Active Direct Box: Ground lift does not fix ground loop!

BEWARE TO THE BUYER! READ!

This is a Samson S-Direct Plus, an active stereo di box. I use it in between my laptop's stereo headphone jack to my mackie mr5's to get rid of that annoying chirping/static sound from when the laptop is plugged into it's power supply to charge the battery. Without the DI box between the speakers the noise is unbearable for monitoring. With it gets rid of the 60HZ buzz, but it only MINIMIZES the PSU noise. i use my multimeter and measured a 0 volt potential with the ground lift button on the back of the unit UN-depressed, and when I depress it to lift the ground, I found there is still about a 5kohm resistance between pin 1 and the unbalanced shield ground, SO IT IS NOT A TRUE GROUND LIFT!

So i cracked this thing open and to my surprise, there is NO ISOLATION TRANSFORMER!

I put a simple Hosa adapter that physically lifts pin 1 for ground and hey NO MORE PSU NOISE!

Just be aware, cheap ACTIVE DI boxes don't offer shit for electrical isolation!! You would be better off with a quality PASSIVE DI box

[stuartp]

The S direct Plus can be phantom powered.Therefor the pin1 shield cannot totally opened. The 5k resistance provides a DC current return for the +48V phantom power. Running with the internal battery, this ground can be totally lifted. I do appreciate your post because I a have this unit and never thought of this application you presented. I've used this box to convert single ended aux outputs from a mixer to xlr balance to run active stage monitors connected to the end of a 150 foot snake.

[danfuerthgillis]

For the Radial guy here nothing else to say Radial makes the best DI boxes Period!!. Passive or Active Radial any day. Transformers made properly and also the magic secret is the MuMetal Can which is why Radials are so good. open up a Radial DI and you will see the Mumetal Can capping the transformer.

[stuartp]

Correction: The S Direct schematic (on unit top) indicates a ground lift switch in series with the sleeve of the TS input connector, not pin 1 of the output. (Note the insulating plastic bushing under the TS jack nut). Most hum is supposed to be eliminated by amplifying the voltage difference between tip and sleeve of the input and not by lifting output xlr pin1. However internal battery use permits the opening of xlr pin1 path. Hum is now further reduced by eliminating the 5k ohm ground path.

[simonoconnor]

Help to an old issue that i used to have as a sound engineer. Last minute fix for earth loops off most audio sources. -remove the eath between the main power supply plug and the transformer/ power supply.  I keep 2 cabls like this in my 'box of tricks'- drilled out the earth pin on the clover leaf plug of one and  could remove the earth wire at the plug top of the other.  NOTE: earthing on devices  is safety! make sure your equipment is in good condition before doing this.

[awebster]

Hi, it's the turtle beach x12 and a standard wired controller. (the newerst black model gloss) I use standard RCA cables and I purchased a ground loop isolator as I receive a slight, undoing with the headset. I also contacted turtle beach and they are sending me a new chat cable. Thank you very much for the response I'll check the site out

[yrussq]

Even the video is outdated - the problem with laptop is not a ground loop but impulse power supply connected to the same contour with your sound device. All professional guides tell that they should not be connected to the same outlet/power hub. Best option to connect the audio device to the separate power line like all high wattage devices are connected (laundry stuff, semi-industrial stuff, etc. etc.).

[DavidMcKeeSmith]

You have an ACTIVE DI there. That is why there is no transformer. Passive DI's use transformers but cheap x-formers sound bad and good ones cost $$$. You can get good sound at a low price with an active DI. Active DI can sound very HiFi and more detailed than a passive but they do not block ground loops. Active DI's are good for instruments that DO NOT use an AC power supply like bass or acoustic guitar (without an amp). Keyboards and and laptops do have a grounded power supply so passive DI's are best for them bc of the transformer isolation. Looks like you might be dealing with line level devices too. A passive DI will isolate them but do you really want the mic-level output? You may need a line level isolator. Full disclosure, I work for Radial Engineering and we make the best DI's in the world. We also now own Jensen transformers the best transformers that can take hot signals and not saturate like cheap transformer. The jensens can take 20dB at 40Hz! Thats alotofbass! Get a passive device to block ground loops but you'll pay around 200 if you want good Jensen or Lundale transformers in it. We also make the TWIN ISO, a pro-audio stereo line-level isolator and several other DI for laptop audio.    

[BrassikMusic]

the noise is driving me crazy, ive tried waves crackle remover plugin but it takes away from the depth of my vocals, are you saying that you dont need a di box if you buy one of the hosa adaptors? my problem is that i use a stealthplug interface which has a 1/4 inch jack plugged into the tape out on an old guitar amp, then i have the microphone with a xlr to 1/4 inch jack plugged into the input on the amp. but i can only find xlr hosa adaptors! id be really grateful for any help!

[AljhonRadaza]

Hello. A quick question.. Do D.I Box can retain acoustic guitar sound Including Tapping? And percussion etc.? Thanks for reply..

[farfymcdoogle]

Why does the audio in this video go from stereo to right only like it's out of phase? It's messing with my ears in a very bad way.

[mickoin]

oh no man i just purchased it 1 minut ago

[awebster]

Yo is there anyway to get rid of the buzzing noise in a headset when using a wide controller (Xbox)