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

6SN7GTA NOS SYLVANIA – Short Base Chrome Top – Black Plates – Matched Sextet – Made in USA 1955 AMPLITREX Tested – VERY STRONG – Matched Sextet – Low Noise & Microphonics Test Results: Tested on Amplitrex AT-1000 Tube Tester: Test Conditions: Va = 250V; Vg = -8V 100% Average: Gm = 2600; Ia = 9.0 mA Test Result: VERY STRONG Sextet Range on Tube Averages: Gm = 2600–2600; Ia = 7.6–7.8 mA Matched Score: 2.60 – Excellent Match Tube #6 Section 1: Gm = 2600; Ia = 7.6 mA Section 2: Gm = 2600; Ia = 7.6 mA Tube #37 Section 1: Gm = 2600; Ia = 7.8 mA Section 2: Gm = 2600; Ia = 7.4 mA Tube #35 Section 1: Gm = 2600; Ia = 7.6 mA Section 2: Gm = 2600; Ia = 7.8 mA Tube #4 Section 1: Gm = 2500; Ia = 7.4 mA Section 2: Gm = 2700; Ia = 8.0 mA Tube #7 Section 1: Gm = 2600; Ia = 7.6 mA Section 2: Gm = 2600; Ia = 8.0 mA Tube #8 Section 1: Gm = 2600; Ia = 7.6 mA Section 2: Gm = 2600; Ia = 8.0 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-matched, 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 6SN7GTA Sylvania sextet, produced in the United States in 1955 and carefully selected as a Matched Sextet. All six tubes share the identical manufacturing code 288 / 513, dating back to the 13th week of 1955, and feature the characteristic Short Base Chrome Top with Black Plates construction. A particularly interesting set due to its construction uniformity and its origin from the same 1950s Sylvania American production run. The measurements performed with the Amplitrex AT-1000 reveal an exceptionally precise match. All six tubes have an identical average transconductance of 2600 µmhos, corresponding to the nominal reference, while the average anode currents are concentrated in the extremely narrow range of 7.6–7.8 mA. Considering the individual sections, the transconductance varies from 2500 to 2700 µmhos and the anode current from 7.4 to 8.0 mA. The Matched Score of 2.60 confirms the excellent overall uniformity, a particularly significant feature for a group of six vintage tubes. Each tube passed 48 hours of burn-in and stability testing, demonstrating very strong and consistent emission, without fluctuations, short circuits, or gas. The tests also confirmed very low noise and microphonics levels, with special Green Dot and Gray Dot selection verified using the Amplitrex AT-1000. Manufacturing code: Sylvania Electric Products Inc., USA – original marking on the base 288 / 513. 288 is the Sylvania internal code. 513 - 13th week of 1955 (March 1955). Discover why our tubes are different →