Hafler DH 101 preamp mods

[Zen Mod]

idea-CCSs instead R17 , R18 , R19 and R20.
comments?

 

[millwood]

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.

 

[fab]

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.

 

[Zen Mod]

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

 

[buchignani]

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

 

[fab]

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).

 

[Zen Mod]

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"