Description

S-12AX7C Select Salvaged Ruby Tubes High Mu Twin Triode Ruby Tubes Box "Selected" means Ruby Tubes has tested hundreds of tubes and "selected" only the best tubes that have low microphonics and high gain. "HG" means High-Grade, Ruby Tubes tests 100's of Tubes. Only the best tubes are labeled HG using Ruby Tubes DSS testing system Made in China Great price for a great tubes !!! Salvage tubes come from customers that have replace the entire set of tubes as a matter of scheduled routine, maintenance, regardless of condition. All the Salvage tubes we sell are tested. Prior to shipping, we retest them again. We do this by using a B & K DYNA-JET Model 707 . The Model 707 measures Dynamic Mutual Conductance . This insures that the tube will perform as specified. In guitar amp circuits practically all tubes (except rectifiers and diodes) are used as some type of amplifier. Even oscillator circuits are basically amplifiers with regenerative feedback. Therefore, the most important characteristic to be checked to determine how effectively any tube will function in its circuit, is its ability to amplify. This, in turn, is governed by its Dynamic Mutual Conductance . All Salvage Tubes have to pass the following 3 tests: Grid Emission and Vacuum Test: Each tube is checked for grid to cathode emissions, contaminated grids, or lack of vacuum. In other words, NO Shorts. Quality Test: This test is made only if the tube passes the NO shorts test above. This test measures the mutual conductance . Measuring the mutual conductance of a tube provides the most accurate and all inclusive single test that can be made on any tube. The tube must meet or exceed the manufacturers specifications for that type of tube. Life Test: This measures the amount of useful life still remaining in the tube. We do this test by reducing the heater or filament voltage to a predetermined amount. If the quality or Dynamic Mutual Conductance remains high, the tube being tested has 90-95% of its useful life remaining.