bbaug14
Active member
Ground lift switch solves a different problem. I had the problem with the ground lift as well, but the problem with the high gain modules is something different entirely.
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bruce egnater
New member
Actually the setting of the ground switch could cause some not so obvious issues under just the right circumstances. The switch on the M4 disconnects the circuit ground from the chassis. This makes it so that when you put it in a rack and it gets chassis ground from the rack rails, you can separate the circuit (audio) ground from the common rack (power ground) to prevent that ground loop. If you were to not have the chassis grounded to the rails and the third prong (ground pin) on the AC plug were not grounded properly, the chassis would not be grounded and would not act as a proper shield. This could surely wreak all sorts of havoc, especially with high gain modules. This would tell you it should never be necessary to list the third prong ground (safety) on the AC cord for any reason on the M4..
rlord1974
Active member
Thanks, Bruce. I'll have some time this weekend to tinker around with it, and I'll try to *finally* take a clip of the problem and email it to you!
All the best,
Rob
All the best,
Rob
HughJasol
New member
Sorry - I should have been more clear and pointed this out: The problem for me actually was with the high gain modules - with the ground lift switch in one position my high gain modules sounded fine; in the other position they squealed like an SOB. I can verify this happened with an SL2X, a GigMods 1087, and a Friedman C45/HBE (although the latter may be a bad example, as Friedman mods inherently seem to feedback more easily than stock modules in my experience). Lower-gain modules appeared to be fine and were basically unaffected by the ground lift switch (as far as squealing/feedback goes) . . .bbaug14":3u9cjp4v said:
To Bruce's point:
The electrical circuit where I had my rack plugged in is up to current codes (i.e., has a 3-prong outlet, etc - my house is relatively modern), and I use a Furman PL-??? in my rack, into which everything plugs in. Not sure if that matters ... just wanted to point that out.bruce egnater":3u9cjp4v said:
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cameron711
Active member
Any resolution on this? I have the same squeal in my sl2 and eg5 in chB...my sl2 has tungsol 12ax7 tubes, and the eg5 has a jj and a sovtek. All tubes on the mod 50 are Mesa boogie and power tubes are 6l6. Would love some advice!
MarcoR
Member
cameron711":1hvsw47c said:
Do you have anything in the loops? I remember this thread when it was first brought up. I never had the issue with my MOD50 and the same modules your using. Recently, I had a high pitched feedback almost whistling and it was caused by a decimator g-string in the loop. It didn't like line level and was corrected using the eganater loop gadget at instrument level. I doubt that will help you but start by stripping everything out of your signal path; i.e. Guitar strait into the front of the amp and nothing in the loop. Try every guitar you have. Does anything make it better or worse?
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cameron711
Active member
Thanks for your thoughts. I'm actually running guitar straight in, no effects, no pedals and I get it. I get a low hum when I get too close the output transformers but a squeal high pitched when using hum buckets, tried prs, sg and lp std and custom. My start and the prs with push pull single coile pulled to cool tap have no problem. Also, I sometimes get a noisy bottom end sometimes no matter whether I use my egnater 2x12 or my diezel 4x12. Help!
rlord1974
Active member
Try swapping out the tubes in the module with ones you know are good.