The Difficulty of Identifying NOS Valves: A Guide for Our Customers

In the fascinating world of vacuum tubes, the acronym NOS (New Old Stock) is often synonymous with superior quality and performance. These tubes, never used and often stored for decades, are highly sought after by audiophiles and vintage electronics enthusiasts. However, identifying with certainty whether a valve is truly NOS or has been lightly used can be a complex task, even for industry experts. In this article, we will explore the reasons for this difficulty and how to address it.

What is a NOS Valve?

An NOS valve is, by definition, a empty that has never been used since its production. These valves come from old warehouse lots, often manufactured decades ago, and are considered new because they have not suffered the wear and tear that occurs during use.

The Challenge of Identification
  • Storage Conditions: Most NOS valves have been stored in varying conditions, sometimes for decades. Even if a valve has never been used, age and storage conditions can affect its outward appearance. Dust, moisture and oxidation can alter the appearance of tubes, making them difficult to distinguish from used tubes.
  • Lack of Documentation: Often, NOS valves are sold without the original packaging because the boxes have been deteriorated over time. The lack of original documentation makes it difficult to verify the history of the valve. In some cases, labels may be faded or missing, further complicating identification.
  • External Similarities: Visually, lightly used valves can appear very similar to NOS ones. A valve that has been used for a short time may not show obvious signs of wear, especially if it has been handled with care. Even laboratory tests may, at times, reveal no significant difference between a NOS valve and a minimally used one.
  • Tests and Measurements: Electrical measurements can provide clues to the condition of a valve, but are not always definitive. Some NOS valves may have variations in measured values ​​due to their age, while used valves may still be within acceptable parameters. Therefore, the use of measurement tests does not always guarantee accurate identification.

What Does This Mean for Our Customers?

At Vacuum Tubes Treasures, we are committed to providing high quality valves and ensuring maximum transparency with our customers. Despite the challenges, we do our best to correctly identify NOS valves, based on careful visual inspection, measurement tests and, when possible, available documentation.

We advise our customers to consider purchasing of valves from reputable sources and to be aware of the difficulties inherent in identifying NOS valves. Our priority is your satisfaction and we are always available to answer your questions and provide you with support.

Kind regards from the Vacuum Tubes Treasures Staff