aleph 2 questions (beginner)

[Luke]

hi all,

Ive been reading this forum for a few months now and decided to give my first DIY project a whirl. Im big Pass fan and decided the only way to listen to one of his amps was to build one . THANKS NELSON!!!

Since this is my first project I have a few questions and yes sorry one is a heatsink question.

I have 12 sinks, 130mm x 160mm x 50mm (5.2 x 6.4 x 2 inches) and starting to doubt if its enough for two monoblocks. Most the aleph 2s on the pass diy forum are a little bigger and wondering if I would need a fan, or should I just go for it and see how it goes?

I need to order some transformers from Plitron, I've decided for 2 X 1kva at 2 x 33 volts. Is this right, as Im ordering new I may as well get the right voltage and VA. im not going to do the pi filter thing so from what Ive read this looks ok?

Found some surplus filter caps out of an old mainframe, they are 4 x 25000 uf / monoblock. Should I try get some more capacitance or will this be ok.

Also never constructed a chassis before and wondering what sort of screws you guys use to mount your fets? Does Digi key supply them?Strange question huh, but its hard finding all that stuff here, or im not looking in the right place. Just dont want it to look butch with big holes going through the sinks. Gonna use IRFP240s I hope.

probably a couple of months from getting everything together but look forward to showing off my new mono blocks

thanks arthur

[marjan]

Arthur
If yor fins are runing vertical at 160mm side you should bi fine with 3 per side of monoblock (don`t know what they look like). It will be deep (390mm) and construction will be litle more complecs, but heat disipation should be suficiente. My sinks 200x300mm per side and mesured heat is aprox. 59-61°C and your fins are even longer than my.
I allso used 33 0 33 toroid 1,5kw and 132 000uF. On the dc rails there is 44,3 + -.
Good luck
rgds Marijan

[Luke]

Hi Marijan,

My sinks are very close to yours in size. Each fin will about 160 x 400 so think it will run at same temp as yours.
Looks like Ive got the hard bits sorted. Now need to sort my pcbs, semis etc.

thanks Arthur

[fcel]

Check out "useful tools and technique" thread for info on building the chassis since you have never build the chassis before. My guess is you'll probably spend more than 50% of the time building the chassis - do some planning first. Use 6-32 screws for the FET's. You can get them from Home Depot or any hardware stores.

[Luke]

Fcel,

Thanks for the tip, will check out tools and techniques.
Embarrasing question is 6-32 a size or quantity.
Will I need to taper the holes or just drill and use self taping.
I used to skip metal work classes cos I was so bad, wish Id gone now.

thanks Arthur

[Jason Hubbard]

When you drill the holes ensure they are countersunk, else a ridge around the rim of the hole will prevent the FET's from bolting down flush to the surface of the heatsink.

I've used both self tappers and standard M3 screws for mounting output devices - either have been satisfactory

[Luke]

thanks Jason,


Will do the M3 thing and tap the holes I think.


ta ab

[Narcisse91]

Originally posted by Luke
Fcel,

Thanks for the tip, will check out tools and techniques.
Embarrasing question is 6-32 a size or quantity.
Will I need to taper the holes or just drill and use self taping.
I used to skip metal work classes cos I was so bad, wish Id gone now.

thanks Arthur

6-32 is a size and thread width. If you go shopping for screws, you'll see some clearly labelled 6-32, so you'll know when you've found them.

When I'm working with heatsinks, I've found drilling a hole, then tapping with a tap handle (as opposed to self-tapping screws) and just using bolts works very well.

[fcel]

Arthur,
Here is another thread that might be helpful in terms of building the chassis.
http://diyaudio.com/forums/showthrea...&pagenumber=10 Check out the thread starting from 4/20/02 at 11:19am. You may notice that I was asking the same questions that you were asking now. It helps me a lot and I thought you may like to read it too. I'm sure there are other helpful threads but I happen to know where I post my questions and I can find it.

[Luke]

Fcel,

checked out the post. Very usefull. I will probably get a tap and do it properly.

Narcisse,

Think here I need M3 as suggested by Jason.
Got all my angle brackets cut and drilled, so reay to assemble the sinks.

Thanks for the posts.