Well i have one of the Valvetronixs amps its a 30 watter and recently ive had a problem with it the sound it will go really loud and then really quiet, there has been no effect in the tone only the sound going loud and then quiet, do i need new tubes???

if i do need a new tube what sort of tube would suit this modeling amp sorry i know very little about amps (but i could tell you too much about guitars )

thanks john
Hit Me With Your Rhythm Stick
Its not an all-tube amp so replacing tubes shouldnt be an issue unless you have had it for aaaages.

check it to see if its loose, check to see if your guitars contorls are all how you want them
well its not the guitars because i have mutiple guitars and it does it on all of them

and ive had the amp for roughly 3 years
Hit Me With Your Rhythm Stick
Check you don't have the noise gate threshold set too high. If you do, it can make some quite strange cutting out sounds.

Press effect bypass, then hold down the tap button and move the effects level dial all the way counter clockwise.

If it's still doing it, it's not the noise gate doing it.

The valve in mine went after 2 and a half years, so it could well be that, otherwise.

Check out watford valves, I stuck one in mine and it sounds proper bo I tell thee.

You just need a single 12A7X valve, which is sometimes called an ECC83.