1. No ad-hominem
2. No spamming or shilling
I mess about with machinery a lot so get lots of ideas from my work. Chain must be tight and be in contact with as many sprocket teeth as possible. Easy with two sprockets as the chain goes almost all the way round each one. Idler pulleys would be useful to take up slack or get more of the chain on the sprocket.
Anyways, read a few threads on modding the CD3.5 (i have already modded the bollox off mine) and a few things cropped up that i had not thought of.
1)I2S can be taken from the connection between the decoder and dac and taken to a new dac if wanted. Has to use the same clock frequency as the dac already in the 3.5 but changing the clock frequency should not be too problematic
2) Another guy bypassed the anologue output stage altogether and reported good results. That gets rid of 6 opamps and loads of resistors and caps. The best opamp is no opamp after all. There is an opamp in the dac which has enough balls to drive what ever comes after the cdp.
Might give the bypassing of the output stage a go. Easily put back if no likey. Lots of components removed from the signal path and a psu with 500va twin ct secondary transformer removed from the equation as well.
What would be really cool would be plumbing the £3.40 Chinese dac in there.
I love it when a plan comes together
Your plan to bypass the analogue output stage of your CD3.5 sounds interesting. Does the CD3.5 also have a Philips 1541 DAC CHIP in it?
Here is a link to the Lampizator site, who did something similar with a CD3 (of course a tube had to be used in the output stage, too ).
http://lampizator.eu/lampizator/REFEREN ... imcd3.html
just food for thought...
Tubes and Vinyl rule, Music rocks!
There's info to be found on this forum about this Chinese DAC (from earlier this year). Just do a search. It is a recommendation of the Doc and everyone who tried it with an external - I believe 5V - linear power supply has been very impressed
Tubes and Vinyl rule, Music rocks!
Thanks for your interest. No, my cdp does not have the lovely 1541 in it unfortunately. They are hard to find now and apparently difficult to apply. Thanks for linking the lampizator stuff, i have read that before many years ago but forgotten much of it now. Tubes scare me to death.
The output stage is a 7 pole bessel filter with the last two opamps being a buffer to the outside world. The weird thing about the dac (TDA1305) is it has an internal opamp IV stage so the rest of the antialias filter can be removed. There may be a decrease in sq however, dont know til you try. Seems to fit in with the less is more, keep it simple philosophy.
I have not heard the Chinese dac yet but have one out of its case and have started to try and trace the voltage supply tracks. Not easy though with the tiny pcb tracks and components.
The TDA1305 dac is a voltage out affair as it has an internal opamp for current to voltage conversion (IV stage). That can be seen as a good or bad thing. Good is I don't have to have another opamp (although it can be done passively) and psu to do it. Bad - I cant change the internal opamp for something better.
So I lifted a leg of the first coupling cap after the dac added 100k resistor to signal 0V and a wire to the output phono sockets. Hey presto - 6 opamps, and 10's of resistors and caps removed from the equation. I was worried there may be pops, clicks and other nasties with the removal of the output relay but I have used all the commands on the remote and there has not been any
Listening has been an interesting experience. More detail for sure, less fatigue and harshness. I was worried about aliasing and hearing nasty dac artefacts as the TDA is a bistream and they are said to need a lot of filtering afterwards. I have one 1st order filter consisting of a 680pf cap to ground as soon after the dac as is possible but that is what Naim had put on the pcb anyway (and is suggested in the data sheet as all that is needed ?). 10uf film coupling cap and 100k to ground take of any DC (which was 2.5V without it). My amps have no coupling caps (obviously) so amplifying 2.5V would have resulted in many melted voice coils
Listening to Stevie Wonder at the moment I am amazed at what this simplicity has brought. Earlier in Led Zep 1 I heard very low level detail that I had not been able to distinguish before.
Not being one to sit still though I decided to play around with my potential divider volume circuit. It has been sat on its own with only phono and din sockets near by and a star ground. 1 metre of new style TIS between cdp and potential divider. No input selector.
I have moved this to the cdp now that the psu for the anologue stage is no longer needed and has been removed. The TIS has been moved to duties between cdp/pre and Avondale monoblocs. NVA based amps already had a TIS.
Currently enjoying a bit of Bob Marley and the musical improvements brought by my recent adventures . Crowd are a bit louder than usual in the background on no woman no cry