50/50 Squeal Problem

[reo73]

So my Studio Pre > 50/50 rig started acting up a few weeks ago. I have been getting a nasty feedback squeal out of it when a gain signal is run into it. The squeal is not present when playing but comes on immediately as the strings are muted. I have narrowed the problem down to being with the 50/50 and not the studio pre or a guitar, pedal, cable, etc. I have changed all the tubes, both preamp and power, and messed with the insides but everything seems OK by appearance.

Is there a wiring component in the 50/50 that could be causing a squeal as gain is increased?

 

[disassembled]

Does the amp make the squealing noise when you don't have ANYTHING plugged into the inputs of the 50/50? Sounds like a feedback loop being created somewhere but if the 50/50 is doing it by itself then that's a bit weird.

What makes you sure the 50/50 is the problem?


Greg

 

[reo73]

When there is nothing connected to the input there is no squeal but if I turn my preamp volume all the way down and turn up the power amp volume I can hear the squeal very softly.

I have changed out every other component in my signal chain...preamp, guitar, cables and the squeal is there every time. I am going to grab my other amp this weekend and see what happens when I run its preamp section thru the 50/50.

 

[disassembled]

When there is nothing connected to the input there is no squeal but if I turn my preamp volume all the way down and turn up the power amp volume I can hear the squeal very softly.

I have changed out every other component in my signal chain...preamp, guitar, cables and the squeal is there every time. I am going to grab my other amp this weekend and see what happens when I run its preamp section thru the 50/50.

I think you are jumping on the 50/50 too quickly. Try just having a cable plugged into the 50/50 input without connecting the other end to an amp input. This isn't a perfect test but it will eliminate other equipment. I am also worried that your cables might be microphonic. What brand of cable are you using? Is your ground switch set properly?


Good luck.

Greg

 

[reo73]

I use planet waves cables and have a bunch that I have switched in and out. I am sure it in not them. Oddly, yesterday it was not doing it nearly as bad and I am wondering if it was just a ground loop thing or maybe a driver tube I replaced that is working itself out somehow.

 

[BertG]

just a stab in the dark...

sounds like a double over gain issue.
could have bumped the gain up a hair by turning something else.
FFS I call it fat finger sydrome.
LOL

2nd By chance have you pickups gone microphonic on you?