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Class D Switching Power Amplifiers and Power D/A conversion

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Old 10th October 2008, 07:28 PM   #21
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Quote:
Originally posted by bwaslo
Though designing an amp AND a speaker makes for much more work, given your limited time budget.
At one stage i had the idea of building a set of active studio monitors. Pitty i don't have the time to.
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Old 16th October 2008, 12:47 PM   #22
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Ok, i have added more questions to my questionnaire, but after dicussing my project with someone more knowledgeable than myself, i have come to a cross roads regarding my target market. What i originally planned to do was a Class D audio amplifier for the HiFi market. However, getting purists to choose a Class D amplifier over a Class A (or AB) based on sonic quaility is not an easy task. Therefore I have 2 options reagarding the direction i take with this project.

Option 1:

Design a hybrid amplifier incorporating Class D and Class A topologies. Some designs exist on the market e.g Yamahas EEEngine. However these designs are based on tracking of the audio signal to provide minimum power to the output stage. One idea was to use a cross over and have an arrangement in which the Class D takes care of the low end frequencies and the Class A handles the high frequency content.

Option 2:

Different Market. Design a Class D amplifier for the PA/Live market. High power, small form factor, light weight, robust..etc

Any comments?
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Old 16th October 2008, 03:35 PM   #23
bwaslo is offline bwaslo  United States
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For Option 2 -- how about musical instrument amplifiers (such as a high power guitar amplifier, integrated with a small wide excursion speaker in very portable box)? It might be kind of neat to have a briefcase sized box with which a guitar guy can blow down the doors!
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Old 16th October 2008, 09:04 PM   #24
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Quote:
Originally posted by bwaslo
For Option 2 -- how about musical instrument amplifiers (such as a high power guitar amplifier, integrated with a small wide excursion speaker in very portable box)? It might be kind of neat to have a briefcase sized box with which a guitar guy can blow down the doors!
Lol..yeah that would be cool,but i am focused more on the HiFi or PA/Live market.

Does anyone know of any amplifiers that exist commercially that are hybrid of Class D and Class A ?
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Old 16th October 2008, 09:37 PM   #25
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Quote:
Originally posted by rob mullen

Does anyone know of any amplifiers that exist commercially that are hybrid of Class D and Class A ?
That would be a very strange marriage of technologies.

There are some ideas for using embedded class D amps for high quality active speakers in the thread titled "Anyone used an STA323W Amp?". Somehow this discussion doesn't show up in the index any longer, but if you do a search on STA323 on this site it shows up. There are links to 2 PowerPoint briefings in my posts that you might find interesting for your research.

I'd be very interested to see the results of a market survery for high quality class-D active speakers. Seems like a good idea, but is there really a market? If you want to help me with the marketing research, I'd be happy to give you some of the working designs that I have, and I would consider a collaborative effort. Actually, I'd give the designs to you anyway, but since I've spent so much time developing some potential products I'd love to get some feedback on whether this stuff could actually sell..
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Old 16th October 2008, 10:05 PM   #26
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Quote:
Originally posted by Neil Davis

That would be a very strange marriage of technologies.
Is it worth the experimentation i wonder?

Quote:
Originally posted by Neil Davis

There are links to 2 PowerPoint briefings in my posts that you might find interesting for your research.
Checked them, pretty cool stuff

Quote:
Originally posted by Neil Davis

If you want to help me with the marketing research, I'd be happy to give you some of the working designs that I have, and I would consider a collaborative effort.
Sounds like a plan,but unfortunately i am tied down to a heavy work load at college for the next 7 months
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Old 17th October 2008, 05:01 PM   #27
Giaime is offline Giaime  Italy
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If you can find it useful, I did a thesis on class D audio power amplifiers for my graduation in Electronic Engineering, on July this year. I can send it to you if you wish.
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Old 18th October 2008, 08:41 PM   #28
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Thanks Giaime, just sent you an email with my contact details.
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Old 20th October 2008, 12:25 AM   #29
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Rob, since the Hypex UcD modules are at the top of the state of Class-D art, I urge that you read all available documents on their design. After all, if you can't build (or at least try to build) something better, why bother? Fortunately there is much information on Hypex's website: look at all the application notes on the applications section and within the technology section. There are also long papers on Bruno Putzeys's AES master classes, extremely good.

http://www.hypex.nl/

http://www.hypex.nl/docs/Bruno%20Masterclass/slides.htm

Bruno also shares much of his experience in his forum on PSW:

http://recforums.prosoundweb.com/index.php/f/45/5274/

Here's a short, fine thread:

http://recforums.prosoundweb.com/ind.../t/15032/5274/

Quote from Bruno, Jan 2007:

"I prefer to be agnostic about the kind of circuit one uses to arrive at a certain sonic outcome. People who try to prove that one technology is inherently better (bar power efficiency) than another usually do so because they have to for commercial reasons, or because of ideology (=insufficient understanding to look at the problem from different angles). I don't think this is the case with the books you're referring to.

What they do mean is that attaining a certain performance level is not at all equally easy or even practical with each thinkable technology. Building a good quality class A amp is rather simpler than building an equally good class D amp. I wouldn't recommend anyone planning to design a power amplifier from scratch to head into class D for musical reasons alone. Especially if you're in the "no sound, maximum transparency" game, class D is tough to crack. It's doable, but easy it ain't.

OTOH, many class D's seem to have an euphonic edge to them (one that is usually liked by the designer and by audiophile reviewers, but much less so by pro users). I've yet to meet a beginning designer of class D amps who doesn't claim his amp to be "the first truly audiophile" class D.

To keep a long story short - for a given amount of research effort (not actual design effort, that depends on one's level of experience and hence past research effort) you'll get the best results (least colouration) with class A, followed by B, and lastly D.

The reason why all my current designs are class D is simply because I've gotten the hang of it, and so far all my customers have been happy so they're good enough apparently."

You have a great opportunity. Best of luck!
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Old 23rd October 2008, 09:35 AM   #30
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Thanks Sam Lord for the links. after a hard long think about this i have decided to stick with my guns on this project. I am not going to bother with a hybrid design,but i am not too pushed on the PA/Live market. So i am going to do a pure Class D Stereo HiFi amplifer for best price/performance trade-off. I am just finishing my Questionnaire at the moment.it will be done in the next 30minutes. I am looking for people take part, so can people PM me with their email addresses and il email the Questionnaire as a word document to them. fill it in and email back as soon as possible. its only 13 questions.

Thanks

Rob
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