EHX also selects the best tubes (well balanced, best test data etc) for their gold line. The EHX 12AX7 has become a standard, known for its high gain and excellent mids and bass. It has a spiral wound filament to heIp cut down on noise and hum just like the vintage 7025 or 12AX7A tubes. These are one of the best deals around, you get rich tone for less! We test and/or match our tubes by Gm & Plate Current using a state of the art digital Maxi-Matcher tube tester.The Maxi-Matcher simulates a real circuit and tests tubes in real-world conditions. We also check our tubes for other issues like shorts on calibrated and vintage tube testers. We match our tubes +/- 5% with an overall tolerance of 10%. While we do screen for noise and microphonics, even the best tube testers are quite bad at finding these faults. The only real test is with your ears. We guarantee that our tubes will be free of noise or microphonics but please be aware that there isn't a whole lot we can do to ensure your tube won't be. We guarantee our tubes for 90 days upon receipt. Noise and/or microphonic issues are covered. The item "New Electro-Harmonix 12AX7 ECC83 GOLD PINS Gain Matched Quad (4) Vacuum Tubes" is in sale since Tuesday, January 15, 2019. This item is in the category "Musical Instruments\Guitars & Basses\Parts & Accessories\Amplifier Parts". The seller is "onlyglass" and is located in Easthampton, Massachusetts. This item can be shipped worldwide.