DI Box to Mic Level?

D

darkecho

New member
Will a Passive DI Box take an instrument level and convert it to Mic level to go into my DAV Mic Preamp? I am trying to figure out if I should get a Passive or active DI for recording guitar into my computer to go into an Amp Simulator software.

what should I get if I already have a good mic pre and just want to record guitar DI?

Hell, do I even need a preamp or can I go straight from the Passive DI into my audio interface?
 
active pickups (emgs, bartolinis, etc) need a passive DI. passive pickups need an active DI.

you go from guitar->DI->micpre->recorder. The DI converts from pickup/instrument level to mic level. you need the mic pre to get it up to line level that the recorder is expecting to see. many mic preamps have a DI input on them, so depending on the mic preamp and the quality of its DI, you may not need a separate DI.


cheers,
wade
 
so regardless, the DI box needs to feed into a Mic Pre that goes into a recorder?

Active Guitar->Passive DI->Mic Pre->Recorder
Passive Guitar->Active Di->Mic Pre->Recorder
?
 
darkecho said:
so regardless, the DI box needs to feed into a Mic Pre that goes into a recorder?

Active Guitar->Passive DI->Mic Pre->Recorder
Passive Guitar->Active Di->Mic Pre->Recorder
?
Click to expand...
You got it! However, you can use an active DI on an active guitar too.
 
with no difference in output? If that is the case, why would I want to own a passive? If it works on both pickup types, I should just purchase an active one shouldn't I? Also, The DI is responsible for changing the impedance and what not so that the levels match, but it doesnt amplify the signal at all? or does it amplify the signal to mic level so that the mic pre can then step it up again in amplification?
 
Farview said:
You got it! However, you can use an active DI on an active guitar too.
Click to expand...
absolutely you can. although i've heard a couple occasions (in the live sound arena, mind you) where an active DI on an acoustic guitar with active pickups has caused crackling or distortion. don't know how common an occurrence that is across the board, but it was enough to enforce in me the "active/passive" and "passive/active" relationships and that's just a rule i always follow. ;)


cheers,
wade
 
darkecho said:
with no difference in output? If that is the case, why would I want to own a passive? If it works on both pickup types, I should just purchase an active one shouldn't I?
Click to expand...
as long as the majority of guitars that you record have passive pickups (typical for most humbuckers, single coils, P basses and Jazz basses), you should get along just fine with only having an active DI.

but as i said, there are occasions i've encountered where an active guitar used in conjunction with an active DI has caused static/crackling/distortion, and that's where (or why) you would need a passive DI.

but as long as you're recording passive guitars, i'd get an active DI and wouldn't worry about it.

darkecho said:
Also, The DI is responsible for changing the impedance and what not so that the levels match, but it doesnt amplify the signal at all? or does it amplify the signal to mic level so that the mic pre can then step it up again in amplification?
Click to expand...
all the typical DI does is change the impedence of the signal. it does not amplify the signal. that's what the mic pre is for.


cheers,
wade
 
darkecho said:
with no difference in output? If that is the case, why would I want to own a passive? If it works on both pickup types, I should just purchase an active one shouldn't I? Also, The DI is responsible for changing the impedance and what not so that the levels match, but it doesnt amplify the signal at all? or does it amplify the signal to mic level so that the mic pre can then step it up again in amplification?
Click to expand...
A DI box does change the level as well as the impedance. A guitar and line level signal are hotter than a mic level signal (I'm sure there are exceptions, but that's the norm) So a DI box brings the level down by a fixed amount.
 
ok so the DI being active doesnt mean that it amplifies. what is the difference between an active and passive DI then? D
 
darkecho said:
ok so the DI being active doesnt mean that it amplifies. what is the difference between an active and passive DI then? D
Click to expand...

An active DI does amplify! But there are two kinds of amplification--voltage amplification, which is also called gain, and current amplification, which is sometimes called buffering. The loss in level with an active DI is usually just a pad circuit, which is by design; there is no inherent drop like with a passive DI.

A passive DI uses a transformer, which trades voltage for current, such that total power remains the same, less a little bit of loss. The main advantages of passive DIs are they don't need power, and they are quieter than active circuits. On the minus side, low distortion, wide bandwidth transformers are expensive, and the input impedance of a passive DI transfomer often is not very high, so there can be loss of signal quality compared with an active DI.
 
Ok. This is all very confusing.

So any D.I.'s job is to LOWER the level of the guitar/Line to Mic level, which is significantly quieter, then the Active DIs amplify the signal but not in volume, just in a way that preserves the signal quality? It is then the Mic preamps job to actually amplify the volume to be sent to the recorder.

does the mic preamp bring it back up to Line level?

coming out of the guitar, the signal is at line level, unbalanced, the DI changes it to mic level balanced, and the preamp amplifies it to line level balanced?
 
darkecho said:
Ok. This is all very confusing.

So any D.I.'s job is to LOWER the level of the guitar/Line to Mic level, which is significantly quieter, then the Active DIs amplify the signal but not in volume, just in a way that preserves the signal quality? It is then the Mic preamps job to actually amplify the volume to be sent to the recorder
Click to expand...

Yes.

does the mic preamp bring it back up to Line level?
Click to expand...

Yes.

coming out of the guitar, the signal is at line level, unbalanced, the DI changes it to mic level balanced, and the preamp amplifies it to line level balanced?
Click to expand...

Not quite, coming out of the guitar, the signal is instrument level, which is somewhere between mic level and line level. But more importantly, it is high output impedance, so it cannot drive a line load.

It is a more straightforward approach to plug straight into a preamp's instrument input, if it has one. That avoids the need to reduce the signal level only to increase it again. But not all preamps have instrument inputs, and it's not always handy to use them if they do--for example, on a stage, you can't run a high-impedance unbalanced signal a long distance to a board without having transmission problems (noise, signal loss), so you need to use a DI close to the instrument, and send a low-impedance balanced signal to the board.
 
ok, so

coming out of the guitar is an unbalanced, instrument level, high impedance signal.
the DI takes this and converts it into a balanced, mic level, low impedance signal.
then the mic preamp boosts it to a balanced, line level, low impedance signal.

I understand the live situation would be best for a DI, but I have an E-mu 0404 and a M-audio Delta 44. Do either of those have instrument inputs?

is there a quality difference in going through an audio interfaces instrument input versus a DI box into a quality mic preamp and then into the computer?
 
darkecho said:
ok, so

coming out of the guitar is an unbalanced, instrument level, high impedance signal.
the DI takes this and converts it into a balanced, mic level, low impedance signal.
then the mic preamp boosts it to a balanced, line level, low impedance signal.
Click to expand...

Yes.

I understand the live situation would be best for a DI, but I have an E-mu 0404 and a M-audio Delta 44. Do either of those have instrument inputs?
Click to expand...

I don't know, but it should say in the manual. I am pretty sure the Delta doesn't.

is there a quality difference in going through an audio interfaces instrument input versus a DI box into a quality mic preamp and then into the computer?
Click to expand...

Too many variables, but possibly, yes.
 
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