Hey Fellow Thunder Walkers, I recently bought a Hartke HA5500 amp head on fleabay. I only paid a couple hundred bucks for it so there was room to repair, etc and make it worth my while for buying a used head versus a new one. After it arrived safe and sound, I hooked it up to my Avatar stack. Tons of white noise, scratchy pots, and extremely loud cooling fans all coming through the cab without so much as a jack plugged in! Turns out the head was 9 years old and was in need of a tune up and time to replace those super loud Hartke cooling fans. I have owned other Hartke HA heads and all have noisy fans straight from the factory. First I cleaned the pots with DEOXIT D5. Then it was time to get rid of the OEM Sovtek 12AX7 pre-amp tube. On a certain tube related website from Canada, the Sovtek tubes are rated 2,3,3 out of 5 based on Noise, Microphonics, and Musical quality. The tube is military grade and hard to break, that why Hartke uses them, easy to ship. I contacted a guy named Doug that sells tubes online and he suggested the Genelex Gold Lion std pin. This tube is dead QUIET, warm and very musical. The Canadian site rated it a 4, 5,5. NO more white noise, scratchiness, etc. Now for the fans. Hartke uses 24 DC V cooling fans only, not 12 dc v or 5 dc v. Hard to find. I managed to replace the rear 80x80x25mm fan with a quieter one, the 60x60x15 mm heat sink cooling was still EXTREMELY loud, and annoying! You shouldnt need to turn you amp up to kill fan noise. I managed to find one online 60x60x10 mm from China, it works GREAT! You can not hear the fan at all, it is truly silent. The guy in China sent me 10, I have 9 left over. If anyone wants one just msg me and I can hook you up. I put it all back together, the amp still retains that gainy Hartke punch but with some more warmth now. The fans no longer sound like jet engines and its at least 80% quieter, that internal 60mm fan is absolutely SILENT. This head nows works great, sounds great, and in my opinion is better than new! Thanks for reading.