From Brian Willoughby Sent Fri, Jan 25th 2019, 07:12
From Brian Willoughby Sent Fri, Jan 25th 2019, 07:12
There=92s more to a capacitor than its capacitance. There=92s also ESR = and leakage, as well as microphonics. Just because the same capacitance = is reported doesn=92t mean it=92s the same cap. Many modern surface mount caps are exactly like their through-hole = ancestors. However, a few kinds of capacitor chemistries simply aren=92t = available SMD. One example is for Sample and Hold, where = super-low-leakage poly caps simply aren=92t available in SMD. Of course, = there are other SMD caps that are good enough for S&H, but maybe those = tropical fish caps were poly? Maybe they were mica? Foil? I=92d be = curious to know the manufacturer and model of those caps. Lots of old caps were really bad, and nobody really wants the problems = any more. Again, it=92s not that their value changes, it=92s that they = don=92t act exactly like a pure capacitor, but more like a complex = combination of capacitor, resistor, and inductor. That said, why hasn=92t someone just recreated the flaws of the old = tropical fish caps by adding parallel or series resistors and inductors? Brian On Jan 23, 2019, at 8:10 PM, M V <xx_xxxxxx@xxxxxxx.xxx> wrote: > Speaking of the new and old SEMs though, it's pretty well known that = there is a clear difference between the new and old filter (more than TO = would care to admit it seems). The former is brighter and sharper when = resonance is at max, and not just because of an increased cutoff range. = However, it came to light recently through the work of Oldgearguy over = on GS that the likely culprit is the tropical fish caps that the old one = uses and the new ones do not. OGG pulled the tropical fish cap on his = old SEM and replaced with a modern hi-fi cap and found that the filter = pretty much sounded the same as the new SEM. So this is sort of proof = through absence of evidence because he didn't/couldn't put the through = hole trop. fish cap in the new SEM's SMT PCB, but it does strongly = suggest that with some very minor tweaking, one could get the new ones = to sound identical to the old.=20 >=20