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Old 29th March 2013, 05:53 PM   #141
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In a Boominator ambient temperature can climb to 35-40 degrees so a vastly oversized heat sink like a quarter brick quarter inch height is always a good idea. Especially since they cost very little and are an industry standard so it always have the same pre-made holes and you can source them from many different places.

You can even get ultra-low cost snap-in mounting bracket for these standard brick heat sinks. I realize that a flat piece of aluminium 3mm thick of the same size as the pcb would be more than enough heat sinking but that would actually cost several times more to get cut in size and pre-drilled with holes than these industry standard ones.

But no, the full 2x50W would be the goal. Although only used when used with batteries in series or a dc-dc converter.

Many of the better coils especially of the slightly lower cost type are also through-hole and would benefit from being on the opposite side as well so that their emitted noise basically only sees the ground plane.

Last edited by Saturnus; 29th March 2013 at 06:14 PM.
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Old 29th March 2013, 06:57 PM   #142
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I did a quick search on Digikey for "half brick" and immediately got a hit for a low cost heatsink.

A 4.7 deg C/watt (natural cooling), 61 mm x 58 mm x 24 mm (fins) aluminum heatsink with pre-drilled holes is $3.65ea in stock. Very nice! Probably cannot handle more than 10 watts, but perfect size for a class D amp.

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Old 29th March 2013, 07:04 PM   #143
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Told you they were under $5 each in single quantity. Simply unheard of price for almost any other kind of heat sink.

To get a little distance to the heatsink a double adhesive thermal pad could be used. They come in sizes that roughly match the chip (a little oversized but that doesn't matter too much) and in thickness' from 1mm to 5mm with 1 or 2 being the most obvious choices.

Thermal conductivity is over the heatsink's capacity.

http://www.digikey.com/product-detai...686-ND/3300344

Also cost next to nothing (under $0.50).

Last edited by Saturnus; 29th March 2013 at 07:17 PM.
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Old 30th March 2013, 01:52 AM   #144
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Half brick is $3.65 but full brick jumps to $21 ea! What's the deal with that? You could buy two halves and be better off.
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Old 30th March 2013, 01:59 AM   #145
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Default Update on TPA3116D2 build

So I squeezed in some time between waking up and going to work to solder the 3116 onto the PCB this morning. Got it done but was in a rush and of course it did not work when I fired it up for the first time. I hate leaving a nonworking build because of time constraints. Anyhow, had more time after getting home to go over it with a loupe and continuity checker and found a microscopic solder bridge between the bootstrap capacitor and the Vcc rail. Need to rework it with some solder braid. Crossing my fingers....
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Old 30th March 2013, 03:53 AM   #146
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Default TPA3116D2 is a Success!

Yep that solder bridge was the problem. I had to take an xacto knife to break it - solder wick could not remove it. Powered it up and it works like a champ. It sounds great. So far I can't tell the difference between this and the 3118 without taking the volume up. It's night time so the extreme volume would not be very good to try out now. I owe a Big Thanks to Dug for his help and providing the PCB.
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Last edited by xrk971; 30th March 2013 at 04:22 AM.
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Old 30th March 2013, 06:34 AM   #147
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Quote:
Originally Posted by xrk971 View Post
Half brick is $3.65 but full brick jumps to $21 ea! What's the deal with that? You could buy two halves and be better off.
I think it might because the full brick is an old standard. Think of it similar to a 5.25" hdd. Would be difficult and expensive to find. These days 3.5" and 2.5" are the used standards much as the half and quarter bricks being extremely cheap.
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Old 30th March 2013, 07:51 AM   #148
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If you really want to get 50 watts/channel into 4 ohm load with the 3116 you will need a real power supply. Laptop 19 volt, 4.65 amp smps bricks are great because they are cheap ($10) and compact but will only provide 90 watts or about 40 watts/ch with inefficiency. To eek out the remaining 10 watts per channel will cost an extra $25 for a real power supply. Is it worth it? Probably not, but if you had to do it, the Meanwell smps at 24 volts and 6.5 amps will provide plenty of power and costs $35 and is about the cheapest ps for this level. S-150-24: MEAN WELL: Power Supplies & Wall Adapters
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Old 30th March 2013, 08:16 AM   #149
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Quote:
Originally Posted by xrk971 View Post
If you really want to get 50 watts/channel into 4 ohm load with the 3116 you will need a real power supply.


I would not dream of ever reconnecting my system to grid power. It's completely solar powered and runs directly on batteries with a 1F stiffener cap.

For me the 50w/channel would be at 24V into 8 ohm speakers. The 24V would be with 2 batteries in series so effective voltage could reach just below 27V. And 8 ohm impedance would actually be real live speakers that could reach 6.4 ohm at impedance minimum. It would still only be about 45w/channel before audible clipping, so we're still on the safe side here with 10% margin.

Also remember that at 19V 5A laptop brick is probably far more than you actually need. Average level in music is about 9-10dB lower than RMS level as an industry standard. That's why class D amps are so much more effective than class AB amps in the first place. Peak or even RMS efficiency is irrelevant with music, it's the efficiency at 10% of RMS output and lower that is important. And here class AB amps generally falls to 18-22% maximum efficiency while class D amp like the TPA3116D2 remains at 76-82% efficiency.

Btw, the above is one of the reasons I am so interested in the TPA3116D2 in the first place. It's got one of the lowest quiescent currents on the marked at only 20mA (@12V, 32mA@24V) and therefore also one of the very best real life efficiency ratings. And it even has the option to improve low power efficiency by using the 1PSW modulation option that basically transform it into a single ended amp at very low power levels with higher THD, yes, but with much improved sound quality and efficiency.

Last edited by Saturnus; 30th March 2013 at 08:44 AM.
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Old 30th March 2013, 12:01 PM   #150
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Saturnus,
The use of two SLA's did cross my head and are actually very reasonably priced. Do you live out away from the grid or is it just a matter of principle not to use the electricity "from the tap"? I did not realize the 3116 has such good efficiency ratings and you are right about real music listening levels and efficiency. I should connect it to some SLA's to see how ling it can run... For camping or powering a stereo at a remote place like a cabin or outpost, the 3116 seems ideal. The SE modulation scheme does get you higher efficiency and the amp has such low THD specs to start with, I don't even think I would notice - although the modulation scheme now involves a zero crossing which will surely change the character of the sound to maybe like a class B amp?

I finally made a proper heatsink now I can push higher powers
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Last edited by xrk971; 30th March 2013 at 12:21 PM.
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