Top ten ways to a better Aleph?

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#144
Thanks. How many watts do they need to handle?

And how huge must my heatsinks be? Everyone goes on and on that you need these huge sinks, but how many c/w do I need?

I really want to have someone qualified for the job to do the semiconductor measuring..
 
#146
EsE said:
How many watts do they need to handle?

And how huge must my heatsinks be? Everyone goes on and on that you need these huge sinks, but how many c/w do I need?
Click to expand...


I understand you are building Aleph 30.

Use 3W size, or bigger if you want, for 0.47 ohm resistors--any make, any type. Use 1/4W size, or greater if you want, for all other resistors--any make, 1% metal film type.

Each Mosfet of Aleph 30 dissipates heat about 13 watts. Meanwhile, Papa always recommends heat sink temperature rise of 25 deg C above room temperature (so, heat sink of 50 deg C with room temp of 25 deg C). This means that you need heat sinks having thermal resistance less than 25/13/1= 1.9C/W when you attach only one Mosfet on the sink. If you plan to attach two Mosfets on one sink, less than 25/13/2= 0.95C/W. If three Mosfets, then 25/13/3= 0.64C/W . . . I believe you could do better calculation than me . . .


:darkside:
 
#147
EsE said:
How many watts do they need to handle? And how huge must my heatsinks be? Everyone goes on and on that you need these huge sinks, but how many c/w do I need?
Click to expand...

The resistors are 3W, which is plenty. Most of the time they
dissipate less than a watt.

The heat sinks should be adequate to hold the temperature
to about 25 deg C above ambient. Loosely figure that the
dissipation of an Aleph is 3 times the output rating and you
can derive a c/w figure

W = watts

Rth = 25 / 3 / W

So for a 50 watt Aleph, you want 25/150 = .16 deg / watt

:redhot:
 
#148
Nelson Pass said:
What I would like to see is some nice 10 uF silver micas
Click to expand...

I've had that line in my head all day, from the mall to the beach, so here goes : for which purpose ?

With a bit of luck and patience, good and cheap applies in particular for diy.
By chance, while shopping for other parts i stumbled on something better than silver mica a few weeks ago, an estimated 50 to 60uF.
Downside, it's 8500 pieces in a 34 value range.
I was thinking of assembling a few 1uF superduper caps with them, for the biggest cap size of the lot i'd have to put about 125 in parallel.
 
#153
Jacco,
you are right, since I'm suffering from low attention span syndrome I did not read everything: ground mica & polymer pressed into thin layers, and aluminium foil which they say is conducting much better than a thin silver film! Obviously Thel claims them to be superb, which they better be considering their prohibitive price.

Btw., not everybody seems to be in favour of Mica caps, they have a fairly high DA and some claim they find their sound annoying.

Actually I believe Nelson is on the phone with Cornell Dubilier "as we speak" so we may find out pretty soon how good they really are 😎
 
#157
Yes, I pulled it out of my Aleph 2's many years ago. Full blast they bias at 4 amps and they sound incredible. Be sure you have adaquate heatsinking though as temperature is inversely proportionate to bias current. Aleph 2 is normally ~3 amps bias and runs hot. When you go to 4 amps is going to be blazing hot. I over heatsinked mine when I built them so no issues. They have been running this way for 12 years!

You can also install potentiometer in there and dial it to your liking and also to safe temperature.
 
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#158
I think heatsink is about twice what is needed for these aleph5 mono's. Ambient temp in the room 18c heatsink temp after 3 hours with normal bias is at 21c. So i see no problems here.
 

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