Aksa Lender P-MOS Hybrid Aleph (ALPHA) Amplifier

And a varistor too.

In other forums, months ago, I wrote:

An externally hosted image should be here but it was not working when we last tested it.


Some weeks ago the very old cables (fabric covered) of the electric company to the building burned -> a phase joined the neutral -> 400 volts!

In the DC Blocker prototype one of the two fuses burned and the varistor too.

Star ground

[URL]http://maty.galeon.com/WP-imagenes/hard/ATL-PSD-08-maty-edition-inside.jpg[/URL]

[IMG] [URL]http://maty.galeon.com/WP-imagenes/hard/ATL-PSD-08-maty-edition-inside-3.jpg[/URL]
 
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I swapped out my input caps (10uF Silmic II and Panasonic 3.3uF 250v MKT) for a Jantzen 5.6uF 400v MKP. And changed the source resistors to metal thin film 1%. It measures the same as before. Listening to it now, I think the sparkle of the highs is better. It’s subtle but there is a difference.
 

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Hi Vunce, great work, have you any pictures and how is the amplifier performing?
Regards

The amplifier is performing very nicely. I’m using speakers on the bench that are not an easy load (4 ohm, low 80’s sensitivity) to an uncomfortable listening level. So, this amp will have no problem “rocking” with 8ohm, 95db and up speakers.
 

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Brilliant, Vunce,

You have marvellous cooling, too. Solid heatsinks, do you cool best with the fins vertical? I assume no fan on them when installed in the case?

Yes, 4R is not the forte for the ALPHA 20. It's a 8R amp. Theoretically you could double the current by halving the Pass CCS sense resistor - no other changes - and it might be OK with those large heatsinks to cope with the heat too.

Congratulations!!

HD
 
Hi X,

My trafo and caps arrived today, I can finish the Juma/Prasi capMx and send some real power to the ALPHA :D

Vunce, what voltage did you settle on for your transformer assuming a 4V loss from the CapMx? Or am I not doing my math correctly? I read through the Easy Peasy CapMx thread quick but it was a little hard for me to follow.

Also got my boards! These are beautiful pieces of work. Thanks again Hugh, X, and JPS for this great amplifier. What a team!
 
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Hi danielrev,

I estimate your heatsink around 0.30C/watt.
With the dissipation of both outputs using 24V rails I estimate each module will create around 75W.
This would increase the heatsink assuming even heat distribution along the heatsink to be 75 x 0.3 = 22.5C.

I assume that inside ambient temperatures in Java would be around 28C. So final temperature would be 50.5C, 22.5C over ambient.

This is acceptable. It will be quite hot but modern mosfets will withstand this temperature for about twenty years.

Go for it - but you will need TWO heatsinks, one for each module.

Cheers,

HD
 
Hi danielrev,

I estimate your heatsink around 0.30C/watt.
With the dissipation of both outputs using 24V rails I estimate each module will create around 75W.
This would increase the heatsink assuming even heat distribution along the heatsink to be 75 x 0.3 = 22.5C.

I assume that inside ambient temperatures in Java would be around 28C. So final temperature would be 50.5C, 22.5C over ambient.

This is acceptable. It will be quite hot but modern mosfets will withstand this temperature for about twenty years.

Go for it - but you will need TWO heatsinks, one for each module.

Cheers,

HD
Hi Hugh thanks for the explanation ,i would try using w/o fan first . if there is no thermal problem i would be happy .
im tempting to build this amp cause no unobtanium jfet and the rest of component i have on my bin .
its recommended to make just single sided board ?