I have tried to capture the history and the chronology of the the 6550/KT88 tube to the best of my knowledge: 1. The coke-bottle 6550 was manufactured by Tungsol and was re-labeled for many other manufacturers. I have personally come across RCA, GE, Sylvania, Stromberg-Calrson and Raytheon labeled Tung-sol 6550 tubes. Tung-sol manufactured the 6550 tubes from ~ 1955-1975* 2. GEC KT88 was manufactured by MOV for GEC. There are Genalex and Gold Lion versions of the GEC tubes as well. These were manufactured from ~ 1957 - 1980s* 3. Straight-bottle 6550A was manufactured by GE. I have seen GE 6550A re-labeled as Philips. GE manufactured the 6550A tubes from ~ 1971-1991* 4. Straight-bottle 6550 was manufactured by Sylvania. I have personally come across RCA labeled Sylvania 6550 tube. Sylvania manufactured the 6550 tubes from ~ 1971-1979* *Dates are approximate. Please add your inputs in the comments section if you have any additional context or information. Thanks!
Wow. Good amount of information and great presentation. Thank you! It would be great to listen to each of these tubes in an amp and get an impression of the sound differences. What's your opinion of each of these in terms of sound? Not everyday that someone is able to get their hands on all of these vintage tubes.. that too with original boxes. What a treat.
They all sound different to each other. Some are drastically different, others are slightly different. At the end it really comes down to personal taste and preference. :)
