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Old 13th March 2001, 03:17 PM   #1
hifi is offline hifi  Sweden
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im planing to build an monoblock version ofthe aleph 4-5 and i wonder does the current source and the voltage follower need to be thermally coupled?...i know the inputstage must because they divide their bias current by Vgs...

and how big transformer would be suitable?...400VA for 1 aleph 5 channel and 600VA for an aleph 4??


/micke
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Old 13th March 2001, 11:24 PM   #2
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From what Nelson Pass uses, the Aleph 4 needs a 1000VA transformer and 100mF capacitors for both channels and the Aleph 5 uses 600VA transformer and 120mF caps. So for a monoblock version you can use for aleph 4 500VA tr. and if you can 50mF. For the aleph 5 300VA and 60mF caps.
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Old 14th March 2001, 09:45 PM   #3
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If you look inside a Pass Aleph 5 (stereo) (and they are all basically the same except for the early 0s etc.) there are 3 transistors on each wall. Thus, there is no coupling between current source halves and "the business end". If you look at the monoblocks, you should have two walls for each upper and lower section. Due to the high heat generation, I would assume there is no coupling between them even though it would be ideal to have this. You can save yourself by using double bias stage, but I say life is too short.

What is interesting though is that you need to have each section on the same heatsink or coupled as you say.

As far as transformer sizing, it does not really matter whether you go over or under the original.

Ditto for caps.
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