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Old 28th October 2001, 03:11 PM   #1
diyAudio Member
Join Date: Oct 2001
Sorry if these are trite questions!
I am thinking about building one of the Alephs (maybe the 4, I love extra power). I would like to know why the 0.47 ohms resistors on the drain of the output mosfets are paralleled after the output mosfet cluster instead of each mosfet having its own resistor. Wouldn't that help with matching issues?
Another question what is the function of C11, the 220uf electrolytic on the -pole of the balanced input? Isn't this cap on the signal path? How important are its sonic characteristics?

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Old 28th October 2001, 08:00 PM   #2
diyAudio Member
Join Date: Oct 2001
Hi dnyt,
the paralleled 0.47R Resistors form the feedbackloop for
the aktive currentsource and the whole amp. The use of more then one resistor makes it easier to have an low value
resistor cheaply and akkurate tolerance.
The 220uF Cap is in the signal path.I think it depends
if you are using sym or asym input. When using sym, take
an MKP Cap with 47nF parallel.
Remember, my opinion - would be nice to hear other comments.
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Old 29th October 2001, 06:20 PM   #3
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Nelson Pass's Avatar
Join Date: Mar 2001
The cap gives the amplifier unity gain at DC and
is used to give low DC offset to the output and
protect the speaker against DC at the input of the
amp. You can safely remove it, but you will find
yourself making adjustments to the offset as the
temperature. The best place for adjustment would
be either R3 or R24 on the Aleph 4 (ref Left channel).

The Aleph 0 had a pot at this location, and no capacitors at all, but there was simply too much field adjustment
required to keep the offset low, and too many users had
DC coming out of preamps.
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Old 15th October 2004, 11:51 AM   #4
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Join Date: Jan 2001
Location: Germany
Does a tantalum cap sound better or worse? I didnīt use a normal electrolytic here.
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Old 15th October 2004, 01:27 PM   #5
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Join Date: Aug 2001
Location: Ingolstadt Germany
Hi Promitheus,

a real tantalum cap distords quite heavily and should NOT be used here. Read the other thread on Aleph Cap for more information.

een ooievaar is geen konijn want zijn oren zijn te klein!
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