Balanced Audio Technology - VK-85 Solid-State Preamplifier

By Michal Czarnota Balance Audio Technology, Product Presentation, Phono Preamplifiers No comments on Balanced Audio Technology - VK-85 Solid-State preamplifier.

Developed in accordance with the company's latest design strategy, it uses improved techniques and internal circuits like: "SuperPack Quattro" and "Second Generation Transformer Coupled Outputs." It also employs solutions known from previous BAT designs: Unistage Design, High-Current N-Channel MOSFET Circuit or Shunt Volume Control.

"SuperPak Quattro" - The design of the power supply has been further improved with the new "SuperPak Quattro" capacitor bank, which provides four levels of power supply filtration. This was achieved by using the highest quality silver film-oil capacitors, which are shunted with an X-cap capacitor. As a result, the beauty of texture, tonal density and harmonic accuracy of the music become much more apparent than with traditional solutions. The new "SuperPak Quattro" dramatically reduces the overall noise floor of the preamplifier, while the connection of the output to the input of the power amplifier using transformers (Second Generation Transformer Coupled Outputs) provides a highly open and dynamic sound, free of both sonic defects and much more durable than typical capacitor-coupled designs.

Unistage Design - in a preamplifier serves to maintain the integrity of the input signal. In the VK-85, this is achieved with only one gain stage - free from the negative effects attributed to both types of contemporary designs which are the passive preamplifier and the multi-stage active circuit preamplifier. The Unistage circuit, which is a BAT trademark, provides the ultimate in simplicity by boosting the signal once, without the need for global feedback to achieve the integrity of that signal. This is a characteristic of BAT's purist approach to circuit topology.

The VK-85's circuit is based on high-current N-channel MOSFET transistors, in which both sides of the waveform are operated by identical components and in identical circuit configuration - ensuring symmetry of the output signal. Highly accurate volume control uses a patented electronic shunt level attenuator with 140 steps of 0.5 dB resolution. This is achieved using a Vishay film resistor (one per channel phase), which is the only component in the signal path. It is the most precise and thermally stable resistor available on the market. Its 140 levels provide precise and repeatable volume settings for both channels simultaneously, which sound to the human ear consistently.

The VK-85 preamplifier is traditionally fully balanced. BAT firmly believes that a balanced circuit is best because it provides simultaneous amplification of the full signal. Something very magical emerges when the limitations of an unbalanced circuit with its half-way audio processing are removed from an audio device. In addition to the well-established signal integrity benefits for long distance connections, balanced circuits also have other advantages. When a circuit becomes symmetrical, the residual effect in the power supply becomes less intrusive - the power requirements of the circuits become less critical so they are easier to design perfectly. For added convenience and compatibility with various source components, the VK-85 includes a mix of balanced and single-ended inputs and outputs.

BAT VK-85 preamplifier key features:
- Balanced topology circuitry
- Revised power supply incorporating new fourth-generation SuperPak topology
- Outputs using second-generation transformer coupling
- High-current circuitry using "N" channel-only MOSFETs (faster and more powerful than "P" channel)
- Noise (unweighted): - 96 dB / THD @ 2V output: 0.01%
- Inputs: 3 x XLR, 2 x RCA
- Outputs: "Main" 2 x XLR and "Tape Out" x 1 RCA
- Patented electronic shunt volume attenuator with 140 steps with 0.5 dB resolution
- Frequency response: 2Hz-200kHz
- Maximum gain: 20dB
- Dimensions: (S x W x G in mm): 483 x 147 x 394
- Weight: approx. 18kg

For more information and a photo gallery, visit the BALANCE AUDIO TECHNOLOGY website.

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