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SYLVANIA

6SN7 GTB NOS SYLVANIA CHROME TOP Green Dot Matched Quad Black Plates Tubes USA '50s

6SN7 GTB NOS SYLVANIA CHROME TOP Green Dot Matched Quad Black Plates Tubes USA '50s

$333.00 AUD
$333.00 AUD
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6SN7GTB NOS SYLVANIA CHROME TOP Matched Quad Green Dot Black Plates Tubes - Same Codes - Made in USA '57

The matched quartet of 1957 Sylvania 6SN7 GTBs, with black plates , chrome tops , green dot selector, and identical part numbers , represents one of the finest and most consistent NOS configurations in postwar American production. The green dot was a factory-applied marking by Sylvania to identify tubes selected for low noise and microphony, intended for critical military, professional, and high-end audio applications. This generation’s build quality, combined with accurate matching, makes them an excellent choice for tube preamplifiers , push-pull amplifier driver stages , or high-end dual mono restorations , where tonal consistency, quietness, and natural musicality are essential.

These valves are distinguished by a transparent and three-dimensional voice , with a neutral but musical character, capable of enhancing the microdynamics without forced colorations.

Bass : tight and well-defined. The low range is articulated, dry, and free of bloat , offering a controlled and stable harmonic foundation. Perfect for maintaining clarity and precision in the lower registers, even in complex passages.

Mids : Clear and natural. The midrange is balanced and free of artifacts , with well-centered vocals and a realistic rendition of acoustic instruments . There is no artificial emphasis, but a consistent transparency that facilitates deep and engaging listening.

Highs : Fine and non-fatiguing. The high range is delicate, extended and airy , with a discreet brilliance and detail well integrated into the musical fabric . Excellent for long listening sessions without fatigue.

Dynamics : Fluid and modulated. The dynamic response is progressive , capable of naturally reproducing minimal nuances , but also of sustaining energetic passages without stiffening. The valves react quickly but in a controlled manner, ensuring constant musicality.

Soundstage : Wide and stable. The soundstage is wide and deep , with excellent instrument placement and coherent layering . Coherence between channels, ensured by matching and identical codes, contributes to a precise and relaxed stereo image.

🎧 Use in Push-Pull Stereo Hi-Fi Amplifiers
This matched quartet is ideal for driver stages, mid-stages, or preamp power amps in high-quality stereo setups. It offers channel-to-channel uniformity, low noise, and refined tonal response , making it perfect for transparent, high-end systems, both modern and vintage.

🎸 Use in Instrument Amplifiers
While not the primary choice for guitar amps, the Sylvania Chrome Top 6SN7 GTB finds its place in boutique designs , jazz guitar amps, or in studio-grade circuits, where controlled harmonic output and transparency are preferred over driven distortion.

🎯 Note for audiophiles and technicians
A rare and valuable NOS selection, with perfectly matched, quiet and stable tubes , perfect for dual mono restorations, balanced stages and applications where precision and musicality must coexist. The combination of black plates, chrome top and green dot selection is considered among the most successful of the 1950s Sylvania school.

Test Results:

Valves tested on Amplitrex AT-1000 Tube tester :

  • Test Conditions: Va = 250V, Vg = -8V
  • Average 100% Gm = 2600 ; Ia = 9.0 mA

Valve #10:

  • Section 1: Gm = 3000 ; Ia = 10.2 mA
  • Section 2: Gm = 2900 ; Ia = 9.8 mA

Valve #12:

  • Section 1: Gm = 2900 ; Ia = 10.0 mA
  • Section 2: Gm = 3000 ; Ia = 10.0 mA

Valve #8:

  • Section 1: Gm = 2900 ; Ia = 10.2 mA
  • Section 2: Gm = 3000 ; Ia = 10.4 mA

Valve #9:

  • Section 1: Gm = 3000 ; Ia = 11.4 mA
  • Section 2: Gm = 2900 ; Ia = 9.4 mA
Additional Tests Performed:
  • Microphonics and Noise : Very Low. Tested and approved for use in hi-fi, including phono stages and guitar amplifiers. Also suitable for V1.
  • Output Quality: Excellent – Very strong and stable output, no fluctuations.
  • Short circuits and GAS: Absent.

Conditions:

  • Condition: NOS - New Old Stock - Tested and working - Supplied in our custom box for optimal protection.
  • Functionality: Fully functional.
  • Cosmetic condition: Excellent – Excellently preserved lettering, minimal signs of wear. See photos for details.
  • Manufacturing Code: 166 722 - Manufactured by SYLVANIA USA - 166 → customer EIA code ( Chicago Electronic Engineering Company, Inc., Chicago 47, Ill. ) - 722 → 22nd week of 1957

Find out why our valves 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.

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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.