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Still, what was the technology all about? From the website and leaflet we took from Munich show we might construct the following. We use construct because unfortunately the English in both media seems to be computer translated. DREI is an acronym for Dynamic Reduction of Electronics Interaction [and it is also German for ‘three’ which will make sense in a moment – Ed].

According to the information, this distortion reduction is achieved purely in the analog domain to not be DSP. Neutral states that music features three basic waveforms. First there is the sine wave, the most natural form which electronics and in particular loudspeakers have the least problems representing. Second there are triangle waves which Neutral claims are not produced by musical instruments but by ‘electronic elements’. Third there are square waves which supposedly are introduced into the musical signal by digital clocks and digital power supplies. We might argue that triangular, sawtooth and square waves are also emitted by acoustic musical instruments like a clarinet, oboe and bowed string instruments but let’s stick to Neutral’s concept.

In the DREI module, the secretive black box—in fact painted gold—which is at the heart of all Neutral Audio models is some kind of filter. This splits the incoming signal into three separate signals. And that’s where the literature becomes confusing. First Neutral states that the DREI module outputs sine waves with higher definition and sharper detail. Triangular waves meanwhile are converted into more or less sine waves and square waves follow the same transformation. Eventually recombined, this output is claimed to be more compatible to the wave patterns which a loudspeakers handles easiest and thus to ‘optimize the electromechanical efficiency’ of the loudspeakers.

But there is more going on in this after-preamp and other Neutral products - "functions that cannot be explained by the company to remain secret". However, the reworked signal more benign to the speakers is split into three once more. Neutral’s images show the incoming signal as chaotic whence the DREI module splits it into three separate frequency blocks. Each block is now input to either 2 buffers in the X-DREI—the device under review—or to 2 to 4 separate preamps in the other models. In total the X-DREI uses 6 buffers. After the buffering or preamplification stages, the signal is passively recomposed and output to the power amplifier. There is a feedback loop from the output back into the DREI module in case the Neutral devices interface with active preamplifiers.

In short, by introducing the X-DREI between your existing preamplifier and  power amplifier, the incoming signal is reshaped then split into three to be buffered then recombined before being passed on to the power amp. All this happens in the analog domain. But there is another capability. This is the possibility to manipulate the impulse response of the buffers (or in the other Neutral models their inbuilt preamplifiers). Controlling the impulse response lets the listener choose her listening position in the virtual concert hall of the home. In the X-DREI a dial positions the listener at the conductor’s stand, farther back to front row or even deeper into the hall. This adjustment can be made on the fly. The X-DREI can be switched off to insert a minimal passive signal path into the usual system (plus of course the added interconnect).