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Old 23rd February 2009, 02:46 PM   #1
star882 is offline star882  United States
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Default "the Prius of home audio" - a friend's project

An engineering friend of mine built what I believe is the world's most efficient audio amplifier. It is a hybrid, which means it has the efficiency of a digital amplifier while still accepting analog input.
http://ecorenovator.org/forum/applia...ome-audio.html
Quote:
Recently, I built an audio amplifier based on TI's hybrid digital chipset. It is made mostly from recycled parts (the only parts I purchased just for it are the chipset, terminal block, and switchover relay). It is built in a case from an old 802.11b router and the power supply is from an old laptop. The chipset uses only 1W (one watt!) at normal listening levels. The power supply is actually quite efficient - level 3 efficiency rating.
...
P.S. I named it after a celebrity. Amanda Harris ( http://barbiebarbell.com/ ) is known for her incredible power-to-weight ratio and that's what first came to mind when I cranked up the volume (the chipset is capable of over 60W RMS continuous in my testing, which is *VERY LOUD*).
I'm not exactly sure of the function of the relay, but it looks like it is used to reroute the speakers to another amplifier or something. The amplifier was recently presented at an university engineering show and I'm very impressed to say the least.

One thing I like about his design is that the power switch actually switches the AC power so there's no standby loss in the power supply when off. Many amplifiers on the market have the power switch on the low voltage side, which means a nonzero standby loss.
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Old 11th January 2010, 04:24 PM   #2
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nice and well made amplifier with use of less components nice job keep it up
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Old 12th January 2010, 12:21 AM   #3
Fenris is offline Fenris  United States
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Isn't this just more or less a textbook application of the TI part? Power switch on the AC side isn't exactly novel, it's just not common with commercial gear because of the UL certification process - much cheaper to buy an off the shelf power brick that's certified than to have yours designed and tested. Plus commercial gear likes remote controls - can't do that without standby power. And 60w RMS? On a single 19v supply? Even with no losses and 4 ohm speakers it's half that at best and into high distortion well before that.
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Old 12th January 2010, 01:13 AM   #4
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"the Prius of home audio" - a friend's project
Not quite the endorsement for "environmentally" friendly and efficiency.
Prius is basically crap, I hope the amp is not the same...remember when top gear ran the prius vs. a Beamer.....
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Old 12th January 2010, 04:40 AM   #5
star882 is offline star882  United States
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Originally Posted by audio-kraut View Post
Not quite the endorsement for "environmentally" friendly and efficiency.
Prius is basically crap, I hope the amp is not the same...remember when top gear ran the prius vs. a Beamer.....
http://www.cleanmpg.com/forums/showthread.php?p=221865
I can only dream of the day when 299 MPGs would be considered terrible mileage. Granted, it's modified, but I would practically fall in love with a car that gets 299 MPGs. (The same one who built the amplifier has an idea for a modified Prius he says would get 500 MPGs, which he is going to name "Allie Moore Prius" after an environmentalist because that makes a good acronym. It basically consists of adding some more batteries and lots of support electronics.)

If you're talking stock production cars only, the Prius is not the most efficient. The Honda Civic Hybrid is. (The original Insight could do even more, but nobody bothered driving it through 48 states yet...)
World Record Attempt

But let's get back on topic.
Quote:
Isn't this just more or less a textbook application of the TI part?
The output filter appears to be simplified (he says that's to reduce idle switching losses) and there's a SE to differential converter on the input. Then he put it all in a case with just a little room to spare and managed to make it look almost like a stock product.
Quote:
And 60w RMS? On a single 19v supply? Even with no losses and 4 ohm speakers it's half that at best and into high distortion well before that.
I'll have to ask, but maybe he's playing square waves to get that number. That's still more truthful than many home audio equipment that would melt down well before their listed output power regardless of what input waveform. The output power would only be attainable under unrealistic conditions, but it will do that without melting down. But numbers aside, it definitely has more than enough power for typical home use.

Just realize that the project is almost a year old. He's now thinking about building another one based on a newer chipset and try to make it smaller and more efficient at the same time. And I bet he'll figure out how to get more output power rating as well.

But no matter what, it's definitely a step in the right direction. Every environmentalist he knows agrees.
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Old 12th January 2010, 09:51 PM   #6
Fenris is offline Fenris  United States
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Quote:
Originally Posted by star882 View Post
2502 Miles 299MPG in a Prius II PHEV! - CleanMPG Forums
I can only dream of the day when 299 MPGs would be considered terrible mileage.
With sleight of hand I can get kind of mileage in my Tahoe too! All I need to do is use ethanol and my miles per gallon of gasoline will shoot way up! Notice of course that the electricity used to charge up at night wasn't used in that calculation so while it's technically correct, it's very disengenuous....

Quote:
Originally Posted by star882 View Post
If you're talking stock production cars only, the Prius is not the most efficient. The Honda Civic Hybrid is.
Why not count the cost of producing the vehicle and recycling the batteries as well? Let's not forget to add in the subsidies that go into the cost, as well as maintenance factors like changing battery packs. I'd argue that my friend's 1992 Honda Civic beats the pants off any hybrid. Approximately 50 MPG for the last 18 years, cost $12K new, and will probably still be running in a decade without needing any serious maintenance. His TCO including insurance for 25 years will probably be under $50K. Personally I would never own it, it handles like crap in the winter, has only a marginal heater, would never survive an accident, and has no cargo capacity.


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Originally Posted by star882 View Post
But let's get back on topic.

The output filter appears to be simplified (he says that's to reduce idle switching losses) and there's a SE to differential converter on the input. Then he put it all in a case with just a little room to spare and managed to make it look almost like a stock product.
.
Simplifying the output filter will really only pass more garbage down to the speaker. While technically this will increase output power and hence efficiency, ultrasonic and RF noise is not what I would want to listen to. The SE to differential will let him run in bridged mode, increasing power theoretically, but will limit him to 8 ohm speakers.

Quote:
Originally Posted by star882 View Post
But no matter what, it's definitely a step in the right direction. Every environmentalist he knows agrees.
Are these the same environmentalists who went to Copenhagen in private jets (and then had to fly them empty to other airfields because there wasn't enough parking space) and rode around in so many personal limos that they had to be driven in from neighboring countries? The ones who have 4 family members in a 10,000 square foot home but want to tell me that I should reduce my consumption? The ones who fudge numbers to get a certain result and then destroy the original data? Yeah, that's my model for efficiency.
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Old 13th January 2010, 05:35 AM   #7
star882 is offline star882  United States
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With sleight of hand I can get kind of mileage in my Tahoe too! All I need to do is use ethanol and my miles per gallon of gasoline will shoot way up! Notice of course that the electricity used to charge up at night wasn't used in that calculation so while it's technically correct, it's very disengenuous....
Here's a Hummer that gets infinite MPG. No gasoline and no electricity, but its top speed is just below 15 MPH.
Green Hummer Project: Home
Quote:
Why not count the cost of producing the vehicle and recycling the batteries as well? Let's not forget to add in the subsidies that go into the cost, as well as maintenance factors like changing battery packs. I'd argue that my friend's 1992 Honda Civic beats the pants off any hybrid.
The hybrid batteries actually last a very long time. But there is a modified 1992 Civic that gets 95 MPG without any special technology. Better than all current stock hybrids, but the modified Prius still has it beat.
Aerocivic - Honda Civic modifications for maximum gas mileage - aerocivic.com

And now let's get back on topic again...
Quote:
Simplifying the output filter will really only pass more garbage down to the speaker. While technically this will increase output power and hence efficiency, ultrasonic and RF noise is not what I would want to listen to. The SE to differential will let him run in bridged mode, increasing power theoretically, but will limit him to 8 ohm speakers.
There are even hybrid digital amplifiers that do not need any filtering if the speaker is right next to the chipset. (Otherwise, wiring capacitance would cause too much losses.) The speaker will not respond much to the high carrier frequency and neither do our ears. The very slight response that does occur is probably partly responsible for the hybrid digital "smug" I talked about before.
Quote:
Are these the same environmentalists who went to Copenhagen in private jets (and then had to fly them empty to other airfields because there wasn't enough parking space) and rode around in so many personal limos that they had to be driven in from neighboring countries? The ones who have 4 family members in a 10,000 square foot home but want to tell me that I should reduce my consumption? The ones who fudge numbers to get a certain result and then destroy the original data? Yeah, that's my model for efficiency.
I'm talking about real environmentalists, not greenwashers. As in Allie Moore, Andrew Chin, Jennie Chen, Mike Lu (the one who built that amp), Tessia Lamison, and I. They all believe in hypermiling (including driving less) and other ways of conserving energy. They all agree to keep the A/C at 78F or above and the heat at 68F or below, preferring natural ventilation when possible. Mike, in particular, has a very good tolerance for hot weather and he does not turn on the A/C until it gets up to 85F. He also does not turn on the heat until it goes below 58F. Allie is even more tolerant of the cold weather and she generally keeps the heat at 50-55F! (I don't know much about the others.) I, on the other hand, keep the A/C at 82F and the heat at 65F. Way better than the average American but not as good as those environmentalists. (HVAC is one area I'm looking into for research so I'll soon have an engineering advantage in that area!)

Mike's quote is, "Allie Moore and I have a combined carbon footprint much smaller than that of one average American."

And to get back on topic again, I'm looking forward to the new hybrid digitals he's going to build. I'm also looking forward to how he's going to build SMD soldering equipment by recycling common electrical junk. (And for the record, he actually does not like lead free solder because it is harder to work with.)

P.S. And before anyone gets the wrong idea, Mike and I are just friends. Three factors tend to keep it that way. He and I both want to specialize in power electronics-related fields, so not a very complementary match. The temptation to "arms race" him is bad enough just as friends, no need to make it worse. Finally, he's with Allie Moore.
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Old 13th January 2010, 06:29 AM   #8
Fenris is offline Fenris  United States
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Quote:
Originally Posted by star882 View Post
Here's a Hummer that gets infinite MPG. No gasoline and no electricity, but its top speed is just below 15 MPH.
Green Hummer Project: Home

The hybrid batteries actually last a very long time. But there is a modified 1992 Civic that gets 95 MPG without any special technology. Better than all current stock hybrids, but the modified Prius still has it beat.
Aerocivic - Honda Civic modifications for maximum gas mileage - aerocivic.com
Yeah, but where I live it was -8 degrees this morning. Let's see how well the "green hummer" does with the black ice and snow. Or even the battery pack on a hybrid. And the modified civic isn't street legal - it visibly doesn't meet at least three Federal and two state safety standards, plus it would probably stick out of a parking spot.


Quote:
Originally Posted by star882 View Post
There are even hybrid digital amplifiers that do not need any filtering if the speaker is right next to the chipset. (Otherwise, wiring capacitance would cause too much losses.) The speaker will not respond much to the high carrier frequency and neither do our ears. The very slight response that does occur is probably partly responsible for the hybrid digital "smug" I talked about before.

And to get back on topic again, I'm looking forward to the new hybrid digitals he's going to build. I'm also looking forward to how he's going to build SMD soldering equipment by recycling common electrical junk. (And for the record, he actually does not like lead free solder because it is harder to work with.)
While much of the audio garbage may not be audible, the energy does have to be dissipated in the form of heat. Adding several continuous watts of heat to a driver, especially something like a tweeter or fullrange in a sealed environment, can have detrimental effects.

A good SMT hot air gun can be made from a Radio Shack desoldering "sucker" iron, a piece of silicone air tubing, and an aquarium pump. Lead free solder is crap, its a feel-good solution to a non-existent problem. It's more brittle and harder to repair, leading to higher failure rates plus less things being repaired and instead being thrown out and replaced.

For the record, I've been an environmentalist my whole life. But I use reason instead of feelings to guide my judgment. I'm also an engineer, so I appreciate effectiveness and efficiency in balance and try to anticipate the follow-on consequences. Every amp case I've ever built has been from partly or fully recycled materials, mostly old IT gear. And frankly, I don't care about my carbon "footprint", it's a meaningless metric built on pseudoscience, politics, and a lack of macro understanding of how the global and solar energy cycle works.

/rant
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Old 13th January 2010, 07:33 AM   #9
poynton is offline poynton  United Kingdom
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Quote:
Originally Posted by star882 View Post
....Quote:
. The chipset uses only 1W (one watt!) at normal listening levels. The power supply is actually quite efficient - level 3 efficiency rating.
...
the chipset is capable of over 60W RMS continuous in my testing,.....
.
If 1 watt is sufficient for 'normal' listening levels, why design an amp to give 60w rms? No matter how efficient the power supply is, it still has to be capable of supplying 60w rms !! No very efficient, really.


....and now, my OT rant ....

Quote:
Originally Posted by audio-kraut View Post
Not quite the endorsement for "environmentally" friendly and efficiency.
Prius is basically crap, I hope the amp is not the same...remember when top gear ran the prius vs. a Beamer.....
'Environmentally friendly' is in most cases a tortology.

The Prius is crap as are most 'green' energy solutions. Where does the electricity come from to charge the cars? From power stations. Just move the source of pollution to another part of the world.

Close to where I live, they are just about to close a nuclear power plant, making hundreds redundant and the nearby aluminium plant that was the reason for building it in the first place. Plans to replace it with a modern nuclear plant are being greeted with resistance as it is not clean.

The greenies solution ... well, we already have 3 wind farms offshore which polute my vision. So, they are to build Britains largest offshore windfarm which will stretch from horizon to horizon and plans are well under way for another further offshore.
How many conventional power stations will they replace .. NONE!
Usually, only half the turbines are moving and on some summers days, none at all.

You guys in the States will only get real about energy conservation when the price of petrol goes up, say to current European levels of $3.00 per litre.


Andy



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Last edited by poynton; 13th January 2010 at 07:37 AM.
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Old 13th January 2010, 01:31 PM   #10
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While hybrid vehicles may be more energy efficient to operate, look at the lifetime energy cost of them (includes manufacturing energy). It's higher than a lot of conventional vehicles, and up until recently, was worse even than a lot of SUVs.
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