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Class D Switching Power Amplifiers and Power D/A conversion

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Old 17th August 2009, 10:18 PM   #11
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I'm just looking at the orientation of the chips, and wondering "how are they going to mount to the heatsink".... Shouldn't they be rotated 90 degrees and at the edge of the board?

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Old 17th August 2009, 11:02 PM   #12
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Well im planing on a few mounting holes to bolt a 160cm heat sink across all of them.

And why are they supposed to be at the edge of the board?
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Old 17th August 2009, 11:35 PM   #13
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I've noticed this chip too and plan on building 2xPBTL to see how it performs. It'll be interesting to see how it distorts and how it sounds under reasonable limits.

I'm really drawn to how efficient it claims to be and of course how easy it appears to be to implement. An easy way for people to experiment with active loudspeakers?
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Old 18th August 2009, 04:17 AM   #14
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Perhaps a drawing will assist. This is how I am visualising mounting a heatsink. for something capable of 300W I would think it should be external and not inside the case. in order to mount to it easily the chips need to be near the edge of the board.

The rectangles on the left represent how I interpret the orientation of the chips on your board. I can't for the life of me see how you are going to mount these to a single heatsink Maybe I'm missing something but the drawing on the right is how I would do the mounting

edit: Note you could bend the chip legs 90 degrees and use a heatsink with a shelf which would mean that they didn't need to be quite as close to the edge (but still oriented as per my diagram on the right). in this case the chips themselves would be mounted horizontally rather than vertically with respect to the board.

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Old 18th August 2009, 05:57 AM   #15
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are you considering to offer a kit or PCB?
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Old 18th August 2009, 08:37 AM   #16
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The distortion goes down because thats THD+N. This D-class has pretty much no THD distortion, what your seing on that graph is the noise of the amplifier. Because of the switching frequency they create inaudible noise at 300Khz that you see here it can be seen very well because the THD is near nothing.


Oh and wintermute you are probably thinking this is a LM3886 like package. Well if you take a look at the datasheet its simply a SMD chip with a thermal pad on top and needs to be mounted to the heatsink pretty much like a Pentium CPU so to cool it all i do is screw a heatsink against the board and its done as the heatsink is then pressing against the thermal pad on the top of the chip. Also i dont plan to stick the heatsink out the case because these chips just dont get that hot. I ran the test board in to a string of big ceramic power resistors with a bass test, while the resistors ware smoking and burning my table the amp was barely warm. (Oh and let me tell you burning the high temperature ceramic smells really bad)

Oh and as for a kit i guess it would have to be offered preambled then too because most audio hobbyists never soldered a SMD before let alone this thing that has a 0,65mm pin spacing. Not that its that hard to solder these SMDs but you need at least a little SMD experience you you dont mess it up. All you need is a soldering iron,solder sucker and some solder wick(or solder braid whatever you call it) Because the tiny 0,65mm pins are too small to go pin by pin i just drag the iron over the whole side of the chip and just suck up the exsesive solder with the pump and then the solder wick. (I desolder SMDs in a similar way)

EDIT:
For those that are interested here is the datasheet for the chip
Datasheet: http://focus.ti.com/lit/ds/symlink/tas5630.pdf
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Old 18th August 2009, 12:32 PM   #17
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Ahhh that explains it!! sorry for confusing the issue, a look at the datasheet cleared things up I was assuming it was in a SIL type package yes a bit like an LM3886, though I realised while I was at work this afternoon (brain was obviously thinking about non-work stuff) were 7 pads on the pcb for the chip, was not enough for two channels and I was thinking I needed to check the data sheet!

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Old 18th August 2009, 12:46 PM   #18
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7 pads?.....Oh so you confused the input connector with a chip. Yeah i agree if those ware chips it would be the worst position to put them in.

This chip being SMD is a nice advantage since the big capacitors and all that are on the other side of the board where they are not in the way of the heatsink.

I love that these chips are so simple yet so powerful. This D class chip is almost as simple to wire up as a usual AB-class chips but dish out heaps of power while heating much less.Without the B class distortion.(This amazing chip just came out recently)

But i can imagine the tiny SMD package puts off a lot of hobbyists.Since building DIY amps is mostly all about trough hole components.
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Old 18th August 2009, 01:22 PM   #19
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yep the three rows of seven pads on the left side of the board I thought were the pads for the chip...... doh

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Old 18th August 2009, 02:05 PM   #20
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Quote:
Because of the switching frequency they create inaudible noise at 300Khz that you see here it can be seen very well because the THD is near nothing.
THD+N at 1kHz usually uses a bandpass from about 100Hz to 20kHz and as these guys love to show nice numbers (see output power ) they certainly used it. So, no 300kHz hash messing up your THD+N figures.

Have fun, Hannes
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