My aleph 2 project

[Jean]

Hello,

This is going to be my first Class A amplifier, I finally got around to getting all the missing components for the driver and output boards. I just need to order output fets and heatsinks and start building my chassis.

Here is a picture of the driver board, I run into a small problem. If you can see in the picture, I can't fit heatsink for Q1 driver. I might have to replace 220uf caps with different kind (smaller diameter).



Capacitors and trasformers won't be a problem, I am going with shielded Victoria Magnetics or Plitron depending on availability in the next month or so.

Heatsinks I am still deciding on, 2 11x11 R-Theata per monoblock or 2 Conrad 30cm by 15cm ridged heatsinks per monoblock

[Jean]

Here are some graphs of the heatsinks I plan on using, two per channel. They are double flanged heatsinks, 300mm in length and 151 in height, 46mm fins.



Thermal Resistance C/Watt for 80 °C rise is 0.25.

Will this be enough ?

Picture of the heatsink - http://www.conradheatsinks.com/images/2005_c.JPG

[moe29]

it may not look as cool, but just stand the MOSFET up, it doesn't
have to be on the board like the others. I don't think you'll find
a cap much smaller than what you're using now.
(you don't really need to use heat sink, but it doesn't hurt)

[bigparsnip]

Hi, could you not just file the hole a littel ont eh heatsink so that it lines up withthe one on the board, as it doesn't look like the transistor quite reaches up as far as the heatsink, so you could be ok.

(Alternatively, you could remove a small part of the heatsink and trasistor next to the capacitor whihc should allow it to fit with out any damage to the part)

[Jean]

I am going to see what I can do later today. What about those heatsinks, any input on those ?

Thanks.

[bigparsnip]

What sort of rail voltages will you be running this at, and what bias currents?

As far as the conrad heatsinks go they seem very good quality to me, and I was thinking of using some of the MF35-151's for my (hopefully) upcoming aleph-x's. Just one question, why are you going for the flanged model rather than the plain flat backed? If you are using plastic package devices I don't realy see the need for the mounting flanges, and it does limit you to a slightly smaller heatsink overall.

[jleaman]

im building the aleph 2's also 2 x mono block's all i need to do is the chassis. that is all..

http://24.70.80.252/gallery/album21

[Jean]

Originally posted by bigparsnip
What sort of rail voltages will you be running this at, and what bias currents?

As far as the conrad heatsinks go they seem very good quality to me, and I was thinking of using some of the MF35-151's for my (hopefully) upcoming aleph-x's. Just one question, why are you going for the flanged model rather than the plain flat backed? If you are using plastic package devices I don't realy see the need for the mounting flanges, and it does limit you to a slightly smaller heatsink overall.

I am looking for 45volt rails, as close to the original as possible. I think with the flanged heatsinks i'll have less of a chance to screw up and drill holes right through the heatsink. Also, I could use those flanges as part of the chassis structure and mount the driver board and or caps on them.

How does it limit me to a slightly smaller hearsink, i think if anything it would have larger surface area ?

[Variac]

Couldn't you just have the leads of the cappacitor a bit longer so it is slightly above the circuit board? Then the heatsink appears to fit under the cap.

[Brian Donaldson]

File the pinchy little heat sink to clear the cap and be done with it.

Looks good. If you can keep the magic smoke in the fets at power up, it'll sound great. (to others. It'll be pure magic to you)