12J5GT VT135 RCA for Western Electric, black plate, NOS/NIB, one pair (2)

Description

One pair (2) RCA 12J5GT  VT 135 tubes made for Western Electric in 1942

This is the military VT135 special quality version made for an order of Western Electric back during WW2.

These tubes feature black plates and  bottom getter. We assume that these were specially selected for Western Electric to their tight specs. These come in the original RCA boxes with all the prints on box as pictured.

The tubes are abolutely new and have not seen daylight for over 80 years. These tubes are in perfect working condition and test 100%+ in terms of emission and gm. We will select pairs with close values as long as the stock allows for it.

All tubes are tested and guaranteed to be in fully working condition.

These tubes are guaranteed to be new/NOS and unused from old military stock!

1. General Description

• Tube Type: Triode – single, indirectly heated vacuum tube

• Structure: Single low-mu triode with glass envelope

• Designation: VT-135 = Military version of 12J5 (civilian)

• Amplification Factor (μ): ~20 (low gain)

• Primary Function: Audio-frequency voltage amplification

• Envelope/Base: Glass tubular (“GT”), octal base (8-pin)

2. Audio Applications

Use in Audio Systems:

• Hi-Fi Audio:

  • Rarely used in modern high-fidelity systems due to low gain

  • Sometimes used in custom tube buffer stages or retro gear

• Guitar Amplifiers:

  • Found in a few vintage amp designs or in driver stages

  • Known for smooth, warm tone, not harsh or aggressive

• Studio Gear:

  • Used in vintage signal chains where linearity and warmth were key

Comparison to Other Triodes:

3. Industrial or Other Applications

• Military Electronics:

  • Designed for rugged applications: radios, radar, field equipment

  • Operated reliably across wide temperature and vibration ranges

• Instrumentation:

  • Used in oscilloscopes, signal generators, and analog meters

• Computing:

  • Found in early analog and logic circuits before the transistor era

• Control Systems:

  • Deployed in process controllers and automation systems pre-1960s

4. Comparison to Similar Tubes

🛠️ VT-135 vs 6J5: Identical internally except for heater voltage
🔁 VT-135 = 12J5 = one half of a 6SN7 (same triode section)

5. Key Technical Data

6. Construction and Special Features

• Envelope: Glass (GT = glass tubular); sometimes seen in metal base variants

• Socket Type: Octal (standard 8-pin)

• Military Designation:

  • “VT” = Vacuum Tube (US Army/Signal Corps designation)

  • VT-135 corresponds directly to 12J5 in civilian numbering

• Suffix Meaning:

  • No “A” suffix → standard heater warm-up

  • “GT” = Glass Tubular

• Notable Qualities:

  • Rugged construction for military spec

  • Low microphonics

  • Used where long-term reliability and linearity mattered more than gain

Summary

The VT-135 is the U.S. military version of the 12J5 — a single low-mu triode with a 12.6V heater and octal base. Known for its excellent linearity, ruggedness, and warm audio response, it found use in military communications, instrumentation, and vintage audio gear. While it doesn’t compete with modern high-gain triodes like the 12AX7, it is valued in custom analog circuits, restorations, and low-gain stages where clarity and reliability are key.