Audio setup for "portable" ultra bright TV

For some weird reason I had an image of you sitting in a one-man tent with a 24" monitor and huge speakers then.

This is for caravan or some other large covered space I assume.

Was a time we could just tap from the speakers or earphone port but some (not all) Class D amplifiers - which are simple, powerful, efficient and cheap) use the inductor in the speaker/headphone driver as part of the output filter.

While not a show-stopper this might mean that a simple resistive load might cause "issues." I can't be sure because i've never tried this and I expect it's mostly related to larger amplifiers where the switching current is much higher.

If you're cautious over the electronics it's far better to stick with something where you're not exposed to high voltage.

This suggests to me that you should be using the headphone out which is expecting a load of 100-600 ohms (less if it's a good amp). In this case you can put a load resistor across each output  from the output to the common and using that to drive a larger class D amp. The efficiency of modern amps with power MOSFETs is eye watering - well it is to me because I grew up in the days of "toobs" and germanium transistors. Silicon power transistors like the classic 2N3055 (bipolar) would often be used in amplifiers with an output of 10 watts at most (with two per channel at that!).

Class D amps use a very high-frequency switch to turn the output on HARD (so very little resistance in the switch, therefore very little wasted power; HEAT) or closes it fully so no current flows. This makes them exceptionally cool-running and a 10W amp can be realised with very few components in a tiny amount of space. In fact, I've got small amplifiers here capable of about 2W that are smaller than the case of a 2N3055 power transistor.

Ali Express will almost certainly have something suitable - but be aware that the 24V power strip is going to need a fair amount of current and the power adaptor may not have enough current to drive an amplifier. It's easy to forget this sort of thing - I've done it myself when I was "upgrading" the USB C microphone. The 1W output of the NMA0515 (which I know better than to assume... cough cough)  was so weedy that my usual choice of NE5532 amps brought it to its knees.

You won't get a Plug and Play system that covers all of this. The potentiometer will have to be a switched dual-log pot and it will mean putting the DC connection through that switch. (You can do this electronically, but that's not a plug-play solution).

The "gotcha" here is that all the current capacity of the system has to go through that switch. So you'll need to know - up front - the current/voltage capacity of the switch and the maximum load that the switch can handle.

https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/P08.pdf

This is semi-random one I found at Digikey - see the switch rating here is just 16V at 3 amp. Now it'll handle 24 volts but you have to de-rate it to allow less current - but 2amps (which is the same load) isn't leaving any room for the amp and a bunch of power LEDs.

Crossovers are weird. I won't go into detail of how they work but what matters is that they need to be matched to each speaker in the system to get the best performance.

It's better, more efficient and far more accurate to use electronic filters (preferably digital ones) and a separate amp for each one - usually with a mid-low range (woofer) and a tweeter. Very low frequencies don't need a crossover (they need a filter)  because they're usually a single "sub-woofer". Directional information is carried by higher frequencies so a sub-bass/subwoofer is a mono system. Better yet, you can put a sub pretty much anywhere in the listening space and just bounce it off the wall.

I'm not trying to put you off here but you're going to need to understand the problem better than you do now (we all have to learn, but it's better to learn BEFORE you spend money)!

Can this be done? Sure.
In your budget? Probably - except for a fancy speaker setup as the drivers are a significant cost, crossovers too.

But you're going to need to find out the power handling capacity of your LED power brick before we can even start.

Perhaps someone else has other ideas, I'm just passing through. 🙂

@marcdraco thank you for the thorough reply

Posted by: @marcdraco

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you're going to need to understand the problem better than you do now

For sure!

Posted by: @marcdraco

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This is for caravan or some other large covered space I assume.

Yes, inside the caravan when it's raining and outside the caravan when it's not. That's the whole point of that "ultra bright" idea anyways (and of course building something unique. It's not that I really NEED this thing...) The idea came to life when we wanted to watch the UEFA Euro 2024 outside during bright daylight with a regular tv set. It just does not work. While the space "outside" is indeed "large" I do not want to excite a big crowd! It's just about being better than the 1W internal speakers.

Posted by: @marcdraco

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But you're going to need to find out the power handling capacity of your LED power brick before we can even start.

I have not yet ordered but my LED stripes will draw roughly 60W max. so I would go with a 100-150W power supply (depending on whatever comes from this discussion here...).

I looked around the internet for a bit and found some stuff that could work (in my naive mind at least). I will just list it here and then you tell me why it's a bad idea 😉

Amplifier with 24V capabilities, potentiometer and AUX input: Amazon

Full-range woofer: Soundimports

Oh and I created the following professional circuit diagram 😉

Maybe you can see what I am thinking of. Is that completely wrong?

Cheers,

Nicky

That looks good. That's a class D amp which will do the job very efficiently.

I'll have to look at your driver choices later - this is an excellent example of where Matt's design comes in.

You'll probably get away (and I'd try first) using a 3.5mm male to male jack extension as you've pictured. The switch on the pot is a bugbear (the example one I found was only capable of about 50W, from memory).

But yeah, I'd say that looks like you're in the right lines and we're all learning here - at least, the smart ones are.... Some people don't like the answers, but I'll always be honest with you.