What is a DI?

If you have used a PA as a tech or stood on a stage as a muso, you probably know something about a ‘DI’. A Direct Input box is used to convert different input signals into a balanced, low impedance signal which goes to the mixing desk. In a later post I will better explain balanced/unbalanced and low/high impedances. Most desks and multicores use XLR connections for their balanced channel inputs.

A DI can be active or passive though most are active. Passive DI’s don’t require power and are generally lower quality than a good active DI. Active DI’s need power. Depending on the particular device, they can be battery powered or phantom powered (power provided from the mixing desk through the XLR audio cable), or some by external power supply plugged into mains power.

1/4'' TS Jack
1/4” TS Jack

Basically an instrument or device using a 1/4″ jack (like on a guitar lead) needs a DI. Examples of this are line out from a bass amp, channels left and right out from a keyboard, and channels out from electronic drums.

Other uses can be for ‘line level’ gear such as cd players, computers and mobile devices such as iPods.

There are times when you definitely don’t use a DI. Too many times I have set up my guitar amp on stage with the friendly sound guy asking me to plug a DI box into my amp. Sometimes I even get a free explanation of how using a DI out of the amp head instead of a speaker cabinet will cut down stage volume and be better for everyone. I’m usually playing through a Laney VH100R all-valve, no-digital bells and whistles kinda amp which sounds horrid through a DI. Any guitar amp without digital cabinet modelling of some kind needs a speaker, which must be mic’ed up. This isn’t your guitarist being difficult, without a speaker a guitar tone doesn’t sound right.

Which brings me to the point that some guitar rigs can in fact go DI straight into the PA if they are designd specifically for it. Many amps will have a line out but only certain amps and effects will offer the proper sound without a speaker cabinet and are gaining popularity as the technology improves such as Line 6 POD units & Spyder amps, Fender Cyber amps and many others.

It’s common for bass guitar amps have a balanced XLR output built in, so a DI box isn’t necessary. Some bass players prefer to mic their cabinets rather than plug into the PA, this is another instance where a DI isn’t required (but you could use both methods and blend them using 2 channels, a cool way to get the most out of your bass tone!). In this case you would probably need a Shure 52 type of microphone which are generally used on kick drums and are better able to capture the low bass frequencies than vocal and instrument mics like the Shure 58 & 57’s.

If you are in doubt about how to get an instrument through your PA, it’s always worth your while to find out properly. Is there internet nearby? Can you ‘phone a friend’? Or does the musician know thier gear and have a certain preference? It’s always good to know the conventional way first for common instrument types. Then if you are in doubt about hooking in a specific instrument you can ‘work with’ the muso by asking intelligent questions about their preferences instead of asking point blank “how do ya plug in a keyboard mate?” and destroying any credibility and confidence you had gained with the band.

The bottom line is, hook in an instrument incorrectly and your tones and mix will be rubbish. Know how to do it right and be a PRO!


4 thoughts on “What is a DI?

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  1. Great blog Aaz…..totally right on about DI-ing amps…..can’t believe people don’t understand how much speakers play a part in the sound…

    But I also get frustrated with this low stage level rubbish……what’s the deal? I mean they are more concerned about that then the tone coming out front……..now I understand not blasting the front row with face melting sounds but I’ve had it with this soul killing ‘can the guitarist use a pod and the drummer get some v drums’ mentality going in churches these days….

    Your thoughts?

    1. Yeah I hear ya, I’ve played many church services with my amp turned off due to rediculous volume constraints where I literally cant hear myself and it really is ‘soul destroying’. Though I still got compliments for some of those silent performances!

      9 times out of 10 the sound tech making this request is not a guitarist or drummer and probably does not have much experience mixing bands outside of church. Possibly someone serving to fill a need and these people need to be respected. Church crowds are a unique blend of people of varying taste, ages, and tolerances. Some church auditoriums, PA, or stage gear just sound bad and do need as much volume pulled out as possible.

      Not all real guitar tones are good either mind you, I’ve mixed my fair share of noisy, low quality tones and these always sound messy, noisy and too loud. I have found myself walking up to the guitarist asking him or her to turn down many times. A great player with great tone is a joy to mix and can afford much more volume than a sloppy player. You are definitely in this category Chris, Ive mixed you many times now in a church setting and its a joy.

      If the stage is putting out a lot of noise, find out what exactly is making that noise. Volume and noise are completely separate issues. For instance, putting a perspex barrier around the drums at C3 Monash was something I was reluctant to do, but once we did it the first few rows were relieved from the loud, harsh trebles of the cymbals and the mix became much tamer, even though the cymbals are excellent quality. Now the cymbals come through the PA with plenty of compression and reverb and sound great. This improved the mix substantially and resolved so many complaints from spectators.

      So the moral to the story: Respect your sound tech wherever they may be in their audio walk, send them a link to this blog, and make sure your guitar or drums sound hot!!

      1. Good points Aaz……..

        I know very well about bad amp tones from my last church…..one of my young players favored the ‘metal zone direct to board all treble with no bass or mids’ sound which was NOT your best life……also then having his amp at his feet meaning he could never hear himself….but the guy 5 metres in front of him (ie ME) would be totured by not only the tone but the out of tune guitar because he had no idea about tuning a Floyd Rose and would only change strings every 5 months…..even though he works part time at a music shop……….

        I’m sure you’re having flashbacks yourself to some memorable moments from your journey…….

        I think we have a great balance at C3, and breath easy knowing you are in charge, but you need to train some more young guys……..

        We need to continue to all work together to sound the best we can, cause right now the world has it over us….and church should be the best…..

        This is a big topic for me and one of the main reasons for me standing down in my last role of leadrship…..it sounds petty but it reflected a difference in direction and culture of the church I was in, and I felt that I needed to be in a different place…..especially one with younger people……..music and worship is powerful stuff……..

  2. Too right Chris, your average church needs to be on par at least with whats going on outside. And we do have some young talent at C3 Monash… the future is looking bright my friend!

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