Active or Passive DI for Reamping?

D

darkecho

New member
Does it matter which one you use? I have read a bunch of old threads but just got more confused.

A.) What exactly does the DI do in the reamping process, why is it necessary? (or is it even necessary?)
B.) what does the Reamp box do in the reampin process?


i am going to make a really basic conceptual stab at this, does the DI box increase the level of the instrument input (usually guitar) to mic level for your computer to receive, and then your computer sends out a mic level into the reamp box, which oppositely lessens the level from mic to line/instrument level for the Amplifier of choice to receive?

from what I understand, Passive DI's do not increase line level at all, so how does a product like the Redeye DI/Reamp work if its a passive DI?
 
darkecho said:
i am going to make a really basic conceptual stab at this, does the DI box increase the level of the instrument input (usually guitar) to mic level for your computer to receive, and then your computer sends out a mic level into the reamp box, which oppositely lessens the level from mic to line/instrument level for the Amplifier of choice to receive?
Click to expand...

Thats pretty much it.
 
darkecho said:
i am going to make a really basic conceptual stab at this, does the DI box increase the level of the instrument input (usually guitar) to mic level for your computer to receive, and then your computer sends out a mic level into the reamp box, which oppositely lessens the level from mic to line/instrument level for the Amplifier of choice to receive?
Click to expand...

it's an impedance thing...
The DI box converts a high impedance signal like that from a guitar, and lowers it to an acceptable signal appropriate for low impedance inputs (like that of a mixer). Not doing so would create tonal shifts/distortion in your signal. It also balances the signal so that it can travel long distances.
The link cusebassman gave you will explain more in detail. (and yes, that is a reputable site...great magazine).
 
ok but when reamping into your computer, dont you need to increase the level signal for the computer?

I recall recording guitar into a computer through a passive DI and the signal was very weak...

dont you need to increase the signal strenght from line to mic level for the computer?
 
darkecho said:
ok but when reamping into your computer, dont you need to increase the level signal for the computer?

I recall recording guitar into a computer through a passive DI and the signal was very weak...

dont you need to increase the signal strenght from line to mic level for the computer?
Click to expand...


There is some confusion here . . .

A passive DI is a transformer. It will convert instrument level, high impedance signals to mic level, low impedance output. The level will drop. -20dB is probably about in the neighborhood of a passive DI, maybe less.

As far as levels and impedances:

Mic: low level, -55 to -30dBV; low impedance, 150-250 ohm output, 1-2K ohm input
Instrument: medium level, -30 to -10dBV; high impedance, 10-25K output, 500K-1M ohm input
Line: high level, -10dBV to +2dBV (+4dBu); medium impedance, 100 ohm output, 10K ohm input


If you plug a guitar into a PC line in through a passive DI, the impedance match will be OK, but the signal will be mic level, not line level. You need to plug into the mic input or a mic preamp.

I don't do reamping so I will let somebody else comment on that.
 
mshilarious said:
If you plug a guitar into a PC line in through a passive DI, the impedance match will be OK, but the signal will be mic level, not line level. You need to plug into the mic input or a mic preamp.

I don't do reamping so I will let somebody else comment on that.
Click to expand...

This is correct. Take the RedEye for example. All the DI does is balance and match impedance. You need to then take that signal an send it through a pre to get a healthy level to track.
 
ok so mic level is has the weakest signal of all, instrument level is next in line, and Line level is the strongest?

so when i plug in an instrument level signal to a DI, it actually is making it weaker, and then i am taking that weaker mic level signal and boosting it to line leve via a pre...

that doesnt seem to be very efficient???
 
well...the drop is signal level is "made up for" by also lowering the impedance into the preamp/mixer - the low resistance signal is then boosted with the preamp gain, which would be much more of a PITA if the preamp was taking on a high resistance signal

...or something like that
 
im not undersanding why a DI wouldnt just convert the signal to line level...

is it because DI's would be more expensive if they had the proper equiptment to boost the signal... IE, built in preamps...


is that what active DI's do?boost the signal to line level?
 
im not undersanding why a DI wouldnt just convert the signal to line level...
Click to expand...

In fact many preamps have "instrument in" inputs so they can be used for direct guitar recording.

It is kind of a matter of where to draw the line with the functionality of each device. Since most studios and live venues already have mic preamps either standalone or in a console, a direct box with a preamp is not necessary and would definitely be more expensive. It probably wouldn't be called a direct box anymore either.
 
darkecho said:
im not undersanding why a DI wouldnt just convert the signal to line level...
Click to expand...
One reason - with active DIs - is that active DIs require a power supply. While many active DIs can run off of a simple 9V battery, there are many models that also use the phamtom power supply available from mixer mic lines. This cannot be done via line ins, which do not have phantom power capability.

Add to that the idea - as has been said - that DIs are really meant to be impedance matchers, not preamlifiers. And if there were preamps in them, they'd require a decent power source, which can be a pain to supply on stage (which is where DIs are used perhaps the most.) So, since DIs are not really purposed to be preamps, since it can be inconvenient to supply power necessary for a preamp to a DI, and since many active DIs can use phantom power from mic lines to power their circuitry, running them to a mic line makes more sense than it may seem at first blush.
darkecho said:
is that what active DI's do?boost the signal to line level?
Click to expand...
No, the main difference between a passive and an active DI is in the circuit design. Active DIs use a transformerless design that needs some external power to run. Passive DIs just use a transformer to carry the work load, and that transformer does not require any external power.

G.
 
im guessing that the Active DI's do a better job at converting the signal to a different impedance without coloring it?
 
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