ground loop hum

The Moog Forum Little Phatty & Slim Phatty Forum
1

Hi all,

…been enjoying the Stage II for several nights now…quite awesome in really every aspect…but more on that in another post…forgive me if I stray just a bit off a direct Moog question, but I have a ground loop hum that seems to occur mostly when I connect my LP to my audio interface for my laptop… the interface is virtually noise-free when running softsynths, etc, and also when plugging in a condenser mic…typical 60Hz hum comes in strong when I plug the LP in… now, I know the problem is probably the laptop power supply (as the hum is very reduced when I run the laptop on battery only)…

Simple question for all of you analog audiophiles!: would it be most effective to always run the LP into a direct box (not sure if passive if best), OR put a product like a Hum-x on the end of the power supply cord of the laptop OR both? As always, looking to not lose any of the great sound that I’ve been hearing. I know my LP is defect-free, as I can run it into an effects unit, then directly into powered monitors and it’s clean as a whistle…

…a last :laughing: …when I plug my old, noisy Oberheim M-6 into the interface, it does NOT cause any ground loop hum…

Thanks for any help in this… I’ve read many articles on the net regarding grounding problems in general, but I’d like to get back to music-making(!)… best, jgirv

2

I solve such problems with DI boxes for most cases…

Against heavy Notebook/soundcard hum the Palmer Line Isolation Box (PLI-03) was most succesful.

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thank you, I’ll give it a try… more later, jgirv

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Are you by any chance running an Apogee Duet?

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no, it’s an inexpensive M-audio MobilePre interface… I’ll eventually upgrade to a FW interface… actually, the MobilePre sounds pretty good when I track vocals into it… been running some tests with the LP, for example, playing it through monitor speakers directly (bypassing the interface and computer entirely) as well as running it through the interface and Cakewalk Sonar… just want to hear if the cheapish interface is robbing me of any of the great sound I hear directly…

6

…on an endnote to the ground loop problem… when I connected a USB cable to the Stage II and then of course to the laptop… end of hum… completely… nothing but silence… and, happily, when playing the LP, plenty of sound… I guess the USB connection provided an electrical exit for the hum… or something!