When I first got my VP20 I went a little crazy with tube swapping. My favorite 12AU7 ended up being a set of Sylvania 12AU7WA mil spec tubes I bought on ebay. I knew they had never been opened as they came in the boxes I remember tham coming in back in the day when I was an electronic tech in the Air Force.
Actually, the nostalgia of seeing those old boxes with the federal stock number may have had a positive influence on how I heard them. They seemed to have the cleanest sound of all the tubes I tried and I have read on other forums that those particular tubes can sound less "tubey" because of their clean high frequency presentation.
Actually, the nostalgia of seeing those old boxes with the federal stock number may have had a positive influence on how I heard them. They seemed to have the cleanest sound of all the tubes I tried and I have read on other forums that those particular tubes can sound less "tubey" because of their clean high frequency presentation.