Steiner VCF probs
2007-05-19 by funkfumes
Hi all.
My name's Evan. I'm a new member here. I've been into analogue
synths for some years, having owned some standard commercial stuff, a
Doepfer modular and, more recently, a small modular called the 'Sir
G', that my friend Gus built, based on "Sounds From Outer Space"
designs.
I have been building the Euro size Steiner filter from Elby deisngs
as part of the VICmod group in Melbourne, basing our work on Ken's
CGS designs.
A couple of us got our Steiner filters finished today, but got the
same problematic results as each other, strangely enough.
I saw mention of similar sounding symptoms on posts from this group,
but no real concrete solutions that I could see.
One problem is that the filter generally doesn't seem to have a very
satisfactory frequency range. Whichever mode (LP, BP, HP) we tried,
and whichever tweaks on the 3 trim pots, we could only get a
frequency range covering about 1/2 to 1/3 the expected audio range.
But the main problem is this self oscillating resonance/feedback
sound that can not be stopped. This same behavious was exhibited in
the two we tried today. The behaviour seems to be most evident in
the resonance part of the filter and can be changed by turning the
resonance pot. Strangely, turning the resonance pot seems to 'tune'
the frequency of the resonant tone, rather than intensifying the
tone, as might be expected in normal operation. When turned
clockwise the resonating tone deepens in pitch. When turnedcounter-
clockwise the pitch becomes higher. Turning the middle trim pot
(p202 on Elby's board) has the same effect of tuning the pitch of the
resonating tone. As I said, the resonating tone cannot be 'turned
off'. This seems to be quite the opposite of what some people on the
list have reported, not being able to get the Steiner into self-
oscillation at all.
Any tips or pointers appreciated!
Evan Lorden.
My name's Evan. I'm a new member here. I've been into analogue
synths for some years, having owned some standard commercial stuff, a
Doepfer modular and, more recently, a small modular called the 'Sir
G', that my friend Gus built, based on "Sounds From Outer Space"
designs.
I have been building the Euro size Steiner filter from Elby deisngs
as part of the VICmod group in Melbourne, basing our work on Ken's
CGS designs.
A couple of us got our Steiner filters finished today, but got the
same problematic results as each other, strangely enough.
I saw mention of similar sounding symptoms on posts from this group,
but no real concrete solutions that I could see.
One problem is that the filter generally doesn't seem to have a very
satisfactory frequency range. Whichever mode (LP, BP, HP) we tried,
and whichever tweaks on the 3 trim pots, we could only get a
frequency range covering about 1/2 to 1/3 the expected audio range.
But the main problem is this self oscillating resonance/feedback
sound that can not be stopped. This same behavious was exhibited in
the two we tried today. The behaviour seems to be most evident in
the resonance part of the filter and can be changed by turning the
resonance pot. Strangely, turning the resonance pot seems to 'tune'
the frequency of the resonant tone, rather than intensifying the
tone, as might be expected in normal operation. When turned
clockwise the resonating tone deepens in pitch. When turnedcounter-
clockwise the pitch becomes higher. Turning the middle trim pot
(p202 on Elby's board) has the same effect of tuning the pitch of the
resonating tone. As I said, the resonating tone cannot be 'turned
off'. This seems to be quite the opposite of what some people on the
list have reported, not being able to get the Steiner into self-
oscillation at all.
Any tips or pointers appreciated!
Evan Lorden.