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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

€149,00 EUR
€149,00 EUR
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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 →

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
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.