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annoying hum coming from NS-10, stuck troubleshooting

Posted: Fri Sep 04, 2009 7:17 pm
by rachmanoff
thought i'd see if anyone has any ideas..

mac pro/rme multiface I >> Mackie Big Knob >> Adcom GFA-545 >> NS-10 = obnoxious ground loop type hum that goes from annoying to intolerable when adjusting the input gain on the Big Knob.

mac pro/rme multiface I >> Adcom GFA-545 >> Ns-10 = no hum at all.

this leads me to believe there is a problem with the Big Knob, so I had a technician friend take a look at it. He didn't see anything wrong with it. I had another friend hook my Big Knob up to his rig and had no issues with it.

I have no idea what could be going on here. I tried an Ebtech Hum-X lift type device on various configurations of my gear to no avail. Normally, everything is plugged into the same Furman PL Plus power strip and thus running on the same breaker.

Any theories?

Re: annoying hum coming from NS-10, stuck troubleshooting

Posted: Fri Sep 04, 2009 7:29 pm
by knotkranky
emf's? crt monitor, amp/s ...

big knob is too close. Move it around a few feet while you listen to the hum

Re: annoying hum coming from NS-10, stuck troubleshooting

Posted: Fri Sep 04, 2009 8:55 pm
by rachmanoff
thanks for the idea, knot. I just moved the big knob all around the room while feeding the speakers with no discernible difference in the hum.

opened up the big knob and saw this..

Image

Image

looked up the part number covered in gunk, "LM317T". google says it's a voltage regulator. does that look problematic? I don't really have much experience in electronics.

Re: annoying hum coming from NS-10, stuck troubleshooting

Posted: Fri Sep 04, 2009 9:08 pm
by Tone Deft
no. an LM317 is a basic adjustable voltage regulator. the paste on there is conductive (conducts heat not electricity) paste for heat dissipation to cool the thing off. don't mess with it. ;) it's a totally robust part but electronics are more fun when they work.

Re: annoying hum coming from NS-10, stuck troubleshooting

Posted: Fri Sep 04, 2009 10:17 pm
by knotkranky
hmm, have you tried turning items/gear on your studio circuit on and off while listening?

is it 60hz hum with a buzz on it?

Make sure your audio interface output is full throttle. Wondering if you have a gain stage issue.

Plug other outputs from different gear into bigknob.

Re: annoying hum coming from NS-10, stuck troubleshooting

Posted: Fri Sep 04, 2009 11:42 pm
by fishmonkey
do you get the hum with just the Multiface connected to the Big Knob, or only when the computer is connected to the Multiface too?

also, is this a new problem, or is it the first time you've tried connecting all this gear together?

Re: annoying hum coming from NS-10, stuck troubleshooting

Posted: Sat Sep 05, 2009 1:12 am
by McQ714
they're broken.. just send them to me. :twisted:
you have no use for them anymore. buy some genelcs now!!!

Re: annoying hum coming from NS-10, stuck troubleshooting

Posted: Fri Sep 11, 2009 8:59 pm
by rachmanoff
fishmonkey wrote:do you get the hum with just the Multiface connected to the Big Knob, or only when the computer is connected to the Multiface too?

also, is this a new problem, or is it the first time you've tried connecting all this gear together?
definitely been going on for a little while, but i've only gotten around to doing something about it now. can't recall exactly when I started noticing.

as far as trying different pieces of gear with the knob goes, it sounds the same regardless of what's plugged into it. in fact, it sounds the same with nothing at all plugged into it. as long as it goes, big knob >> adcom >> NS10, it always sounds the same.

one other thought, and I don't know if this is indicative of an electrical problem in my house.. when I turn my ceiling fan on or off, I hear a 'pop' through the ns10s - it's pretty loud. but i have one of those simple ground test plugs and tried it on the outlet that everything is getting juice from, and it says all clear.

effing weird!

Re: annoying hum coming from NS-10, stuck troubleshooting

Posted: Fri Sep 11, 2009 10:12 pm
by Tone Deft
try taking a piece of wire and connecting the phono ground on the Mackie Big Knob to the metal case of something you know is grounded. also try touching it to the metal jack plugs and other metal parts of the Big Knob.

the fan could be radiated (through the air) or conducted (through metal) radiation. something like that will cause noise because when electric motors first turn on, in that first microsecond before the motor's coils are magnetized the motor is a short circtuit = low resistance = high current (inrush current) many amps.

NS10s are magnetically shielded so they themselves should be impervious to radiated emissions.