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Subject: Re: [motm] 480 Mods

From: Charles Stella <cstella@...>
Date: 2006-01-09

Yeah it's there. I use my filters more as audio processors so I often don't have a VCA involved. The white noise is noticeable for sure. I have one of every MOTM filter and they are all very quiet and don't exhibit this broadband noise. So that's the benchmark for me. And my studio setup is very quiet and I am very picky :) I love the 480 filter though and it sounds great. It will be interesting to learn more about this circuit as I do Richard's mod. 

Charles.




On Jan 8, 2006, at 2:41 PM, Dino Leone wrote:

Charles,
you're right! Just tested that. It's up to about 30mV
peak-to-peak and goes away when LP Freq is decreased.
I never noticed that before since the filter is before
the VCA in my setup and with a blast of SAW or
whatever fed into the filter it's like 50x less than
the signal itself.
Even when I connect the filter directly into the amp
without any VCA it's very very little - as you said
-75dB. What I notice a lot more are the transient DC
offsets that happen when LP freq is changed. Those can
go up to 0.2V. But after googling for that I found
that this happens in many (all??) state-variable
filters... I think this is from the CA3280.

Best,

Dino


--- Charles Stella <cstella@...> wrote:

> The LP out with Freq LP at 10 generates white noise
> at about -75dB. 
> The Noise lessens as the Freq LP pot is rotated CCW
> (LP working!)
>
> I had asked Paul about it when was here for AH and
> he said that was 
> 'normal' for this filter.
>
> I would be very happy to learn this is not the case
> and that is is an 
> part or construction problem.
>
> Anyone else have this?
>
> Thanks, Charles.
>
>
>
> The noise
> On Jan 8, 2006, at 12:14 PM, Dino Leone wrote:
>
> > --- Charles Stella <cstella@...> wrote:
> > > I wonder while we are at it is there a
> > > way to address the
> > > noise problem the 480 exhibits in LP mode?
> Thanks,
> > > Charles.
> >
> > Noise problem? What are you talking about? Maybe
> I'm
> > deaf... could you explain?
> > Best,
> >
> > Dino
> >
> >
> >
> >
> >
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