Aleph-X: High-Power Version

[labjr]

Regarding this spreadsheet.


x berekening-nania v3 b.zip

I thought the RMS output power was about half of the peak, not .707

Correct me if I'm wrong.

[roddyama]

Originally posted by labjr
Regarding this spreadsheet.


x berekening-nania v3 b.zip

I thought the RMS output power was about half of the peak, not .707

Correct me if I'm wrong.

Here is the comment from the author of the original spreadsheet on this version #3.
http://www.diyaudio.com/forums/showt...874#post275874

[wuffwaff]

Rms power = rms voltage x rms current = (peak voltage/ 2^0.5) x (peak current/2^0.5) = peak voltage x peak current / 2

william

[Coulomb]

Thanks Guys, I was thinking of a small intake fan at the bottom suing a temp sense circuit to control it's speed. I will Perforate the top as suggested.

See this link below if you want to see more pics of my work in progress. I am working on an awsome CD player you might find interesting. Will be posting more pics tonight.


Thanks

Anthony

http://24.70.80.252/gallery/view_alb...umName=album04

[Brian Donaldson]

Instead of perfing the top, consider drilling small holes in the base of the heat sinks near the middle (of hieght) to exaust air through heat sinks and in effect give you forced air cooling rtheta numbers for the sinks.
That's what I did with my oversized Aleph 2. I haven't ran them with the case closed yet to see how much of a difference it makes, but It sounds good in theory.
The four holes on top and bottm row are for fets, The row in the middle is exaust holes, the thre and four on the sides are for turret terminals to hold busses.

[Brian Donaldson]

Here's a pic with components.
I fried 3 with static (I think). Good think I bought 100!
I had to rematch.

[Coulomb]

Thanks Brian, I will contemplate your suggestion. On a side note, how does your spouse feel about you using the Dining room table to work on?

Regards

Anthony

[grataku]

Originally posted by Brian Donaldson
Instead of perfing the top, consider drilling small holes in the base of the heat sinks near the middle (of hieght) to exaust air through heat sinks and in effect give you forced air cooling rtheta numbers for the sinks.

You are joking, right? How did you come up with that idea?
You need LOTS of positive air flow to get forced air behavior, and flow needs to happen along the fins not across. I am not a fluid dynamic physicist but I have the feeling that the small holes do absolutely NOTHING at all.

For effective convection you needs lots of open space and constant air velocity.

[Brian Donaldson]

Regardless of direction, airflow will increase dissapation. If for no other reason, Because I'll have cool air between the fins rather than the 160 deg air that is there now.
But the real reason for the fans is to keep the inside (electrolyc caps) cool. Two slabs of 160 deg aluminum and 4 slabs of around 120 deg aluminum will yeild 130 - 140 deg caps.
After I get the case closed, I'll post real measured data and you can decide for yourself. My guess is I can drop sink temp 15 to 20 deg without enough added noise to be noticed.

Check out the R Theta website's r theta calculator. You could reason that rtheta should be proportional to size, but it's not because adjacent fins heat the air in the vacinity of their neighboring fins and decrease temp diff and adversly affect rtheta. But by moving fresh air in, you can reduce that effect.

Grataku,
You are correct that I won't aproach forced air r theta numbers, but I would wager that a small amount of forced airflow through the holes in the sinks will inprove cooling by 50%.

PS that's what I do when she's out of town visiting her family

[Blues]

Hot air rises... so holes on the top cover too will help a lot to dissipate warm air to the amp's surroundings. Holes on the bottom plate will force some cold air into the box as the warm air rises. At least that's how I remember thermodynamics.

But if you're in TX during summer the noise of airconditioning will be louder than a fan