Class D audio power amplifier research

[rob mullen]

I am currently in my final year at college studying Product Design Engineering(from an electronic engineering background). For my final year project i have decided to design and build a working Class D audio power amplifier. However since my course incorparates business related subjects, my project must be designed and developed as if it was by a "real world" company. Therefore, marketing and customer needs must be employed. So before jumping into the technical end (circuit design ..etc) i need to show that there is a need for my Class D Stereo Power Amplifier. I have done some research and i can see that alot of the focus on the Class D topologies are mostly based on mobile applications (phones, portable audio products..etc). The power efficiency of the designs and less heat dissipation makes it appealing for small low powered devices. I have not yet found any information regarding the advantages of Class D audio amplifier design in power amplifiers with respect to high-end audio.

Was wondering if anyone could shed some light on this?

[ashok]

Some thoughts....

Fist of all why classD ? I would think the main reason would be to improve efficiency. Less loss of power ( as heat ) per watt output. Very important with battery operated equipment ( portables and non portable ) AND even more so now in EVERY energy consuming product on Earth. We need to conserve energy use urgently and classD is a good way of doing it.
Now coming to classD being used in high-end audio. It all depends on if it can sound as good as the best available standard equipment.
This subject is being debated right now.
I have used some classD amps and I think they do some things amazingly well. From a price point they are winners. BUT come to meaurements and they are poor in some areas.

How much of the measurements matter in real life is being debated hotly by some people.
But then again amplifiers sound different due to many reasons and you will find hundreds of opinions on the subject.

MY opinion would be that they should refine classD ( which is very young right now ) to a stage when it can outclass the best tube and solid state equivalents. So ( design wise ) you have a challenge right there !
Do a search on this forum and you will find plenty of information. Or just go to the classD section and look under the posts it has. Will keep you occupied for a while !
Wish you all the best. Enjoy being on this forum.

[dweekie]

It seems many of the same reasons for class D in portable audio still apply for high end audio. Heat is certeinly a factor. Big class A solid state and tube amps can run very hot, which act as a space heaters. Energy savings is always attractive from both an environmental and marketing perspective. Price is also a consideration. Class D amplifiers generally run cool and do not require large, expensive heatsinks and enclosures. The cost to manufacture drops as a result. Aesthetics can be a factor as well. Class D amplifiers can generally be smaller and less obtrusive. This fits into the modern trend of stylish, smaller devices (WAF factor) that allows it to have broader appeal.

[Buckapound]

I would think you could do your project a favor by getting your hands on one of the low-cost, low-power tripath 2024 boards out there and listening to it. There's a ton of them on eBay and in other threads on this forum. They really do have a unique sonic quality, and other benefits that others have just noted.

Good product design and marketing come from passion about ideas, and those are best when fueled and tempered by real life. Too many products are thought up by guys sitting in cubicles, trying to use new technology or looking to fill "holes" in the market.

--Buckapound

[rob mullen]

Well, i had other ideas for my final year project including an Analog Synth, and a tube pre-amp, both of which my lecturers weren't really feeling. Yeah of course i chose the Class D with regards to efficiency. Less power, smaller heat sinks, smaller form factor..etc

Originally posted by ashok
Some thoughts....
MY opinion would be that they should refine classD ( which is very young right now ) to a stage when it can outclass the best tube and solid state equivalents. So ( design wise ) you have a challenge right there !

Probably why my lecturers let me do this project, there is still a lot of on going development within the field of class D design.

Originally posted by dweekie
It seems many of the same reasons for class D in portable audio still apply for high end audio. Heat is certeinly a factor. Big class A solid state and tube amps can run very hot, which act as a space heaters. Energy savings is always attractive from both an environmental and marketing perspective. Price is also a consideration. Class D amplifiers generally run cool and do not require large, expensive heatsinks and enclosures. The cost to manufacture drops as a result. Aesthetics can be a factor as well. Class D amplifiers can generally be smaller and less obtrusive. This fits into the modern trend of stylish, smaller devices (WAF factor) that allows it to have broader appeal.

Exactly what i was looking for!..

Originally posted by dweekie
Aesthetics can be a factor as well. Class D amplifiers can generally be smaller and less obtrusive. This fits into the modern trend of stylish, smaller devices (WAF factor) that allows it to have broader appeal.

I have two main personal goals from this project too. My main interests are circuit design and industrial design. Aesthetics i find to be an important part of product design. One thought i had regarding the use of class D is the smaller form factor.


Thanks very much to the both of yous (ashok & dweekie). Both made very valid points.

[justblair]

I think that the advantages of class D are severalfold.

Form Factor - Small is beautiful
Flexability - Power suplies need not be bulky or expensive
Low cost -- You can either use this to make a cheap project with cheap parts throughout, or a mid range product with high end components inside.

Option 1: Since your project is aiming to be commercial in nature, I would either take your Class D amp in one of two directions.

Esoteric Audio, perhaps in a creative designer case, the small form factor would allow for creative solutions here.

http://www.audioinnovations.co.uk/main.htm

It is possible to produce a very nice sounding amplifier with money left over for the finish. Trouble is the mid range audio market is pretty much saturated, so to produce a competitive product, you must either have a technically excellent product, or a suitably desirable design.

Option 2: Cheap and innovative. The Ipod aftermarket is huge, Class D can be used to make portable, the streamed media thing is getting bigger all the time as well. Trouble is there are a multitude of products competing here and accessories are generally cheap and chearfull.

A product that is innovative, yet not too costly can become the next best thing in this market in a short space of time.

The third option is a blend of the two, high end amps for high end streaming sources, or high status products for Ipod owners could perhaps survive by selling exclusively and at a premium.

I am sure others may have other ideas

Oh check out the maxim 9744 digital amplifier IC. It may give you ideas for the second option!

[albin]

check out www.41hz.com forum piccies,they put 5kgs of tubes into a matchbox.
regards

[rob mullen]

Originally posted by Buckapound
Good product design and marketing come from passion about ideas, and those are best when fueled and tempered by real life. Too many products are thought up by guys sitting in cubicles, trying to use new technology or looking to fill "holes" in the market.

--Buckapound

I couldn't agree more, Il check out the tripath 2024 boards. Thanks

[rob mullen]

Excellent stuff justblair, thank you very much.

[chicks]

Originally posted by justblair
I think that the advantages of class D are severalfold.

Form Factor - Small is beautiful
Flexability - Power suplies need not be bulky or expensive
Low cost -- You can either use this to make a cheap project with cheap parts throughout, or a mid range product with high end components inside.

the streamed media thing is getting bigger all the time as well.

A product that is innovative, yet not too costly can become the next best thing in this market in a short space of time.

Sonos is a leader in the streaming market, with Olive http://www.olive.us/home.html aiming for the higher end. Logitech just introduced the SqueezeBox Boom, adding an amp and speakers to their streamer.

A compromise product that has the streamer and Class D amp, but allows external speakers for better separation and sound, at a price closer to the SqueezeBox than the Sonos, might work.

Here's my attempt a such a compromise: an Omnifi DMS-1 streamer with an added Sure Electronics amp:

http://www.chicksolutions.com/dms1/100_1040.JPG
http://www.chicksolutions.com/dms1/100_1041.JPG