Overview

KOJO Technology (brand of Kojo Seiko Co., Ltd.) is a Japanese manufacturer established in 1990 and headquartered in Hirakawa City, Aomori. It focuses on grounding accessories such as “virtual ground” boxes and cables for high-end audio systems. The Crystal E/E-G boxes use multi-layer dissimilar-metal stacks and advertise very large effective conductor surface areas (the Crystal E-G claims a total ~68,000 cm²), but the company publishes no evidence of corresponding improvements in standard audio metrics. [4][5][6][7][8][9]

Scientific Validity

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Independent, measurement-focused evaluations of comparable “signal grounding” boxes have not demonstrated objective, positive changes in THD, noise/SNR, frequency response, or crosstalk; one well-known bench test on an Entreq unit found no useful current flow and introduced spurious noise peaks when connected. KOJO’s own materials list construction details (layer counts, materials, surface-area claims) but do not provide standardized audio-performance deltas. In the absence of credible, third-party evidence of audible or measurable benefits, scientific support remains very weak. [1][5][6][7]

Technology Level

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Build execution is competent for a passive accessory: Crystal E uses an 8-layer metal stack (stainless/brass/copper), dual M4 ground terminals, and a compact, heavy chassis (~775 g; 80 × 111 × 35 mm). The limited-edition E-G version adds etched plates and internal capacitor modules. Despite the careful mechanical work, the core concept lacks demonstrated efficacy on audio performance, so the engineering value is average within this niche. [5][6][7]

Cost-Performance

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Representative market prices (USD): Crystal E ~379.99 USD; Crystal E-G ~699.99 USD. A measured and widely recommended way to address actual ground-related noise is a line-level isolation transformer, e.g., Jensen ISO-MAX CI-1RR, which shows transparent performance in bench tests and retails around 139.99 USD. Using Crystal E as the representative KOJO product:

• Comparator (equal or better function/performance): Jensen ISO-MAX CI-1RR (measured isolation, low distortion/noise) → 139.99 USD. [2][3][7][10][11]
• Target: KOJO Crystal E → 379.99 USD. [2]

CP = MIN(1.0, 139.99 ÷ 379.99) = 0.4.
(For context, the E-G at 699.99 USD against the same comparator would yield 0.2, but we base the company score on the mainstream Crystal E.) [2][3][7][10][11]

Reliability & Support

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The firm has operated since 1990 and builds largely passive, low-complexity products that should be physically robust. However, we found no transparent data for failure rates, warranty terms, or international service responsiveness. The company’s physical presence appears Japan-centric, which may affect global support. [4][8][9]

Rationality of Design Philosophy

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The portfolio prioritizes elaborate “virtual ground” mechanics and surface-area claims over verifiable audio-performance outcomes. Without controlled, reproducible improvements, the design approach does not align with transparent, measurement-driven audio engineering, and risks confusing buyers with technically irrelevant metrics. [1][5][6][7]

Advice

If you are chasing lower noise floors or hum removal, prefer proven methods: proper system grounding practices, balanced interconnects, and measured isolation transformers or differential interfaces (e.g., Jensen ISO-MAX). These deliver predictable, testable results at a fraction of KOJO’s price points. [10][11]

References

[1] Audio Science Review Forum, “Entreq ‘signal grounding’ Measurements”, https://www.audiosciencereview.com/forum/index.php?threads/entreq-signal-grounding-measurements.476/ (accessed Aug 14, 2025). AP-analyzer bench test on a competing ground box reports no helpful current flow and added noise components.

[2] AccessoryJack, “KOJO Technology Crystal E Audiophile Ground Box”, https://www.accessoryjack.com/products/kojo-technology-crystal-e-audiophile-ground-box (accessed Aug 14, 2025). Lists Crystal E at ~379.99 USD and shows product details.

[3] MTMTAudio, “KOJO Technology Crystal E-G (Limited)”, https://www.mtmtaudio.com/products/kojo-technology-crystal-e-g-limited-edition-audiophile-ground-box-made-in-japan (accessed Aug 14, 2025). E-G pricing around 699.99 USD and claims (e.g., 68,000 cm²).

[4] Kojo Seiko (KOJO TECHNOLOGY) – Company/Shop Info (address), https://shop.kojo-tech.jp/html/company.html (accessed Aug 14, 2025). Shows HQ in Hirakawa City, Aomori.

[5] Kojo Seiko – Crystal E spec sheet (PDF), https://kojo-seiko.co.jp/img/news/20200524_1.pdf (accessed Aug 14, 2025). Dimensions, weight, terminals, accessories.

[6] Kojo Seiko – Crystal Eop-G brochure (PDF; surface-area concept), https://kojo-seiko.co.jp/img/news/250422.pdf (accessed Aug 14, 2025). Notes extremely large effective surface-area claims.

[7] Sagami Audio (retailer), Crystal E-G details (layering, surface-area figures ~68,000 cm²), https://sagamiaudio.co.jp/kojo-crystal-e-g/ (accessed Aug 14, 2025).

[8] Kojo Seiko – Corporate site, https://kojo-seiko.co.jp/ (accessed Aug 14, 2025).

[9] Kojo Seiko – “For Dealers / Agency” (address block), https://kojo-seiko.co.jp/agency.html (accessed Aug 14, 2025).

[10] Jensen Transformers – ISO-MAX product line/pricing (CI-1RR), https://www.jensen-transformers.com/product_line/iso-max-2/ (accessed Aug 14, 2025). Shows CI-1RR at ~139.99 USD and key specs.

[11] Audio Science Review, “Jensen ISO-MAX CI-1RR Review (Isolation Transformer)”, https://www.audiosciencereview.com/forum/index.php?threads/jensen-iso-max-ci-1rr-review-isolation-transformer.24104/ (accessed Aug 14, 2025). Bench measurements indicating high performance in isolation and low distortion/noise.

(2025.8.14)