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The Soulnote Philosophy by Chief Designer Kato (Part 11,12)

Oct 27, 2023Jeff Wells
Soulnote Audio

SOULNOTE Chief Designer Kato's Design Philosophy Series Part 11

Chassis Resonance

In this instalment, we delve into the "resonance" of the chassis. Along with damping, it adversely affects sound.

Every object possesses its own unique vibration. Strike it, and it emits a distinct sound. This phenomenon is unavoidable. However, if the natural vibration's sharpness, or resonance strength (Q value), is high, it results in a powerful and enduring sound, reminiscent of a "Kahn" or "keening." This distorts the sound, making it sound repetitive and mundane. Hence, powerful resonance is undesirable.

Just as with a chassis, one can predict the sound of an electrical component based on the noise it makes when struck. For instance, a film capacitor that emits a sharp sound upon tapping likely has a shrill sound quality. I believe that physical properties influence sound quality more than electrical properties.

Consider how a guitar remains silent when its strings are slack. To counteract intense resonance, damping materials like rubber are typically utilized. While this does indeed suppress resonance, it concurrently mutes and degrades the sound. In essence, damping does more harm than resonance. This will be elaborated upon later.

One straightforward method to diminish resonance without resorting to damping is to loosen the structure. This weakens the chassis's overall strength and thereby reduces the resonance's intensity. A relaxed structure also prevents the resonance from one part from transferring to another, much like how a guitar with slackened strings has diminished resonance.

In a previous edition, I mentioned how securing the top cover too tightly can compromise the sound. While air damping was discussed as one potential reason, another could be the intensified resonance across the entire chassis. This happens when the affixed top cover forms a monocoque structure, amplifying the chassis's overall strength. If a tightened top cover not only makes the chassis less open but also hardens the sound, this is the culprit.

SOULNOTE's non-fixed top cover aims to prevent air damping, control the chassis's overall resonance, and stop the top cover's resonance from transferring to the main chassis.

Although an all-aluminum chassis appears attractive, it's highly resonant. SOULNOTE's chassis comprises an ideal blend of aluminum and steel plates. The strength at the joints is minimized to regulate resonance.

Yet, the chassis still vibrates due to sound pressure and power transformer vibrations. It's crucial that these vibrations aren't transmitted to the printed circuit board (PCB), as most electrical components are mounted on the PCB and would vibrate in sync. However, suspending the PCB using rubber isn't the solution, as it introduces damping issues.

At SOULNOTE, the PCB is supported at three points and remains unfixed. It's merely placed atop three pillars without any stress, ensuring that chassis vibrations don't reach the PCB and sidestep the PCB's own resonance.

Moreover, the terminals are unfixed to shield against cable vibration, and the chassis's damping effect due to cable weight is also minimized.

Resonance vs. Damping

Both are detrimental, yet they affect sound differently. Resonance primarily disrupts frequency, while damping interferes with timing. In the past, the focus in audio was predominantly on quelling resonance. However, I deem damping equally, if not more, troubling. I believe humans are acutely attuned to timing, setting SOULNOTE's philosophy apart from other brands.

In the next segment, I'll discuss sound quality criteria in product development, encompassing all that I've previously shared. When I develop SOULNOTE products, my ears are my primary tools. Yet, I don't endeavour to "create" sound. I'll expound on this in the next chapter.

Soulnote Audio


SOULNOTE Chief Designer Kato's Design Philosophy Series Part 12

In this final instalment of the series, we focus on the most vital facet of SOULNOTE's design.

I always design with music playing in the background.

Earlier, I explained the trade-off between static performance (measurable) and dynamic performance (related to timing and hard to quantify). Additionally, I emphasized how a chassis's structure impacts sound quality.

To what degree should static performance be optimized? My stance is clear: if no issues arise when listening to music, it's acceptable.

For instance, consider the residual noise from a phono equalizer. If this noise is less audible than the scratch from a cartridge tracing vinyl, we deem it acceptable. Our main objective then shifts to maximizing dynamic performance. Ultimately, we rely on our ears for judgment.

Measurement is a later step, mainly to identify production flaws during mass manufacturing. During design, I consciously avoid measurements. I'd rather not let catalogue specs skew my judgment.

Had I measured before listening, the Non-Oversampling Sound (NOS) wouldn't exist. Previously, I was convinced that an oversampling digital filter was indispensable. However, during a DA converter experiment, an accidental setting produced a vastly superior sound. Examining the waveform later revealed its stair-stepped nature, a result of inadvertent oversampling deactivation. Had I seen this waveform initially, I'd have immediately rectified it, depriving the world of NOS's unique sound.

SOULNOTE endeavours to respect sound sources—be it vinyl records, CDs, or digital files. Our commitment lies in extracting the utmost from every sound source without altering its essence.

"How does SOULNOTE craft its sound?" is a common query. My reply? We don't. We believe audio equipment shouldn't "create" sound. Sound sources inherently possess brilliance, but it's crucial to harness every piece of information within. And this is where conventional designs, prioritizing static performance, falter. They produce drab, stale sounds. Often, these sounds are then "enhanced" with component tweaks. Yet, if dynamic performance takes precedence, such adjustments become redundant. The key is to remove performance bottlenecks. Once achieved, the sound becomes phenomenal.

Focusing solely on static performance disregards the time element, causing the sound to lose its freshness. No subsequent adjustments can restore it. The analogy is simple: stale sushi cannot be refreshed, regardless of any added seasonings.

In the realm of food, if sound sources are the meal, audio equipment should act as the cutlery. Audio gear should neither be flawed nor artificially sweetened. Prioritizing sound quality means consistently listening to various music genres and periods, barring those overly processed digitally.

Sound quality isn't solely the purview of experts. Most can discern it. Faithfulness to timing makes these differences evident to all, which simplifies my development process.

In conclusion, every piece of music is a human masterpiece. The essence of past musicians is preserved in their recordings. Audio devices must revive this soul. The challenge lies in breaking free from Fourier's confines. At SOULNOTE, our mission is to reawaken this soul, and I'm elated to be at its forefront.