The Balanced Gold Pin ECC83S is located in V2 which is the farthest from the input jack in the front row, the Gold Pin ECC82 is located in V4.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 two power tubes and the GZ34. These are available and a set of three large Damper rings.