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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

Regular price ¥3,800 JPY
Regular price Sale price ¥3,800 JPY
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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

Burglar-Resistant Security Seal Policy:

Each product is sealed to ensure quality and integrity.
The right of withdrawal is subject to the tamper-proof seal being kept intact, as required by the Consumer Code.


Eco-friendly packaging:

The valve will be shipped in protective packaging to ensure safety during transportation.
We use recycled and recyclable paper for packaging, and brown tape ECO-KRAFT , eco-friendly and solvent-free.


Important Notes:

This tube, manufactured to the standards of the time, is designed to work in equipment compatible with vintage tubes.
It is recommended to follow the safety guidelines to avoid malfunctions or damage.


Security Guarantee:

While not tested to modern GPSR regulations, this valve has been designed to operate safely under the conditions for which it was manufactured.
We recommend using it with equipment that supports vintage tubes, to avoid the risk of malfunction or damage.

Important note: The technical data shown is based on another manufacturer's datasheet, as a specific datasheet for the production of the item in the catalog is not available. Features may vary slightly depending on the batch and production.


Safety Information:

  • Attention: Keep out of reach of children.
  • To be used under adult supervision.
  • Use this product only with equipment designed for vintage tubes.

Condizioni di vendita e sicurezza

Anti-Tamper Security Seal Policy:
Each product is sealed to guarantee quality and integrity.
The right of withdrawal is subject to the seal remaining intact, as provided for by the Consumer Code.

Eco-Friendly Packaging:
The tube will be shipped with protective packaging to ensure safety during transport.
We use recycled and recyclable paper for packaging, along with brown ECO-KRAFT adhesive tape, eco-friendly and solvent-free.

Important Notes:
This tube, manufactured according to the standards of its era, is designed to operate in equipment compatible with vintage tubes.
It is recommended to follow standard safety guidelines to avoid malfunctions or damage.

Safety Assurance:
Although not tested according to modern GPSR regulations, this tube was designed to operate safely under the conditions for which it was manufactured.
We recommend using it only with equipment that supports vintage tubes, in order to avoid risks of malfunction or damage.
Technical data note:
In some cases, the technical data provided may be based on datasheets from other manufacturers or on equivalent historical specifications, when a specific official datasheet for the production batch of the listed item is not available.
Electrical characteristics may vary slightly depending on the production batch and manufacturing period, as is typical for thermionic components.

Safety Information:
Warning: Keep out of reach of children.
To be used under adult supervision.
Use the product only with equipment designed for vintage tubes.

Shipping & Returns

Shipping & Returns

Shipping Costs

Shipping costs vary depending on the total amount of the items in the cart and are calculated automatically during the checkout process.
All shipments are fully insured. The courier is automatically selected based on destination, weight, and shipment characteristics.

Shipping Times and Delivery

The indicated delivery times are purely indicative.
Any delays, storage issues, or operational changes made by the carrier (for example during peak periods such as holidays) are not attributable to Vacuum Tubes Treasures.

In such cases, we will nevertheless provide the Customer with all necessary support to open claims or assistance requests with the appointed courier.

International Shipping (Non-EU Countries)

For orders shipped to countries outside the European Union, any customs duties, import taxes, or additional charges are the sole responsibility of the recipient.
Vacuum Tubes Treasures has no control over these costs, which may vary from country to country. Customers are therefore advised to contact their local customs authorities prior to placing an order.

Warranty

All products sold by Vacuum Tubes Treasures are covered by the legal warranty of conformity, in accordance with Italian Legislative Decree No. 206/2005 (Consumer Code) and the Italian Civil Code (Articles 1490 et seq.), under the conditions set out below.

Warranty for Vacuum Tubes

Vacuum tubes, being components subject to wear and of vintage or specialized nature, are covered by a specific warranty of 6 (six) months from the date of delivery.
The warranty covers exclusively proven manufacturing or conformity defects that arise during proper use in accordance with technical specifications.

The warranty does not cover:

  • normal wear and tear,
  • subjective sound preferences,
  • use in incompatible equipment,
  • tampering or improper use.

Right of Withdrawal

Purchases made on the Vacuum Tubes Treasures website are governed by Italian regulations on distance contracts (Legislative Decree No. 206/2005).

Consumers have the right to withdraw from the contract within 14 (fourteen) days from the date of receipt of the goods, without providing any reason.

Conditions for Exercising the Right of Withdrawal

The right of withdrawal may be exercised only if:

  • the product has not been used,
  • the product is returned in its original condition,
  • the tamper-evident security seal is intact and not broken.

📌 Returns are not accepted for reasons related to sound preference, tube rolling, or subjective audio evaluation.
As with a music recording, a vacuum tube cannot be returned simply because its sound does not match personal taste.

Effects of Withdrawal

In the event of a valid withdrawal:

  • all payments received, including standard shipping costs, will be refunded,
  • refunds will be issued within 14 days from receipt of the returned goods,
  • the refund may be withheld until the goods have been received and inspected.

Refunds will be made using the same payment method used for the original transaction, unless otherwise agreed.

Return Shipping Costs

Return shipping costs are borne by the Customer, except in cases of:

  • verified defective products,
  • errors attributable to Vacuum Tubes Treasures.

In such cases, return shipping costs will be fully covered by us.

Damaged or Incorrect Items

If the Customer receives a damaged or incorrect item, it must be reported within 5 (five) working days from delivery, by email or telephone, clearly stating the issue.

Uncollected Parcels, Storage, and International Shipments

It is the Customer’s responsibility to monitor the shipment and promptly arrange for collection or customs clearance.
Any costs, delays, or losses resulting from:

  • failure to collect the parcel,
  • prolonged storage,
  • abandonment of the parcel at customs,

do not entitle the Customer to any refund.

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
www.vtt.store | www.vacuumtubestreasures.com
📧 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.