From Jason Proctor Sent Fri, Jan 25th 2019, 18:43
seems like someone has yet to discover the filter cutoff knob? i loved the Doepfer SEM filter but somehow could never find two that sounded anywhere near alike. i know #analogue but they weren't even comparable. i thought one i had was a Wasp filter behind an SEM panel, even... On Fri, Jan 25, 2019 at 10:41 AM skkatter <xxxxxxxx@xxxxx.xxx> wrote: > > SEM filters sound great. I tried sticking two SEM oscillators into five S= EM filters and mixed all the bandpass outputs together to get this: https:/= /www.instagram.com/p/Biu7s0UgekB/ > > -Stephen > > On Fri, 25 Jan 2019 at 16:50, Royce Lee <xxxxxxxxxx@xxxxx.xxx> wrote: >> >> SEM filter observations: hopefully these comments will not be off topic. >> Perhaps this may be relevant to the conversation about Oberheim filters = and component differences. First the disclaimer that the only SEM filter I = have is the Dopefer and Studio Electronics SEM filters. But I do like both = of them. >> >> Recently I've been using the Nord Modular is a digital oscillator for a = Eurorack system, feeding the SEM/doepfer bandpass. I noticed that when send= ing the SEM a polyphonic signal, say a duophonic oscillator with arbitrary = pitch spacing (fifth, seventh etc.) the result sounds a bit ring modulated.= It took me a lot of patching into alternate filters and double checking ev= erything to conclude that it is the SEM filter is what was doing this. Perh= aps this is simply the effect of filter saturation. But this filter does it= more than other filters I use. >> >> Royce >> >> >> On Fri, Jan 25, 2019 at 9:47 AM Sam Mims <xxx@xxxxxxx.xxx> wrote: >>> >>> The tropical fish caps are made by Mullard - here's one used in the >>> Minimoog: >>> >>> https://syntaur.com/Items.php?Item=3D1285 >>> >>> Sam Mims >>> Syntaur >>> >>> >>> >>> On 1/25/2019 1:14 AM, Brian Willoughby wrote: >>> > There=E2=80=99s more to a capacitor than its capacitance. There=E2=80= =99s also ESR and leakage, as well as microphonics. Just because the same c= apacitance is reported doesn=E2=80=99t mean it=E2=80=99s the same cap. >>> > >>> > Many modern surface mount caps are exactly like their through-hole an= cestors. However, a few kinds of capacitor chemistries simply aren=E2=80=99= t available SMD. One example is for Sample and Hold, where super-low-leakag= e poly caps simply aren=E2=80=99t available in SMD. Of course, there are ot= her SMD caps that are good enough for S&H, but maybe those tropical fish ca= ps were poly? Maybe they were mica? Foil? I=E2=80=99d be curious to know th= e manufacturer and model of those caps. >>> > >>> > Lots of old caps were really bad, and nobody really wants the problem= s any more. Again, it=E2=80=99s not that their value changes, it=E2=80=99s = that they don=E2=80=99t act exactly like a pure capacitor, but more like a = complex combination of capacitor, resistor, and inductor. >>> > >>> > That said, why hasn=E2=80=99t someone just recreated the flaws of the= old tropical fish caps by adding parallel or series resistors and inductor= s? >>> > >>> > 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 w= ould care to admit it seems). The former is brighter and sharper when reson= ance 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 t= he likely culprit is the tropical fish caps that the old one uses and the n= ew ones do not. OGG pulled the tropical fish cap on his old SEM and replace= d 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 S= EM's SMT PCB, but it does strongly suggest that with some very minor tweaki= ng, one could get the new ones to sound identical to the old. >>> >>