Rare GEC CV2901 12AX7 Blackburn B3D5 Original Box

Test Results are available upon request if not photographed in the listing or already stated. 90 % of our tubes are Tv7 tested.

Tubes tested on tv7u the Military standards were tubes needed to meet 60% (minimum value). All our tubes have been tested for. GAS SHORTS TRANSCONDUCTANCE & EMISSIONS. Please see my notes on noise tests below. We have a few different testers available to ensure the quality of the tube (as some tubes can not be tested on the tv7). Tv7 testing is tedious and I spend 12-13 hours a day testing tubes and double testing tubes - if you notice a mistake(like a picture doesn't match the title) please be gracious and let me know. UNLESS PHOTOGRAPHED WITH THE ORIGINAL BOX- tube will come in repackaged white boxes- 50-90 year old cardboard packaging doesn't hold together well. We have over the last 20 years amassed a huge collection of vintage amps/ parts / tubes and have decided to downsize that collection. Every tube has been marked for tracking and security purposes - these marks wipe off easily and without the mark no return will be accepted.

Sound quality is tremendously SUBJECTIVE. This is a very marginal test, only for. This test needs sound amplification; hearing listening to noise with headphones would indicate a real disaster inside a tube (THE shorts test WOULD already BE evidence OF THIS).

There is nothing wrong with performing that noise test. This test is not going to tell you whether the tube will be silent in your SET (single ended triode) amp or in anything else.

Ultimately, the best way of testing a tube for microphonics is in an actual chassis or amplifier similar to one in which it is intended to be used. Since amps have a wide variety of circuit designs and tube placement, this test is most effective in YOUR AMP or one that is almost identical.

Hence, most people advertising tubes as tested for Noise or Microphonics are probably NOT testing them in any meaningful way for you. "Noise" and "Microphonics" are often buzzwords for other issues. There is a small percentage of tubes that have a problem with noise but far less than most people think. In properly designed circuits objectionable "tube noise" is seldom found. In other words, it is a rare tube that will be noisy when used in most circuits.

Always check the data sheet of the tube you plan to use. Tube testers and noise testing. Tube testers do not test for these problems in the manner in which you think, except to the extent that a tube tester with sensitive leakage detection will find far more "noisy" tubes than a tube tester with only "fair" leakage sensitivity, to the extent that the noise is due to this problem. Listening through headphones to tube on a tester is half as good as putting in amp and listening for noise. PLEASE message me BEFORE you open a return.

PLEASE NOTE: Tube silkscreen (lettering on the tubes) is VERY fragile. It can be wiped off and destroyed VERY easily.