anyone here ever change the 12AX7 tubes and the 12AU7 on an SVP Pro -- what is the location of the 12AU7 ?? there are no marks I can tell on the chassis - I've read from somewhere online it might be socket #4, which I thought might be counting L to R looking from the front with the top off - however it is from the back you can read the numbers (serial no.) on the board where tubes go - so now I don't know. the online manual only says that tube changes should be done by qualified service personnel, also, the phone number for customer service I have for them was a modem beeping/screeching - this preamp was shipped to me with tubes seperately packed - I just want to get this together to try out - not even tweaking anything yet. I figured it might be worth a try to get a quicker response from someone here at TB, than before I can get a response from tracking down someone from Ampeg service or seller -- Thanks.