Awesome. Thanks Bob. I don't do much with or know much about Mics, so this also is very helpful.Bob Lee (QSC) said:
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Need help understanding "D.I out", XLR out, etc.
- Thread starter Skel
- Start date
I am about to acquire a Dr J Sparrow bass driver D.I. box, for use only in emergencies should I have any (more) amp/speaker cab failures during live shows. My backup emergency plan would be to use the D.I. box to connect my bass directly into the P.A. and send enough of the bass signal back though the monitors to hear myself for the rest of the gig. The Dr J Sparrow box has two outputs: a 3-pin XLR and a quarter inch. My question is, which of the two outputs would be better to connect the box to the P.A.?
Usually the XLR, because see the last paragraph of post #6.
Thanks, but my intention is to use the box only in the event of amp/speaker cab failure (and I’ve had more than my fair share of this in recent months). Could the 1/4” output from the box be used to connect to the P.A., via instrument cable?
devnulljp
Supporting Member
Not really pre or post gain, but pre or post EQ.
Most FoH people will want pre EQ, so they can EQ you for the room.
Yes, but I'd use it only if there isn't any mic inputs on your board, and that is rare. The reason why is because lines to the board are usually long, and too long of a 1/4" instrument cable results in poor sound.
Thanks, that’s useful to know. But does that not mean using the 1/4” output from the box to an amp, via instrument cable, will result in poor sound at the amp?
You can usually get away with a much shorter cable to your amp than you would need going to the board. Some board have upwards of 100 ft or more cable lengths due to placement and use of snakes.
Thanks. Most of our gigs are in small clubs and pubs, so the run to the P.A. board isn’t any more than a few feet. The XLR cables we use to patch our microphones into the P.A. reflect this and are maybe around 20 feet in length. For this situation, would it still be better to use the XLR output from my D.I. box to connect to the P.A. board, rather than the 1/4” output? The Dr J Sparrow bass driver/D.I. box has a ground lift switch too.
Yes. The DI’s 1/4” output will be at your instrument's level and is designed to carry your instrument signal through the DI to your amp when the DI is located in between them. If you’re only using a DI to go to the PA because your amp has failed, in most cases you won’t have a need for its 1/4” output.
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Ah, so the D.I. box’s 1/4” output is designed to deliver the level of signal an amp normally takes. That’s good to know. Is the signal level from the box’s XLR output different to that from the 1/4” output?
Yes, it’s at mic level, so it makes the bass’ signal look like a microphone to the board and it can be set within a “normal” input range using the board channel’s gain control.
Thank you, I feel I understand this better now, ahead of receiving my bass driver/D.I. box. So I guess I should also buy a spare XLR cable and carry that in my gig bag along with my box for backup in the event of amp/speaker failure. Just to clarify, when you said the box’s 1/4” output will be at instrument level, is this the same as “line level” that I read about? My understanding is that mic level, such as that delivered from a D.I. box’s XLR output, is lower voltage than instrument (line?) level. Is that correct?
There's a lot of overlap as has been covered in this thread but usually 'line' is the strongest/loudest/hottest signal, then 'instrument', then 'mic' is the lowest.
Thanks. So if a D.I. box’s XLR output produces a mic level (lowest voltage) signal, I’m unsure what the 1/4” output from a D.I. box produces? I assumed it would be instrument level, to be compatible with an amp’s input, but I’ve also heard on here that the 1/4” will output a line level signal. I thought maybe line and instrument levels were one and the same and that speaker level was the highest voltage audio signal? I’m a bit confused.
As with most things in audio, it depends. Connectors are just physical interfaces, they're nothing more than a way or arranging wires. They often correlate with specific uses and they often don't. In the 80s it was common to use XLR for speaker level signals, like ones between an amp and a speaker cabinet. For that matter there's nothing to stop someone from using a speakon connector as DI output.
A 'proper' DI box like say a Countryman 85 will have a 1/4" parallel output that's an exact copy of the input signal. So if you input an instrument signal, that's what you'll get out. Same for line, mic, speaker, whatever. A preamp pedal like your Sparrow will have a parallel output and ALSO a 1/4" output that tends to be after the preamp circuitry and is either instrument or line. Sometimes, as in the Sparrow, it's instrument level. Sometimes (some sansamp products) you can choose either, and sometimes (like a Behringer MIC100) it's line.
I have seen amps and cabs fail on stage, but more frequently I've seen cables crap out. If you're bringing a PA, I'd look at this a little differently. I'd recommend bringing a few spare XLR cables to have on hand for general use... and then you can use one with your DI if it's ever needed (which will probably be just slightly more frequently than never).
- Feb 12, 2006
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- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
The XLR output on a DI is much lower impedance than the instrument's impedance, one of the two primary functions of a DI. The other function is to balance and isolate the signal to allow the signal ground to be lifted to eliminate ground loops.
The 1/4" output on a DI is usually a parallel pass through that doesn't have the above properties.
DIs with added features (such as overdrive, eq able cabinet simulation) will often have active buffered 1/4" outputs in addition to the XLR output.
Using the 1/4" output to the PA is usually a poor way to do this, especially with a passive bass. The input impedance of most 1/4" inputs used in the PA world are much too low.
The 1/4" output on a DI is usually a parallel pass through that doesn't have the above properties.
DIs with added features (such as overdrive, eq able cabinet simulation) will often have active buffered 1/4" outputs in addition to the XLR output.
Using the 1/4" output to the PA is usually a poor way to do this, especially with a passive bass. The input impedance of most 1/4" inputs used in the PA world are much too low.
Other features can be added this "mix" as well. My SansAmp BDDI is a DI box plus preamp. The 1/4" has a boost button, just in case you need a hotter signal to an amp input. Also, the XLR supports phantom power, obviously to supply power from the main console. Lot's of options available from two different connectors.
