introducing the black hole

[kevin gilmore]

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 December 17, 2011 by kevin gilmore

[cobra_kai]

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:

[n_maher]

Doesn't look like it'd be very easy to attach a TO220 device to that heat sink. Not saying it couldn't be done but the picture clearly shows something pretty different.

[cobra_kai]

lme49830 is not TO-220

http://www.ti.com/li...nk/lme49830.pdf

Anyway I emailed the guys who make the thing in that picture to see if they are willing to tell me the part number. Fingers crossed they are nice...

Edited December 19, 2011 by cobra_kai

[kevin gilmore]

That is the heatsink i want. Have not figured out what it is yet.

[cobra_kai]

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:

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.

[JoaMat]

Heat sink for LME498**:

http://www.aptaudio....PA_Parts_1.html

[kevin gilmore]

why does the simple stuff have to get so complicated sometimes.

[cobra_kai]

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.

[kevin gilmore]

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 January 20, 2012 by kevin gilmore

[MASantos]

While the primary use could be headphone duty, it would be nice to have the option to scale up easily. this wouldn't add much to the board cost.

[kevin gilmore]

current version with the dual power supplies, i still think its a bit silly.

Virtually 100% ground plane.

http://gilmore.chem.northwestern.edu/blackhole2.jpg

[kevin gilmore]

sillyness continues

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

now compatible with both kinds of fet layout GDS and GSD

also usable with darlington bipolars

and either lme49830 or lme49810

[ujamerstand]

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

[cobra_kai]

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

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 January 22, 2012 by cobra_kai

[ujamerstand]

I see. I thought you could increase the voltage in the second stage for some reason...

[cobra_kai]

It makes it so you can use a really nice linear regulated supply for the lme 49830 and an unregulated supply on the output. So you don't have to have a massive regulated ps if you want to power speakers.

[kevin gilmore]

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 January 22, 2012 by kevin gilmore

[ujamerstand]

It makes it so you can use a really nice linear regulated supply for the lme 49830 and an unregulated supply on the output. So you don't have to have a massive regulated ps if you want to power speakers.

Ahh, I see. Got it.

[MASantos]

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.

[cobra_kai]

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.

[kevin gilmore]

There is a shortage of all sorts of transistors these days, and the floods in taiwan probably influence

this very little, who knows. Its a massive pain in the ass to source parts these days.

[MASantos]

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.

[luvdunhill]

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 February 18, 2012 by luvdunhill

[jezz]

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.