help identifying the problem with my mark V?

[rispsira]

i went to the rehearsal room yesterday and plugged the amp. It sounded great on its own until i activated the loop: from hard bypass to loop active.
Then the sound became very low and thin (like listening through radio speakers). No extra noise crackling or popping just the problem mentionned above.

I activated the loop because i wanted to use my decimator pro rack g. On that unit all settings were minimum (threshold and the other knob i forgot the name of). Then i bypassed the channel on the decimator sio it wasnt active and the problem remained. I then took out the unit and still the same.

Could it be coming from the tube in charge of the loop? i am asking that because i dont know wether a faulty tube could do that. Im used with all sorts of problems coming from tube such as noise crackling and popping or just no sound but never that.

i also played with the send level but to no avail.

any ideas?

 

[bryan_kilco]

Same thing happens with my 5150 when I engage the loop. I hear a lot of talk about dirty Send/Return jacks.....but I'm not so sure that's my issue. Good luck, sucks when something like this happens, especially to a new $2K amp.....

 

[rispsira]

thanks man! ill let you know IF i am able to solve it so you could try with your 5150 as well..