DC 5 pre-amp tube suggestions

I've been having issues with my DC 5. I'll play a clean chord and there is a faint hissy noise in the background. I think it's probably a pre-amp tube issue. I've owned the amp for a little over a year and I have no idea how old the tubes a may be. I switched out the power tubes with Mesa's tubes first but now I'm moving on to the preamp tubes but I don't want to drop $20 a tube. Any suggestions for a more affordable brand. I just bought a new Lonestar Special and my pockets are wearing thin. Also if you think I might have another issue let me know.

Try plugging a cord from the send to the return of the effects loop. This is a known problem area.

As for preamp tubes, new ones are what they are. Scope your local area for vintage tube gear, do not overlook old organs. They may be on craigslist, in thrift stores, on bulletin boards in supermarkets, etc.

I have ended up with some nice preamp tubes scavenging this way but persistence is key.