Dowser
Learning to bodge again..
So, 3 years after buying and fixing up an old Naim CDi I am finally going to mod it to see whether its performance can be brought closer to my LP12. Original thread is at http://www.pinkfishmedia.net/forum/showthread.php?t=33604 - I bought it faulty and with Les' help got it up and running for around £200 with a new laser to boot, it's the best CDP I've heard.
Mods I intend doing are listed below and I, of course, have some questions ;
1.) PFM Flea fitting - I bought a kit a couple of years ago, but never got around to assembling it. Recently bought a built one from Mus, just need to swap the crystal, hence the motivation to actually do something...
I few questions though;
a) I have a simple small encapsulated xer and a small bridge rectifier that was originally part of a white noise +/- 15v PSU kit which I intend using to provide a dedicated 30v supply for the Flea. How much difference does the quality of the raw supply impact the performance of the Flea? Should I use Schottky diodes and decent smoothing caps instead of the junk I have now? What sort of uF value for the smoothing is best, and any value in a RC filter (I have lots of 1 ohm high watt resistors)?
b) Is there any value in my using the unbuilt Flea I have to power one of the other chips too? And how should I do it? Talking with Les when he helped me get it up and running initially he mentioned the NOS mod as being a big step forward - what does this actually do? Remove the 7220 chip form the cct? Rather than simply using the Flea to power another chip, and then look at further mods later, I'd rather do it in one go. Anyone been there, done that? Or suggestions for another approach, and use for a 2nd Flea as a regulator? How did those early adopters go power the TDA1541 with a Flea - did it survive? And can I hang 2 Fleas off the one raw supply I will be using? Should I put any additional filtering in too?
2.) Schottky rectifier diodes in CDi PSU - I want to do this, but also probably need to if I want to fit the Flea raw PSU inside the CDi - see photo below, not a lot of space - if I use Schottky's they'll have a smaller footprint and hopefully a bit of juggling will give me required space for the Flea xer with bugged rectifier/smoothing. Anyone tried this in a Naim CDP, and what were results (and what Schottky's did you use - MBR2020s?)?
3.) Smoothing cap replacement in CDi PSU - any recommendations for replacement smoothing caps (I remember Laverda using BHC T-Nets)? I guess if they are smaller that is good, but if higher value will give better results I can work something out I guess. Does anyone know stock value of smoothing caps in a CDi (I am being lazy, I know...)?
4.) Tant replacement - I have 20 odd 10uf/35v tants from Les, and another 30 or 40 Wima 10uF little red jobbies. Does anyone know which tants I should target for replacement, or just do them all?
5.) What else should I be doing while everything is apart? I intend to test after each mod to limit risk of a screw up causing grief, but want to get maximum benefit from having the thing in pieces (it's taken me 3 years to drum up the motivation to pick it apart!). One day I intend taking output from DAC straight through an unfiltered and simple discrete output stage - but this is definitely something I will do after all the above.
As always, many thanks for any comments or advice.
Richard
Mods I intend doing are listed below and I, of course, have some questions ;
1.) PFM Flea fitting - I bought a kit a couple of years ago, but never got around to assembling it. Recently bought a built one from Mus, just need to swap the crystal, hence the motivation to actually do something...
I few questions though;
a) I have a simple small encapsulated xer and a small bridge rectifier that was originally part of a white noise +/- 15v PSU kit which I intend using to provide a dedicated 30v supply for the Flea. How much difference does the quality of the raw supply impact the performance of the Flea? Should I use Schottky diodes and decent smoothing caps instead of the junk I have now? What sort of uF value for the smoothing is best, and any value in a RC filter (I have lots of 1 ohm high watt resistors)?
b) Is there any value in my using the unbuilt Flea I have to power one of the other chips too? And how should I do it? Talking with Les when he helped me get it up and running initially he mentioned the NOS mod as being a big step forward - what does this actually do? Remove the 7220 chip form the cct? Rather than simply using the Flea to power another chip, and then look at further mods later, I'd rather do it in one go. Anyone been there, done that? Or suggestions for another approach, and use for a 2nd Flea as a regulator? How did those early adopters go power the TDA1541 with a Flea - did it survive? And can I hang 2 Fleas off the one raw supply I will be using? Should I put any additional filtering in too?
2.) Schottky rectifier diodes in CDi PSU - I want to do this, but also probably need to if I want to fit the Flea raw PSU inside the CDi - see photo below, not a lot of space - if I use Schottky's they'll have a smaller footprint and hopefully a bit of juggling will give me required space for the Flea xer with bugged rectifier/smoothing. Anyone tried this in a Naim CDP, and what were results (and what Schottky's did you use - MBR2020s?)?
3.) Smoothing cap replacement in CDi PSU - any recommendations for replacement smoothing caps (I remember Laverda using BHC T-Nets)? I guess if they are smaller that is good, but if higher value will give better results I can work something out I guess. Does anyone know stock value of smoothing caps in a CDi (I am being lazy, I know...)?
4.) Tant replacement - I have 20 odd 10uf/35v tants from Les, and another 30 or 40 Wima 10uF little red jobbies. Does anyone know which tants I should target for replacement, or just do them all?
5.) What else should I be doing while everything is apart? I intend to test after each mod to limit risk of a screw up causing grief, but want to get maximum benefit from having the thing in pieces (it's taken me 3 years to drum up the motivation to pick it apart!). One day I intend taking output from DAC straight through an unfiltered and simple discrete output stage - but this is definitely something I will do after all the above.
As always, many thanks for any comments or advice.
Richard