Fender Blues Junior hissing sound on certain notes

[dpve1@aol.com]

I am noticing a faint hissing sound only when I play certain notes.
It only seem to happen when I have the preamp at 5 or above.

I have tested my guitar and cable in another amp and it does not
do it. So I am convinced it is the amp.

I have pushed on the tubes and they seem to be seated fine.
I have also lightly tapped on the tubes with my guitar unplugged
and volume up to see if I could isolate to a tube but no good.

Any ideas of how to troubleshoot this.

TIA

[Jazz P Bass]

The amp needs a tune up?
Can you very that fact that it is not the speaker?
The preamp at 5 may be a hint. The pre is starting to push at that point.
Do you have spare tubes to try?
I would suggest changing one at a time.

[dpve1@aol.com]

The BJ manual lists the tubes as
6BQ5 6BQ5 12AX7 12AX7 12AX7

I find there are several brands and price levels to choose from.

Would there be any suggestions?
Can you replace just 1 tube?

Pros/cons?

[monsteranus]

The two output tubes should be replaced in matched pairs even if one is bad. If you have had it a long time and use it often you should consider replacing all the tubes at one time. I just got a set for 62.00 dollars including shipping a few days ago.