DI box for laptop - active or passive?

[Alan25]

I'm looking for a dual channel DI box. I'm running a 3.5mm TRS from the headphone socket of my laptop to 2x 6.3 TS. I'll plug them into the DI box and then run a pair of XLRs to the mixer (XR18 at the side of the stage).

Active or Passive - or does it not really matter for this application? If it was a keyboard (the most likely alternative scenario) does that make any difference?

Studiospares offer both options https://www.studiospares.com/dual-passi ... lsrc=aw.ds

Or Orchid offer a dual di box which appears to be active only http://orchid-electronics.co.uk/Dual_Micro_DI.htm

[resistorman]

Since you're on the cheap end of the spectrum, I'd go for the Orchid active which has a very good rep. Passive boxes are defined by the quality of their transformers which can get pricey for good ones.

[shufflebeat]

ART DTI:

https://www.soundonsound.com/reviews/art-dti

[Hugh Robjohns]

Technically, it won't really matter much. Passive DI boxes are usually slightly cheaper than active ones, but don't present a hugely high input impedance. Devices with electronic outputs like keyboards and laptops don't care about that, so passive DIs work fine. However, guitars and basses do care and so active DI's are generally required for them.

Obviously, active DI's require power, and that's usually best (and most reliable) if provided via phantom power from the mixing console.

The other thing to consider is galvanic isolation. All passive DI boxes and most active boxes incorporate an output transformer which electrically isolates the mixer from the source, and that can be a literal lifesaver if there's a major fault in one or other half of the rig.

So if I'm performing on stage and working with an unknown PA company, or I'm providing the PA and working with an unknown band I always use DI's with isolation transformers, just for peace of mind.

If it's your own mixer at the stage side then the risk is much lower and you can feel reasonably confident that it's all safe and well maintained, and so isolation transformers aren't needed...

... which is just as well if you're considering the excellent Orchid micro DI's because they don't have transformers. But they are superb value and extremely clean and transparent sounding — the latter in no small part to the fact that the cheap transformers used in budget DI boxes inherently colour the sound.

https://www.soundonsound.com/reviews/or ... s-di-boxes

Just for completeness, there are a couple of other options worth considering.

The 3.5mm headphone sockets on laptops are notoriously unreliable and in some cases (mostly Macs) the OS can get arsy and refuse to send an output signal because it doesn't think anything is connected!

So a higher quality alternative is a USB DI box which takes a digital output via USB and converts it to analogue mic level. Radial Engineering do a very nice one called the USB Pro Laptop Direct Box:

https://www.radialeng.com/product/usb-pro

It's not cheap, obviously, but it is built to survive a lifetime, even if it involves strategic nuclear weapon discharges, so the cost will pay off over time! It's plug'n'play — no drivers required — and supports the usual standards up to 24/96. Similar products are available from other suppliers.

A more traditional alternative that I've used for years now is the Radial JPC:

https://www.radialeng.com/product/jpc
https://www.soundonsound.com/reviews/radial-j48-jpc

One of it's claims to fame is that it is specifically designed to overcome the grounding issues that can often plague laptop replay, resulting in hums and buzzes etc. It also has a convenient selection of connectors to make interfacing easy with a wide variety of domestic replay sources. It's also built like the proverbial outhouse. Mine is over 15 years old and has had a lot of use, but still looks like new and works perfectly.

... but much as I rate Radial hardware, I have no hesitation in recommending the Orchid Micro DIs (and dual micros) if it meets your needs and budget.

EDIT: The suggestion of the ART DTI is another worthy option. It has the possible advantage that it maintains the line-level nature of the laptop output, rather than reducing it to mic level. It has the possible disadvantage that there is no easy option to provide a ground for the input source...

[shufflebeat]

Peavey's alternative to the Radial USB box Hugh mentioned - can't comment on comparative engineering but has been on my watchlist for some time:

https://www.amazon.co.uk/Peavey-3001370 ... B004A4PSEU

[pk.roberts]

Unless you have a good reason to take the signal down to mic level, I'd go for one of these;
http://orchid-electronics.co.uk/dual_isolator.htm
I've found them to be of very good quality and Orchid have 'customised' them for me in the past to have XLR outputs for a very reasonable extra cost.

[Hugh Robjohns]

Functionally the same as the ART Cleanbox2 which is the same as the ART DTI except it only has TRS sockets for inputs and outputs.

As you say, handy if you want to maintain a balanced line level output, but I've found situations where the lack of ground passed through to the source causes hum and buzz problems.

I get why devices like these don't pass the ground between output and input — they're called isolators for a reason — but actually they become so much more versatile and useful with a user-selected ground lift switch for those times when you just want transformer balancing, with grounding for a Class II source.

A traditional DI box (or USB interface) usually provides that option.

[BigRedX]

Why not run the audio via USB from the laptop to the XR18?

[Alan25]

Thanks for all the responses.

This may be a one off situation for me (hence the shallow end suggestions) where a singer will be using their own laptop, onstage to play backing tracks.

Usually my laptop is within a couple of metres of the XR18 and I'm happy just plugging directly into the ch17/18 TRS jacks.

The ART DTI is an interesting suggestion and would mean I could still plug into ch17/18 TRS jacks.

The 3.5mm headphone socket still seems to be the most universal output and avoids worrying about the plethora of USB or lightning options that I could end up with.

[resistorman]

A good DI box is handy to have around