DI Box vs. Pre amp

4

47ronin

New member
What exactly is the difference between a DI box and a pre amp or are they essentially the same thing? I understand a DI box might be used for instruments rather than for mics, but in effect many people play their guitars/basses through what are essentially "mic preamps"....any thoughts?

thanks

47ronin
 
A Di Box and a Preamp are 2 totally different things....

A DI Box is mainly for Changeing output impedances and createing a Ballanced/Unballanced output....

You would use a DI Box when Say Plugging your High impedance Guitar signal into a Low impedance Mic or Line input....If you just plugged the guitar directly in it would sound Like crap because your Guitar has a Very high Impedance (1m ohm +) and a Line input expects a Low Impedance of about 10k ohm and a Mic input expects a impedance of between say 200r and 10k....

Also if you are running really long cable lengths from your Guitar the Signal will start to sound worse as the Cable gets longer but if you use a DI Box and Ballance the Signal out into a Ballanced input you can run very long Cables without introduceing Interferance or Noise.....

A Pre amp is Basicly just for takeing a Low level Input signal (eg: Mic) and boosting the signal so that the signal is strong enough to use...A Preamp can also change Output inpedances and create a Ballanced output but a Mic preamp still won"t work well with a Guitar signal and a Guitar Preamp will not work well with a Mic......

I"m sure someone will chime in with some other differances between Preamps and DI"s but this is the basic jist of it.....

Cheers
 
Thanks for the explanation. I still think it is kind of a matter of semantics though, or marketing language. Check out this page: http://avalondesign.com/preamps.html It seems that the DI boxes are referred to as preamps and vice versa, and the ones identified as preamps are talked about as great for guitars...
 
A preamp, as the term implies, is designed to add gain (but will often include EQ, etc.). whereas a DI box is primarily an impedance matching device, as the earlier poster explained. So very different animals, actually. No, you would never plug a microphone into a DI box (well, you can try, but you'd look pretty stupid doing it).

It's quite common for a mic preamp to also double as an active DI box by offering a line input (so you record bass direct to tape, for example), which may be what's confusing you.
 
I think that is what I was confused about. You can use a mic pre to record guitars direct, though it is not really a DI
 
47ronin said:
I think that is what I was confused about. You can use a mic pre to record guitars direct, though it is not really a DI
Click to expand...

A preamp should have a intrument in jack to serve as a DI as well usually. Impedance thing again, the mic jack will not normally want to acept a guitar level signal.

Daav
 
Yeah, what these guys are saying. While a pre-amp might have an "instrument" In, the mic-pre itself is different from a DI. The DI is what you need to get an instrument down to mic level/impedance so you can plug it into a mic pre.

Guitar -> DI Instrument IN -> DI Mic Out -> Mic Pre IN
(DIs also usually have an Instrument Thru, so you can send the guitar signal to an amp as well.)

I hope I'm not being redundant here but essentially
Mic Pre: Mic level/impedance Input, Line Level/impedance Output
DI box: Instrument level/impedance Input/Thru, Mic level/impedance Output
 
Thanks for your help. Would this qualify as something that could be used to record guitar direct? (I realize it has compressor,etc...)
 
47ronin said:
Thanks for your help. Would this qualify as something that could be used to record guitar direct? (I realize it has compressor,etc...)
Click to expand...

If you're referring to the Avalon boxes from your earlier link, then yeah. They all have Hi-Z instrument inputs that you can plug a guitar directly into.

Similarly, the majority of USB/FW interfaces have XLR/1/4" combo jacks, where the XLR is a Lo-Z Mic In, and the 1/4" is a Hi-Z Instrument In (for plugging guitars/basses directly in).

If all you have are XLR Mic Ins, and no Hi-Z Instrument In, that's when you need a DI box.
 
47ronin said:
http://www.musiciansfriend.com/product/ART-Tube-PAC?sku=180069

i forgot to post the link above...could this be used as a di as well as for mic preamps?
Click to expand...

Looks like yes. I just looked at the User Manual from the link you posted. There's a nice picture too, but here's an excerpt:

"The Tube PAC is ideal for use as a DI box. Plug the instrument into
either input and use the XLR, 1/4, or both outputs to connect to
your recorder, board, or PA system. Experiment with different input
level settings for different textures."
 
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47ronin said:
http://www.musiciansfriend.com/product/ART-Tube-PAC?sku=180069

i forgot to post the link above...could this be used as a di as well as for mic preamps?
Click to expand...

That page has a link to the PDF manual, page 12 shows it to be used as a DI, so yes.

Check out http://www.musiciansfriend.com/product/MAudio-DMP3-2Channel-Mic-PreDirect-Box?sku=241101
As well, doesn't have built in compression, but has 2 channels of well respected preamp/DI gain for the money. THe ART piece you are linking is a lot of flash with compression and "tubeness" but it is basically combining two pieces of fairly crappy gear into one.

Daav
 
thanks. I think you are right about avoiding too many "combination" devices in the low price range, I'd probably end up wanting a different compressor/eq anyway. I mostly use softsynths and samplers so I've never really recorded guitars directly....that M audio looks nice.
 
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