Why when I bypass the power supply caps with better caps does the sound improve dramatically but S/N ratio suffer? Is S/N ratio anything that we really need to worry about or are we putting too much emphasis on this one spec & losing actuall resolution as a result?
In my experiments into obtaining higher perceived resolution I have found that when I achieve my goal that S/N ratio suffers some as a result. My SACD player was a perfect example as after my mods the player sounded much better than stock but actual noise when no signal was present was high enough that you could easily hear the DAC's idle tones when volume was set to a normal lestening level. The S/N ratio according to the manufacturer was suposed to be 106db which would have made these tones inaudible though in this case they did have muting transistors at the output to block the sound when there was no signal to the DAC's & i removed these transistors so this may be in part why it increased though in part I believe that the difference is that the bypass caps I used in the power supply to the analog section & the DAC allowed me to hear the true nature of the idle tones from this DAC. There was no off setting negative phase DAC output to be able to cancel these idle tones as there is in my soundcard DAC & the sound of the idle tone were what I would describe as motor boating & were definately coming from the DAC, not anywhere else as these tones were present even when all other activity was stopped.
On my sound card the DAC has balanced outputs & as such the idle tones are cancelled quite well & remain inaudible even after the cap bypass mods , however the S/N spec suffered here as well though interestingly even though the distortion spec went up also the distotion level & spectrum distribution remained Identical only the noise part of the spec went up by about 10db. Part of this may be the noisy computer environment but I believe that the actual reason the noise portion but not the actual distortion went up is there is an improvement in the actual resolution of the DAC at very low levels & analog section that it is able to actually resolve the nature of the noise better than before the power supply cap bypass mod.
In my experiments with amplifiers Electrolytic caps used to control the gain of a high gain amplifier going to ground from the negative feedback loop were notoriously lossy in terms of sound quality & when either wire or a metalized film cap was sustituted the sound was much better in every way.
Power supplies for transistor gear must use electrolytics in order to have sufficient storage capacity to function properly however by themselves appear not to be a totally adaquate solution & there remains some loss of resolution at the low levels as a result & of coarse that is also where noise resides which is at the lowest levels. So what appears to be happening is that the low level noise goes up in proportion to the gain in resolution but actual distortion remains at the same level as before. At 108db S/N ratio the noise is still inaudible so I'm not worried that noise went up because the actuall distortion reamains very low as in identical to stock except for the noise componant of the distortion spec, no change in the level of the distortion spectral componants according to RMMA tests Nor is there a change in frwequency response according to RMMA tests. Interestingly the distortion spectrum that I get actually looks better than the ones that Robscix got in his tests. My 2nd & 3rd hamonic were identical in level to his on his review of the X-fi Titanium HD card but all componants bove the third harmonic were much lower. 4th through 6th were virtually nonexistant & higher harmonics were present but at a much lower in level than Robscix's tests. Noise was 10db higher accross the board in this test. So much for the theory that my mods increase distortion that some have expressed.
The fact that the noise is increased across the board lends creadance to the fact that it is not so much computer generated noise as noise coming fron the DAC or ADC input circuits. If the the noise was due mostly to EMI interferance I believe the noise would be more focused in one or two areas as opposed to being across the board.
Edited by germanium - 7/21/12 at 12:46am