Tube location info: The balanced High Gain ECC83S is located in V3 for the phase inverter, which is third in line from end. The 6V6 goes in V4 next to the power tubes.This kit ships with E34L power tubes by default.Combo amps are very hard on tubes because of vibrations which can cause tube rattle with any brand of tube. If you play by yourself in a quiet environment or record with your amp you may want to consider using the EuroDamper tube damper rings for the power tubes. These are available in the "Related Products" tab as a set of three and will greatly decrease tube rattle.