Could someone enlighten me as to how this device works? - Page 1
Forum section: electronics / beginners

author: josephpate
author_rank: Contributor
timestamp: October 29, 2015, 02:47:01 am
content: http://smile.amazon.com/gp/product/B000KUD2G4?psc=1&redirect=true&ref_=ox_sc_sfl_title_1&smid=ATVPDKIKX0DERSeems simple enough that I could make my own, of course I'd need to know the basic principle of how it works!Is it just some sort of 60hz filter? or does it have transformers or something? (can you eliminate ground hum with transformers? seems doubtful to me, but what do I know)Google search for a teardown brought up nothing.

author: Delta
author_rank: Super Contributor
timestamp: October 29, 2015, 02:55:57 am
content: It's a ground loop isolator. A pair of audio transformers. Very useful in pro audio situations.The description it a bit bollocksy, but it's a genuine product at a reasonable price.

author: Cliff Matthews
author_rank: Unknown
timestamp: October 29, 2015, 02:59:08 am
content: This is commonly known as a direct box.

author: josephpate
author_rank: Contributor
timestamp: October 29, 2015, 03:01:46 am
content: Quote from: Delta on October 29, 2015, 02:55:57 amI'm guessing there's different types or audio transformers? Or is there pretty much only one type? So I would just wire a TS jack to each side of the transformer and be done?Quote from: Cliff Matthews on October 29, 2015, 02:59:08 amAh lots of good google images on that. Thanks!

author: Delta
author_rank: Super Contributor
timestamp: October 29, 2015, 03:04:17 am
content: Quote from: Cliff Matthews on October 29, 2015, 02:59:08 amHmmmm, don't really think it counts as a DI box as it's completely passive...?

author: obiwanjacobi
author_rank: Super Contributor
timestamp: October 29, 2015, 05:55:48 am
content: Yes, DI boxes can be passive and/or active. Lots of flavors.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 29, 2015, 06:10:15 am
content: Lots of types, yes. There are many characteristics of a transformer; at the most basic, you need at least power (or signal level), impedance, bandwidth, efficiency and size.Audio transformers are typically designed for modest bandwidth (the cheap ones you'll find in a catalog are maybe 100Hz to 10kHz), small power levels (no more than a couple watts), and rated impedances (like 2.5k:8 ohms and such).Pro audio types are designed with an emphasis towards high bandwidth (at least 30Hz to 15kHz, but preferably more like 10Hz to 50kHz) and typical impedances (8, 50, 600, 10k, 50k ohms..). Special materials are usually used, like mu-metal cores.As mentioned, line isolation transformers have an emphasis on isolation, which might mean lower capacitance in the design. Balanced design (e.g., XLR devices) may also be handy, as well as baluns (balanced to unbalanced conversion, with isolation an added bonus).Tim

author: Cliff Matthews
author_rank: Unknown
timestamp: October 29, 2015, 12:00:15 pm
content: @Josephpate - "So I would just wire a TS jack to each side of the transformer and be done?"No, equipment like this uses TRS jacks (tip/ring/sleeve) where the T/R part is isolated from the ground like an XLR connector. You also may notice the use of all black plastic 1/4" jacks (even the nut is hard plastic) on one or both sides, lot of flavors here along with ground lift switches too.

author: obiwanjacobi
author_rank: Super Contributor
timestamp: October 29, 2015, 01:03:51 pm
content: Just google "di box schematic" images to get an idea...

author: josephpate
author_rank: Contributor
timestamp: October 29, 2015, 10:56:15 pm
content: Quote from: obiwanjacobi on October 29, 2015, 01:03:51 pmYep I have been. Most of those seem to convert a 1/4" jack to XLR, though I guess that's easily remedied.Quote from: Cliff Matthews on October 29, 2015, 12:00:15 pmMost of the diagrams I'm seeing look like TS jacks, though I guess you could make it work either way.