all right i'm dave rat and today i want to talk about
di boxes impedance and a little bit about balance and unbalanced lines but primarily about um
ways to use a di box and in conventional and unconventional ways and why we even use them
before i get into the di box directly let's talk about impedance and how
it relates between the various signals that we're dealing with in pro audio we're dealing with a
wide variety of signal levels starting from kind of the lowest level would be mic level which
is extremely low level minus 60 db or more or less then we've got kind of the instrument
level which would be like what comes off of a guitar or um kind of this lower mid level
that is you know minus 20 to minus 40 db and these aren't exact numbers but just you know
maybe 20 to 40 db uh more 20 to 40 more db than the mic level stuff and then we get into
kind of the semi-pro line level which you know the minus 10 db stuff that you know in home
hi-fi runs a lot of that and then you get into the pro level which is you know plus four plus 20 plus
18 and these higher pro level and then beyond that we get into amplifier levels where we're um
we're you know spinning out thousands of watts we switch to watts there but that
might be plus 40 db or plus 50 db plus 60 db plus 30 db so it can be related in a db scale
so that's one thing we have this varying levels from very low to really high level signals
second of all or the next thing we can look at is the format in which we transport these signals we
can transport them in unbalanced lines which would be like a guitar cable with a thin wire down the
middle and a shield around the outside typically quarter inch connectors or rca connectors
is another unbalanced signal format that's really common then we also have for
a mic level for extremely low level stuff we get into balance line where we have the two
to the twisted pair of wires inside of a shield to give us some more rejection due to the line
balancing and i've done another video i've done another video on that so i won't get into it too
much and then for like the real high level stuff speaker level we just use a you know a pair of zip
cord for home stereo speakers or a pair of wires maybe twisted maybe not or very few twists
inside of like an nl4 or an nl8 and we've got these high level signal cables um
the next part of this equation so we've looked at the different various different
levels and we've looked at the formats and the methods that we transport these various levels
and then we have impedance and impedance is a little more complex or you know there's a lot of
misunderstanding around it or just kind of be like well it's complicated
i don't i don't even really worry about it um doesn't matter too much or whatever that is
um impedance is interesting impedance is in a way it's uh the same as resistance but it's frequency
dependent um it's frequency dependent resistance but for that i don't want to get real technical
on it i'm going to do another one of my crude kind of uh practical examples to demonstrate this it's
an imperfect actually i just thought of it today as i was putting this video um thought together
high impedance is
it typically is a higher voltage and a very low current and what that means is that it's
i'll get into that second i'll give you a little demo low impedance is a lower voltage
and higher current and you can transition from high impedance to lower low impedance
signals and one of the units that does that is the di box i mean that's its purpose
one of its purposes is the transition from a high impedance high voltage
low current signal unbalanced and to a lower voltage higher current balanced signal
and then the third thing that the DI box does besides alter the impedance voltage and impedance
it also balances the line and the third thing it does it offers us a ground lift switch and
some isolation to give you an example to help you understand impedance if you if you
know electronics you're into this um you got this then yeah i realize this is not a perfect example
But this might help people that don't um have a full who want to know it better
high impedance can be looked at like a long thin stick now let's say my hand
is creating the signal it's going and maybe i had a string on it and i'm
making waves in that string you know if you do that you can see the waves go down well
my hand is generating the signal and if i have a high impedance output
we can think of it as a long thin stick so even for a small motion in my hand the stick moves
really far so it's a high voltage but the current is the is kind of the force by which it pushes
so if i have a certain amount of strength here and this is a long thin stick it's really easy
to stop this from moving it's not very uh it doesn't have a lot of energy a lot of power
at the end or power is not the right word for it a lot of strength or a lot of push but it does
move far and so we've got a lot of voltage which would be the swing of it and very little current
which is the amount of push that it would have low impedance conversely would be like a shorter
heavier stick and for the same amount of motion in my hand we don't get near the voltage we don't get
near the amount of displacement at the end but it's got a lot more power it's got more energy
it's harder to stop it from moving okay so low impedance is low impedance outputs are
typically lower voltage higher current and high impedance outputs are higher voltage lower current
now it turns out you can transition from one to the other and the math is current times voltage
so if you have a high voltage you have a voltage of 10 and a current of one then you've got a watt
uh oh the wattage would be one watt or ten watts i'm sorry one and ten one times ten
ten watts if you have a voltage of 1 and a current of 10 amps you can also have 10 watts
the high voltage low current is a higher impedance circuit and the lower voltage high current is
a low impedance circuit all right so what a di does is it takes this high voltage this big swing
and it's almost like it's like almost like a fulcrum it takes the big swing on one side
and it's got a pivot point maybe let's say it's 10 to 1 for example then this would move 10 times as
much as this and those transforms you have a 10 to 1 transform inside of a di box then you would
get a 10 to 1 transition from a high impedance to a low impedance from a low a high a low current to
a high current output so a transformer you could have a one to one transformer for an isolation
and it does the same thing on either side and then you can also have splitter transformers
that would be multiple sticks attached together so when you move one two move on the other side
now you get a little lost to the transformer but that's pretty much how it works
all right so that's pretty much the foundation by what we're dealing with here i'm gonna do another
video i'll finish this up in a part two where i'll do some demonstrations with this di box here
and some signal levels and we'll kind of look at all the stuff that i just talked about
cool