Stereocheck Reviews:

BAT introduces the VK-85 preamplifier and REX 300 power amplifier on Axpona

The American manufacturer Balanced Audio Technology (BAT) introduces the VK-85 preamplifier and REX 300 power amplifier at the Axpona fair in the US. Both devices have a fully balanced topology....


The American manufacturer Balanced Audio Technology (BAT) introduces the VK-85 preamplifier and REX 300 power amplifier at the Axpona fair in the US. Both devices have a fully balanced topology. Delivery will start during the second quarter of 2024.

BAT stands for fully balanced circuits

Of paramount importance to the VK-85 and REX 300 – and all previous BAT models over the past thirty years – is the reasoning behind the use of fully balanced circuitry. Balanced Audio Technology believes that balanced is better because it simply provides full signal representation. This principle is even incorporated into the manufacturer’s name. Something very magical happens when the limitations of a single-ended circuit with its half-signal processing from an audio component are removed and replaced with a balanced circuit topology.

In addition to the established benefits of signal integrity for long interconnect cables, there are other benefits to balanced circuits: As a circuit becomes more symmetrical, the residual effect of the power supply becomes less intrusive – the demand on a power supply becomes less onerous – so it becomes easier to provide a balanced to design a circuit that better matches the technical ideal.

BAT REX 300: Little Emperor

Power amplifier REX 300 is essentially a lower power version than the flagship REX 500 . The REX 500 can deliver 500 Watts per channel at eight Ohms and not everyone needs that. That is precisely why BAT built the REX 300 and the REX 300 can deliver 200 Watts per channel and has the same sound properties as the REX 500. After all, the REX 300 has almost all the exceptionally advanced circuits on board that its big brother also has. possess.

The REX 300 starts with a massive power supply and uses the same TWIN-Path (split power topology) as the REX 500. These individual power paths allow the power supply to deliver much higher current than traditional designs. This power supply design is further enhanced by BAT’s new “SuperPak Quattro” capacitor bank which offers four levels of power filtration. This is achieved through the use of high quality third level silver foil/oil capacitors connected by an X-cap. As a result, the textural beauty, tonal density and harmonic accuracy of the music become much clearer.

Because the best sounding fuse isn’t a fuse at all, the REX 300 follows its big brother with a protection circuit that eliminates internal fuses, allowing it to handle higher currents without interfering with circuit operation.

The REX 300 represents the pinnacle of simplicity for modern high-power amplifier design thanks to an amplifier circuit consisting of just two gain blocks. Furthermore, the output stage is based entirely on “N-channel” MOSFET devices (as opposed to the traditional complementary “N” and “P” channel devices where “P” is inherently slower and therefore inferior according to the manufacturer), making both sides of the waveform that can be processed by identical devices in an identical circuit configuration, ensuring symmetry of the resulting signal.

Finally, there is the “Intelligent Power Upgrade” where a REX 300 can be ordered as a stereo amplifier or as a monoblock. BAT provides a transparent upgrade path that allows an owner of a stereo REX 300 to easily convert it to a monoblock configuration at any time. There is no need to trade in the amp to get more power. A simple conversion of a customer’s existing stereo REX 300 to a monoblock and ordering a second REX 300 monoblock to match. Technically, the conversion from stereo to monoblock is achieved by connecting the inputs and outputs in parallel.

BAT VK-85: preamplifier

Preamplifier VK-85 is the result of a new design strategy that takes advantage of several improved internal circuit technologies, including the aforementioned “SuperPak Quattro” and the “Second Generation Transformer Coupled Outputs”, as well as proven BAT circuits such as Unistage Design, high-current N-channel MOSFET circuit and shunt volume control.

The new “SuperPak Quattro” dramatically lowers the overall noise floor of the VK-85 preamp, while the new “Second Generation Transformer Coupled Outputs” deliver a very open and dynamic sound, free from both the sonic and longevity drawbacks that are common in capacitor-coupled designs. While all BAT preamps use transformer-coupled outputs, the VK-85 is at a whole new level of premium output transformer design.

BAT VK-85: Unistage Design

Unistage Design in a preamplifier serves to maintain the integrity of the input signal. With the VK-85, this is achieved using just one amplification stage – one that is free of the negative artifacts that can be attributed to both extremes of modern preamp design: passive preamps and multi-stage buffered active circuits. The BAT registered Unistage circuit provides the ultimate simplicity of amplifying the incoming signal just once without using global feedback to double the integrity of that signal. This remains a hallmark of BAT’s purist approach to circuit topology.

The VK-85 circuit is based on High-Current N-Channel MOSFET devices where both sides of the waveform are handled by identical devices – in identical circuit configuration – ensuring symmetry of the resulting signal, just as described for the REX 300 The high-precision volume control uses a patented electronic shunt volume attenuator with 140 steps with a resolution of 0.5 dB. This is achieved using a single Vishay bulk film resistor – the most accurate and thermally stable resistor available – per phase. This is everything that is in the signal path. Discrete metal film resistors are used to route the unused signal to ground. The 140 steps provide precise repeatable volume settings that sound continuous to the human ear.

For added convenience and compatibility with source components, the VK-85 includes a mix of balanced (XLR) and single-ended (cinch) inputs and outputs.