AW: VCS3 Filter Cap values

Magnus Danielson magnus at analogue.org
Fri Jul 17 21:47:29 CEST 1998


>>>>> "HJ" == Haible Juergen <Juergen.Haible at nbgm.siemens.de> writes:

 >> I am in the process of breadboarding the VCS3 filter and was
 HJ> wondering if
 >> anyone knows what value 47Kpf or 10Kpf is as indicated on the
 HJ> schemos that
 >> are out there? 

 HJ> Just multiply the factors. k=1e3, p=1e-12, kp=n=1e-9.
 HJ> As curious as it may look, it's even mathematically 
 HJ> correct. (;->)

Note that while this looks curious it is not at all uncommon with
capacitors. You may find SMD caps marked 103 which means 10*10E3 pF
which is 10 nF. Similar things occur on most cheramics I have seen.

However, writing 47 kpF is not allowed in the SI system, there you are
required to write it as 47 nF. I have seen people using kM and MM
instead of G and T respectively, this is equalently broken.

Thus stacking prefixes is not allowed and is greatly
deprechieated. Things isn't ideal and one must also recall that the SI
system still is fairly young after all. At least there is something to
strive for.

BTW. An US inch is not exactly 25,4 mm as the SI system specifies, the
diff is a few PPM if I recall things right. I guess that most rules
will be the same anyway :)

Another thing, a bilion isn't the same in USA as it is in the rest of
the world. We others stick a miljard in before we get to the bilion.
This shows that these language prefixes can be a source of confusion.

 HJ> BTW: The filter schemos show a 10u capacitor across the
 HJ> CV input ( C31, parallel to the 1k lower divider leg).
 HJ> This will slow down modulation transients. S&H sounds
 HJ> like using a portamento, for example. I have no idea if
 HJ> this is an error in the schemos or if it's actually inside the 
 HJ> VCS3, but I've cut it out on my clone yesterday, and it sounds
 HJ> much better now.

Oups.

Cheers,
Magnus



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