Di Box for notebook ground loop

[Ghost Snake]

I don't know if this is the right place to post this but....
I 'm having ground loop problems recording guitar with my notebook .
My soundcard is a Line6 Gx. I get all sorts of wideband noise when I plug the notebook PSU (battery doesn't work anymore), no matter which socket I plug it in. My guitar electronics has been shielded from a tech.

So, what I had in mind was a Di Box with a 1:1 isolated audio transformer, that would ideally 'eat' the ground loop noise... the problem is that I'm BROKE right now ! And Jensen transformer are pricey, minimum 70 $ .
Is there a cheaper (and safe, no cutting the ground please) way to solve this problem ?

[No_Use]

Had the same problem with laptop and (supposedly) ground loop in a rehearsal room.

Bought this, which totally solved it for me.

https://www.music-group.com/Categories/ ... 00/p/P0387

edit:
Thinking about it, might be a bit different situation than in your case. I got the ground loop when the laptop was going over the rehearsal room P.A., so I put the HD400 between my soundcard's output and the mixing desk. Can't tell really if it works as well if a guitar is involved as in your case.

[Ghost Snake]

Oh yeah, that would work great I think, it was on my 'to-buy' list. I was just trying to see if there was a 'DIY' solution other than an audio transformer

[Hink]

this is more suite for hardware so I am moving it there but will keep a shadow topic here

[Aloysius]

Roland Quad-Capture has a ground lift button. Perhaps other external soundcards do as well. Since you're planning on spending money, I thought I'd submit it as a suggestion.



http://www.rolandus.com/community/rolan ... group/1500

[ghettosynth]

I have used very inexpensive isolation transformers from modems and phones in such settings. In fact, I've used the same transformers with my Traktor controller to DJ and if anything it improved the sound.

That said, I ground lift my laptops at the drop of a hat. That's not advice, be safe and all, but I think that the concern over this is blown out of proportion because of the threat of litigation.

Consider that you almost certainly have wall warts in your studio that are two wire connected. They provide no protection and that's ok because the likelihood of the negative output rail, which is the only thing possibly connected to the powered device's chassis, shorting to the hot side of the AC line through failure is exceedingly low to the point of being non-existent. The AC line is isolated from the output by a transformer. In order for the output to become hot with respect to AC ground the transformer would have to fail in such a way that the secondary would come in contact with the primary. Most/all transformers that are in your studio have been UL approved without a three wire grounded adapter.

Your laptop power supply is almost certainly a single voltage supply in a plastic case. There is no chance that the case of the power supply itself is a safety risk unless you break the case. The only concern is that some failure in the power supply causes the negative output rail to be connected to the hot side of the AC line. Just as with other wall warts that don't have this protection, the chances are virtually nil. All of my apple laptops have shipped with a three prong cord or a simple two prong plug that eliminates the cable. Essentially, they ship(ed) from the factory with a ground lift plug.

The safety reasons that really drove three wire AC are cases where there is genuine concern, largely, power tools. In a metal power tool there is a real concern that a motor failure could cause the hot side of the AC line to be connected to the metal case of the power tool. The use of a proper three wire ground gives a path to ground that does not go through your body.

I'm an absolute safety nazi when it comes to genuine grounding concerns, I pay a lot of attention to this when I'm working outside with power tools. When you're outside the chances of being more firmly grounded, e.g., through wet shoes, is much higher. I check my outlets to make sure that the ground pin is actually grounded, do you? I learned at an early age how to work on high voltage stuff (always one hand in the back pocket), and I'm super diligent about this stuff whenever I'm working on things like tube amps. But, I lift the grounds on my laptops all the time.

If you don't understand enough about electronics to know what can be lifted and what can't, then it's probably better that you never lift anything. That's why codes are what they are, they protect against ignorant mis-application of grounding principles. However, if you're really that concerned about this kind of safety issue then you shouldn't be using two prong wall warts either.

[bungle]

Check out orchid electronics
http://www.orchid-electronics.com/dual_isolator.htm
That box changed everything for me, not only does it kill all that laptop noise but also balances anything you put into it
Extremely cheap and the guy is amazing, when i popped in he was fixing a DI under warranty, the DI was 20 years old hahaha

[khanyz]

Check out orchid electronics
http://www.orchid-electronics.com/dual_isolator.htm
That box changed everything for me, not only does it kill all that laptop noise but also balances anything you put into it
Extremely cheap and the guy is amazing, when i popped in he was fixing a DI under warranty, the DI was 20 years old hahaha

+1 John at Orchid is great and I use the single isolator (with XLR output) on my pedalboard, on the speaker emulated output of my Blackstar HT-DUAL, along with their Muting DI pedal or Amp Interface. They works great.

[Ghost Snake]

The safety reasons that really drove three wire AC are cases where there is genuine concern, largely, power tools. In a metal power tool there is a real concern that a motor failure could cause the hot side of the AC line to be connected to the metal case of the power tool. The use of a proper three wire ground gives a path to ground that does not go through your body.

You have made some good points here. I myself have been in contact 3 or 4 times with Ac current (230 V here in Italy), working as a boiler tech, ALL these times I managed to get shocked even if I had put the mains switches on the OFF position (unproper unipolar mains switches installed by idiots, I am still so fuckin' angry with them ! ), on old electric house systems. I have been lucky, but nowadays I always switch the whole house off when I see a suspicious / old Mains Switch.

Anyway, in my home studio ALL the sockets have 3 conductors connected in, and the earth goes to a safety circuit breaker.

Regarding the 'earth lift', I still have doubts about it, just because of my ignorance, and because both the electric guitar and the soundcard don't have a Mains cable ! So, what earth am I lifting there ?

[Ghost Snake]

Check out orchid electronics
http://www.orchid-electronics.com/dual_isolator.htm

That looks really interesting !!

+1 John at Orchid is great and I use the single isolator (with XLR output) on my pedalboard, on the speaker emulated output of my Blackstar HT-DUAL, along with their Muting DI pedal or Amp Interface. They works great.

Cool, but will it work on a mono input ? My crappy soundcard has only a guitar input. Can I use a XLR -> MONO cable and still have the 'insulation' working properly without the extra connector ?

If not, I think I will have to upgrade the soundcard. The Roland one looks great BTW.

[khanyz]

The dual isolators are independent, and there is also a single version (which I use). They can handle balanced or unbalanced signals and come with TRS or XLR sockets in any combination.

I don't have issues with my Line6 UX1 now, but my old laptop did cause noise problems.

In that one there was a power issue (on both battery and PSU) which meant that when the hard drive required more power, the USB power dropped and the fluctuations caused the noise. I only recognised the link because of the noise coinciding with the drive spinning up.

[Ghost Snake]

The dual isolators are independent, and there is also a single version (which I use). They can handle balanced or unbalanced signals and come with TRS or XLR sockets in any combination.

Sounds like a smart product ! I will keep it in my list cheap as well !

In that one there was a power issue (on both battery and PSU) which meant that when the hard drive required more power, the USB power dropped and the fluctuations caused the noise. I only recognised the link because of the noise coinciding with the drive spinning up.

Man... sometimes I think making music on a laptop = more problems than music . I wish my main desktop computer wasn't broken.