DI box Input Impedance

[Downtuned]

Could someone explain to me how the input impedance of a DI box affects your DI signal? I know higher the number the better the DI signal gets but I'd like to know why instead of blindly just knowing facts.

ATM I have a passive DI box at 47 kohms but I've ordered a new active one which is 1 Megaohm.

I feel I have always had problems with dull sounding DI's and takes never felt like they were the best quality, even with new stings and EMG's with a fresh battery so I'm looking for solutions to this and I figured I'd start with the DI box.

Thanks.

 

[John_C]

If you have your volume control on the guitar at full (or no volume control at all) then what you need to do is consider the output impedance of the pickup compared to the input inpedance of the DI box

a rule of thumb is that your fine if the input impedance is 10x or more the output impedance.

Something to be aware of: engaging a pad on a DI box can VERY dramatically change in input impedance, for example the countryman type 10 has an input impedance of 10Mohms without the pad, but only 10Kohms with a the pad engaged.

The output impedance of an EMG 81 is 10Kohms, which means you will start to see problems with your tone if you use the pad.

 

[Downtuned]

Thanks for the reply. Your description helps a lot and i probably would be ok with my old passive but do you think my new active DI box will make any difference?

 

[Mutant]

Too low input impedance acts kinda like a low pass filter.

High frequencies will be lost and the tone will get sucked dry.

 

[Downtuned]

Yeah that's sort of how I feel my DI's are. Very dull and quite mushy sounding when put through ampsims etc regardless of how I EQ. No crispness at all or even-ness in the distortion.

Thanks for that, I'm sure my new DI box will make a difference!

 

[OneDaySky]

So 10Mohms (without the pad) on the Countryman with EMG81's (active) is right?

 

[LeSedna]

So 10Mohms (without the pad) on the Countryman with EMG81's (active) is right?

EMG's output impedance = 10kohm
The Countryman type 85 or 10 input impedance = 10Mohm = 10000kohm

10000/(10000 + 10) = 99.9%

All maths considered it's a perfect match, in theory leading to minimal loss of volume, minimal difference of impedance leading in less unwanted tone alteration, filtering or any secondary signal going back to the guitar etc. It seems it's not all about maths, but in your case it's what you need. In fact I actually just ordered a Countryman myself even if I my instrument IN are 1mOhm, just to check if a dedicated DI sounds better which I believe can be true.

 

[Mutant]

So 10Mohms (without the pad) on the Countryman with EMG81's (active) is right?

Yep.

 

[Leon--]

the active DI box needs electricity,that means that will colorise the signal more compared to a passive DI box.
it also really depends in what kind of pickups you have.
generally i prefer an expensive passive DI box compared to an active one because it doesnt colorise the signal for reamping with active pickups.
of course this is also a matter of taste

 

[John_C]

the active DI box needs electricity,that means that will colorise the signal more compared to a passive DI box.

This is rather misleading. Active and passive both have advantages and drawbacks, colouration is entirely dependant on the individual design and op-amp (in active designs)

 

[OneDaySky]

So what would the result be if you weren't using active pups? Like standrard ibanez humbuckers? Would the DI become pointless?

 

[LeSedna]

So what would the result be if you weren't using active pups? Like standrard ibanez humbuckers? Would the DI become pointless?

To my knowledge, the fact pickups are active or not is only a matter of the difference of input impedance. For example, EMG are 10kohms. You don't need to think about it more than that.

 

[Mutant]

Passive pickups have about 20kohm to 35kohm output impedance.

The lower output impedance and the higher input impedance the better.

 

[Mutant]

The formula:

a/(b+a)*100=c

a = input impedance
b = output impedance
c= % of signal that passed through

So for passive pickups with output impedance of 30Kohm and a DI box with input impedance of 220Kohm it is:
220/(30+220)*100=220/250*100=0.88*100=88
88% of the signal.

And for active pickups with output impedance of 10Kohm and a DI box with input impedance of 10000Kohm it is:
10000/(10+10000)*100=10000/10010*100=0.999000999000999000999000999001*100=99.9000999000999000999000999001
Pretty good huh ? 99.9% !

 

[damas]

oh man this threads confuse me everytime even more. i have a somewhat similar question and it seems to somewhat fit this thread

atm im going right into the Hi-Z input of the emu 0404usb which is 1Mohm. guitar is schecter c7 with 707 emgs. considered to buy a j48 but i am not sure if there will be an improvement. the output impedance of the guitar and the input impedance of the box seem to match. since the guitar seems to interact with the transformer of the di, people claim that the overall load or sound will change. is his true? for passives or active PUs? but what about the impedance match of the di and the mic in on the interface? does it really matter if i use the hi-z input or go thru a good di box into another similar "shitty" input of my interface?

my di tracks still sound somewhat dull, even with fresh strings. i actually did a test a while ago at another bedroomwarriors studio and the j48 seemed to be a lot more clearer and brighter BUT im not sure if the low cut on it was engaged (most likely it was...i really dont know) so the test was/is not really reliable.

so from the formula a j48 would suck ass since like 5% of the signal are lost compred to emu0404 input and another 30 percent of the left signal would be lost because of the impedance mismatch of the j48 output to emu 0404 mic input. so the clarity i heard was the loss of bass information from the signal???? wtf? or am i overthinking this shit? throwing away like 200€ would be retarded. so i would be really glad if someone could answer this questions or simply: do i need a j48 while running a 3meter cable to my audio interface?

 

[OneDaySky]

The formula:

a/(b+a)*100=c

a = input impedance
b = output impedance
c= % of signal that passed through

So for passive pickups with output impedance of 30Kohm and a DI box with input impedance of 220Kohm it is:
220/(30+220)*100=220/250*100=0.88*100=88
88% of the signal.

And for active pickups with output impedance of 10Kohm and a DI box with input impedance of 10000Kohm it is:
10000/(10+10000)*100=10000/10010*100=0.999000999000999000999000999001*100=99.9000999000999000999000999001
Pretty good huh ? 99.9% !

Thx man, that helped a lot. What percentage do you rate is the bare minimum for good quality DI'ing?

 

[Mutant]

atm im going right into the Hi-Z input of the emu 0404usb which is 1Mohm. guitar is schecter c7 with 707 emgs.

If your interface has a hi-Z input, you don't need to buy a Direct Injection box.

but what about the impedance match of the di and the mic in on the interface?

DI boxes are made for this exact purpose (they have low enough output impedance), so you don't have to worry about it

A typical mic in has maybe about 500 to 600 Ohm input impedance so:

600/(10000+600)*100=600/10600*100=0,056603773584905660377358490566038*100=5,6603773584905660377358490566038

5,66% of the signal if you would go from your EMG707 directly to mic in hahahaha

 

[OneDaySky]

So what difference would it make if say for example. A passive pup of 35 Kohms output goes into my countryman with an input impedance of 10000 K ohms leaves me with 77 percent signal (assuming this already a bad signal?) What difference would it make going from there into my Line 6 UX2 input of 1M ohm?

 

[OneDaySky]

If your interface has a hi-Z input, you don't need to buy a Direct Injection box.



DI boxes are made for this exact purpose (they have low enough output impedance), so you don't have to worry about it

A typical mic in has maybe about 500 to 600 Ohm input impedance so:

600/(10000+600)*100=600/10600*100=0,056603773584905660377358490566038*100=5,6603773584905660377358490566038

5,66% of the signal if you would go from your EMG707 directly to mic in hahahaha

Gosh, that would surely sound awful...

 

[damas]

If your interface has a hi-Z input, you don't need to buy a Direct Injection box.



DI boxes are made for this exact purpose (they have low enough output impedance), so you don't have to worry about it

thx dude, now im really glad i didnt bought a di and am confident that i dont really need one, at least till the next how do impedance thread