Comparison of AD1 and Ed Military Tubes in Power Amplifiers (Wehrmacht)

April 14, 2025 at 12:05 am, No comments

Military electronics during World War II were at the forefront of technology, and the German Wehrmacht was one of the leaders in the application of tube technology. Among these, the AD1 tube stands out, along with its rare alternative – the Ed tube, which was also found in military equipment. As vacuum tubes still hold a special place among audio enthusiasts and hi-fi amplifier fans, this article compares these two tubes, evaluating their price, specifications, historical significance, sound characteristics, and providing a summary from both military equipment and modern audio enthusiast perspectives.

1. Tube Price

The price of a tube is closely tied to whether it was manufactured for military purposes (indicated by the Wehrmacht stamp with an eagle and swastika on the tube). Listener experience suggests that Wehrmacht-stamped tubes sound better, likely due to the rigorous selection process—only the best-performing examples were chosen for the army and marked accordingly.

German army stamp on a Valvo Ed tube – eagle with swastika

AD1 – Original AD1 tubes made by Telefunken or Valvo are extremely expensive on the collectors' market today. They were also used in Wehrmacht equipment. Due to high demand and limited supply, they are often regarded as the "Holy Grail" of audio tubes. Prices can reach €1000–€2000, thanks to their historical value and legendary quality.
Ed – The Ed tube was possibly used as a military alternative or experimental version of the AD1. It is rare and therefore more expensive – approximately €1250–€2500 depending on condition and manufacturer.

2. Specification Comparison

Parameter	AD1	Ed
Filament Voltage (Uf)	4 V	4 V
Filament Current (If)	0.95 A	1 A
Anode Voltage (Ua)	250 V	250 V
Anode Current (Ia)	60 mA	60 mA
Transconductance (S)	6 mA/V	6 mA/V
Anode Resistance (Ra)	2.3 kΩ	2 kΩ
Max Anode Voltage (Ubmax)	250 V	310 V
Max Anode Power (Namax)	15 W	20 W
Interelectrode Capacitance (cg/a)	2.3 pF	18 pF

Key Differences:

The Ed tube can operate at higher voltages and power levels, which would be useful in military equipment requiring greater output strength. This also benefits amplifiers with higher power demands and less sensitive speakers.

The AD1 offers lower capacitance (cg/a), ensuring better high-frequency transmission—important both in military communication systems and in modern high-fidelity audio. Lower capacitance is vital for high-frequency signal quality, especially in sensitive audio systems.

3. Historical Significance

The AD1 was developed in the 1930s in Germany (Telefunken) and soon became a benchmark for European audio power triodes. It was widely used in high-quality radio receivers and audio amplifiers. Original tubes today are not just audio components but collectible artifacts. The AD1 was also one of the most important German military triodes, extensively used in Wehrmacht transmitters and communication devices. Its construction and reliability made it a top-tier component in Nazi Germany’s military technology. Today, it holds historical significance both in military history and among audio collectors.

The Ed tube is less well-known and likely served as a later or alternative version of the AD1. It doesn't have the same cultural and historical legacy as the AD1, but it remains a respected choice among vintage audio circles. The Ed tube was also used in military equipment as an alternative or experimental solution. Although its historical documentation is limited, its presence in collections indicates its practical use in military contexts.

4. Sound Comparison

The sound of the AD1 is often described as highly musical and warm, with an excellent midrange, wide soundstage, and high detail. Its precise high-frequency response and low internal capacitance make it ideal for high-end SET (Single-Ended Triode) amplifiers.

The Ed tube provides stable and balanced sound, with slightly less high-frequency resolution, possibly due to its higher interelectrode capacitance. However, it can deliver greater power and dynamics, which is an advantage when using less sensitive speakers or listening to modern, energetic music that requires a faster response from the tube.

Amplifier Tower-Ed by VS-Audio with Wehrmacht-stamped Valvo Ed tubes (43)

5. Summary

Criterion	AD1 (Military Classic)	Ed (Practical Alternative)
Price	Very high, collector’s value	Very high, rare find
Power	Medium (15 W)	Higher (20 W)
Frequency Response	Precise, suitable for comms	More power, some sound tradeoff
Historical Value	High, Wehrmacht standard	Lesser-known, but with potential
Sound	Warm, detailed, musical	Powerful, slightly more robust

Conclusion:

The Wehrmacht-era AD1 tube remains a technological and historical icon – ideal not only for restoring vintage devices but also for high-end audio applications. The Ed tube, although not as famous, offers a practical and powerful alternative, especially when higher power and dynamics are needed. Both options are historically and technologically significant, each representing German engineering excellence in their own way.