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NATIONAL UNION

6V6GT NOS National Union Matched Pair Smoked Glass Black Plates Foil Getter Made in USA '50s

6V6GT NOS National Union Matched Pair Smoked Glass Black Plates Foil Getter Made in USA '50s

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6V6GT NOS NU (National Union) – Smoked Glass – Black Plates – Foil Getter – Matched Pair – Made in USA ‘50s

VACUUM TUBES TREASURES Selection – Low Noise & Microphonics

General Description

We offer a fascinating matched pair of 6V6GT NOS National Union (NU), manufactured in the USA in the 1950s, one of the most iconic eras for vacuum tube production.

These tubes are distinguished by a construction typical of high-quality American manufacturing:

  • Smoked Glass
  • Black Plates
  • Foil Getter
  • robust and refined internal structure

The National Union brand is historically recognized for productions with a distinctive sonic character, often highly valued for musicality and naturalness.

The tubes have been selected as a Matched Pair within NOS tolerance (Ia 10% / Gm 20%), ensuring consistent and reliable electrical performance.

⚠️ The tubes have different manufacturing codes, but are perfectly compatible and correctly matched electrically.

Sonic Characteristics

The 1950s National Union 6V6GTs offer a warm, musical, and deeply engaging sonic signature.

Bass

Soft yet present, with good articulation and naturalness.

Mids

An absolute strength: full, textured, and rich in harmonics, with extremely realistic vocal reproduction.

Highs

Sweet and rounded, never aggressive, perfect for extended listening sessions.

Dynamics

Progressive and musical, with a fluid response that prioritizes timbral coherence.

Soundstage

Natural and believable, with good depth and excellent separation.

🎧 Use in Hi-Fi Amplifiers

Perfect for:

  • single-ended and push-pull amplifiers based on 6V6
  • hi-fi systems oriented towards musicality and timbral realism

Thanks to selection and low noise, they are also suitable for sensitive configurations.

🎸 Use in Musical Applications

Ideal for:

  • vintage-style guitar amplifiers
  • tube preamps

They offer:

  • soft and progressive breakup
  • rich harmonic response
  • warm and three-dimensional sound

🎯 Note for audiophiles and technicians

  • National Union – Made in USA – 1950s
  • Smoked Glass – Black Plates – Foil Getter
  • Matched Pair (NOS tolerance)
  • Selected and tested in our laboratory

⚠️ Cosmetic conditions:

Good – legends partially eroded but still legible.

One tube has a crack on the plastic base, visible in the photos.

This is an exclusively cosmetic defect that does not affect functionality, as verified in tests.


Test Results:

Tube tested on AMPLITREX AT-1000 Tube Tester:

  • Test Conditions: Va = 250V; Vg2 = 250V; Vg = -12.5V 
  • Measurements taken after 10 minutes of warm-up.
  • Average 100%: Gm = 4.1 ; Ia = 45 mA
  • Test Result: VERY STRONG

Tube 1: Gm = 4.3 ; Ia = 41.6 mA

Tube 2: Gm = 3.8 ; Ia = 45.8 mA

Additional Tests Performed:
  • Microphonics: Low. Tested and compliant for use in hi-fi, including phono stages and guitar amplifiers.
  • Emission Quality: Excellent – Very strong and stable emission, without fluctuations.
  • Shorts and GAS: Absent.

Conditions:

  • Condition: Vintage Tubes - Tested and perfectly functional. Supplied in our custom box for optimal protection. 
  • Functionality: Perfectly operational, with excellent test results.
  • Cosmetic conditions: Good – Legends partially eroded, but still legible. 

    One tube has a crack on the plastic base, visible in the photos. This is an exclusively cosmetic defect that does not affect functionality, as verified in tests. See photos for details.

Manufacturing code: 

  • 51-39 → RMA/EIA Open Date Code → manufactured in the 39th week of 1951
  • KR S → undecipherable, identifiable by construction characteristics. 1950s

Discover why our tubes are different →

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.