Aleph-X builder's thread

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#2,704
clarify , what exact AC voltage (full specs - 2x ??Vac , or ??VacCT (center tapped))

even before that , say that 800VA is usually covering up to 250-300W of steady power consumption/dissipation

for that , you need much more outputs per channel , or your amp will be either current starved , or non-reliable

see Babelfish XJ , or JX …….. or whatever (Aleph X servo for Greedy Boyz) for more info
 
#2,706
18Vac per rail will result in something as 22V5dc , loaded

say that you have 250W of dissipation per channel , 4 quadrants of outputs ........ that's 62W5 per quadrant , which calls for no less than 2 mosfets per quadrant , to keep dissipation per device in sane bracket

you must have matched all per quadrant , so matched pairs

though , it demand some thorough planning - what value of source resistors and few other details , to ensure that amp is stable dynamically and temperature-wise

now when you know numbers , try looking for example someone already built

Eric's web page about his Aleph X adventures is good place to start
 
#2,707
Link is in my signature... Some of the images are a bit fuzzy, but all of the text is there for planning an Aleph-X amp. The nice thing about this design is you can easily customize it to suit your specific needs: optimize for 8 ohm load, optimize for 4 ohm load, adjust for specific power output figure.

An 800VA transformer can net you about 125w into either 4R or 8R loads. You'll need to have LOTS of heat sinking for each channel.
 
#2,712
Eric said:
All varieties of this amp use an identical PCB. If you opt for the original 15w version, just stick one mosfet in each corner of the board and you're all set. If you want higher power, you need to parallel the mosfets and use the "Ext" pads on the pcb to do your own wiring off-board.
Click to expand...

I guess this is what I'll do. I was trying to avoid point to point wiring for stability purposes given the high bias currents used but I guess this would be unavoidable.
 
#2,715
I understand your concern - I had that same thought as I was building mine. I wired my parallel mosfets together with 12g solid core 8" "pigtails" that are used for grounding household electrical sockets and wired these directly to the caps in my PSU with 12g stranded wire. Then, I just ran a separate run of smaller gauge wire from the PSU to the circuit board. This way, everything gets its power, but the output stage is wired with heavy wire.
 
#2,716
Eric said:
I understand your concern - I had that same thought as I was building mine. I wired my parallel mosfets together with 12g solid core 8" "pigtails" that are used for grounding household electrical sockets and wired these directly to the caps in my PSU with 12g stranded wire. Then, I just ran a separate run of smaller gauge wire from the PSU to the circuit board. This way, everything gets its power, but the output stage is wired with heavy wire.
Click to expand...

If yours was stable enough then I guess this is sufficient proof for my impending design as well, thanks.
 
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