Overview

The Crystal E is a passive “virtual ground” box from KOJO TECHNOLOGY (Kojo Seiko, Japan). It uses an 8-layer dissimilar-metal stack in a compact enclosure and includes RCA-Y and Y-Y ground cables. Marketing claims include a “darker background” and “better definition,” but no independent measurements corroborate audible improvements. Note: the Crystal E-G (upper model) is the one that touts 68,000 cm² total surface area; this figure is not for the standard Crystal E [10].

---

Scientific Validity

\[\Large \text{0.1}\]

Independent tests on similar grounding boxes have failed to show improvements in THD, SNR, frequency response, or crosstalk; some even added noise peaks when connected. In the absence of reproducible, third-party evidence for Crystal E itself, we rate scientific validity very low [1].

---

Technology Level

\[\Large \text{0.5}\]

The machining, 8-layer metal stack, and solid hardware indicate decent engineering execution. However, without measured benefits, this remains well-made hardware in search of a proven effect [2].

---

Cost-Performance

\[\Large \text{0.2}\]

• Crystal E street price (Japan): around ¥35,740 at major retailers [3][4].
• US pricing: 379.99 USD at AccessoryJack [2].
• Cheapest equal-or-better alternative for the same user function (provide a reliable earth reference) with the same measured outcome (no proven audible improvement): iFi Groundhog+ at 89 USD [5][6][7].

Given these prices, value is poor relative to a purpose-built ground kit; hence 0.2.

---

Reliability & Support

\[\Large \text{0.4}\]

A passive, all-metal device has few failure modes and should be robust long-term. Documented warranty/field reliability data are limited; support quality likely depends on the retailer and region [2].

---

Rationality of Design Philosophy

\[\Large \text{0.0}\]

Specs like larger surface area and multilayer stacks are not, by themselves, evidence of measurable audio improvements. Given the lack of third-party verification and negative results with similar products, the design rationale is weak [1].

---

Advice

• Start with proper grounding practice and ground-loop troubleshooting; measure your system to identify noise sources.
• If you need a ground reference, a purpose-built ground cable kit (e.g., iFi Groundhog+) is much cheaper and function-appropriate [5][6][7].
• For audible, repeatable gains, invest in components with proven measurements (DACs/amps/speakers).

---

References

[1] Audio Science Review Forum: Entreq “signal grounding” Measurements. https://audiosciencereview.com/forum/index.php?threads/entreq-signal-grounding-measurements.476/
[2] AccessoryJack: KOJO Technology Crystal E – product page & pricing. https://www.accessoryjack.com/products/kojo-technology-crystal-e-audiophile-ground-box
[3] Fujiya-Avic: CRYSTAL E (¥35,740). https://www.fujiya-avic.co.jp/shop/g/g200000050545/
[4] Bic Camera: CRYSTAL-E (¥35,740). https://www.biccamera.com/bc/item/8191594/
[5] Suncoast Audio Direct: iFi Groundhog+ (89 USD). https://www.suncoastaudiodirect.com/products/groundhog
[6] Sweetwater: iFi Groundhog+ Earth/Ground Connection (89 USD). https://www.sweetwater.com/store/detail/GroundhogP–ifi-groundhog-earth-ground-connection
[7] B&H Photo: iFi audio Groundhog+ Ground Accessories Cable Kit (89 USD). https://www.bhphotovideo.com/c/product/1572674-REG/ifi_audio_306022p_groundhog_ground_loop_isolator.html
[8] The Cable Company: Entreq Micro Kit Groundbox Kit (285 USD). https://www.thecableco.com/micro-kit-groundbox-kit.html
[9] EDION (Japan): KOJO CRYSTAL E (reference pricing). https://www.edion.com/detail.html?p_cd=00066797029
[10] Amazon.co.jp: KOJO CRYSTAL E-G (spec sheet indicates “Laminated surface area: 68,000cm²”). https://www.amazon.co.jp/dp/B0CL5SXLVW

(2025.8.14)