DI Boxes, Impedance and Transformers Part #2

all right i'm dave rat and let's do part two of the video discussing um di boxes impedance and um balance and unbalanced you know signal transport and just kind of chatting about some various subjects here and get our heads around it a little bit so in the first part i talked about the various signal levels as well as the methods of transporting that we use balanced versus unbalanced versus unshielded you know like speaker cable as well now for various types of cables that we use i also discussed kind of an analogy trying to get uh some clarity on high impedance versus low impedance high impedance is kind of like um if this is the signal sending and this high impedance output would be like a long stick for very little motion on the uh for the same amount of energy here the same amount of strength and motion in my hand which we'll say is the power or the wattage that is being generated if that is sent through a high voltage low current output high impedance output then we would see a lot of swing a little bit of resistance will drag it down and you'll see that with high impedance outputs if you put plug them in to a low impedance input it'll drag down that voltage and you'll get some you'll lose some level there um low impedance is a lower voltage higher current and they do kind of balance out so if you have the same the they trade off so if you have a voltage of 10 and a current of 1 then your wattage would be 10 and if you have a current of 10 and a voltage of 1 your wattage will also be 10. so it's just a different distribution of transmitting the same amount of energy so i've got a little setup here where i've got a pink noise signal source it's coming out of that it's going into this sound tools mic switcher swapper i've got a little picture i drew of how it's wired i'll show you there and it come the signal comes out and it goes into switcher swapper and then it goes into the input of the di and then out of the di into the mixer and then when you switch the switcher swapper the signal will now go into the output of the di and come out of the input of the di and then go into the mixer so we have the ability to listen to this di box run in reverse and what happens is since instrument levels are fairly high levels and microphones are very low levels when we take and run a direct from an instrument or uh instrument amp output into this mic level the levels these consoles that we use are typically built a lot for uh mic levels is very low level or we want to get all these things into the same level range um another example might be even if the console will handle a very high level input from a line level out and you can just put the pad on having a 10 or 20 or 50 microphones going down an audio multi-core cable and all the signals are down in that minus 50 to minus 80 db range minus 60 db range very low level and now you're running this minus 10 or zero db super hot signal down it's going to want to cross talk into the other signals and it's just kind of unwieldy you know a miss patch you've got something that's so much louder intermingled with a lot of things that are very quiet so getting everything into that same lower range is beneficial oops so we want to get a di box is a great way of doing it it takes a high impedance input and then it sends out a low impedance lower voltage output we plug our instrument into there and also the di box have the advantages of ground lift and balancing okay so what we're going to do is first we'll listen to the signal that is being sent and then you can also see on the scope here as i bring it up and i will gain this up a little bit and we can see the signal there that's what's being sent into the the di box now this is what's coming out of the di box so it's reducing the level of that signal considerably i'm going to go ahead and gain that up and that's at 50 millivolts per division and i'm using about a single division a little more and then we'll go and look at this and at 50 millivolts per division it's using the entire screen if i drop this down to 500 millivolts per division i get about the same thing so it's about a 10 to 1 trans transformer and if we look at that with the stick a 10 to 1 if this was 10 times the length of this and we had a little fulcrum right here then there's our high impedance input over there our high impedance output of our guitar or amp or whatever and then the amount that this moves here would be our low impedance higher current microphone preamp so what happens if we hook the di box up the other way oh first before we do that why would we want to hook the di box up all the way well the di box is great for coming out of a console and you could daisy chain a bunch of them together and then have take four of them put them together run a quarter inch into one out of the console and then connect all the rest of them and have four mic level outs you drop that over on the riser and if you have a camera crew coming in they're gonna love you because they have all these mic level outs if you don't have a dedicated press box um i've got this zoom player here that is fairly old and it's got a couple built-in mics and a couple of xlr inputs and i went to go ahead and put this up and record shows that i was doing and um the mics work great and these are mic level only you cannot pad these down enough to not distort you could turn a console down to like one and a half and then turn this all the way down to like five you know on this level out of a hundred and then it's okay but it sounds like crap so um a couple di boxes come out of the console i came out of the insert sends with quarter inch jacks into di boxes out of the di boxes it dropped the level down plugged it into here boom it works perfect sometimes you want to balance a line you're going to send it over a long distance and um and also like i talked about before high impedance outputs don't like to be loaded down so if you have a high impedance output or a quarter inch output getting it to a low impedance higher current output so it doesn't get drugged down outputs get dug down um you can hear them you put a y adapter on the output of it [Music] plug it into the input of a console input or whatever you're gonna do and plug it into something else and if you're unplugging and the level's dropping on that wide out um that's not good i won't get into that too much let's go ahead and look at this oh why would we want to run a di box the other way um let's say you want to take a microphone and plug it into a guitar app if we're in effect do you want to hear what it sounds like or you have an um an old pa head a vintage pa head or you've got a some old mixer or something that has a microphone quarter inch input that if you take a regular balanced line modern mic put an xlr to quarter inch low impedance output mic you plug it in you end up turning that gain up all the way you're getting a bunch of noise you're not getting all the gain you need or everything's out of whack running a di box backwards is one way to solve that this only works with transformer di boxes active di boxes have electronics they will not take the signal the other way but a transformer is just two coils of wire and it doesn't care if the input or the output there it doesn't care which way the energy goes through it which way the electricity goes so let's go ahead and watch what happens when we hook this up the other way so there's our initial signal which is about one square there and that's the output of the di box in its conventional set now if i flip this the other way there's the original signal and there's the new output of the vi box and let's go ahead and take i'll drop this down here that's about two votes per division and five so uh we're seeing about a four to one the other way we're not seeing the you know that huge drop in level that we saw coming the other way because the output of the di box is now high impedance and we're running it in even though we're getting level gain we're also running this output into a console which is low impedance input so we should see more gain oh we could check that out there we go okay so there's our output of the di box with into the high impedance input of the scope which can handle it and that's 5 volts per division and now what we'll do is look at what's going into the di box to look at the amount of gain that we're sending to it or i see the signal we're sending to it and there it is and that's 500 millivolts so it's a little more than 10 to 1 maybe 12 to 1 which is what we saw so that's great so we got an example two of what happens when because we're using the di box backwards and we're driving into the low impedance input and coming out of the high impedance output we're getting all that gain but since we plugged that high impedance output into the low impedance input of the console it's collapsing it back down again it's dragging it down so what's happening is we have this high impedance output we have a low impedance input here that's got a good amount of resistance to it and when it's driven off at low impedance output we're all good this has got some drag to it now we've taken this high impedance output which wants to do this when it's plugged into the scope or we're sitting in open air and hitting a high impedance input and we're plugging into a low impedance input and it's trying to do it and this is offering enough resistance to where this can't hit full swing um maybe not the greatest analogy but um hopefully enough to grasp it and then also you know study it and figure out and learn it um for real all right i think that's enough di boxes used backwards um isolation transformer yeah transformers are cool because just coil's a wire just coil a wire near a coil of wire if you have if you take a a wire you coil it around a hundred times with another wire right next to it a hundred times there's a hundred on this and a hundred and this whatever you send in will come back out the other side almost exactly the same or very similar um if the high quality transformer i get a little lost through it but it will come out if you put a hundred coils here and ten coils here or a thousand coils here and 100 here we have 10 times as many then a high voltage coming in here you'll lose you'll lose it'll come out one tenth the voltage and 10 times the current so it'll convert it from a high impedance high voltage to a low impedance high current and then the opposite if you turn that around the other way and you have 10 uh 100 coils here going to a thousand coils then it'll bump it up 10 to 1 to 1 to 10. it'll get 10 times bigger coming out this is going to have a lot of voltage and less current and this will have to have this can have lower voltage and more current and then you can have one coil of wire and then take two more coils of wire and wind all three of them together you can have one in and two outs or three outs and you lose a little bit but just the fact that you can coil some wire together and transfer energy from one to the other and the wires never electronically touch is super cool all right that's just a kind of a fun chat i wanted to do and hope you enjoyed it so thank you for hanging out and i hope you found this video and others that i do interesting and informative and check out soundtools.com take a look at the products i personally designed some solutions for the pro audio industry analog over cat5 a bunch of testers and other useful tools ratsound.com has got our sales department rental department install department we sell a wide variety of pro audio and av gear we do installations small to large and we do rentals for everything as small as local clubs and backyard parties all the way up to coachella festival and artists like pearl jam jack johnson blink182 and thanks for hanging out [Music] hmm

Channel: Dave Rat

Views: 8,138

Rating: 4.9678283 out of 5

Keywords: Dave Rat, Pro Audio, Rat Sound., Mixing Tips, Pro Audio Mixing, Pro Sound, Live Sound, SoundTools, Rat Sound Systems, Audio Engineer, Sound Engineer, DI Box, Impedance

Id: m-Gm8oKfDc0

Length: 15min 40sec (940 seconds)

Published: Mon Apr 12 2021