Aleph J illustrated build guide

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#981
Trying to get motivated to start my second build. Transformer question: will the antek, 4218 400VA 18V work OK? The 300VA that I used last time is out of stock?

I have everything else except the back panel parts kit from the store which is "sold Out".
I think I could cob the kit together is I knew the exact part numbers and sources particularly for the
M3 standoffs
M3 bolts for securing PCBs to heatsinks
M3 Mosfet/Diode mounting bolts
M3 fender washers for Mosfet/Diode mounting.
 
#985
I'm getting ready to pull the trigger on a chassis for an upcoming AlephJ build and am thinking about the deluxe 4U. But first a question:

Does the top metal plate and the faceplate function to shield the innards from RF/noise? I envision substituting those with nice wood (allowing for proper ventilation of course) and am hoping not to give up any sound quality…..thanks in advance,

Mario
 
#986
Both are aluminum I think. You could always put some steel plates inside. I enclosed my Toroid on the bottom with the perforated steel plate, and built sides and top from the sections available in the DIY Store to shield the sides and top of the toroid. As my amp sits by itself between the speakers, I'm not overly worried with external RF. I just keep the power cord away from the ICs and speaker cables.
 
#988
If you are still not sure, look at my aleph J build on post #801. It sounds very good with no problems. I am very happy with it. Putting wood on top and bottom will give you a very nice amp indeed, one you can be proud of. It is doubtful you would ever have a problem. Besides it is easy to add foil or something inside if you found you needed it. Go for it.
 
#989
The Deluxe 4U is the way to go - if you want to dress it up a bit, by all means do.

Make sure a different top plate is well ventilated.

Also, get everything working and happy and burnt-in before making any changes. 🙂
 
#993
Some figures after a few hours of listening

- 0,65 amp/device
- offset 0,002V
- 24VDC @ 500VA
- temperature is hot, but i can hold my hands on the heatsinks...... >> 5 secs

I heard some oscillation sounds for a few seconds during listening. It ocurred several times, but i guess that's due to the lazy wiring for this test setup.
(long wires to the mosfets)

By the way, sounds very nice !!!!!
 
#994
Here a crappy picture of the amp working.

The heatsink were found "somewhere".
It looks like a SK102 to me, with about 0.45K/W
They get very warm, but i can keep my hands on 'em. So i guess it's okay !

Regards,
Nick
 

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#996
Aleph J Problem

My Aleph J had been working just great for the last 4 month.
I took it out of my main system, opened it up and (long story) a standoff fell behind the left channel amp board. I loosened the standoff screws and those holding the mosfets and the standoff fell through.
I inadvertently turned the amp on later on without tightening the screws. A fairly loud hum and no sound came from the left speaker. That was about a week ago.
I pm'd 6L6 and he told me that I should check the insulators for the mosfets. I did and they seem fine.
Any suggestions?
I am going to try to send some pictures.
 
#999
The amp ran fine up until I loosened the screws to get the standoff out and then did not tighten them up and turned the amp on. I am wondering that running the amp, for even a brief time, without the mosfets firmly attached to the heat sink, may have damaged either the mosfets of some other component. Could this have happened, and if so, what component(s) would have been vulnerable?
 
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