Overview
Soulnote recently caught our attention at a prominent Hi-Fi show in North America. The sounds being produced were so impressive that repeated visits were made to their listening room to verify our initial impressions. What we discovered with this relatively obscure Japanese brand is very special indeed – creative audio designs that strive to keep the listener engaged at a fundamental level. With three simple and distinct products ranges, Soulnote has a solution for music enthusiasts at all price and performance levels.
Design Philosophy
In the world of Hi-Fi design, following your gut instincts (not just measurements on a oscilloscope) can often yield unpredictable yet excellent results. Chief Soulnote designer Hideki Kato knows this well. Throughout his long career with companies such as Marantz, NEC & Philips, Kato was determined to find out why improvements in static performance (lab measurements) and sound quality did not always correspond. Kato named his hypothesis ‘Dynamic Performance’.
The adoption of the NOS (non-oversampling) mode for PCM digital playback as well non-NFB (negative feedback) circuit in amplifiers stem from this hypothesis. Curiously, he discovered that these design concepts may worsen the lab measurement results, but a remarkable improvement can be achieved during actual human listening tests.
While unmeasurable using conventional methods, he decided that maintaining accuracy of the original music waveform on the time axis is one of the most important considerations for music playback. At Soulnote, listening tests are heavily relied upon to determine parts selection and mechanical construction. This approach is a kind of antithesis against the supremacy of static performance, an approach not widely adopted by other manufacturers.
Amplifier Technology
To extract the best from the unique characteristics of SOULNOTE’s original perfectly balanced, discrete non-NFB circuits, we re-examined every minute detail of our amplifiers for possible improvements, like incorporating ground plane star wiring, centralizing local non-NFB regulators, implementing direct coupling routes, optimizing the tuning of the drive current, and more. This helped us achieve even more vibrancy and speed while also providing a wider sound range.
Every type of connector in the signal system has been eliminated to create a completely contactless construction. A three-dimensional print board assembly results in lower impedance in the power supply lines and wiring that focuses on star wiring. This improves S/N and removes any concerns about contacts deteriorating over time.
The output transistors feature low Cob, high Ft, and have extreme accuracy. We have selected and paired these components based on their characteristics. They work together to increase sound image focus and deepen three-dimensionality.
Power Supply
In addition to a newly developed bifilar wound, large capacity toroidal transformer with independent positive and negative windings, we have lowered the impedance by connecting multiple high-voltage, small-capacity filter condensers in parallel and incorporating a fast recovery rectifier diode. We have also completely refined the smallest details in order to boost the power supply, such as making current loops as short as possible by placing the rectifier diode close to the power transformer. This further increases S/N and speed.
Chassis Construction
Spikes connect to the bottom of the transformer’s center of gravity to directly expel harmful vibrations without interfering with the unit housing itself. This achieves both supremely vibrant musical expression and a high S/N.
The housing’s symmetrical construction increases rigidity balance while controlling the sharpness of resonance (Q factor). This eliminates the usual sensation of sound containment in highly rigid systems and creates the high resolution, expansive SOULNOTE sound. The newly developed, heavyweight aluminum front panel design also helps control resonance.
