Direct Box

[easychair]

In a home studio project, and in order to connect a workstation/arranger keyboard to a multitrack recording software, is it necessary and or a plus to use a DI?

Probably not, if you have any kind of line inputs.

 

[easychair]

I agree. WTF happened to this website?

If you read and understood the post, you wouldn't have agreed.

 

[giraffe]

too many people willing to open their mouths, even when they don't know shit.

if you're not sure about the answer to a question...... don't answer it.

 

[easychair]

too many people willing to open their mouths, even when they don't know shit.

if you're not sure about the answer to a question...... don't answer it.

Thanks for the apology, don't feel too bad, it's not your fault you don't know shit about direct boxes.

 

[giraffe]

And even that one is off the mark, in some ways. (no offense, Farview)

DIs do change signal level, downwards. Passive DIs use step-down transformers. So they don't convert line level to mic level per se, but step down the gain of the input by a certain amount by nature of the transformer. 20db is pretty common, as many passives use 10:1 step-down transformers. Good thing, really, as most mic inputs can't handle a line or instrument signal without some kind of padding.

Active DIs have losses as well, all circuits do. A zero-loss or boosting active DI has some kind of amplifier inside. No getting around it.

so when i plug my bass into a di, i'm loosing according to you, about 20 db of gain?

 

[giraffe]

please god, hurry up, i need to hear the answer to this.

 

[giraffe]

come on! i've got to go soon.

 

[easychair]

so when i plug my bass into a di, i'm loosing according to you, about 20 db of gain?

Sorry it took me a sec, dude.

Into a passive DI, with a 10:1 step-down transformer, like most of the passive DIs on the market? Yes, by definition of what a transformer does.

Whirlwind Director
Level change -20db, pad out

Whirlwind IMP
Level change -20db, pad out

Rapco DB-100 -24db

Radial and Whirlwind Jensen-equipped DIs use the Jensen JT-DBE transformer, voltage gain -22db, 12:1 ratio.

So your signal voltage drops by a factor of about 10, which is 20db. Like I said, that's good, as you plug it into a mic pre, which won't take line or instrument level too well.

 

[giraffe]

no shit.

is that a forced by product of the impedance matching?
or is it done separately and on purpose? (me knows jack about electronics)

what i'm thinking about is when you (and by you i mean me) put an amp in one room and use the 2 di box trick to get there, what are you loosing?
guess it can't be too bad, cause i've never noticed it, but hell........ 20db is a lot to lose on the way to a git amp, any where really.

this is all of course assuming that the second, run backwards, and un powered di box isn't somehow magically giving it back. which sounds stupid, but at this point i'm not going to take anything for granted because i apparently didn't notice i was loosing 20ish db of gain whenever i used a di box.

 

[easychair]

no shit.

is that a forced by product of the impedance matching?
or is it done separately and on purpose? (me knows jack about electronics)

what i'm thinking about is when you (and by you i mean me) put an amp in one room and use the 2 di box trick to get there, what are you loosing?
guess it can't be too bad, cause i've never noticed it, but hell........ 20db is a lot to lose on the way to a git amp, any where really.

this is all of course assuming that the second, run backwards, and un powered di box isn't somehow magically giving it back. which sounds stupid, but at this point i'm not going to take anything for granted because i apparently didn't notice i was loosing 20ish db of gain whenever i used a di box.

The loss is from how a transformer works. It's two coils of wire wrapped together. One is for the input, called the primary. One is for the output, called the secondary. They don't touch, the voltage gets passed from coil to coil by induction. The primary induces a voltage in the secondary. But they are physically separated. That's part of how DIs break ground loops. Using a DI with a ground lift means the two pieces are completely isolated, but signal still passes.

The turns ratio of the primary to the secondary determines the output voltage in relation to the input voltage. A 1:1 will get you the same voltage out as in. A 10:1 transformer gives about 1/10 the voltage out as in.

The turns ratio also determines the impedance that gear hooked to the DI sees.

A DI is an interface, kind of a window. When you plug a keyboard into a DI and then to a mic pre, the keyboard sees the mic pre impedance (say 1500ohms) multiplied by 10, or 15,000ohms, just about perfect for most line-level gear. The mic pre sees the keyboard's output impedance and signal level divided by ten, so it gets a nice low-level signal that has a much lower impedance. Typical line-level gear is about 1000ohms output impedance. Divide by 10, you get 100ohms, which goes perfect with a 1500ohm mic pre.

Sorry, I'm in kind of a rush. I don't know if you know the whole input/output impedance ratio thing, which says for best signal transfer, input impedance should be about 10X output impedance.

That's why passive DIs sometimes don't work well with passive instruments like electric guitar. DIs basically just multiply the impedance they are hooked to, they don't have any on their own. So most DIs have about 15-30,000ohms impedance, basically 10 times whatever mic pre they are hooked to, which isn't enough for passive pickups, which typically need 150,000ohms at least to work well.