Assistance with possible Loop and Tube issue

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Mungo Zen
Mark II
Posts: 142
Joined: Wed Jun 25, 2008 5:53 pm
Location: Vancouver B.C. Canada

Assistance with possible Loop and Tube issue

Post by Mungo Zen » Mon Aug 13, 2018 2:42 pm


I have an issue I think i have isolated and am looking for a second opinion.

Perceived Issue: When running the Effects Loop there is a loss of tone and power, sluggishness in the lows and a loss of some harmonics

Theory: V4 and V6 12AX7 need to be replaced

Stripped everything down to Guitar -> Amp -> Cab (This includes 0ing out the Loop Volume, turning off reverb, etc)
Disabled Effect Loop by Toggle
Hard Set Channel 3 on back
Set Tone and Note Volume
Engaged Effect Loop Toggle and bring Master Volume up to match above step

I repeated this in all three channels in 45 Watt

Findings: Most notably in Channel 2 and 3, when engaging the Effect Loop I had the above symptoms and have come to the conclusion it is the Tubes. Looking for feedback that confirms or suggest an alternative I should look at.
Shut Up and Play

2009 Mesa Boogie Mark V Head #310 (EL34)
1986 Peavey 412M (Sheffield 1290's)
2010 Rectifier Cab (V30's)
2008 Schecter Jeff Loomis (EMG 707 Active, 18v Mod)
2012 Schecter Hellraiser Solo 6

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