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introducing the black hole


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Yes of course i can mill down the heatsinks. I want something that others can build with

no trouble. The heatsink fins need to be vertical to be efficient, so that ohmite thing

probably won't work, but i can buy a couple from mouser next order to see.

The other problem is that the lme49830 part would sit very low on the heatsink so

the clips probably don't work. Which is why the original part i picked works poorly

as the supplied snap clip only touches half of the part.

Edited by kevin gilmore
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Been doing a bit of searching for a heatsink, it seems that Aavid heatsink is the reference one that national lists. I found a site with a picture of a heatsink that looks really good but haven't been able to find the part number for it. Here is the picture though:

amp40-2.jpg

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I got a response from them about the heatsink, apparently the heatsink itself is manufactured in China and is rather large, then they must mill it down to size. See this image:

heatsinkimage.png

They said they could sell it to me machined down. I'll ask them how much it would be for the same size they are using, in quantity of ~100.

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  • 5 weeks later...

Been spending a bit of time on diyaudio recently and came across a very similar project to this:

http://www.diyaudio.com/forums/solid-state/196932-wire-amp-class-ab-power-amplifier-based-lme49830-lateral-mosfets.html

It has one feature that I particularly like - the ability to have a regulated power supply for the lme49830 front end and choose between the same for the output transistors or a separate unreg supply. I haven't spent the time to read through and see what heatsinks people are using but there may be some info in there.

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I did eventually decide on the ohmite heatsinks, some are on their way to me. Board size increased a bit to 3.6 x 3.6 inches.

the idea of multiple power supplies is something i'll think of, not so hard to do, but really i'm doing this for a headphone

amp, and don't need to run the thing at silly voltages and powers. (not the same heatsinks that the wire uses)

The alfet parts sound so much better than the irf parts...

Edited by kevin gilmore
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sillyness continues

http://gilmore.chem..../blackhole3.jpg

now compatible with both kinds of fet layout GDS and GSD

also usable with darlington bipolars

and either lme49830 or lme49810

lookin good beer.gif

what kind of output voltage could you achieve with dual power supplies?

lme49830 can handle +/-100, as can the alf16. You won't be able to swing all the way to the rails so maybe +/- 95 on the output theoretically. No idea what you would need that much voltage for, and it probably wouldn't work on this pcb as capacitors for that voltage would be a lot larger. Something in the +/-40 volt ballpark should be adequate for almost all speakers I would think.

Edited by cobra_kai
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all the capacitors are 100 volt rated.

possible output transistors sets usable at full voltage

(really, don't do this +/-40V is already more than overkill)

alf16n20w/alf16p20w

2sk1058/2sj162

BUZ901/BUZ906

2sk1529/2sj200

MN2488/MP1620

MJH11020/MJH11019

Edited by kevin gilmore
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In the wire amp thread over at diyaudio they got best results in simulation when feeding the Lme with +10v than the output stage. This is quite simple with a regulated front end ps.

There seems to be a shortage of lateral mosfets at the moment because of the floods in Taiwan, so this might be difficult to build in the next few months.

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Was there any discussion on the amount of power that can be dissipated with them? The datasheet claims 250 watts in the T0-264 package but I am a bit skeptical of that.

There's a spreadsheet somewhere in the first pages with a wide selection of ps voltages and respective power output at different loads.

According to it, the combination could feed over 300w into speaker loads with sufficient heatsinking.

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  • 4 weeks later...
Combine 4 channels with my balanced preamp, and have one serious kickass thing guaranteed to drive anything,

so, can't you drive this from a balanced input signal using a single board?

If so, I'd take the two prototype boards.

edit: nm, it's input voltage is too low for my application.

Edited by luvdunhill
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  • 3 weeks later...

Does anyone know if the Exicon ECW20N20-Z/ECW20P20-Z are rebranded ALF16N20W/ALF16P20W? I've read through the datasheets and they report a few slightly different characteristics (Ciss, Coss, Crss, Ton, Toff), but are otherwise identical down to the unit price.

If they are rebrands, they could be another source for the ALF16 200V parts, which appear to be unobtanium. Newark still has a few 160V parts at least.

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