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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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In Reply to: Re: FRENCH ART - more on tweaks, STEVE and STEVEN posted by Steven S. on October 14, 2001 at 16:14:56:
Hi Steven,Nice to read you again, your are rather quick!
So we will both go the AD825 way, that is if I find somebody downtown who ACCEPTS to work on my double faced board! No one really wants to, and I was horrified to find out that most electronic shops were using the same 10$ non-regulated soldering iron as me! How did you overcome this problem???
Regarding the tweaks you did, I guess you know already my opinion from the previous posts : the phone jack + adapter sonic’s influence was 0, the output caps removal was +4. Your final findings are similar to mine. I get well used to it, but my problem is that I now hear the current weaknesses in the highs, and that the balance has slightly moved to the bright and transparent side, reducing slightly in comparison the bass and its impact. Well, I guess my main problem might be to be a perfectionist on holyday!!
I expect a lot from the diodes in order to clean the highs a bit (am I naive, what were your findings?), and even more from a correct output stage that would bring a lot more musicality, corpus and impact, larger bandwidth, music and details together. But otherwise, I have to say the cap mod has removed the unit one class higher in terms of details, soundstage and definition as you described, so we are on the right way I guess.
“During the tweak, as I traced down the audio output line, I found it's being fed back to the ADC input. This means that even if we don't use the ADC, the portion of the circuit is still working and drain current.â€
Yep, you are surely right. My incomplete schemes do not allow to see that, but it seems that some of the output goes back into the unit! A simple observation : my green 0dB led is sparkling during music in DAC mode. That means surely some of the signal comes back to the op amps in order to allow this indication. However, on my scheme, it is obvious that this could only happen “after†the output stage, ie I still believe we can remove both quad op-amps and simply replace them by 2 AD825. Yes, the green led will not sparkle again, but I guess that’s all! Let me know if I am wrong!
The other leds, those that are important for the DAC set up (X2 and so on…), are commanded by the daughter board, so again no change to expect in DAC modus on that matter IMHO.“But if we plug in the ADC input phone plug, this feedback will be disconnected, and the ADC input will take what comes in from the plug. So I put in the phone plug to RCA adaptor I used before for the audio output, and short the RCA side to ground. I tried to plug in and pull out this grounded plug, but couldn't hear too much difference. But I just feel it should be better to ground the ADC input.â€
Remove the op-amps as stated and you will surely get the most benefit (sound and current) on this subject. Keep us posted!“I also noticed when I plug in the daughter card which contains the DAC chip, the background noise becomes much bigger.â€
Err, sorry, my English shows its limits, I can’t follow you! How can your DI/O run without its DAC board? What exactly do you mean by the background noise becomes much higher : what are the 2 ways to run the unit you are referring to?“I'm considering replacing all the cheap resistors on the signal path with high precision metal film resistors. What do you think?â€
Honestly? I think not worth the effort! Ok, a bit quick. I know the Canadian guys I use to order my parts from (Sonic Frontier), or Audio Note, are keen on this. Well, I expect more a business issue, but can’t comment as I didn’t do it inside the ART. Anyone to comment this? Low tolerance (fine), but metal film (magnetism, inductance) resistors might also not be the best.
However, I have worked on amps and on the output stage of my CD player on that subject, and I must say that this is a very painful and “dangerous†(for the board) job, and, at last, you don’t know what resistances were used or how better the new ones will perform (sonic balance). But mostly, I have tried replacing resistances in the signal path by first grade ones… even jumping them at all when possible, and I honestly never could hear the difference! Whereas replacing the volume potentiometer with a better one for example brings big benefits.The only other sonic improvements I had where from the caps in the signal path (not even when as part of the output filter or current filter once you use smaller decoupling caps), hence my tweak on C17 and C18. To be true, the caps we removed were especially crap (cheap electrolytic – polarized- low capacitance and voltage caps), so nearly the worst case. Jumping is the best possible solution. Moving to a better (higher value, first grade cap), provided we had the place (both would be nearly as big as half of the unit), would have give us 50 to 70% of the sonic improvements. If we had had already good electrolytic caps with higher values inside the ART, and would have replaced them by the same state of the art expensive polypropylene caps, then we would surely only have half of the sonic benefit we noticed. That’s my experience on other machines. I might be wrong, and this might be the tweak of the year for the ART… but, honestly, I am not the one who will try this first! They are surely better improvements… Anyway, good luck!
I hope to read you soon,
Sincerely
Claude
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Follow Ups
- Re: FRENCH ART - STEVEN - Claude G 10/15/0108:43:33 10/15/01 (1)
- Re: FRENCH ART - STEVEN - Steven S. 13:33:37 10/15/01 (0)
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