Carvin xb100 makes noise at high volume

[rds]

hi. i am new to the site. i just bought a carvin xb100 100 watt tube head. it sounds good to me, but i dont know the history, if its been retubed, maintenanced, ecc. it sounds good. but when i turn it up to 50 percent it makes a slight breakup/signal noise sound when i play certain barr chords. its not every chord. its not the guitar. i tried different ones. i have no clue what could be happening. it still plays even with this problem. any ideas would be appreciated. thanks.

Symptoms are: when volume is at 50 percent or higher after warmed up i get a breakup electric noise in the background when i play certain barr chords (not all chords just certain barr chords). this amp has a 50watt or 100 watt switch on back. no symptoms in 50 watt mode. amp has way more balls in 100 watt mode anyway, i dont know when or if it has been tubed. it has 6L6's. the sound can be heard while making the chord in the background. its not speakers, not guitar frett buzz. its not like that. it is for sure something from the amp. the sound breaks up and goes away after it pronounces itself. any ideas or help with this i would appreciate. thanks.

I examined and found my tubes are mesa415 6l6gc tubes made in usa. this seems to indicate original tubes for this carvin. i understand these arent even made anymore. does anyone know of these tubes. are they good tubes as i seem to be reading? what would be a good replacement for them in your opinion? i am not certain this is the problem. does anyone know if the carvin x100b from 80's amps are fixed bias? i have also read that once but dont know if its right. thanks for looking.

[Twist]

It may be your tubes. Leave the guitar unplugged and turn up the controls. Then one at a time flick the tubes with the hard part of your finger nail. If you hear a noise then the tube is faulty or the socket is dirty. Also dirty pots and jacks can make a static noise from vibration even when you dont touch them.

[Enzo]

Hi rds, welcome to the forum.

6L6s are generic. people have ones they like better than others, but the amps are not critical circuits. The current crop of tubes like SOvtek and JJ work just fine in amps like yours. If your tubes are original they are probably overdue for replacement.