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Old 9th July 2008, 10:10 AM   #1
amhlee is offline amhlee  Hong Kong
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Default Aleph 60 DIY experience

Is there any one has DIY Aleph 60 experience ? Would like to build one in the near future . What is the value appropriate for R1 and R8 on the service manual. I read the manual and apparently no mention of the value of the resistor.
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Old 9th July 2008, 10:32 AM   #2
Peppe is offline Peppe  Italy
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Hi,

you will not find all the information on the manual.

googling your question I found more link like this:

http://www.diyaudio.com/forums/showt...3012#post13012

Cheers
Peppe
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Old 9th July 2008, 12:05 PM   #3
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Assuming you mean the 2 resistors at the input differential :

the one between the source and gate of the negative input 9610 adds a little DC, this further opens the MOSFET and more current will flow out of the drain.
The input differential is CCS by the top 9610 (Q3 ?), if more current flows out of the negative input MOSFET less current will flow through the + input one.
Less current through the + input MOSFET means less current through the 392 Ohm resistor at the bottom=> less voltage drop across it.
That closes the driver side of the output stage=> lower DC level.

The 2nd resistor, the one from source to drain of the - input device, makes current flow from the output of the constant current source(Q3 again ?) to the negative rail.
A small DC current does nothing to lower the - DC voltage on the other side, because there is a BIG negative DC powersupply on yonder side.
But there's a voltage ripple superemposed on the rails, both on the positive rail and the negative one, caused by the bridge rectifier diodes charging the powersupply caps at a 100Hz speed and the quiescent current sucking the lytic caps dry on both rails.
The IRF9610 CCS (Q3 ? once again) is a bit of a simpleton, when the + rail voltage fluctuates a little the voltage level on the drain side of the CCS also does.
The beauty is that the ripple on the positive rail is exactly 180 degrees out of phase from the one on the negative rail, due to the operation of the bridge rectifier.
So, when there's some current flowing from the output of the CCS to the negative rail it's adding the ripple from the + rail to - rail, that lowers the ripple level across the input differential, et voila : a higher Power Supply Rejection Ratio level !
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Old 18th July 2008, 05:35 PM   #4
amhlee is offline amhlee  Hong Kong
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Thank you ....
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