Balanced Audio Technology

Balanced audio Technology has revamped the entire upper range of their preamplifier offerings with the release of four new units, the VK32 at $5495, the VK32SE at $7495, the VK52SE at $9995, and the REX at $17,995. While the first three of these represent improvements over the previous VK31, VK31SE, and VK51SE, the REX is an entirely new concept and represents the pinnacle of BAT's preamplifier design achievements.

The VK32 uses the same 6922-based voltage gain stage as the VK31, but it has two significant improvements. First, the power supply has been converted from solid state to tube rectification, giving the VK32 the added purity of a tube current source. Second, BAT has made significant improvements to other areas of the power supply used in this model. The stock VK32 uses the 5881 tube in the power supply, but there are two other optional configurations. If the owner wishes a less warm, more analytical sound than that provided by the 5881, it is possible to purchase and plug in optional X-PAK boards which provide the capability to use either the 6C19 or 6H30 tubes as current sources. This allows every VK32 owner to customize the sound to match personal taste and/or the characteristics of the rest of the system. There are also performance enhancements such as the SUPER-PAK, SIX-PAK, and upgrade all the way to the VK32SE which can be purchased with the original unit or as later upgrades. (It is worth mentioning that the VK31 has not been discontinued. BAT has kept it in the lineup as an alternative to those wishing a less expensive solution.)

The VK32SE has several important enhancements over the VK32. It has the same three options for a tube current source as the VK32, but it comes equipped with the 6C19 X-PAK board by default. Balanced audio Technology considers the 6C19 to be the most neutral option, but the user can easily switch to the 5881 as used in the VK32 or purchase the 6H30 X-PAK board to experiment with different sonic balances. There are two other very important design enhancements that are built into the VK32SE by default. First, this model uses 6H30 SuperTubes for audio amplification in the voltage gain stage. We've already talked in detail about the sonic advantages of this tube in prior newsletters. Second, the VK32SE has the SIX-PAK and SUPER-PAK options which afford a marked improvement in sonics. Furthermore, the SUPER-PAK uses BAT's latest generation of BAT CAP, an oil-filled capacitor that has been in development for over 18 months. These capacitors enhance the SUPER-PAK performance to a level far beyond that which was available in previous generations of BAT preamps.

The VK52SE has one important sonic upgrade and one important physical upgrade as compared to the VK51SE. The sonic improvement derives from the use of those latest generation BAT CAP parts discussed above in the SUPER-PAK. This gives the VK52SE a smoother midrange as well as airier, more spacious, more liquid high frequencies. The physical change involves convertibility to the REX preamplifier discussed below. The VK52SE is configured so that it can be upgraded to a REX any time the owner wishes. This upgrade path, as well as those mentioned above for other models, is part of BAT's continuing dedication to avoiding obsolescence by providing as many upgrade paths as possible to BAT owners.

And now, THE REX! There are two very significant differences between the VK52SE and the REX. The first is the use of the three tube-based, rectification options discussed above. (5881, 6C19, and 6H30) The REX comes with all the parts needed to implement any of these options, so no extra cost is required to make the changes. Second, the humongous power supply of the REX is divided into the main preamplifier chassis and a second chassis of the same size. Essentially, the power supply of the 52SE is divided into two pieces, a positive polarity which resides in the main chassis and a negative polarity which resides in that second box. Then each half is significantly enhanced over what exists in the VK52SE. REX is not just a preamplifier with an external power supply since this conventional partition suffers from several well-known drawbacks, all resulting from the remote placement of the power supply. REX is a very different beast altogether, with its low-impedance power supply directly connected to the critical gain block. Indeed, REX takes the Balanced Audio Technology tradition of massive and non-conventional power supplies to a level far beyond any previous BAT design. The REX approach to a two-box preamplifier is balanced design taken to a new extreme, with each individual power supply similar in size to that found in many power amplifiers. Both modules maintain true dual-mono architecture, of course. The ten-tube Power Module's supply gets its raw power from vacuum tube rectifiers. The DC voltages then undergo several steps of filtering including the use of C-multipliers and AC Shunt regulators to minimize low-level power supply noise. The final stage of filtering incorporates BAT's newest custom oil capacitors, the same capacitors that are also used in the Control Module's SUPER-PAK. The extreme performance of the REX power supply works in conjunction with the high-current, differential gain stage, composed of four 6H30 SuperTubes per channel. The gain stage continues the tradition of Balanced Audio Technology's Unistage approach that incorporates only a single gain element with no buffers or followers and no global negative feedback to preserve the purity of sound. In summary, REX takes the ultimate simplicity of the Unistage topology to a new level by backing it up with an innovative power supply of extreme heft and purity.