6SN7GTA NOS SYLVANIA Chrome Top Matched Quad - Same Production Code - Low Noise & Microphonics - AMPLITREX Tested

6SN7GTA NOS SYLVANIA – Short Base Chrome Top – Matched Quad – Same Data Codes – Made in USA 1955 AMPLITREX Tested – VERY STRONG – Green Dot & Gray Dot – Low Noise & Microphonics Test Results: Tubes tested on an Amplitrex AT-1000 Tube Tester: Test Conditions: Va = 250V, Vg = -8V Average 100% Gm = 2600 ; Ia = 9.0 mA Test Result: VERY STRONG Tube #15 Section 1: Gm = 2600 ; Ia = 8.2 mA Section 2: Gm = 2600 ; Ia = 8.0 mA Tube #22 Section 1: Gm = 2500 ; Ia = 8.0 mA Section 2: Gm = 2700 ; Ia = 8.4 mA Tube #5 Section 1: Gm = 2600 ; Ia = 8.4 mA Section 2: Gm = 2600 ; Ia = 8.2 mA Tube #39 Section 1: Gm = 2620 ; Ia = 8.6 mA Section 2: Gm = 2600 ; Ia = 7.8 mA Additional Tests: Burn-in / Stability Test: 48h – OK Microphonics and noise: Very Low. Tested and suitable for use in hi-fi equipment and guitar amplifiers, including the most sensitive audio stages. Balance: Very Good. The sections are consistent and well-aligned, making the tube suitable for use as a phase inverter in hi-fi and instrument applications. Emission: Excellent – Very strong and stable emission, without fluctuations. Short Circuits / Gas: none Description Exceptional NOS quad of 6SN7GTA Sylvania, produced in the United States in 1955 and carefully selected as a Matched Quad. All four specimens share the identical manufacturing code 288 / 513, traceable to the 13th week of 1955, and feature the characteristic Short Base Chrome Top construction. A particularly desirable set for those seeking the authenticity and build quality of 1950s American Sylvania production. The measurements performed with an Amplitrex AT-1000 highlight an electrical matching of remarkable precision. The average transconductances of the four tubes are between 2600 and 2610 µmhos, virtually coinciding with the nominal reference of 2600. Even more interesting is the uniformity of the average anode currents, concentrated in the range of 8.1–8.3 mA, compared to the reference of 9.0 mA. The individual sections feature transconductances between 2500 and 2700 µmhos and anode currents between 7.8 and 8.6 mA. An overall picture that confirms a very well-matched Quad, with small differences and particularly consistent electrical characteristics. All four tubes passed 48 hours of burn-in and stability testing, maintaining a very strong and constant emission, without fluctuations, short circuits, or gas. Specific tests also confirmed very low noise and microphonic levels, with special Green Dot and Gray Dot classification. A selection that takes on particular value in sensitive audio stages, where silence and stability are important requirements. The 6SN7GTA Sylvania tubes find application in hi-fi preamplifiers, headphone amplifiers, driver stages, and compatible phase inverter circuits. The uniformity of this quad makes it particularly interesting for equipment requiring multiple tubes with homogeneous electrical characteristics. 1950s Sylvania production is also traditionally appreciated by audiophiles for a musical presentation that is natural, open, and well-articulated, with a pleasant combination of definition and expressive richness. The opportunity to bring together four authentic NOS Sylvania tubes from the same production week in March 1955, with perfectly preserved original markings, excellent cosmetic condition, and such close electrical values, gives this quad particular interest. A carefully matched vintage set that combines historical authenticity, electrical uniformity, and verified reliability, intended for enthusiasts who wish to equip their audio system with original American tubes of documented quality. Condition Condition: NOS - New Old Stock - Tested and working - Supplied in our custom box for optimal protection. Functionality: Perfectly operational Cosmetic condition: Excellent – Markings perfectly preserved, minimal signs of age. See photos for details. Special selection: Green Dot and Gray Dot, with low noise and microphonics verified using an Amplitrex AT-1000. Manufacturing code: Sylvania Electric Products Inc., USA – original marking on the base 288 / 513. 288 Sylvania Internal code. 513 - 13th week of 1955 (March 1955). Discover why our tubes are different →