As to your first question, there are others you can use. I suppose the closest thing to a generic name for this family of tubes is the "6dj8 family" of high transconductance twin triode tubes, which includes the 6dj8, 6922, and 7308 tubes. The European equivalent names (someone correct me if I'm wrong) are the ECC88, E88CC. and E188CC. Also compatible to a certain extent is the Russian 6n1p. The 6922 was marketed as a premium industrial version of the 6dj8, and the 7308 was the top of the line guaranteed low noise version. However, I don't think there is much agreement as to whether 6922 and 7308 designations correspond to actually better sound than a 6dj8. As to your second question, I think it is most definitely possible to make a major mistake with the "more cash, better sound" theory. Certain tubes will sound better in certain applications than others, but that depends both on the component used and the user's preference. I do recommend you avoid the Sovteks if you are looking for better sound - I'd take the Philips tubes you already have. The best thing you can do is talk with a dealer who has experience with the tubes in your particular application. Kevin Deal of Upscale Audio is well respected in these circles as someone to go to, but (again, correct me if I'm wrong) for the time being he is only selling 6dj8 tubes to customers who actually bought their components from him. However, his web site is a good source of information. Another good source of information is the audioasylum tube FAQ (www.audioasylum.com). It contains a list of dealers, and some reviews of the 6dj8 family. From my personal experience, I'm a fan of the Amperex 7308's, but its getting to be tough to find. I also recommend Mullard 6dj8's/6922's. I find the Telefunkens to be a little overpriced for the sound quality offered, but that's based on admitedly limited experience. Best of luck in your tube search!
