Stupid guy wants to build class D amp

[Jimmy154]

I need an amp for a Dayton Audio RSS315HF-8 (8 ohm) subwoofer.

I guess it should be 300 watts at 8 ohms?
Doesn't need any controls.
Just going to use a RCA input and maybe a gain.
I would like it to be cheap.
I can find heat sinks and transformers.
Maybe even certain caps/parts.
I can solder pretty well.

But I need a design. That's where you guys come in.
And maybe also a source of cheap parts.
Maybe I should just buy a pre-made board?

 

[nigelwright7557]

I have used the irs2092 with good results.
Care needs to be taken with pcb layout and decoupling.

 

[Tekko]

I feel the IRS2092 is a bit too steep for a beginner.

The 25-1200w with two mosfets class d would be a simpler thing to build for a beginner as for a subwoofer, the switching frequency could be limited to around 50-100kHz, thus allowing for a simpler layout.

 

[nigelwright7557]

I feel the IRS2092 is a bit too steep for a beginner.
.

I agree and disagree.

It took me 3 pcb revisions to get one working so starting from scratch probably isn't a good idea.

However, if you take one the Internation Rectifier iraud projects they even provide pcb layout for you.

 

[paskal9]

I feel the IRS2092 is a bit too steep for a beginner.

The 25-1200w with two mosfets class d would be a simpler thing to build for a beginner as for a subwoofer, the switching frequency could be limited to around 50-100kHz, thus allowing for a simpler layout.

that simple class D is good to start, but not really suitable to drive a sub as it's easily go unstable doing high power duties. the aud600 should be a proper design capable of doing high power duties, but the extra protection circuitry does add to the complexity, especially for beginners.

class d have an inherent problem of dumping the extra current back to the supply rail causing bus pumping problem. more so with low impedence and high power application, like in sub duties. i've never been able to eradicate the problem during my journey, until i bridge them.

the dayton RSS315HF have a rated rms power handling of 400w, burst of 800w. you need quite a high voltage rail if you don't intend to bridge them, to get 800w power into 8 ohm.

the best solution is to get the 4 ohm RSS315HF-4 (if you don't already buy them). then bridge the amp to drive 2 ohm. that way you don't need to work with high rail voltage, get away with lower rated transformer, and have eliminate the bus pumping problem.

but if cost is a major concern, then just buy the ready made class D pcb in ebay. they're stable into 4 ohm minimum so you could get away with 2 modules, bridge them and get enough power to drive the sub.

 

[Spec]

I would go pre made.

Connexelectronic something like this

 

[Jimmy154]

Stupid guy feels he now wants to buy a class D amp.
All this is too confusing.
I was thinking of using a velodyne subwoofer.
Some one had one on here for sale.
Just going by the pictures, it looked much more impressive and better build than most subwoofer plate amps. It was for a Velodyne DD 10(B) subwoofer (1250 Watts RMS).
Here is what is looks like:
http://www.diyaudio.com/forums/swap...yne-digital-drive-series-plate-amplifier.html

Looks really neat and tidy to me. Also has 6 big caps, which look pretty cool.
How hard is it to build something with his kind of power and quality?
Should stupid guy just buy one, next time a good deal comes along?
What would be the advantage of building one? Keeping in mind that wasting time soldering and getting a feeling of accomplishment when done, is not an advantage for me.

 

[Tekko]

A diy amplifier will never reach the quality, robustness and dependability of a storebought amp no matter of professionally done it is.

And to drive sub you need not only an amp, but also a active lowpass filter, so buying a premade amp is usually cheaper but building one might give more pleasure.

At this time i would say buy one, but you could still diy one just to get a feel for it.

 

[xrk971]

I would disagree with a blanket statement that a diy amp cannot be as dependable or as rugged as a store bought amp. Depends on brand and price point. For example, take a $20 Lepai, it is not as dependable as a nicely made PCB class D with quality components, caps, pots, connectors, etc. Simple designs using single IC class D amps with nothing more than external bypass caps, a few resistors, and output LC filter can be very reliable. DIY ideas from scratch using opamps, self oscillating, MOSFETs may be a different story though.

 

[nigelwright7557]

Good quality home made amps can be considerably better than shop bought amps.

Cheap shop amps are often designed down to a price and run on the ragged edge of the transistor specs to save money.

I have bought a couple off ebay and was horrified at what was inside them.
Tiny transformers with small heatsinks.
Then bloated specs which were no where near the real world output capability.

 

[Jimmy154]

Stupid guy needs more help

I found a nice design: AUD600, but I don't know of a good way to get parts.
Seems like if I order everything from digikey or somewhere similar it will cost me at least $200.
Where do you guys get parts?
I'm thinking most of you work on these things, so you have parts lying around and have accumulated parts over the years, perhaps from used items, maybe.

 

[nigelwright7557]

I usually have to buy in parts.
I buy from Future, RS, Farnell and Cricklewood electronics.

The most expensive item will be the transformer. Shop around.