KEN-RAD JAN CKR

6SN7GT VT-231

GENUINE KENTUCKY RADIO

BLACK BEAUTY

*WEAPONS GRADE*

CHROMED FOIL

STAGGERED PLATES

MATCHED SET

EXTREMELY RARE

EXCLUSIVE HIGH FIDELTY TUBE

🔥 KEN-RAD 6SN7GT VT-231 – MATCHED WWII BLACK GLASS MONSTERS 🔥

True 1940s Ken-Rad VT-231 black glass tubes remain among the most coveted and emotionally engaging 6SN7 variants ever produced — famous for their thunderous bass, liquid mids, and haunting vintage American tone.

This is a BEAUTIFUL matched pair featuring:
⚡ Genuine smoked black glass envelopes
⚡ Heavy black plate military construction
⚡ Perfectly balanced testing / closely matched sections
⚡ Vintage-style presentation boxes included
⚡ Date coded W2/Z2 production
⚡ Authentic wartime VT-231 build architecture

These test essentially Like New with exceptionally strong and balanced mutual conductance, placing them firmly in the upper tier of surviving Ken-Rad VT-231 inventory.

Audiophiles chase these legendary “Tough Dogs” for their:
🎵 Massive, room-filling bass response
🎵 Dense, holographic midrange presentation
🎵 Rich harmonic layering
🎵 Smooth, non-fatiguing highs
🎵 Explosive dynamic authority

In 300B amplifiers, headphone systems, and high-end preamps, the Ken-Rad black glass presentation is often described as:
🔥 Darker
🔥 Bigger
🔥 More muscular
🔥 More emotionally immersive than later GTB-era tubes.

The W2/Z2-era production examples are especially respected for their rugged wartime metallurgy, thick mica support structure, and unmistakable old-world American manufacturing quality.

⚠️ TRUE NOS-CONDITION MATCHED BLACK GLASS VT-231 SETS ARE BECOMING EXTREMELY DIFFICULT TO FIND — especially with strong balanced testing and presentation packaging intact.

📦 Includes vintage-style Ken-Rad presentation boxes modeled after the original wartime military packaging aesthetic. Beautiful period-correct display and storage presentation.

Perfect for:
🎧 Woo / Feliks / Schiit / Decware / Cary systems
🎧 300B & SET amplifiers
🎧 High-end vintage tube collections
🎧 Serious reference-level tube rolling

⚡ REAL WWII AMERICAN BLACK GLASS MAGIC ⚡


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

★★★ Amazing Historic Military Tubes ★★★

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

Production Year: Owensboro, KY - 1944

Closely Matched Codes: W2 Z2

Tall Black Base

Platinum Label

Set of Two (2) Tubes

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

Made In the U.S.A.

 

★★★ These Tubes are Very Rare in Like New Condition ★★★ 

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


★★★ HICKOK TESTED ★★★

Tested on Hickok 750 for Emission, Mutual Conductance

Where 50 (μ) is Good these tubes peg at 73/78 for Emission

Where 2,600 (ma/V) is Good these tubes peg at 3,000/3,200 for Mutual Conductance

Tube 1. Plate 1. - 76 (μ) - 3,200 (ma/V)  at Idle - Test Like New

              Plate 2. - 73 (μ) - 3,000 (ma/V)  at Idle - Test Like New

Tube 2. Plate 1. - 74 (μ) - 3,000 (ma/V)  at Idle - Test Like New

              Plate 2. - 78 (μ) - 3,100 (ma/V)  at Idle - Test Like New

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

Nicely Balanced - Rare and Exceptional

Full Tonal Range - Powerful Emission

Zero Drop in Tube Life Test


***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 (µmhos), not emission in milliamps (mA) or microamps (µA). Confusion likely arises because micromhos are based on a ratio of a change in plate current (measured in µA) 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 (μmhos), which is sometimes abbreviated as μmos. The unit is a measure of a vacuum tube's transconductance (g{m}). Here's a breakdown: Micromhos (μmhos): 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).μmos: 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 Global 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!

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★ *Honesty, *Reliability and *Integrity are *Everything ★