G.E Matched Pair (2) 7581A KT66 premium tNOS AT1000 TESTED Vacuum Tubes tight match 35 Watt 6L6 Beam Power Tetrode (like 6L6GC) 1960-1975

This listing is for a Pair (2) of 7581A KT66 6L6 Beam Power Tetrode (like 6L6GC) premium vacuum tubes in the ST (Coke bottle) tube shape. They have a black bakelite octal base, grey plate, and dual side halo getter.

The 7581A variant is rated at 35 Watts on the plate. Completely compatible with KT66 and 6L6GC. These two have a perfect match in plate current!

Your tubes have been fully tested on a computer-regulated, USA-made Amplitrex AT1000 on Fixed Bias setting with like new, NOS results (tNOS). Here's what that means: to qualify for this listing, several stringent conditions must be met by the power tubes: The plate current must measure between 68 mA and 102 mA AND transconductance must measure between 5040 uMhos and 7560 uMhos, consistent with original 1960 RCA, Western Electric, Sylvania, GE, and/or Tung-Sol datasheet specifications for new tubes of this type. The tubes must also show no shorts, show a gas current less than 8.5 mA, and a heater-to-cathode leakage of less than 10 microamps (10 uA). The tubes might have mechanical wear or have the label rubbed off - these are very old! Used-testing tubes are available in a separate listing at a significant discount. Every tNOS or Used Good tube you receive from Sound By Doc is guaranteed against failure for 60 days after purchase, an industry extreme!

These photos are not stock photos. You are looking at the actual tubes you will receive. If a box or boxes are in the photos, you will get them. If test results appear in the photos, look close, because those are the test results of the tubes you will receive! SKU 6L6-7581. Please note that matching is nearly always possible for us from stock that is inventoried but not yet listed. If you need a matched pair or quad etc., please use the make-an-offer feature through Reverb. Matching requires an extra burst of effort, so please add $5 per tube to your offer for 10% matching and $10 per tube for 4% matching. [Matching is based on plate current for power tubes, voltage drop for rectifiers, and GM for all other tubes. If you also require the label or internals to match, please specify that in your offer.]