I heard that the stock tube in the Eden preamp was less than good, so I tried a few others. The sound was quite different. The stock 7025(No markings) was very hard and crisp sounding compared to a Sovtek 12AX7WB, a Jan Phillips 12AX7WA sounded more defined and fuller, but not as twangy. I even tried a counterfeit Telefunken. This tube was rounder sounding, like the Sovtek, but all the notes were easy to hear, but not as Juicy as the Jan Phillips. I know this sounds more like a salad bar, but how do you describe sound? It is very subjective. Also, I have tin ears, so one day somethig will sound better than the next A lot of people describe tube sounds from the quitarist point of view.