Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: Mansoor on July 20, 2011, 08:46:44 PM
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Hi all,
I am working on an audio amplifier for a rowing shell. I will need to power more than three 8 ohm speakers in parallel. The main factors that will determain what chip and design I will use are
1. Battery Life.
2. At least 15 W output
3. long part life
4. audio quality
I have researched Class D amps for a couple of days. They offer high efficiency when compared to classical amplifiers. My question is has anyone had experience with a certain chip that fit the criteria above?
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Hi,
"Boat Audio" and "Robot forum"... How off-topic can we get? ;)
I'd recommend taking audio related questions to a site like DIY Audio or similar, where all members have a keen interest in the subject (most of them wouldn't know the first thing about 'bot's though).
I am working on an audio amplifier for a rowing shell. I will need to power more than three 8 ohm speakers in parallel. The main factors that will determain what chip and design I will use are
1. Battery Life.
2. At least 15 W output
3. long part life
4. audio quality
This tells me that you...
A) Don't row for the peace and quiet on the sea :D
B) Either have a substantial hearing loss, very inefficient speakers, or no clue about SPL.
C) Need to read up on amplifier classes.
D) Think that integrated circuits are build to fail(?)
I have researched Class D amps for a couple of days. They offer high efficiency when compared to classical amplifiers. My question is has anyone had experience with a certain chip that fit the criteria above?
Not with chipped Class-D amplifiers, only discrete designs, but unless you have "Golden Ears", which the above doesn't point towards, I'd assume them to sound fairly equal withing a certain range of output powers.
Good amplifiers do sound equal - all the rubbish about eg warm or colored sound are just nitwits way of describing distortion of the original signal. A really good amplifier pass the signal without adding or subtracting anything (sadly they are few and far apart).
Class-D amps will have the best efficiency.
Class-C have the same efficiency, but is only used for stuff like power stages in radio transmitters, robots and such like, as it would sound ghastly (you could see Class-C as "half" a Class-D).
Class-B is still the most used "class", but it has the inherent cross-over distortion problem that needs carefull design.
Class-A, the cleanest sound, but with a constant high power drain, whether the input is going full blast or silent.
Your options are thus Class-B or Class-D. While I have no experience with the integrated ones (a quick search turned up a 1W chip and a 3.2W chip). They seems easy enough to use, if you can find one that accepts an impedance of 2.7 Ohm and gives you the output power you think you need.
The lifetime of an IC is mainly determined by the design it's used for, temperature extremes and physical vibration. With a sensible design and a little care, it may out-live you (electrolytic capacitors on the other hand...)
Class-D amplifiers will have the same power drain for the same power output - their own drain is negligible compared to the output.
A well designed loudspeaker box with sensitive units don't need much power for an adequate SPL - You can get very unpleasant sound levels from a 5W amp with the right box. And sticking to a lower output power equals a longer battery life.
Personally, I really enjoy the silence, on the rare occasions I get ;D
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I have tons of experience in this area. Maxim makes some chips in the range you need
http://www.maxim-ic.com/datasheet/index.mvp/id/4851 (http://www.maxim-ic.com/datasheet/index.mvp/id/4851)
http://www.maxim-ic.com/datasheet/index.mvp/id/6495 (http://www.maxim-ic.com/datasheet/index.mvp/id/6495)
http://www.maxim-ic.com/datasheet/index.mvp/id/5688 (http://www.maxim-ic.com/datasheet/index.mvp/id/5688)
Other companies to check out would be National and TI, and finally you can try find some Tripath chips on eBay.
The Tripath route would probably be the easiest if all you need is a one-off circuit since they have many non-smt packages.
I wouldn't connect more than 2 8 ohm speakers in parallel. Do two in parallel for an effective 4 ohms, then double that in stereo.
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Thanks for all the help
you are right this is off topic, but I got a lot more help here than on the DIYaudio forum. maybe my lack of enthusiasm for audio quality turned them away.
The amp is needed for a racing rowing shell. and 8 man shell. It is super long and the coxwene is not able to get their voice all the way to bow from stern. this is why cox amps are used.
I did a lot of reading about different classes and it is clear to me that i am going to use a class D for the efficiency. The reason I ask about part life is that i read online that because of the switching done in class D amps part life is reduced.
In the end i decided to go with the ADAU1592. it interfaces well with micro controllers and will supply enough power for my design i think. The datasheet shows both outputs tied in mono mode so the combination should be enough to drive the three 8 ohm speakers I have.
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I have tons of experience in this area. Maxim makes some chips in the range you need
http://www.maxim-ic.com/datasheet/index.mvp/id/4851 (http://www.maxim-ic.com/datasheet/index.mvp/id/4851)
http://www.maxim-ic.com/datasheet/index.mvp/id/6495 (http://www.maxim-ic.com/datasheet/index.mvp/id/6495)
http://www.maxim-ic.com/datasheet/index.mvp/id/5688 (http://www.maxim-ic.com/datasheet/index.mvp/id/5688)
Thanks Afroman. These chips seam very well suited for my application. I will read more about them.
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Hi,
The amp is needed for a racing rowing shell. and 8 man shell. It is super long and the coxwene is not able to get their voice all the way to bow from stern. this is why cox amps are used.
OK. Placing the loudspeakers spread out at the full length should help.
I did a lot of reading about different classes and it is clear to me that i am going to use a class D for the efficiency. The reason I ask about part life is that i read online that because of the switching done in class D amps part life is reduced.
Do you remember where you read that?
Components usually have a shorter life if operated near their limits, but a good design always stay clear of such.
In the end i decided to go with the ADAU1592. it interfaces well with micro controllers and will supply enough power for my design i think. The datasheet shows both outputs tied in mono mode so the combination should be enough to drive the three 8 ohm speakers I have.
If all else fails, or perhaps just to test the needed SPL, you could make a simple (Class-B) amp with a TDA2003. It's cheap and rugged and while you seem quite worried about power drain, I don't think it would be a problem. After all, it's very intermittent use compared to playing music.