How does a subwoofer high-level input work?

how does a subwoofer high level circuit work okay we're going to get into surrogates again alexander in edmonton canada writes to me and he says paul you advocate me to using high level inputs on subwoofers before yep i know that one can splice off the amplifier outputs into the high level my question is what does a high level circuit look like is it as simple as passing the signal through a high ohm resistor or is there more to it than that thanks so much yeah i mean that's basically what it is but it is a little more complicated than than that okay but not by a whole lot it's basically what it is and there's a couple of ways to do it so let me explain what he's referring to typically a subwoofer is fed from if you have a home theater situation or a stereo situation you take an rca cable or an xlr cable and you hook it up to the output of a pre-amplifier or your surround sound processor and you plug it in to the low level inputs of a subwoofer they have their own built-in amplifiers i have been an advocate for many years of not doing that and taking the actual power amp outputs the speaker terminal outputs on a power amplifier that feeds your speakers and use those to a high level input on a subwoofer now you're not drawing any watts out of your power amplifier when you do that you're only just drawing the signal so why would i advocate for that well one of the reasons that you do that is because the goal of a subwoofer is to augment the base of your main speakers and therefore you want that subwoofer to sound as close to those main speakers as possible and since power amplifiers pre-amplifiers and the entire electronic chain in your stereo or high your home theater system have an impact on the way your music or your soundtracks sound then we'd want to actually whatever that amplifier is doing you want to take that sonic character or signature and pass it on to the subwoofer and the easiest way to do that is to tap off the high level outputs the speaker level outputs of your power amplifier now there's a whole bunch of debates saying well you know but anyway that that's the right way to do it so how does that work well there's a couple of ways to go about it and the simplest way is as who oh i don't remember his name already i can't remember i can remember this stuff but i can't remember people's names anyway i'm sorry i apologize um the uh circuit oh yeah okay so here here is remember our triangle is always an amplifier we're going to say this is our power amp right and this is just one channel and we've got the power amp has two output i should have drawn that the other way okay plus minus right ground and the output of our power amp and this would be your red terminal on your power amp and this is your black one so red and black normally these two would go over here to your speakers and and you play music right one channel but if we want to tap off and all you do is just put them in parallel here's your one here and because we're not connecting and over here and now this is your subwoofer right and this is going to the high level inputs on the sub and and so you're just putting them in parallel sometimes you have multiple like our power amps all have dual sets of binding posts so that you can do that now one of the problems with this turns out to be that not every amplifier has ground for its black terminal many amplifiers including ours are balanced on their output what does that mean it means that there is no ground that in fact our amplifier is really made up of two amplifiers and so this is it's actually a two channels working like this you know where this is going up and that's going down that's called a balanced or bridged amplifier and you don't want to tie that to ground because here on your on your subwoofer it's actually ground and if you do that you're going to short out this this channel so you don't want to do that right so that that be the problem okay how does this all work well it shouldn't be a problem because everyone that i've ever designed and at genesis we helped out infinity but mostly at genesis we made it balanced input it was really simple so the circuit base the simple the circuit most subwoofers use unfortunately is a single-ended circuit and i don't know why and that looks like this okay so let's say that this is a 100k and then there'll be a something here to neck this down maybe this is uh i don't know you know uh 3k okay this is a divider so here's your red terminal coming from your power amplifier it goes into this 100k resistor which uh is a big resistor it gets you know so you've got this big signal and that now we're going to have this little signal and this goes out and feeds the power amplifier inside of the subwoofer the problem is the black terminal on on your sub amp is going straight to ground right so this is really simple to to fix if the subwoofer amplifiers got their heads out of their butts um you just make a balanced like this okay that's the circuit 100k 3k and this is the black okay that's a differential input a balanced input it's it's it's you're talking two cents in parts and a little bit of engineering ingenuity um it's not it really isn't hard so this is that that's it that's the circuit so it comes in it gets necked down it comes out it this is 100k doesn't matter you can tie that to the to you know the output of the other side of your amplifier if it's a bridge damp and all that but anyway that be it okay hope that answered your question talk to you later bye [Music] you

Channel: Paul McGowan, PS Audio

Views: 56,051

Keywords: Ask Paul 2

Id: uiVXXeINRog

Length: 7min 44sec (464 seconds)

Published: Wed Dec 23 2020