I just bought a Vox AC50 (hooray me!) and was wondering if anyone had any advice on tubes. I switched out the Ruby EL34 power tubes for a set of Electro Harmonix 6CA7's, and it sounds a lot better.. much warmer and a lot less harsh. However, I was wondering if anyone had any recommendations or knowledge about tubes, and which ones had particular characteristics. Any advice would be most appreciated!!!!