71A SYLVANIA NOS Matched Pair – Silver Plates – Hanging Filaments – Foil Dimpled Getter – Made in USA – Same Data Codes 4V
AMPLITREX Tested – VERY STRONG – Low Noise & Microphonics
Matched pair of 71A Sylvania NOS – Made in USA, selected for vintage amplifiers, period restorations, and low-power single-ended projects based on small directly heated triodes.
The 71A is a DHT – Directly Heated Triode, belonging to the great American tradition of early audio amplification. It is a tube increasingly sought after today for its intimate, natural, and highly musical sonic character, particularly appreciated in simple and refined circuitry.
This pair features a construction of great historical charm: ST glass, silver plates, foil dimpled getter, hanging filaments, and a black 4-pin base. Both tubes have the same 4V code, a positive detail for selection consistency. Production is likely attributable to the 1940s, prudently indicated as likely 1940s production.
The aesthetic conditions are excellent, showroom quality. The only note concerns the 71A marking on the glass of one of the two tubes, which is less visible/partially faded. The tubes are not supplied with original boxes. See photos for details.
The pair has been tested on Amplitrex AT-1000 with a VERY STRONG result and has been selected as Low Noise & Microphonics. The measured values are consistent with Sylvania operational data at the typical point Va = 135V, Ia approximately 17.3 mA, Mutual Conductance approximately 1650 µmhos, confirming the excellent electrical condition of the pair.
From a sonic perspective, the 71A Sylvania offers an intimate, fluid, and natural performance, with open and communicative mids, delicate and well-integrated highs, and dry and controlled bass. Its strength lies in microdynamics: nuances, presence, and timbral naturalness emerge with great vintage charm.
Suitable for low-power single-ended amplifiers, philological restorations, vintage equipment, and compatible DHT projects, where tube quality, electrical consistency, and quietness are essential elements.
A rare and fascinating 71A Sylvania NOS pair, truly selected, tested, and matched by Vacuum Tubes Treasures: not just vintage tubes, but a historical, strong DHT selection ready for refined applications.
Test Results:
Tube tested on AMPLITREX AT-1000 Tube Tester:
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Test Conditions: Va = 135V ; Vg = -27V
- Measurements taken after 3 minutes of warm-up.
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Average 100%: Gm = 1.5 ; Ia = 17.5 mA
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Test Result: VERY STRONG
Tube 1: Gm = 1.6 ; Ia = 14.6 mA
Tube 2: Gm = 1.7 ; Ia = 18.2 mA
Additional Tests Performed:
- Microphonics: Low. Tested and compliant for hi-fi use, including phono stages and guitar amplifiers.
- Emission Quality: Excellent – Very strong and stable emission, without fluctuations.
- Shorts and GAS: Absent.
Conditions:
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Condition: NOS - New Old Stock - Tested and working - Supplied in our custom box for optimal protection.
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Functionality: Perfectly operational, with excellent test results.
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Cosmetic Condition: Excellent – Markings excellently preserved, minimal signs of age. The only cosmetic note concerns the 71A marking on the glass of one of the two tubes, which is less visible/partially faded. See photos for details.
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Manufacturing Code: 4V - Made in the USA - The construction suggests probable 1940s / early post-war production, with ST glass structure, black 4-pin base, silver plates, foil dimpled getter, and hanging filaments, characteristics consistent with Sylvania's American production of that era. Both tubes bear the same "4V" code, a detail that reinforces the historical, aesthetic, and constructive coherence of the pair.
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