NAD C541i Mods
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Reference:
http://www.diyaudio.com/forums/showthread.php?s=9b3bf9cf3b7113e1c27fce9d54579250&threadid=43902&perpage=25&pagenumber=1


One: Ferrite on power to board.
Two: Damping - putty on transport, drawer, sides, and bottom. Soundcoat on top inside chassis case. 3M sheet on outside top.
Three: Blackgate FK 2200uf  35v replaced Nichicon Fine Gold 1000uF 25v
Four: Blackgate 1000uf  16v replaced Nichicon Fine Gold  470uF 16v
Five: secured the clock with mouting putty [detail picture below]
Six: Blackgate 470uf  25v replaced Nichicon 470uF 25v
Seven: Sonicraft 4.7uF 400v + Russian K40Y-9 PIO .1uF 400v + Russian FT-1 teflon  .01uF 200v replaced Nichicon 100uF  16v [detail picture below]
Eight: LM4562 replaced OPA2604 /w Blackgate NX-Hi Q .1uF / 50v on pin 4+8 [detail picture below]


capacitor secured on the bottom with mouting putty
clock secured completely with mouting putty

output caps secured with two sided 3M tape

Blackgate
NX-Hi Q .1uF / 50v across opamp pins 4 & 8
seated in place with some putty


So, the sound after these changes? the usual, bass better, tighter, etc, midrange approximates the word lush, detail is sweeter with some airy shimmer, there is more coming thru not meaning volumes but previously it was thin and now is is nice. I have a CDs I now pull down to play whereas previously it was Lp only. These changes brought this CD section to LIFE baby. The HDCD always was a winner but with the changes even the kid [14yr old] went "Wow! It is like they are there."
...
After several months the caps must have fully stretched out becuase it kicks a little ass now. Very full rich midrange with sweet powerful presence. Larger wider image field. Incredibly analog. I was pleased at first, the oil caps at output really made a profound difference, but over the last week it has somehow ... I guess the lesson is to give your Blackgates a fair ammount of time to show themselves. I am told that BGs tend to mature over several hundreds of hours. Clock upgrade will have to wait for some time

8/14/2008: Swapped out the output caps for Sonicraft and Russian PIO plus added BG non polars to the opamp.  The sound was a bit thick and over time I wanted some more open space along with impact. The Russian PIOs are smooth, extended and the Sonicraft are detailed with nice bass. BGs on the opamp boost the punch. Much more 'alive' now. Those MojoTones were dragging it down.

10/13/2008: Added Russian FT-1 .01uF teflon caps to the array at output; It still has the slam bass, solid PIO mids, and the teflon opens the top way out. Better control and focus on the midrange and bass.



After all this hard work the output is easily bettered by the VALAB NOS DAC.
All the chassis and transport damping help the C541i as a transport.
No locking issues with the DAC ...



Coaxial Termination

There is a 75 ohm
RCA digital coaxial output as well as a Toslink output. The coaxial output needs to be terminated with a 75 ohm terminator or the signal will reflect back to the DAC causing jitter.

Read about it @ diyparadise http://www.diyparadise.com/75ohmtweak.htm

End result was less fuzz and increase in clarity...just as promised.

I am using parts from Radio Shack ... "F-to-Phono adapter": part# 278-252 + 75-ohm "F" type terminator: part# 15-1156





November 22 2008