wanna try troubleshooting this?

[12AX7]

I know, longshot over the internet, but here goes. Homebuilt amp thats about 5 years old, similar to a marshall master vol amp but the preamp is a design i came to thru much experimentation. I plugged in one day and the sound just wasn't right. It lost that round fluid neck pickup tone you get with distortion and single note lines up around the 12th fret. You know that tone. Anyways, I plug in one morning and that is about 1/2 as fat and hollow/round sounding as usual and has a harder harsher attack unlike it's normal fluid feel. First thought is tubes, and i ended up swapping them all out for known good ones of the same type. Biased the power tubes the same as the other set too.  then tried other guitars and different cord. Shot every pot and jack with deoxit. Pulled the chassis and looked for bad solder joints but all seem good.  Gain seems the same and i hadn't touched it since this started, but the tone just isn't right. Any thoughts on what could cause that?

[Ritchie200]

You mentioned on the bad solder joints comment that you looked at them and all looked ok?  Maybe go one step further and chopstick around, a push and shove might identify something.  I am also assuming that this is a single channel amp so there is no way to compare it to a "good" channel?  Is there an effects loop?  If so, double check jack tension there.  Is your OPTX on an ohm switch?  Double check the switch and maybe wire a speaker direct to verify.  Speaking of speakers, have you played through the current speaker setup with another amp?  Definitely eliminate the easy stuff first!

Good luck!
Jim

[12AX7]

Yeah, did the chopsticking and it's a single channel w/no loop. Even sprayed the impedance selector, and it's a high quality one. Checked and cleaned the speaker terminal too.

[jim]

You could have a loose ground.  Tighten all screws, pots and jacks,  These get loose over time with  vibration.  Jim

[DummyLoad]

did you check the speaker(s)?

--DL

[drgonzonm]

Are you experiencing this with another guitar?.