ADA Depot - A Forum To Support Users of ADA Amplification Gear

Please login or register.

Login with username, password and session length
Advanced search  

News:

Temp "Time Format" issue Fix in Discussions

Pages: [1]   Go Down

Author Topic: Ground Loop Hum?  (Read 7830 times)

0 Members and 1 Guest are viewing this topic.

McLeanAB

  • Full Member
  • ***
  • Offline Offline
  • Posts: 162
    • Adam's Music
Ground Loop Hum?
« on: Time Format »

Howdy all!

So... I have an issue with my lovely ISP Theta Combo amp.  By itself, she's awesome.  Hook up an effect unit like my Rocktron Xpression and she's still awesome.  The moment I decide to connect her to my little mixing board (Peavey PV8) to record direct (either with or without the Rocktron) and there's a ferocious hum... very loud.  It sounds like the 60hz hum I found on youtube:

https://www.youtube.com/watch?v=Vf6Bq-vStLA

It's annoying and loud... ugh.

I live in an old house with mostly two prong wall outlets (no ground?).  So, everything runs through a Furman Power Conditioner Rack Rider or two and then I have to use a 3 to 2 prong adapter to go to the wall outlet.  Now... I've done this before at my old house in Boston with my Theta (and MP-1) Preamp and my Rocktron Velocity Power amp into a 2x12.  The direct out (or line out) on the Theta went to the mixing board so I could here the cabinet emulated sound through the monitors and the 'regular' guitar sound through the 2x12.  Never a hum...

It's only with the Theta Combo that this happens...

I've tried some three prong outlets in the kitchen and other areas of the house and it still seems to do it...

Should I try to grab up a Ebtech Hum Eliminator or will something explode if I do that?

Any and all thoughts are greatly appreciated!
Logged
-Adam
ISP Theta Preamp, ISP Theta PRO, ISP Theta Combo and Vector 2x12 with Celestion Alnico Creams, and Charvel Wildcards with EMGs!

AxeHarmony

  • Newbie
  • *
  • Offline Offline
  • Posts: 21
  • Vintage ADA = Cool
Re: Ground Loop Hum?
« Reply #1 on: Time Format »

my Carvin 2x12 is like that, it needs the earth ground (proper up to date home wiring)

let me know if you find a solution :)

Logged

GuitarBuilder

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 278
Re: Ground Loop Hum?
« Reply #2 on: Time Format »

The Ebtech would be a good bet.
Logged
ADA and Rockman Heads
Marshall amps
Strats and Les Pauls

Sparker

  • Full Member
  • ***
  • Offline Offline
  • Posts: 103
Re: Ground Loop Hum?
« Reply #3 on: Time Format »

Hi -

You will always have GND difrerences between various equipment, its just a question of how bad and how much hum this introduces onto the signal.
This can be reduced by running balanced signal cables between the various bits of kit with the GND lifted in one end of the signal cable (not the power cables). Your ISP may havea balanced output on the direct outs, in which case you would then have to find a matching balanced input on your mixer (a balanced mic input with a switchable line level pad and non phantom, for instance). If you don't have this then the transformer would be the best way to go.

Behringer also do similar products to the Ebtech.

Hope this helps
Logged
ADA Gear: MP-1 Tube Board

McLeanAB

  • Full Member
  • ***
  • Offline Offline
  • Posts: 162
    • Adam's Music
Re: Ground Loop Hum?
« Reply #4 on: Time Format »

Thanks for the prompt replies, fellers!

Yep... the balanced outs on the Theta to the balanced ins on the mixer doesn't help either...

So, even though the wiring in the house is old, using the Ebtech wouldn't outright damage anything or electrocute me?
Logged
-Adam
ISP Theta Preamp, ISP Theta PRO, ISP Theta Combo and Vector 2x12 with Celestion Alnico Creams, and Charvel Wildcards with EMGs!

Sparker

  • Full Member
  • ***
  • Offline Offline
  • Posts: 103
Re: Ground Loop Hum?
« Reply #5 on: Time Format »

Quote
Yep... the balanced outs on the Theta to the balanced ins on the mixer doesn't help either...

Did you cut the ground wire in the cable that you used to connect these? I had to do this with my mixer outputs to powered monitor inputs, the complete balanced connection between them still hummed until I cut the ground (screen) in both the connecting cables (left & right).

The Ebtech should do no harm at all, they are usually just a passive isolating audio transformer.
Logged
ADA Gear: MP-1 Tube Board

McLeanAB

  • Full Member
  • ***
  • Offline Offline
  • Posts: 162
    • Adam's Music
Re: Ground Loop Hum?
« Reply #6 on: Time Format »

Thanks!

Going for the Ebtech... stay tuned...
Logged
-Adam
ISP Theta Preamp, ISP Theta PRO, ISP Theta Combo and Vector 2x12 with Celestion Alnico Creams, and Charvel Wildcards with EMGs!

DaveM

  • Newbie
  • *
  • Offline Offline
  • Posts: 46
Re: Ground Loop Hum?
« Reply #7 on: Time Format »

Running ungrounded electronics is never a good idea....

Back on topic, I'd suggest getting the Ebtech "box" vice the cheaper "plug", and pay attention to direction of signal flow on the box itself because it matters. 

One Ebtech box got rid of ALL the line noise in my entire rig.  They're mighty good at what they do......

Also.....if you STILL can hear the hum in recordings, you can always run a notch filter on the fundamental freq and its harmonics.  They are super easy to spot on a spectrum analyzer.
« Last Edit: Time Format by davem »
Logged
HEADS: Mesa Boogie Mark-IVa, Egnater TOL-50
RACK: ADA MP2, Peavey Classic 60/60
PEDALBOARD: Line6 M13, MXR Carbon Copy, Fulltone FD-2 MOSFET, "Slash" WAH, Morley Lil Alligator, Digitech Jamman
CABS: Avatar and Genz-Benz
GUITARS: Ibanez, Fender & Schecter
WIRELESS: Line 6 G50
STUDIO: Cubase 6.5, Focusrite interface, M-Audio MCU-PRO DAW controller, Novation Impulse controller, KRK monitors, AKG phones, reamping courtesy of Radial

Sparker

  • Full Member
  • ***
  • Offline Offline
  • Posts: 103
Re: Ground Loop Hum?
« Reply #8 on: Time Format »

Quote
Running ungrounded electronics is never a good idea....

Completely agree, for power grounds, e.g. mains power   :nono:

Balanced signal grounds are different. That's why a lot of equipment have ground lift switches on their balanced outputs, for removing ground loop hum   :thumb-up:
Logged
ADA Gear: MP-1 Tube Board

rnolan

  • Administrator
  • Superhero Member
  • ******
  • Offline Offline
  • Posts: 5998
Re: Ground Loop Hum?
« Reply #9 on: Time Format »

I'm not sure how relevant this is in your situation but it's important that all the kit (who's grounds are being interconnected) are on the same circuit and the same power boards.
Logged
Studio Rig: Stuff; Live Rig: More Stuff; Guitars: A few

McLeanAB

  • Full Member
  • ***
  • Offline Offline
  • Posts: 162
    • Adam's Music
Re: Ground Loop Hum?
« Reply #10 on: Time Format »

UPDATE:

Got the Ebtech Hum Eliminator, and BAM!  Silent as death...

Holy crap... I have the ISP Theta Combo pumping out killer tones with a signal from the effects loop going to a Rocktron Xpression for cab sims and chorus/delays... HOLY CRAP.  Not practical for a live or recording, but the sound of the guitar speaker plus the cab sims (and effects) in the room is monstrous!  And the Ebtech cleaned up all the hum... damn! 

Excellent product... two channels with 1/4 inch in/out and XLR in/outs and you can mix and match (1/4 in, XLR out, etc)...  great purchase...
Logged
-Adam
ISP Theta Preamp, ISP Theta PRO, ISP Theta Combo and Vector 2x12 with Celestion Alnico Creams, and Charvel Wildcards with EMGs!
Pages: [1]   Go Up