Can i lower the bias current in the alpeh 5 to reduce power and heat? - diyAudio
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Old 6th March 2001, 02:09 PM   #1
hifi is offline hifi  Sweden
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simply by replacing the 1ohm bias resistors with larger ones seems to work or do i have to alter more of the ciruit?

I dont need more than 30w and i got a +-31v powersupply (288mF kickass...) i got rather hefty cooling but the darn thing runs hot in 5min....


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Old 6th March 2001, 03:58 PM   #2
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Do you have the amp ready or are you going to start making it ? If it is ready making the resistor bigger would help. If you are going to build it you can use less output devices too. Lower bias current is better for the fets you can run them on higher heatsink temperature. It has though higher distortion. So it depends what you can do.
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Old 6th March 2001, 05:41 PM   #3
hifi is offline hifi  Sweden
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i have made the the board but i can still remove some mosfets thats no problem....thoug it will screw upp my matching.....

the problem is that the heatsinks gets to hot to touch in about 5-7min thats to bad.....but since i got then i might aswell use them....and the powersupply....

so what about just removein one of the mosfet per triplet (and the other components envaled) and maybe lower the bias current say with 50->100%

will the distorsion spec go thro the roof?....the output power and heat will drop anyway.....

maybe i will try to build the "hybrid" amp that i found somvere...if it can live of a +-31v suppply and build a better case with proper cooling for the aleph for...

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Old 6th March 2001, 11:26 PM   #4
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Default Lower input voltage


Pick up PSU designer and work out if you can use inductor loaded input to lower the input voltage (so you don't have to buy a different transformer). This will give you average input voltage instead of peak input voltage. Do this as well as changing current will improve your heat issue. Also, you can simply disconnect a set of output devices as suggested. Be sure to also disconnect the gates which will improve your frequency response in the higher end.

Good luck
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Old 7th April 2002, 07:48 PM   #5
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how did it work with runnung the Aleph5 with less mosfets ?

I am dying to build a pair of 4-channel-Alephs, but I want also smaller heat-dissipation...

Energy is expensive... And 8 amps eat a lot !

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