Quick Lonestar Special Question -

[iwkil]

Hi,
When i enable the "hard bypass" switch on the FX loop I get a screaching sound that doesnt sound good? are you supposed to insert a loop between SND and RET in the loop before engaging the "hard bypass" switch?

Thanks
Rob

 

[plan-x]

No, that's why it's called a bypass. I've never heard that one before. Maybe a tube has gone microphonic. Although it should be doing it when you kick in the loop. :?

 

[iwkil]

so I should be able to flick the switch to "hard bypass" with nothing plugged into the loop, end os story?

Thanks for your help.

 

[egkor]

so I should be able to flick the switch to "hard bypass" with nothing plugged into the loop, end os story?

Thanks for your help.

That is correct. Nothing plugged into the loop, switch to "hard bypass", done. This takes out the loop, output, and solo controls, and one(?) 12AX7. So you are actually reducing the preamp tube count when doing this.

You could call Mesa Support and ask them about this "screach", they probably will have some suggestions.

Look at the LS Owner's Manual for 12AX7 placement and significance in the signal chain. I would try to see if the 12AX7s are microphonic first by removing the cans/keepers (rotate until they pop off, reverse procedure to re-install) and gently "tapping" on each 12AX7 with a pencil eraser for example, as described in the Owner's Manual.

Also You could buy a new 12AX7 tube and swap the new tube in to each 12AX7 location (starting with V1) until it changes or eliminates the screach behavior. Of course, power down the LS and back up between each tube swap.

I have labeled 12AX7s with a Sharpie to indicate which position they were in originally, just to keep track. The tube that was in V1 should stay in V1, unless it is the one that is microphonic, causing the screach.

Good luck, watch for hot power tubes and post back on what you find.

If you are not comfortable with this, please get help! Find a knowlegeable friend or a pro amp tech. Hope this helps.

-Gary K

 

[iwkil]

Thanks Gary, I'll check that out tonight, I have a few spare 12AX7's so if it is a bad valve i should be able to trace it.

Cheers
Rob