[CaptBubba]

Ah, slowly but surely. After seeing that wonderfull soldering job on the Cmoy amp lower on this forum, I went back and re-did ALL of my connections in my amp, it looks nothing like what it used to. Oh, btw, what's the best place to order some OPA 132s and a decent POT, say a noble, from?

I'm one of those people that like to keep things cool. My Szekeres amp I went ahead and mounted an obsene heatsink. Its about 5cm by 13cm and is hooked up to the mosfets via a short length of aluminum. Right now I don't have any silicone paste on it. The heatsink gets only very slightly warm, even after 30+ mins of operation (it was/is late and I don't feel like running it more), while the mosfets got hot, probably around 150F. (water did not boil on contact). Now, it bothers me that the chips are so hot and the heatsink doesn't heat up, but I know heat is conducted because the moment I turn the amp off, the mosfets are cool by the time I can get my fingers to them. Is that normal operating temp for MOSFETS? I guess when I get the silicone things should be better.

I finaly have the case too. I got out the saws and sand paper and went to town. I have found some wonderfull wood that just got thrown out while we were building a deck. It has knots and such, so that's why it isn't in the deck, but boy, sanded down this stuff makes a case to be proud of. I promise I'll post pics as soon as I can get a hold of out digital camera.

Ah, it feels good to ramble.

 

[Apheared]

ramble on... and now's the time, the time is now... to sing my song...

heh sorry..

5x13cm, sounds like my "summer mod".. an old tall vane P-III heatsink with the alignment pins sanded off and bolted to the back with a layer of copper grease, and the mosfets bolted on the other side with Bergquist Sil-Pad K10s (non-conductive transistor heat transfer pads) The heatsink gets hot you don't want to touch it.

Even so, 150F is a dream for me... I'm runnin, even with this config, 90C/195F... it's all about your source resistors/CCS.. (and if your box is vented!

) 150F is about half the breakdown rating of that mosfet. You're doin great!

 

[rickcr42]

Man I really gotta post some pics of my Szekeres

You want heat sinks,we GOT heat sinks

Big mother 3X5X1,but can't see it man

Tucked away inside , ****load of holes in the chassis cover over the 'sink

And the "look" is totally retro

hammertone finish , big ass toggle switches , bakelite knob ,no LED but NEON lamp

cool as ****

 

[Serow]

I picked up two low-voltage Peltier junctions approx 2 inches square from a surplus store... Now I just have to decide to build something hot enough to use them, maybe a small speaker amp

.

 

[CaptBubba]

Apheared, I've got ya really beat now. Before I was using very thin aluminium flashing to connect the mosfets to the heatsink. Now I switched to 2mil aluminum, and boy what a difference. The entire array is only warm to the touch, including the MOSFETS. That's after two hours of operation (yes, it is actualy on). I used an old Athlon heatsink and have 20 ohm source resitors with the MOSFETs biased at 10V. I would guess it is around 25-40C. The regulator on the other hand gets HOT, the sucker draws .55A at idle. I'm getting a little cross-talk, but I suspect that is from the way I have my jacks temporaraly mounted. Oh, and there's no reason to apologise for a little zepp.


The case is coming along great too. I shellaced the wood (that's a fun word to say), and it looks purty. The only trouble I am having is finding jacks to go through the wood. I found a deep panel 1/4 jack, but am having problems locating other hardware. If anyone would happen to know of some stuff that can be mounted in 1/2inch thick wood, I'd love to know. I've found a combination of drill bits that lets me mount everything I have (and create a nifty countersunk look) , but I don't feel like doing it now, especialy if I don't have to, but I may, it looks really profesional.

Oh, and a little warning about Peltier coolers. They actualy increse the need for heat dissapation. What are they rated, 10W maybe? Just remember that you have to dissapate the heat from both the chip and the peltier. I've seen overclocked computers that use them, but most who do opt for water cooling.

 

[Possum]

Definitely use a very large heatsink on the peltiers. If the hot side of the peltiers aren't dissipating heat fast enough, then the peltier will end up heating the cold side too (you can see this happen by hooking a bare peltier up to a voltage source and feeling both sides, carefully.

Also adjust the voltage supplied to the peltiers so the cooling is only moderate and doesn't cool to the point where condensation will occur if the whole peltier setup isn't properly insulated.. I've had experiences where a homemade CPU peltier assembly dripped water, frying my video card last year after I moved home from school, since the weather at home is much more humid. (same thing almost happened this year

).

 

[Serow]

Possum, what voltage range would you be talking about? There are no markings on the units.

 

[Possum]

Doh...

I guess you'd have to try different voltages with the peltier in the whole setup to see if the temperature is cool enough. Start with very small voltages and work your way up, since you can probably notice the chip and cold side getting cooler and cooler to a point. If you start too high, your heatsink may not be able to dissipate the heat and you'd just see very high temperatures.

 

[Apheared]

Bubba, that's pretty damn cool for 20 ohm source resistors! (in both senses)... although remember the magic of it all... get it too cool and it might lose that sound, silicon devices are so fickle... (mine big main Szekeres runs about 625mA idle, although man the inrush at turn on, closer to 2.5A!)

As for deep panel mounts, ow.. yea the 1/4" headphone is probably the easy one to find... toggles, well, they don't work if the bushing is a couple inches long... that's why you can't find em. You can find deep panel mount rocker snap-ins, but other than for power it'll probably not look the way you want... I'd stick with the fat bit/size-of-bushing bit technique to make the stair-stepped countersunk taps.. alot more work but in the end will look so sweet... (and depending on wood be careful, just as you get it all nice, that thin 1/8" layer you left for bolting down on cracks or snaps off and you'll cry!)

Another option is to use shaft extenders, but this only works with rotary controls/switches. Another option is to make the faceplate metal and have a thin wood overlay... have the controls mounted on the metal behind it and just stick thru the wood, not actually mounted to it.

 

[CaptBubba]

The darn cross-feed thing is coming through the power supply and through the resistors to ground at the output, but the power supply is the biggest culprit. Looks like I'll have to go dual power supplys and solve both problems (an excuse to build something else, yay!). Heh, you know your a perfectionist when you try to get rid of cross feed, but are planning to add one before the amp.

I have a bit larger margin of error than that. Most of the fittings I have use 1/4 bushings. If I screw up I can always just rebuild the case, which would take 30mins or so. I have access to a drill press, so I should be able to make accurate depth holes. My mother will be back soon and will bring home the digital camera, so I'll take some pics and post them, umn do you know a place to store images, large ones (400K)?