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Aleph J-X

This article is intended to provide information on building the Aleph J-X

Origin of AJX Discussion

Link to Forum Discussion

Amp Board Availability

"A single board (2 x AJ channels + daughter board) would be good for 100W one AJ-X channel." -Peter Daniel phdaniel@sympatico.ca

Group Buy
Group Buy 2nd run

Photos of AJX Boards

Post #266
Photos of AJX Boards

Transistors and their Matching, Compatibility or Substitution

Nelson Pass:
IRFP240's are such common parts, it's hard to imagine why anybody would bother selling fakes. You can check them
by measuring Vgs, and see if they fall in the range of about 4.5 volts at 1 amp.
Mosfet Matching
Q5-Q6-Q7-Q8 should be matched to .1 Vgs or better.

Bill of Materials

Resistor Recommendations:

Dale CMF50-
They fit board nicely and sound pretty decent. I used them for F5 and didn't notice much difference when switching to Caddock/Vishays. -PD
Rs and Rg

I use 10k for Rs, someone else uses 22k, I think.

Rg depends on the output power. If you are using 4 MOSFETs for an X, then 33R 3W is absolute minimum, and I would not hesistate to use 5W. For high power versions, I have been using 100R, 100W Caddock TO247s.

So I suggest leaving Rg out of the board, and connect them at the speaker terminals (or power supply ground). But it's a matter of taste.

Patrick (EUVL)

Component Designation|Description|

Power Supply

+-24v Power Supply

Transformer: 18+18 400VA minimum for Aleph J-X using a quality, conservatively rate transformer like Plitron or Antek. 600VA highly recommended. Higher VA is ok.

C-R-C Filter Section:

Universal Power Supply available from- phdaniel@sympatico.ca

Constant Current Source (CCS)
To refresh everybody's memory, I'm attaching proposed FE schematic for the X version.

The value of Rp/P1 was never discussed in depth, and since J74 as CCS was EUVL's idea, you need to contact him directly for any suggestions. In fact Rp is a buffer resistance for P1 and it's value will depend how much adjustment range you require there. You might not need Rp at all; I needed something to 'go over' a trace and thought that instead of a jumper additional resistor could be handy

I guess experimenting would be most recommended action here.

In case you are using J74 for CCS, Q2 is not needed and so all the other parts 'around' it, including R5.

Front End CCS Schematic ...Peter Daniel
Heat Sinks
With 1.8A bias per side is about 180 watts per ch. Mount the parallel FETs on the same sink (Q5 with Q6, Q7 with Q8).

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