Edit: I've been able to reduce the offset swing to between +1v and 0v with the 'initial frequency' trimpot.
Dean
Dean
--- In cgs_synth@yahoogroups.com, "goldencardigan" <dean.lowe@...> wrote:
>
> Hi all,
>
> I've just finished building the serge filter and while everything looks and sounds like it is working correctly, I have noticed a bit of dc offset on the lowpass output. With no input signal, the dc voltage swings between +4v through 0v and back to +1v as I turn the cutoff knob.
>
> It appears that the offset would not normally be this high, but I have installed the resonance mode, including using the buffer stages to compesate for the gain loss.
>
> The offset disappears when I turn on the low freq mode.
>
> I'm just not sure if this is normal behavior for the circuit or if I should be chasing a fault. I could of cause add a dc blocking cap to the output, but this would kill the low freq mode.
>
> Has anyone else experienced this?
>
> Cheers
> Dean
>