Optoisolated gate drive Class D Amplifier

[ronsimpson]

The reason i run a small woofer in free air is because i dont want the neighbours, my landlord and the police kicking my door in for beeing too loud while i do a power output test,

My first BIG classD amplifier, I used car headlights as a load. Head lights do not shake the earth. very quite. You can still parallel with a speaker + pad resistor.

 

[Experimentonomen]

Alittle more, but ran out of solder so cant continue for a few days:
https://i.imgur.com/o5arFrX.jpg
https://i.imgur.com/enJW1Ug.jpg
https://i.imgur.com/j6jGQTP.jpg

 

[cowboybob]

I hadn't thought of using the clad PCB to also make a box. Slick idea. Thanks.

 

[audioguru]

My first BIG classD amplifier, I used car headlights as a load.

But incandescent light bulbs are ptc resistors. Their resistance increases as they heat up which unloads the amplifier.

 

[Experimentonomen]

Well same goes with a power resistor as it heats up, not to the same extent as a light bulb, but still. My dummyload is i think six 25 ohm 50W DALE resistors in parallel for around 4 ohms total, and i use to dunk it in a pot of water for higher power tests.

 

[audioguru]

A wirewound resistor increases its value a little when hot but a modern power resistor does not.

 

[cowboybob]

A wirewound resistor increases its value a little when hot but a modern power resistor does not.

Only if you keep it within the stated (listed) tolerances.

Get outside of those and all bets are off, of course. My guess is that this OP might, occasionally, do that.

 

[Experimentonomen]

The only reason for my woofercooker videos is to have a bit of fun, see of much power random junk woofers i find on the side of the street can take. Yea i know whats the point of shooting video of such thing when youtube is already flooded with these car audio bassheads doing it, or using the wall outlet on even their brand new woofers they bought just to destroy.

 

[4pyros]

Alittle more, but ran out of solder so cant continue for a few days:

Ran out of solder. Now thats funny!
Keep up the good work.

 

[4pyros]

Cokkin/bakin a woofer with around 123 watts rms:

What no smoke??

 

[Experimentonomen]

Not enough power. In the near future this project will be married with a 2 x 85VDC 1.5kVA power supply

Btw there are more crazies than me out there, like this one:

 

[Experimentonomen]

Some more work has been done on this project.

A stereo modulator and gate drive board is beeing built:
https://i.imgur.com/VeMvVMx.jpg

And a stereo version of the output stage have been built, and one half of it is beeing tested here:

 

[ronsimpson]

I used car headlights as a load.

But incandescent light bulbs are ptc resistors. Their resistance increases as they heat up which unloads the amplifier

Getting rid of 1000s of watts of heat is a problem. I have large heat sinks with 100 watt resistors and fan. I have buckets of oil with resistors in them. I have tried buckets with water but the water boils and leaves hard water deposits on the resistors. Light bulbs is a cost effective means to dump power. I know the load is not temperature stable.

Now that it is hard to get old light bulbs I may have to change my plans. I hope headlights will be available for a while.

 

[cowboybob]

What is the black blob of noise on the sine wave that corresponds with the square wave bottoming out?

It's there with or without an audio input.

 

[Experimentonomen]

I suspect those blotches are layout based.

 

[cowboybob]

I can see that. If you reduce your time base it might reveal the frequency(s) of the noise and possibly lead you to the component(s)/layout area that's causing the ringing (some manner of coil field collapse and a nearby trace created capacitance tank thing going on, perhaps)...

Although, it doesn't seem to affect the audio out, so not a biggy...

 

[Experimentonomen]

It could be bad capacitors as if i take one and hook it across the speaker output, the resulting carrier residual gets alot bigger, so im gonna replace those caps with better ones.

 

[Experimentonomen]

An ever so slight uppdate:
https://i.imgur.com/5ddoms1.jpg
https://i.imgur.com/7UNjMc3.jpg

If this works at all i think im gonna cad a proper board, because this just looks awful.

 

[cowboybob]

Compared to what you had, and especially as a homebrew rig, it doesn't look that bad to me. Quite good, actually.

 

[Experimentonomen]

I think this part of the thing might be done now:
https://i.imgur.com/Whug0Iy.jpg
https://i.imgur.com/Pj6tjz6.jpg