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Old 10th November 2008, 09:19 AM   #1
cloud is offline cloud  United States
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Default Output Devices !

If a Aleph-30 uses 6) IRFP240 devices per channel and the Aleph-60 uses 12 ! What would be the out-come in using 8 ? Based on the Brian GT pcb's what would be the result when using a single 500va 2x25v trans and 132000uf per channel ?
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Old 10th November 2008, 09:59 AM   #2
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Aleph-40?

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Old 10th November 2008, 10:20 AM   #3
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The reason for the above question's are 1st those are the parts I have aquired over time ! Also I would like to have better spacing of the output devices being mounted to the output pcb's ect.... And last I do not believe my heatsinks can handle 12 IRF's !
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Old 10th November 2008, 12:27 PM   #4
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Quote:
Originally posted by cloud
[snip]And last I do not believe my heatsinks can handle 12 IRF's !

You mean mounting space wise or power wise?

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Old 10th November 2008, 04:57 PM   #5
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Power-wise ! My original goal was to construct a stereo amp like the Volksamp-30, Hoping for a little more power I thougt to construct something between a Volks-30 and a stereo version 60. Using 8 devices per ch would the above transformer be ok ?
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Old 10th November 2008, 10:08 PM   #6
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Go for it.

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Old 10th November 2008, 10:08 PM   #7
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With 25V secondaries, you'd end up with 32-33 volts after rectification/caps. You could safely bias it to 3-4 amps, but you'd have to make sure you can dissipate the heat. 4 amp bias@32V with 8 outputs, would give you roughly 260watts dissipation, and well in the safety range for fet reliability (depends on the heatsinking). 50w@8ohm, 100w@4ohm. Brians main amp board would be fine, but you'd have to P2P the output stage. If you give us the dimensions of your heatsinks that would narrow it down a bit.


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Old 10th November 2008, 10:25 PM   #8
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I have 2 heatsinks each one is 1.375" tall w/1.0" fins spaced roughly 0.25" apart ! The length is 17.0" and the hieght is 8.0" Also I had planed on using the BrianGT output pcb's ! Being designed for 3 devices each my plan was to omit the center device. Again hoping for better spacing and less heat ! The sinks in question un-painted or anodized, they were purchased from surplus ect.... If they are not large enought please point me in a direction for something more ideal ! Also if the heatsinks were to be used at say a 45 degree angle as aposed to 90 would this help to improve there effiency ?????
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Old 10th November 2008, 10:38 PM   #9
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You would probably want to limit bias to 3 amps, for 190watts dissipation per channel. The sinks are big, but the fin height may be the limitation here, you'd probably be alright, just keep an eye on fet temps. Build it, test it, rebuild if necessary.
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Old 10th November 2008, 10:57 PM   #10
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Being fan assisted and at a 45 degree angle would this help enough to run at a 4.0 bias point ? Picture a triangle shaped enclosure with the top chopped off. Now with some portion of the top being flat mounting a couple fans to cool the interior as well as assisting the sinks, would not the draw be enough to improve cooling ect....
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