L'Amp: A simple SIT Amp

[juma]

Hi vdi_nenna,
I think that the main thing that ZM wanted to warn you about is that heat tends to go upwards and if you mount your SITs so high up the heatsink the heat won't spread evenly, and the lower parts of the heatsink will be much cooler i.e. unused and your SITs will needlessly be exposed to much higher temperature. Lowering the position of L-profiles to about 2-3 inches above the bottom would put your SITs in much more comfortable temperature zone.

[flg]

Originally Posted by vdi_nenna

Generg, love your work and your persistance. Keep it up. I have always been interested in your Mu/J2 work.

Case appearance doen't matter. A friend in my audio group saw my system and didn't think much of it on appearance. Once he heard it, he said and I quote, "You can't let the others in the group hear this, you'll have a revolution on your hands." Best compliment I ever received!! Owe it all to you guys and I never take credit for any of it. You are the geniuses!

generg, What he said! Choos (sp?)

[vdi_nenna]

Thanks Juma. I know, but I can't move the L bracket on one of the heat sinks. See pic attached.

On the right heat sink back corner is a set of stacked plates that are not physically flush with the face of the heat sink. It's imperfect. The plates are more or less cometic.
If the L bracket is moved down, the same problem exists because of the plates, except it's half the heat sink in the lateral direction that's not being utilized.

This heat sink was meant for an F5, where there would be more space to mount TO-247 directly on he heat sinks, without the aid of the L bracket.

If I mount the L bracket vertically, that's not good either. Best thing to do is flip the heat sinks and have the bracket be lower, but does that make sense?
Heat distribution is still uneven. It's still not in the middle of the heat sink.

[juma]

Originally Posted by vdi_nenna

... I can't move the L bracket on one of the heat sinks. See pic attached....

Yes, this way or that way there's always something that needs extra care or attention. Never you mind, it won't kill the SITs for sure. It's just that nagging feeling that it could have been made a bit better...

[vdi_nenna]

It's just that nagging feeling...

I know, and thanks to all you for the suggestions and concern.
Why I got stuck with a heat sink like that, I have no idea. Well, maybe because it's surplus.

Thanks again. I'll speak up again after I give it a listen. Hopefully by this weekend.

[juanitox]

cool work! and don't worry so much about the heatsink i have small ones and can lay my hand on it few minutes without "barbecue" effect with 40W on the 2SK82

just to say i found that the SIT needs a good preamp in front of it , i have a passive LDR and it never sound good with it. so i have built a little DC coupled B1 buffer and the combo sounds far better

[vdi_nenna]

Thanks juanitox.

don't worry so much about the heatsink i have small ones and can lay my hand on it few minutes without "barbecue" effect with 40W on the 2SK82

This makes me wonder if my smaller heat sinks, already drilled for TO-03, would have worked. Will take picture and post it. I have 4 of them. They are maybe 5x5x3 inches in size, but have fins in all directions like Mike's photo in L'amp CCS article. Although on visual inspection, not as heavy an extrusion as Mike's heat sink.

Do you have a photo of your amp here?

Found a picture on the web. the one in the back. Not exact, but close. Mine is more like a cube.

Damn.

[juanitox]

this is mine..

[vdi_nenna]

That's it?!?!?! That's all? Tell me they go into the case, please!

Had no idea it could be that small!! The extra heat sink I have are at least that big, maybe bigger.

Also have 8 heat sinks that are bigger than that one, if I take apart my Zen v1. I used the transfo from the Zen 1. It ran at 2 amps.

did I mention I have 2 extra 2sk82s not in use?

Nice wood case.

[KASUMI]

Got the resistors juanitox...thanks
What did you use as an alternative ?