5Y4G NOS NIB NU National Union – Black Plates Foil Getter Rectifier Tube USA 1950s

5Y4 G NU NATIONAL UNION NOS NIB Black Plates Foil Getter Rectifier Made in USA '50s

Description:

The 5Y4G National Union , in this rare NOS NIB version from the 1950s with ST bottle structure, compact black plates and disc getter (foil getter) , is a low current direct-heated rectifier, electrically similar to the 5Y3G but with a different pinout. Made in the United States by NU , a company known for the quality of its industrial and military tubes, it represents a choice of great tonal coherence for audio systems with a vintage character or for philological restorations.

This valve is distinguished by its progressive behavior , robust construction and relaxed musicality , particularly appreciated in low-power single-ended amplifiers , valve preamplifiers and power supplies of vintage hi-fi radios.

Bass : soft and controlled. The low range is more rounded than deep , with excellent integration into the overall musical message. Where authority is needed, it offers stable and harmonious pulsation , never intrusive.

Mids : natural and musical. The mids are fluid and sober , with a well-articulated central voice and a sonic presence that favors coherence and organicity over analyticity. Excellent performance with acoustic instruments and male voices.

Highs : delicate and velvety. The high range is silky , with a controlled brilliance and free from harshness. The details emerge gradually and gracefully , without ever exceeding in definition, contributing to a soft and engaging listening experience.

Dynamics : smooth and predictable. The transient response is linear and unhurried , ideal for contexts where musicality and naturalness are preferred to dry or rapid impacts. Particularly suitable for intimate genres and acoustic reproductions.

Soundstage : Coherent and compact. The stereo image is well focused , with realistic depth and credible positioning . The soundstage tends to be more contained , but rich in nuance and environmental details.

🎧 Use in Headphone Amplifiers and Driver Stages Hi-Fi
This 5Y4G is ideal for low-current tube power supplies , especially in systems that require stability, silence and natural timbre . Perfect with sensitive headphones such as the Grado RS1 , ZMF Aeolus or Sennheiser HD650 , where it enhances microdynamics without ever going overboard in brightness.

🎸 Use in Guitar and Bass Amplifiers
Rarer in guitar circuits than other rectifiers, but ideal for small vintage combos or low-wattage custom amps , where it delivers a sweet, compressed, organic sound with natural sag and mellow dynamic touch , perfect for traditional jazz and blues.

🎯 Note for audiophiles and technicians
A tube with a calm and coherent voice , ideal for those looking for transparency of timbre without fatigue and a reliable electrical base. In NOS configuration with original box , it also represents a smart collector's choice , especially in restorations that require authentic first-generation American components.

Test Results:

Valve tested on Funke W19 Tube Tester:

• Test Conditions: Va = 100V ; Vf = 5.0V
• Average 100%: Ia = 92 mA
• Test Result: VERY STRONG

Valve:

• Section 1: Ia = 101 mA
• Section 2: Ia = 93 mA

• Microphonics: Standard. Tested and compliant for use in hi-fi and guitar amplifiers.
• Output Quality: Excellent – Very strong and stable output, no fluctuations.
• Short circuits and GAS: Absent.

Conditions:

• Condition: NOS - NIB - New Old Stock, New In Box - Tested and working - In original box.
  
• Functionality: Fully functional.
  
• Aesthetic conditions: Excellent – Perfectly preserved writing, minimal signs of wear. See photos. The original packaging is very compromised.
  
• Manufacturing Code: JR - Code not decipherable. Year of manufacture detected by internal structure. Manufactured in the 1950s.

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