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Aleph 2 Help
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Old 8th July 2019, 12:44 PM   #1
hifileslie is offline hifileslie
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I purchased my Aleph 2 monoblocs based on KK PCBs as kits about 10 years ago. I immediately built one , but have only now started on the 2nd. I have just noticed that when I built the first one I did not fit R27 ( 221ohm) which, I think is R15 on the original circuit ( highlighted on attachments). I am almost certain that I did not fit R27 based on the advice of the kit seller, but I can not remember the reason given. So some advice please:

What is the function of R27 and what is the impact of not fitting it?
Is it now recommended not to fit it to the KK boards?
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Old 8th July 2019, 12:55 PM   #2
Zen Mod is offline Zen Mod  Serbia
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that transistor is practically overcurrent limiter for lower half of amp , and without said resistor - it's nonfunctional

if you are having some salt between ears , you don't need it

if you're lacking in salt between ears , even that protection isn't enough
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Old 8th July 2019, 12:59 PM   #3
hifileslie is offline hifileslie
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Thank you for replying?
Do you recommend fitting R27?
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Old 8th July 2019, 01:20 PM   #4
Zen Mod is offline Zen Mod  Serbia
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nothing wrong if you put it in place
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Old 9th July 2019, 05:09 PM   #5
hifileslie is offline hifileslie
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If I decide not to have current limiting and do not fit R27 can I leave Q4( current limiting transistor ) and the 150 ohm resistor that forms the voltage divider with R27 still connected on the PCB without any detrimental effect on the amp?
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Old 9th July 2019, 05:14 PM   #6
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yup

that way transistor is closed , same as not present at all
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Old 9th July 2019, 05:51 PM   #7
hifileslie is offline hifileslie
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Thank you
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Old 9th July 2019, 08:38 PM   #8
Nelson Pass is offline Nelson Pass  United States
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Some people do think that the existence of a transistor protection circuit spoils the cows milk...

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Old 10th July 2019, 04:40 AM   #9
hifileslie is offline hifileslie
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Nelson, Thank you for taking the time to respond. I have decided not to retrofit R27 ( R15 in original circuit ) and leave the over current circuit disabled.
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Old 10th July 2019, 08:09 AM   #10
ne5532 is offline ne5532  China
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I think it's better to remove this resistance after confirming that the amplifier is stable.
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