Aleph J-X Amp Project

[Peter Daniel]

The shape of things to come

 

[EUVL]

Now you can build a ML33 type monoblock tower by placing each of the main boards on a heatsink, and the daughter board between them in free air, joining them with short pieces of HF wires. And you would be 90% close to my monoblock layout.

http://www.diyaudio.com/forums/showthread.php?postid=1744005#post1744005

http://www.diyaudio.com/forums/attachment.php?s=&postid=1744005&stamp=1234550786




Patrick

 

[Peter Daniel]

Daughter board almost ready. On a right side I placed stock current source, on the left 2SJ74 with a variable source resistor (do I have it right?)

 

[kraljmatjaz]

I'm interested in a stereo set.

Regards,
Boris

 

[SRMcGee]

Peter:

What would be required to make a high powered version of this project?

Regards,
Scott

 

[jrsun]

Daughter board almost ready. On a right side I placed stock current source, on the left 2SJ74 with a variable source resistor (do I have it right?)

Hi Peter,

I would like to have a stereo set of Ax-J, thanks!
Is the wiki ready?

 

[DaveM]

I am in for a set.

 

[Peter Daniel]

PWhat would be required to make a high powered version of this project?

... my AJ-X 100W is more than happy with 1x 2SJ109 driving 16 output MOSFETs in total, with 910R drain resistors. Bandwidth over 300kHz.

 

[JEKYLL]

1 stereo set for me !

 

[EUVL]

> Daughter board almost ready.

A bit too wide for monoblock towers ?
Any chance of keeping the width to 100mm max?

> on the left 2SJ74 with a variable source resistor (do I have it right?)

NO !!

The 2SJ74 source is connected to one end of the trimmer, the other end of which goes to the positive rail. The wiper goes to the J74 gate. That way you can vary Vgs, hence current.


Patrick

 

[Peter Daniel]

Alright, fixed that.

What'd you mean 100mm? It is 85 mm already and I added another set of holes for even tighter fit (the rest of the board can be trimmed). The mounting holes distance at the tighter fit is 69mm and can't be reduced any further. That makes for 300mil output boards spacing when placed side by side. At full length it would be 0.75"

I also moved C5 caps further away to make room for jfet heatsinks.

 

[EUVL]

I didn't realise it was 85mm.
69mm hole centres is fine for my use. Thx.

The current source is now correct, as far as I can tell.
But I think you understand now how it works, right ?
(The Idss of that J74 has therefore to be larger than the required current of the LTP).


Patrick

 

[EUVL]

> That makes for 300mil output boards spacing when placed side by side.

I was thinking of something else ......

http://www.diyaudio.com/forums/showthread.php?postid=1861318#post1861318


Patrick

 

[Peter Daniel]

Yes, I'm thinking about that too, that's why I added another set of holes. The heatsink spacing in my ML chassis is only 3"

What is the recommended pot value for jfet trimpot?

 

[EUVL]

That depends on the Idss of the JFET, the Vgs of the MOSFETs and the drain resistor of the LTP.

But I would start with 100R. In some cases probably 25R is also OK.
One can also replace it with a fixed resistor after trimming.


Patrick

 

[Melon Head]

What is the optimum range of Idss for the jfets?
I am planing on runing three pairs of output mosfets per channel and 4.5A bias.

 

[nopcat]

Count me in for 2 stereo sets plz.

Thanks

 

[Mishkaa]

Does anyone have a good US - based source for suitable heatsinks, or an international source that can reliably deliver here?

 

[flg]

http://www.diyaudio.com/forums/showthread.php?s=&threadid=142917
http://www.diyaudio.com/forums/showthread.php?s=&threadid=146427

http://www.diyaudio.com/forums/showthread.php?s=&threadid=138031

 

[Mishkaa]

Thanks - looks like some good places to start at least.