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however I'm not at all willing to experiment without previous knowledge that this is a worthwhile exercise.
Wima polyester and polyprop caps look identical. The pic of the 1200 modules on the six moons review of the Atsah shows 6 caps per channel. That would make them .33uf each. This is the largest value you can get the polyprop caps in. So, are they .33 polyprops or polyesters? In any case they have steel leads are are not marked for outside foil so they are not necessarily in the right direction. Loop area? The modded caps are mounted one third inch above the board. You think you can hear that? Changing one .68 polyester to two .33 modded and properly marked Wima polyprops on the NC400 simply sounded better. I trust my ears.It will be interesting to see if the Mola Molas sound better than the Atsah or Merrills. Right now I am looking at the Job 225 amp (will be listening and modding one in the next week or so). It may be this years giant killer. What, Ncore already outdated? We shall see.
if "there is no question about the goodness of polyprop caps versus mylar" i wonder what keeps Bruno from using polyprops in the first place?
Ric, I suggest you do a little more research. Polyester Wimas have silver printing on them, and the polpropylene ones have black printing. They do not have identical appearance. They also have the model numbers marked. Not that I am suggesting that polyester is good!<SNIP>
Greg: Right on! I think your suggestion regarding PPS caps is worth a try. I have used some of those in mods to cheaper DACs, replacing SMD ceramic caps used in the analog filter with the PPS films with good results, but I have never compared the sound of PPS to polypros or polystyrenes, but they are compact and could be made to fit on the board very well.I do not know that the 3 caps on the NC-400 are acting as one, tracking the traces on the board is not so easy, but next time I have one off of the heatsink I will take a look and see what I can determine. I am just not sure how the LPF would be "more complex" than the simple LC I assume it is? Do you have ideas about this? Most class D amps where I have seen the schematic just show the LC, and the output of the NC-400 being single ended seems to support this, or maybe my thinking is all wrong here? Please let me know what you think.<SNIP>
<SNIP>We are talking about the NC-400 here, Ric's mod with the stacked caps doubles the lead length of that cap. Considering how much Bruno stresses the importance of PCB layout and lead length, critical to fractions of a mm, that additional lead length bothers me. Without doing some precise measurements it is impossible to know if it causes a problem for the module.RE differences between NC-400 and NC-1200. Both have the discrete regulators (based on the Hypex HxR regs) for powering the input stage. But the NC-400 uses a discrete input circuit as well, and the NC-1200 uses an IC opamp for the input circuit. Hence the Mola Mola amp using a separate, discrete, input circuit, and Audience also using a discrete input circuit of their own design. Considering how accurate the Ncore output stage is, I suspect these different input circuits would be responsible for much of the difference in sonics of these amps. Even in well designed class A/B amps, the input gain stage is often what defines much of an amplifiers sonic character.
How they measure with the new caps?
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