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Class D Amp for 28v (for a 24v lorry)?

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dunkh View Drop Down
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    Posted: 09 May 2016 at 1:28am
Im converting a horsebox into a live in vehicle and would like to have a small sound system I can place outside the lorry.  Probably 2 small speakers.  I would like to use a Class D amp as the efficiency is good.  Something over 20w per channel.  However most are rated up to 24v.  The supply would be 2x 12v lead acid batteries which are more like 28v.  Are there any class D chips out there that can cope?  Or perhaps a more traditional class A/B chip amp?  Or should I get a 24v to 12v dc converter and use that?




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jannes View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jannes Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 2016 at 6:30am
Both the STA508 and TK2050 will work with your supply voltage.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dunkh Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 2016 at 11:33am
Nice one, the TK2050 max is 28v so might die is left connected whilst charging the battery but the STA508 looks ideal.  50w a channel and 34v max.  £9 too!
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studio45 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2016 at 2:43pm
Since the power output of those amps is directly related to the rail voltage, you stand to lose a few watts as the batteries discharge. This might not be too much of an issue, but you could avoid it - and any potential over-voltage issues as well - by using a "buck/boost regulator" board, commonly available on eBay. These take in a wide range of supply voltages, usually 5 to 30v, and keep their output voltage set steady at some point within that range. This would ensure your amps were always seeing a solid 24v regardless of what the battery or charging system was doing.
Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sweex Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2016 at 3:08pm
Originally posted by studio45 studio45 wrote:

Since the power output of those amps is directly related to the rail voltage, you stand to lose a few watts as the batteries discharge. This might not be too much of an issue, but you could avoid it - and any potential over-voltage issues as well - by using a "buck/boost regulator" board, commonly available on eBay. These take in a wide range of supply voltages, usually 5 to 30v, and keep their output voltage set steady at some point within that range. This would ensure your amps were always seeing a solid 24v regardless of what the battery or charging system was doing.

The downside is that the often only has an effiency of 80% och less :/. i have one that i mesured to an effiency of 62%
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 12 May 2016 at 3:00pm
True that, it's a tradeoff between power, sound quality and battery life. The efficiency goes up with output current though, so if you're powering multiple amps from one board that figure can be improved.
I'm of the opinion that direct battery power can be quite "spongy" and poorly regulated, depending on your battery's condition, state of charge and your wiring, and that's generally not a good thing for power amplifiers - they tend to work best when given a very solid power supply that doesn't change voltage much under load. So from that viewpoint, some form of regulation is a must. But, if your goal was maximum battery life and you were prepared sacrifice a little volume to achieve it, I suppose a regulator would be unnecessary.
Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
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