Alpha Nirvana 39w 8ohm Class A Amp

[andyr]

What is the maximum safe temperature limit in the body of the mosfet that should work?

Hah - that is the $64,000 question!

@Andy do you measure the temperature on case of the body mosfets ? also on the heatsinks? 5U box?
we have the same current about 2.6A.

Yes, my new bias current is ~2.5a, I think, Nikos.

As I use a 20mm diam washer on top of the mosfets ... it is hard to measure the temperature of the body. So I point my laser temp gun at the head of the bolt which clamps the mosfet to the heatsink.

 

[Nikos]

What are your measurements even with the laser on the body of the mosfet but also on the heatsinks?

 

[andyr]

What are your measurements even with the laser on the body of the mosfet but also on the heatsinks?

I will measure that for you tomorrow, Nikos.

 

[Vunce]

The IR temp gun will not give an accurate reading aiming at shiny metal objects like washers and hardware. Apply kapton tape to the washer for better accuracy.

 

[adason]

Be aware that ir sensor and laser pointer originate in two different spots...meeting at a distance. In close proximity, they do not coincide yet. Just my personal observation with my handheld device.

 

[Nikos]

. My assessment is that the operating points of the outputs are on the limit; my view is that dissipating so much heat we should monoblocks; perhaps 4U would be OK but each heatsink could then serve ONE output device, not two. You can see his excellent work at #3045 post in this thread, in fact.

During the beautiful journey of building this particular amplifier for me, I tried to place the mosfets in a common heatsink 41cm x16 x 5 , the ambient temp now in my room in Greece is 29-31 C we always talk about version 4R and I know it's forbidden. The temperature that develops in the body of the mosfet scared me quite a bit. Since I have nothing else hahahah. Τhe transistors of the power supply must not be placed together with the mosfets outputs. I have mentioned this in my previous post...I said NO WAY.....

 

[AKSA]

Nikos,
No more than 100C at the securing bolt, maybe no more than 65C at the top package.

 

[Nikos]

Then I'm fine...I measure on the metal surface of the mosfet about 50C and on the housing on the mosfet about 45 degrees Celsius. This with the second stage setup 40-55C of the controller pwm fan where the fans play much more relaxed and are not heard at a distance of half a meter .
Thanks Mr Hugh.

 

[karucho]

Hi, I found this information about the "Sonus Faber Olympica Nova III" speakers. Maybe it can help @rdb64
Regards

https://www.hifi-voice.com/testy-a-...-podlahove/2332-sonus-faber-olympica-nova-iii