| Author | Message | ||
     Adam |
Hi all, I have a 412 65 with the tube pi. When it's on I can hear the tube rush. Can you tell me where this is comming from, is it new tube time?} | ||
| Langley |
Adam - Based on the info provided, I can't venture a guess. If you could provide a wee bit of data, perhaps something could be suggested. Please define: "tube rush" (frequency, volume, duration, etc..); Positions of controls; Any issues with controls; Issue with 1 or any Channel/Input; How you got 4 12"s into that combo; Which speaker(s) the noise is coming from; Reverb / Tremolo on/off w/settings; Type, brand, age, of all tubes; Colors generated inside each tube; Color of the writing on each tube; Amount of heat emitted by output tubes, when on; Tubes microphonic?; Visible rust on transformers or chassis. Any 'mods' done to the amp; Blowing fuses; Overall sound quality; Line voltage; Line noise (try different power sources/outlets); Are you near an aitport or microwave tower(s); Last date of and type of service performed; Service provider (pro or not). | ||
| adam |
Whew! Ok here goes... Tube rush- a sound like air rushing past. "shhhhhhhhhhh" occurs when the amp is on-not in stand by. the sound is evident as long as the volume is up on either channel (and the master of course). I should have written 4-10 not 4-12 sorry. I don't know if the sound is from any one speaker, I believe it is being generated at the amp, which is incredibly clean for its age. Except for some very light surface rust it is spotless. Even the corners and handles are clean- but definately original. Tubes are Sylvanias with white lettering, they glow normally and do not seem to generate any excesive heat. I bought this amp used so I don't know when the last service was done- no mods I'm aware of. Adam | ||
| Langley |
That noise is "Hissing". Some hiss is normal, from either tube or solid-state amps. If it's objectionable you might try a new Phase Inverter tube to see if that helps. A 12AX7EH is a good general use tube. If that didn't quite 'do it', change the output tubes. EL-34S's (Groove Tubes call's em E34LS, relabeled Svetlana's). Switching new output tubes requires re-biasing. And that means a trip to a tech, but at least you wont pay tech-shop prices for the tubes. | ||
| Langley |
Here's an additional "Hiss" resource: http://www.geofex.com/ampdbug/hiss.htm | ||
| adam |
Thanks for the info, I'm going to go play now, Adam |