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NATIONAL UNION

6C6 ( CK108 ) NU National Union NOS NIB Graphite Glass Tested Tube Made in USA

6C6 ( CK108 ) NU National Union NOS NIB Graphite Glass Tested Tube Made in USA

€19,90 EUR
€19,90 EUR
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6C6 ( CK108 ) NU National Union NOS NIB Graphite Glass Tested Tube Made in USA

Description:

A true expression of the American school of construction, these 6C6s (military designation CK108) produced by National Union are distinguished by their characteristic graphite glass, designed to reduce internal light interference and improve thermal stability.
Selected NOS NIB examples, ideal for both high-end audio applications and philological restorations of vintage equipment.

Timbre characteristics and sound description

Bass:
Clean and compact, with a dry and well-controlled timbre. The low end is never intrusive, but integrates seamlessly into the musical fabric.

Medium:
Refined and natural, with excellent reproduction of vocals and acoustic instruments. The harmonics are rich and coherent, giving a sense of realistic presence.

Highs:
Extended yet silky, with controlled brightness and no harshness. The high-frequency response is pleasant even over long listening sessions.

Dynamics:
Responsive and fluid, capable of rendering micro and macro details without perceptible compression.

Soundstage:
Well-focused scene, with stable positioning of the sources and a realism that enhances both mono and stereo recordings.

🎧 Use in Hi-Fi Amplifiers

Perfect for vintage amplifiers and preamps requiring 6C6, where the graphite glass contributes to a clean, interference-free sound. Ideal for high-efficiency systems and those seeking natural tonal quality.

🎸 Use in Music Applications

Suitable for vintage radios and instrument amplifiers, they deliver a warm, defined and harmonically rich sound, ideal for authentic vintage contexts.

🎯 Note for audiophiles and technicians

The graphite-glass National Union 6C6s are a particularly stable and quiet version. Matched pairing ensures consistent and reliable performance, making them an excellent option for high-end restorations or specialized hi-fi projects.

Test Results:

Tested with AMPLITREX AT-1000 Tube tester:
Measurements taken after 10 minutes of preheating.
Test Conditions: Va = 250V ; Vg2 = 100V ; Vg = 3V
AVERAGE 100%: Gm = 1200 ; Ia = 2 mA
Test Result: VERY STRONG

  • Valve: Gm = 1000; Ia = 1.4 mA
Additional Tests Performed:
  • Microphonics: Low. Tested and approved for use in hi-fi and guitar amplifiers.
  • Output Quality: Excellent – Very strong and stable output, no fluctuations.
  • Short circuits and GAS: Absent.

Conditions:

  • Condition: NOS - NIB - New Old Stock, New In Box - Tested and working - Supplied in original box.
  • Functionality: Fully functional.
  • Cosmetic condition: Excellent – Excellently preserved lettering, minimal signs of wear. See photos for details.
  • Manufacturing Code: MR - undecipherable

Terms of Sale & Safety

Sales Terms & Product Safety

Each vacuum tube is carefully selected, tested, and verified in our laboratory before shipment. Where stated in the listing, test results, matching data, and declared characteristics refer to measurements performed using the specified test equipment and operating conditions.

Sound descriptions are provided for guidance only and reflect the characteristics generally associated with that particular tube type. Personal sound preferences, tube rolling, or perceived differences between audio systems do not constitute a product defect.

Before installation, please verify the tube’s electrical and mechanical compatibility with your equipment and follow the manufacturer’s instructions.

New production and NOS tubes are shipped with a tamper-evident security seal and internal technical documentation to ensure traceability of the product’s condition at the time of shipment.

Product Safety (GPSR)

Vacuum tubes are electronic components intended exclusively for use in compatible equipment and must be installed in accordance with the equipment manufacturer’s instructions.

Due to their historical or vintage nature, certain technical specifications may be based on original datasheets or equivalent technical documentation when documentation from the specific manufacturer is unavailable.

Use only with suitable equipment. Keep out of reach of children.

Shipping & Returns

Shipping & Returns

We ship worldwide using carefully selected express carriers and protective packaging specifically designed for vacuum tubes.

If you change your mind, you may exercise your right of withdrawal within 14 days of delivery, where applicable under the relevant consumer protection laws. The product must be returned complete with its original packaging and accessories, in the same commercial condition in which it was received. Return shipping costs are the responsibility of the customer.

Every returned item undergoes a technical inspection. Installation, use, tube rolling, or any other handling may reduce the product’s commercial value and may affect the refund amount, in accordance with applicable law.

If you believe the product has a lack of conformity, our laboratory will carry out the necessary inspections and apply the remedies provided by the applicable consumer protection legislation.

For further details, Customers are invited to consult the “Terms and Conditions” and “Refund Policy” sections of our website, or to contact us before placing an order.

Vacuum Tubes Treasures
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📧 info@vacuumtubestreasures.com

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  • ATTENTION PLEASE

    Please understand that the writing on the glass of vintage valves has become very delicate over the years and comes off easily. You must handle them with extreme care to avoid this. Wear and damage to the writing on the valves reduces their market value and causes damage. Please exercise extreme caution.

  • ATTENTION PLEASE

    We wish to inform you that any attempts to manipulate shipping destination information in order to obtain lower shipping rates may be considered fraudulent acts. Please provide accurate information and contact us if you have any concerns. We reserve the right to review and, if necessary, cancel orders that we deem to be in violation of our conditions. Thank you for your understanding and cooperation.