LPF Change In Functioning?

[DougieFunk]

So I was playing around with my dodgers today and all of a sudden (without changing any settings) I heard this really loud, low frequency. After bypassing a few Of my pedals, I isolated the noise to my LPF. The resonance was set to approximately 8.5. Before today, my LPF never generated a tone that loud in the absence of me actively inputing a signal. I mean this is really loud (i.e, shakes the entire apt when my bass and my amp are turned all the way down). And it is a constant signal if the resonance is set past approximately 7.8 - the only way to adjust the volume of the tone is to turn down the mix. So I know that above 8 on the resonance puts the LPF into a self/oscillating "mode" where something like this can happen, but my LPF has never done this anywhere near this magnitude before. Usually and I get a frequency of moderate volume dependent on the drive control and input volume as well as cool self-oscillating echo-like effects. Long story short, my LPF changed how it behaves.

I spoke with Ross (I think) at Moog and he said that nothing is wrong and perhaps the unit fixed itself...but I don't believe that it was broken to begin with. It is a brand new (4-weeks old) pedal and sounded great before this. I dont think i explained my issue to him adequately and he seemed adamant on insisting that ut was fine Now I feel like I've lost some functionality and have a really annoying frequency to deal with if I want to get my LPF to self-oscillate. Does anyone else experience a truly ridiculously LOUD tone when the resonance is set above 8? Assuming that it is broken rather than having miraculously fixed itself after 4-weeks of use, what is wrong with it? Is there anything I can do to fix it?

[Sir Nose]

Does the frequency of the loud tone change when you sweep the cutoff knob? If it's just self oscillation the pitch should follow the knob.

[DougieFunk]

Yes, the pitch changes when I attenuate or increase the frequency. The fact that the tone is so over bearing in terms of volume is what has me concerned. Furthermore, any setting above 8 on the resonance does not change the behavior of the tone - it's just really freaking loud. :/

[EMwhite]

Indeed, what he said. The right combo of cutoff vs. resonance with an incoming signal to start the madness can set off a low frequency rumble that will shake your house off it's footings.

It's actually an impressive tonal color if you can harness it. I had a FreqBox -> LPF patch dialed up once with my bass and certain two not chords with the right attack and combining harmonics produced a sound that was absolutely incredible. I was playing from my MusicMan Stingray with just the right combination of eq.

Play around with whatever instrument you were playing through it and the knobs; see where it happens and where it doesn't. Unlikely to be a problem.

[DougieFunk]

"The right combo of cutoff vs. resonance WITH AN INCOMING SIGNAL to start the madness can set off a low frequency rumble that will shake your house off it's footings."

That's the thing- even with no signal being supplied to the pedal, the LPF produces this monstrous tone on it's own (even if there are no inputs and I just turned it on). That's what I want to know - is it normal even though there is nothing being fed to the pedal???

[DougieFunk]

Sorry, guys. I don't want to beat a dead horse here (I know it's probably too late and we'll be having horse stew tomorrow night ) but can someone do a quick experiment to satisfy my neurosis? Turn all of the pots on your LPF fully clockwise (except for the resonance at anywhere from 8-10). Without sending any
Sound into the pedal, does it make a sound? Thanks and I'll be quiet now; I promise!!

[EricK]

With everything counterclockwise and the resonance at 8, at first mine oscillated but afterward, the only thing that created any sound was by tweaking the cutoff knob which is what Im confident that it's supposed to do.

Does this quell your neurosis?

[SteveD]

Hi All -

From p. 6 of the pdf of the manual:

"The RESONANCE knob changes the way the filter sounds. Or, in technical words, it
changes the shape of the frequency response. When RESONANCE is near 0 the low
overtones come through evenly. When RESONANCE is turned up to around 7, the
overtones near cutoff will be boosted, creating a whistle-like or vowel-like quality. When
RESONANCE is above 8, the filter actually produces its own tone at the cutoff
frequency. That tone interacts with your instrument's tone when you play your instrument
through the filter."

BTW - Bob wrote that....

The Resonance control sets the amount that the output of the filter fed back into the input of the filter. It adds a peak @ the cutoff frequency, and if the gain is enough (past the "8" position)the filter goes into self-oscillation - the tone produced is very close to a sine wave. So yes, this is totally normal and it *should* make a sound when the resonance goes above 8. It's part of the wonderful world of the Moog Filter. It can be loud - watch your ears and speakers.

Cheers,
SD

[MarbledMoog]

Sounds like you're just getting self-oscillation. Since its self-oscillating, it doesn't matter if something is being fed into the input or not, the filter is self-oscillating.
You can make some insane sounds with it, but be careful. The sounds are enormously loud, which is normal. If you want to harness this effect, try setting the reso. so its just on the verge of oscillating, the volume should be a little lower IIRC.