Aleph J Case - would heatsink be ok?

[dakku]

Hi All,

I have 2 of these cases, the dimensions are:

External:
width: 211mm
height: 90mm
depth: 257mm

Internal:
width: 161mm
height: 84mm
depth: 246mm

Pics attached..

I am looking to build 2 mono Aleph J amps using these Cases and had a couple of questions:

- Would the case be sufficient to accommodate 200VA Transformer + rectifier (inc caps) + mono Aleph J
- Would the heatsink be sufficient?
- How can I mount a mono Aleph J so i can use both left and right heatsinks?

Regards

 

[Zen Mod]

better give precise dims for heatsinks

 

[dakku]

Hi Zen Mod,
I will post measurements of the heatsinks.
Here is what they look like..

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

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

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

Height of the heatsink is 90mm and length is 256mm

 

[dakku]

is there any downside (sound quality / interference) of mounting mosfets like this?

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

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

 

[WalterW]

I think the heatsinks are not big enough, I see ext. width 211mm- internal width 161mm = 50 mm for the sinks. so 25 mm each for the length of the fins.
So I guess they will be around 0.7 C/W, maybe worse...
Aleph J mono is 4 outputs around 25 Watt biased, so 100 Watt. 100 x (0.7/2)= 35 degrees Celsius above room temperature.
Also the DIYAudio PCB can not be used, so you have to make your own PCBs with 2 outputs a side.

 

[dakku]

Also the DIYAudio PCB can not be used, so you have to make your own PCBs with 2 outputs a side.

would it not work with extension pigtails like shown in the example pic?

 

[WalterW]

Maybe it works, but please don't twist the wires and place the gatestopper resistor close to the MOSFETs, so not on PCB, but I don't like it
Chance of parasitic oscillation.... but hey, I'm used to build RF stuff.
Maybe ZM can tell?

 

[Zen Mod]

it'll work

made exactly like that zillion times already

though - it's always best to have gate resistor ditto at mosfet pin

also , from experience , there is no so desperate need for tight thermal coupling between upper and lower mosfets

btw. example how its best made , for multiple output pairs :

if sole output pair is used (one IRFP150 is practically two IRFP240 in one case) , all you need is 2 thick and one thin wire per mosfet