I am not a tech or engineer. This one stumps me. Running two amps stereo with effects unit. One amp EF-86 front end. One 12ax7 front end. Equal volume. Cornish buffer is 1st pedal. 5 OD pedals after buffer.. EF-86 amp hooked up but not turned on. Pedals into 12ax7 amp sound fine , unity gain. Turn on EF-86 amp but keep it in standby mode and 3 of the 5 pedals are 1/3 less volume in 12ax7 amp. You can actually hear the volume go down in the 12ax7 amp (with one of the 3 pedals on) as the ef-86 amp warms up. Remove ef-86 tube and put amp on standby and there is no volume drop in the 3 pedals into the 12ax7 amp. Pedals into EF-86 amp sound fine , no volume drop when both amps are on.. I decide to take the 3 pedals that drop volume in the 12ax7 amp (when the EF86 amp is on) and move them before the Cornish buffer. Problem solved. No volume drop in 12ax7 amp when EF-86 amp is powered up. . Anyone want to venture WHY ? The amps both spec out perfectly no stray voltage ect.