VCF OverDrive and warble

isak

Hi guys

my soundlab is finley finished Cool

i have this problem with the VCF section, when i turn the reso pot all the way up and turn the filter pot down the filter is with overdrive and warbles.
when i turn the reso pot on 3:00 o'clock position its sounds ok, but.. i want the reso to screem more.
what do thing the problem is ?

thanks
Isak.

isak · Posted: Mon Feb 08, 2010 2:44 pm Post subject:

any one..? not even a clue ?

stinkebeest · Posted: Thu Feb 11, 2010 3:05 pm Post subject:

Hey, I have the exact same problem ! funny, i was thinking of a way to describe it, and you're right, it definetely warbles... and maybe wiggles a little bit.

Did you have any luck fixing this ?

I made a quick sample of the phenomenon, so maybe it's a little bit
more clear what the problem is exactly.

I turn the initial vca up for a continious tone, then turn reso all the way up,
then slowly turn the cut off down, let it sit for a while somewhere in the middle, then turn it down further.

soundlab filter freakout.wav

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soundlab filter freakout.wav

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isak · Posted: Fri Feb 12, 2010 12:48 am Post subject:

i'm afraid its the same problem, its exactly the sound i get.
and no, i didnt fix it.

maybe now that u'v upload the soundclip someone will be nice and investigate this matter. Wink

(i hope)

BTW i wrote a mail to ray about this problem and this is what he said.

"Check everything in the VCA and VCF schematic page. Especially the values around the inputs of the VCA and VCF.
Also remember that its easy to look at a resistor backwards and think its one value when it is a completely different one. For example 270K (red, purple, yellow) could be confused with 4.7K (yellow, purple, red). It can happen so look very carefully."

so i did check and everything is ok.

if i'll have an update i'll post here and if u fix it befor me please update Smile

thanks for the soundclip stinkebeest Smile

Isak.

jordroid · Joined: Jan 17, 2010 Posts: 193 Location: ithaca, new york

Mine also sounds like that, but i have the feeling that it is just the way it sounds. This exact thing has come up several times over the 20 something pages here and the conclusion usually seems to be that the filter just sounds like that. I personally am pretty happy with the sounds i can get out of it, but i am also planning on building a more fully featured filter soon.

isak · Posted: Sat Feb 13, 2010 5:23 am Post subject:

well, i dont think it suppose to sound like that.
i need to do some experiment on the filter i'll update asap and let u guys know if i fix it.

peace,
Isak.

stinkebeest · Posted: Sun Feb 14, 2010 4:19 am Post subject:

hi,

yeah, after searching the forum some more, i did see it come up
a couple more times. but i'm still not sure it is supposed to sound like
that. i didn't hear similar things in the MFOS samples. And the maximum
resonance i can dial in, before it starts freaking out, is not really mind blowing. but hey, i don't know.

hey, maybe if someone who doesn't have this issue could make a quick
sample, similar like mine, osc tuned to some nice interval and then max the reso. for comparison.

isak · Posted: Sun Feb 14, 2010 6:11 am Post subject:

Hi stinkebeest

do u use 1% resistors on the vca and vcf sections or 5% resistors?

LektroiD · Posted: Sun Feb 14, 2010 11:29 pm Post subject:

My filter is exactly the same. I just figured it was down to building the stripboard version at first (early layout). I did use metal film resistors, which later turned out to be Chinese fakes (there's another thread about this somewhere). I may replace the resistors with better quality ones when I get a moment and report back. Which would be the most likely resistor(s) to cause this?

isak · Posted: Mon Feb 15, 2010 3:00 am Post subject:

Hi LektroiD

globe town free arts lab · Posted: Tue Mar 23, 2010 2:07 pm Post subject:

here's a sample of my sound lab to compare to

lfo and envelope are turned off

first:
1 oscillator, no resonance
then:
1 oscillator, full resonance
then:
2 oscillators, full resonance

hope this is useful

drew

soundlab filter sweep.mp3

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soundlab filter sweep.mp3

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haxster · Posted: Tue Mar 23, 2010 4:38 pm Post subject:

The type(brand) of 13700 seems to matter also. I seem to like JRC brand from Japan. I was getting Rough square/tube like distortion with the rez with NTE 13700 equivalents. The Cap type also effects the Filter itself. But in general the Sound Lab FIlter was never meant to sound clean like the Mfos 12db Module VCF. I do believe some have figured out how to improve the Rez on a soundlab, even to make a decent sine wav. I never bothered.

Resistors should not be really critical weather you used 5% or 1%. That would only matter with the Cutoff Tracking and that would not effect the fact that the Rez goes chaotic like. The 12db MFOS module is a better design and I have built it with 5% resistors and it still sounds smooth.