Up for sale is an incredibly rare, highly sought-after matched pair of two pieces (2 Pcs) of vintage original Brimar 12AU7 twin triode vacuum tubes. Universally acclaimed by high-end audiophiles for their expansive soundstage, highly detailed textures, and dead-silent low-noise operation, these classic British-engineered triodes are a superb upgrade for premium preamplifiers, phono stages, line drivers, and high-fidelity tube gear.
As shown in our reference verification and the detailed structural close-up this pair represents the absolute pinnacle of early Brimar craftsmanship. Structurally, they feature the coveted Long Black Plate construction paired with the highly desirable vintage Square Getter configuration, giving them a distinctively warm, liquid, yet deeply resolving sonic presentation. Both valves are pristine, unused, and clearly stamped near the base seals with their original production codes—4L5 / 571 on the left tube Serial 2021019 and 3K5 / 571 on the right tube Serial 2021016—and come safely housed in fresh protective white collector boxes.
Testing & Verification: This dual-triode pair has been rigorously screened and balanced on our laboratory-calibrated Amplitrex AT1000 tester. Measured under full operational factory voltages against the standard 12AU7 factory datasheet parameters of Ip = 10.5 mA and Gm = 2,200 uMhos, both sections across both tubes show excellent electrical health, robust emissions, and tightly balanced mutual characteristics perfect for premium stereo configurations.
| Sr. No. / Date Code | Test Triode | Parameter Ip mAdc | Result Ip mAdc | Percentage Ip | Parameter Gm uMhos | Result Gm uMhos | Percentage Gm |
|---|---|---|---|---|---|---|---|
|
2021019
Code: 4L5 / 571 |
T1 | 10.5 | 8.2 | 78% | 2200 | 1900 | 86% |
| T2 | 10.5 | 8.2 | 78% | 2200 | 1900 | 86% | |
|
2021016
Code: 3K5 / 571 |
T1 | 10.5 | 9.0 | 85% | 2200 | 2000 | 90% |
| T2 | 10.5 | 8.8 | 83% | 2200 | 1900 | 86% |
We are specialized suppliers of high-grade vintage vacuum tubes and valves, maintaining an industry lineage established back in the 1970s. With an extensive inventory of nearly 300,000 components, we serve high-end audiophiles and vintage equipment restoration collectors worldwide. Every tube is strictly evaluated using calibrated industrial testing instruments such as the Amplitrex AT1000 to guarantee absolute transparency.
Notice: Custom duties and Taxes are the Responsibility of the Buyer in their Country.
NOS Audio Tubes — Mumbai, India