KEN-RAD CKR 6SN7GT 

VT-231 *BOGEYS*

GENUINE KENTUCKY RADIO

LEGENDARY '1940s' BLACK BEAUTY

U.S. MILITARY TUBES

U.S. ARMY SIGNAL CORP

U.S. NAVY ANCHOR

*WEAPONS GRADE*

HEAVY CHROMED FOIL

BOTTOM D GETTER

VINTAGE U.S.A. TUBES

2 HOLE BLACK PLATES

PERFECT MATCHING SET

EXTREMELY RARE - NIB
(Original Factory Boxes w/ Military Waxed Wrapping - RESEALED)

EXCLUSIVE HIGH FIDELTY TUBES

***AUDIO EQUIVALENT TO THE 
TUNG-SOL BLACK BEAUTY***

UNOPENED FOR 80+ YEARS 

πŸ”₯πŸ’Ž HOLY GRAIL ALERT! πŸ’ŽπŸ”₯

πŸ”₯ 1944 JAN-CKR KEN-RAD 6SN7GT VT-231 BLACK GLASS πŸ”₯

⚑ ULTRA-RARE MILITARY NOS β€’ PERFECTLY MATCHED β€’ TRUE BLACK BEAUTIES ⚑

πŸ”₯πŸ”₯πŸ”₯ THESE ARE THE TUBES SERIOUS COLLECTORS WAIT YEARS TO FIND! πŸ”₯πŸ”₯πŸ”₯

πŸ’₯ Genuine 1944 JAN-CKR Ken-Rad VT-231
πŸ’₯ Original Black Glass construction
πŸ’₯ Authentic WWII U.S. Military production
πŸ’₯ Military-spec JAN (Joint Army-Navy)
πŸ’₯ Factory-matched NOS pair
πŸ’₯ Perfectly matched and fully tested
πŸ’₯ Original military cartons included
πŸ’₯ Guaranteed authentic
πŸ’₯ 80+ years preserved in exceptional condition

❀️πŸ”₯ These legendary Black Beauties have earned an almost mythical reputation among tube enthusiasts for their huge, authoritative bass, rich midrange, effortless dynamics, and holographic presentation. The Ken-Rad VT-231 is widely regarded as one of the finest vintage 6SN7 variants ever produced and remains a benchmark for premium audio systems. (Head-Fi)

πŸš€ Features

πŸ”₯ 1944 WWII production
πŸ”₯ Genuine JAN-CKR military issue
πŸ”₯ Rare black glass envelopes
πŸ”₯ Legendary Ken-Rad construction
πŸ”₯ Factory staggered black plates
πŸ”₯ Exceptionally low noise
πŸ”₯ Perfectly balanced sections
πŸ”₯ Strong emission
πŸ”₯ Carefully tested and guaranteed
πŸ”₯ Collector-grade cosmetics

🎯 Perfect For

🎡 McIntosh
🎡 Cary Audio
🎡 Audio Research
🎡 Woo Audio
🎡 Schiit
🎡 Feliks Audio
🎡 Decware
🎡 Bottlehead
🎡 Custom high-end amplifiers
🎡 Serious tube rolling enthusiasts

πŸ’Ž Collector's Dream

These are not ordinary vintage tubes.

These are authentic WWII-era Ken-Rad VT-231 Black Glass tubes that have survived for more than 80 years in remarkable NOS condition. Genuine collector-grade matched pairs have become increasingly difficult to locate, especially with original military markings and cartons. The 6SN7GT/VT-231 was introduced during the early 1940s and became one of the most respected dual-triode designs ever made. (R-Type)

πŸ”₯ Own one of the most iconic American audio tubes ever produced.

⚑ Buy with confidence.
βœ” Professionally tested
βœ” Perfectly matched
βœ” Carefully packed
βœ” Fast shipping
βœ” Satisfaction guaranteed

πŸ”₯🎢 When only the best will do... the Ken-Rad Black Beauties deliver. 🎢πŸ”₯

***Please read the entire listing thoroughly and ask any questions prior to purchase***

β˜…β˜…β˜… Amazing Historic Military Tubes β˜…β˜…β˜…

U.S. ARMY  U.S. NAVY  JAN  Military Specification Tubes

Production Year: 1944

Matched Codes: U4

Tall Black Base

Platinum Label

Set of Two (2) Tubes

***The Tubes Pictured are the Tubes Offered***

Made In the U.S.A.
 

β˜…β˜…β˜… These Tubes are Very Rare in Brand New Condition β˜…β˜…β˜…

BEST TUBES ON THE MARKET...  NO SHORTS...  NO LEAKS...


β˜…β˜…β˜… HICKOK TESTED β˜…β˜…β˜…

Tested on Hickok 750 for Emission, Mutual Conductance

Where 50 (ΞΌ) is Good these tubes peg at 80/81 for Emission

Where 2,600 (ma/V) is Good these tubes peg at 3,200/3,300 for Mutual Conductance

Tube 1. Plate 1. - 76 (ΞΌ) - 3,300 (ma/V)  at Idle - NOS

              Plate 2. - 76 (ΞΌ) - 3,100 (ma/V)  at Idle - NOS

Tube 2. Plate 1. - 75 (ΞΌ) - 3,100 (ma/V)  at Idle - NOS

              Plate 2. - 76 (ΞΌ) - 3,200 (ma/V)  at Idle - NOS

Typical NOS (New) Tube Ratings are anything above 2600 (ma/V) for Mutual Conductance and 70 (ΞΌ) for Emission

Perfectly Balanced - Rare and Exceptional

Full Tonal Range - Powerful Emission

***We are Top Rated for a Very Good Reason. Buy with Complete Confidence***


*Test Ratings are Specific to My Fully Calibrated Test Equipment! The tubes are put through a Life Test and each plate is warmed and measured for mutual conductance, emission, leaks, and shorts... Each tube is thoroughly inspected, they are described accurately and listed based on fair value!

My Return Policy: 30 Days - Seller pays return shipping! All tubes are Guaranteed to be as described... Tube rolling will not be tolerated! Any and all returns must be in identical condition as when they were received... Test Driving Vintage NOS Tubes is completely unacceptable and highly unethical... Buyer will be charged for mishandled and damaged returns! 

I mark every tube in order to avoid tube rolling! ***Variations in Line Output and Test Equipment excludes any claims regarding matching test results on any equipment other than mine... ***Test results from different Test Equipment IS NOT Guaranteed...


A Hickok 750 tube tester measures mutual conductance in micromhos (Β΅mhos), not emission in milliamps (mA) or microamps (Β΅A). Confusion likely arises because micromhos are based on a ratio of a change in plate current (measured in Β΅A) to a change in grid voltage. 
Here is a breakdown of what the Hickok 750 measures and why it's not only an emission tester:
  • Mutual Conductance: The 750 is a dynamic mutual conductance tester. This is a more sophisticated test than a basic emission only test, which only checks the cathode's ability to emit electrons (super heated).
  • Micromho units: Mutual conductance is measured in micromhos, which translates to a specific change in the plate current per a change in the control grid voltage. The unit ma/V is the same as 1000 micromhos.
  • Superior test: A mutual conductance test is performed under simulated operating conditions and is considered more reliable for evaluating a tube's actual performance. This is why the Hickok 750 can identify weak tubes that might pass a simple emission only test.
  • Emission vs. Mutual Conductance: In contrast, a simple emission tester (like a Heathkit and many others) treats a tube like a simple diode, measuring only the cathode's emission strength. While useful for finding dead or very weak tubes, this method is not as thorough and test results are very unreliable.
A Hickok 750 tests for mutual conductance in micromhos (ΞΌmhos), which is sometimes abbreviated as ΞΌmos. The unit is a measure of a vacuum tube's transconductance (g{m}). Here's a breakdown: Micromhos (ΞΌmhos): This is the unit used to measure mutual conductance. A mho is an older term for the unit of electrical conductance, now called a siemens (S).Transconductance (g{m}): This is the technical term for mutual conductance. It is the ratio of the change in plate current (measured in microamps or milliamps) to a change in grid voltage (measured in volts).ΞΌmos: The term "umhos" or "umos" is sometimes used colloquially as an abbreviation for micromhos. Although the Hickok 750 measures the effect of microamps and volts to determine the final reading, the scale on the meter is calibrated to show the overall mutual conductance in micromhos.

International Buyers Welcome! I use eBay International exclusively, unless otherwise stated... I am unable to change declared value on customs forms, and International Buyers are responsible for all taxes, customs and additional fees!  Each tube is fully insured, boxed and shipped safely!

 β˜… Expedited Shipping β˜…

β˜… Shipping times may vary based on region β˜…

β˜… *Honesty, *Reliability and *Integrity are *Everything β˜