Heads up to anyone considering buying Sovtek EL84 tubes... I'm building a stereo Hi-Fi tube amp for my home and decided to save some money by utilizing as many things in my stash as possible. I had a brand new pair of Sovtek EL84 tubes from several years ago (probably from a guitar amp I re-tubed for someone and maybe they changed their mind about the tubes and wanted something better, IDK). Anyway, I needed a second matched pair so I could use them in my hi-fi amp. I first ordered a pair from www.tubesandmore.com and tested them when they came in. Much to my amazement, the grid leakage test for the tubes did not go over very well. While they passed this test, it was not by much. I contacted the store and arranged for an exchange, citing the test results. The next pair came in and I tested them. I was blown away when one of the tubes actually failed the grid leakage test! Can you believe this? A brand new tube actually tested bad. Frustrated, I returned the tubes for my money back and took my business elsewhere. I went to tubedepot.com, who I have purchased many tubes from over the years and never a problem once. When I placed this order with them, I cited in the customer comments section of the order my terrible experience thus far and asked if they could please check the grid leakage before shipping the tubes to me. When the tubes arrived I tested them again. The first tube passed everything with flying colors and I was starting to feel relieved, until I tested the second tube. During the grid leakage test this tube become unstable and began to read in the "?" area of the test range, which for all intents and purposes indicates a bad tube. Are you freaking kidding me? I specifically asked for the grid leakage to be checked before shipping these. I'm sending these tubes back and asking for my money back. This time I will cut my losses and buy a quartet of much higher quality tubes in hopes on not having to go through this crap ordeal anymore.
I'm not sure who is at fault here, but I suspect its a pile of fault starting with Sovtek and ending with the dealers not testing there tubes sufficiently before shipping them. If I didn't have a tube tester I would be a victim of tubes that failed within a month or less, leaving me in a situation where I would have to buy more tubes and if I was a person who didn't know how to bias my amplifiers I would also have to pay to have a tech do that work for me each time. What a nightmare. Word to the wise, Sovtek tubes are garbage and the stores don't do extensive testing, so buy the good tubes and you'll be okay.
About the Author
Mike Congilosi II, Owner/Designer/Electronics Engineer at Lightning Boy Audio and Owner/Audio Engineer/Music Producer at LBA Studios.