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Old 18th January 2005, 07:51 PM   #1
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Default Remote mosfet ouput stage

Hi All

I need to place an A5 in a cupboard (due to WAF)

I am considering placing the heatsinks with the output mosfet and their gate and source resistors outside the cupboard in free air (but still out of view) all other circuitry , inc power supply would remain in the cupboard .
My question is basically how long can these leads/cables to the output stage be,?.
The heatsinks would have the mosfets attached along with a small pcb for each bank of 3 mosfets to hold the above mentioned resistors immediately adjacent to them.(Mark Finnis design)

I dont want to mount all the active circuitry outboard if possible due to space constraints.
Ideally I would like to get a distance of 600mm or so.


Thanks in advance.
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Old 18th January 2005, 07:59 PM   #2
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I would just split the psu out, and have all the other circuitry mounted on the heatsinks. The actual circuit isn't that big, it's the caps and traffo that take all the room.
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Old 18th January 2005, 09:41 PM   #3
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You would be surprised how far you can stretch the leads
before it gets unstable. But the above advice is the best way
to go about it.
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Old 18th January 2005, 10:13 PM   #4
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I heartily second Pinkmouse's comment. My amplifier chassis barely takes up any more room than the minimum required for the heat sinks. See my new thread "Another Aleph-X":

Another Aleph-X

Jeremy
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Old 19th January 2005, 03:54 AM   #5
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Hi all and thanks for the replies

Does anybody think 2 metres between driver boards and outpaut stage is stretching the friendship, remember the output boards have the reistors to the irf240's on them and hopefully this will avoid the amp becoming unstable, (i have used a few pF acroos the source (I think) in the past to cure oscillation on another mosfet amp bit IFIRC the sound was dulled by the inclusion.

Cheers from downunder
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Old 20th January 2005, 01:41 AM   #6
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I would call that stretching the friendship - but if you place
the Gate to V- resistor with the output stage and the cap
which whould be across the npn transistor on the positive
output current source, then it probably would work, sez I.

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Old 20th January 2005, 11:16 AM   #7
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Hi
Nelson, Many thanks for the reply and advice, I will most likely be following pinkmouses suggestion when my new (larger) heatsinks arrive.

Mark Finnis will be dropping in for a listen when the system is "sorted out " and I have put aside a fine red (Western Australian Shiraz) for the occasion to toast to your health and generosity, particularly in respect to support and encouragement for the Aleph projects..

Cheers and excessive health to you..
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