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Old 30th April 2004, 11:14 PM   #1
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Default Hafler DH 101 preamp mods

idea-CCSs instead R17 , R18 , R19 and R20.
comments?
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Old 1st May 2004, 02:39 AM   #2
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if you have to, r17 / 19 can be replaced with current mirrors.

However, I am not sure if the difference (active load vs. resistor load) is audible.
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Old 1st May 2004, 11:37 PM   #3
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You can try active current sources in place of R18 and R20.
You can install degeneration resistors to improve the linearisation of the input diff. stage.
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Old 2nd May 2004, 07:52 PM   #4
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Quote:
Originally posted by fab

You can install degeneration resistors to improve the linearisation of the input diff. stage.

please,clarify that little- I'm more sort of tube afficionado,but without too much subtlety for SS ........
TIA
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Old 3rd May 2004, 12:32 AM   #5
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Default A few other things to do

I've got one of these as my second system preamp. I did the following, pretty much all together, and it made a very rewarding difference:

Replace all polarized caps in the signal path and some others with poly films: C11, C13, C14, C17 bypassed, C20. [Didn't aplter the phono section, as I don't use it].

In the power supply, replace C24, C25 with a low ESR 4,700 uF cap, C27 and C28 with 220 uF and film bypass.

Norman
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Old 3rd May 2004, 12:52 AM   #6
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Quote:
Originally posted by choky



please,clarify that little- I'm more sort of tube afficionado,but without too much subtlety for SS ........
TIA
I can not explain it better than on the Douglas Self site: http://www.dself.dsl.pipex.com/ampins/dipa/dipa.htm#5. Check particularly section 5.1 for input stage linearity wich includes the degeneration resistors advantage (more constant gm).
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Old 3rd May 2004, 01:24 AM   #7
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tnx to all ;
I'll check later Self article (just saved ) ,and mebbe in several weeks time,I'll upload some info about complete refurbishing of that little jewell........
good enough to be "near PC preamp"
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