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I'm a juggler, selling a circus-musical to theatres in Europe and I have been gradually buying all the equipment that I need to perform with, without borrowing it from each theatre I go to.

One issue that I often face is that technicians often ask me to bring a DI-Box, in order to convert the piano's output from jack-jack to jack-DI-XLR. I also believe it helps when covering large distances of cabling to the sound desk,

The thing is, I already own a Focusrite 2i2 audio interface, and my question is: Can I use that instead? If I did, I would be able to record the audio from the show in a high quality way, every time. But will I still receive the issue with distance from the technicians' console?

Sorry about how I have no idea what I'm talking about 🙈
Please and thank you in advance!

3 Answers 3

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I suggest you get a DI box with a transformer. That kind of DI box handled three problems in one:

  • Getting the correct level of signal: most signals from stage to mixer expect and preferr microphone level and the transformer handles that. The computer interface does not handle this as it outputs a much stronger signal.
  • Making a balanced signal: again, the mixer preferrs a balanced signal. I am not sure about this, but my impression is that the Focusrite has a "pseudo balanced" output, not a true balanced. There is a long technical discussion to this, but let it suffice to say that I would note expect the signal from the Focusrite to work perfectly on a very long cable.
  • It allows for ground lift: as your stage equipment ( piano ? ) is connected to a power source on stage and the mixer is connected to another power source, it happens that the ground connection may introduce a lot of mains hum. Lifting the ground of the DI often is the solution to this. This is in my mind the single most important reason to get a DI. I cannot really count the number of times it has saved the sound for me.

This kind of DI-box often is called "passive" (as opposed to active), the box should not have a battery. You can find one of these for about $25 ( or €25 ).

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I also believe it helps when covering large distances of cabling to the sound desk?

yes, that's correct. The DI converts your piano output to a balanced connection, which reduces the chances of the cable picking up interference.

You could use the Focusrite in this role: the line outputs are balanced (you'll need to buy or build two 1/4" Jack to XLR-male cables to connect to the mixing console), and in 'direct monitoring' mode these outputs have no latency.

Can I use that instead? If I did, I would be able to record the audio from the show in a high quality way, everytime.

If you connect the Focusrite's inputs to the piano, you'd be able to record the piano only. To get a full recording of show audio, you'll want to connect the Focusrite to an output of the mixer instead.

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  • Just a note here. Balanced connections don't pick less interference but they provide a mean to get rid of it at the receiving end. Still, the message is passed, I'm just throwing a quick clarification here :). Additionally, you should make sure you'll use a TRS 1/4" (Jack) and not a TS (TRS: two black lines, TS: one black line) for the Jack-to-XLR conversion.
    – ZaellixA
    Jul 4, 2020 at 11:30
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The principal problems with using a soundcard as DI:

  • a) Reliability: if it hangs up or resets itself, the output is dead.
  • b) Quality and latency: even when using “direct”, “no-latency” monitoring, the signal paths run through analog low-pass filters, A/D conversion (either at terminal sampling rate or an internal one), DSP processing, D/A conversion and more analog low-pass filters. And with most high-quality D/A-A/D converters, you have internal oversampling which adds additional digital filtering stages introducing delay. For very high-quality “direct” “no-latency” monitoring, you still get about 6ms of latency. That corresponds to 6 ft (1.83 m) of distance in sound traveling, which is sort of irrelevant for most purposes except for monitoring where it affects how well the original sound blends with the amplified sound for the player.

But “very high quality” is not a given for consumer soundcards. Also, part of the premise for a DI is galvanic separation from the signal ground of the PA (at least when engaging “ground lift”). That's not of much relevance for microphones on a stand or battery-powered instruments. For a digital piano on mains, that ground separation or lack thereof may or may not make for hum or other disturbances (like USB noise).

So there is some argument to be made for simple analog gear in this context.

Compromise monitoring solutions are good analog(!) mixing consoles with digital output (have one with Firewire card) but you might still need a DI if you find that their balanced outputs are not as quiet when fed into the PA as you'd like. Essentially, a DI should be in your toolbox as a musician, including enough cables to wire it up. Often you can make do without it, but if you find yourself starting to fiddle around, you should prevent getting stuck for lack of one.

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