serial/parallel filters

[mwvm]

hello,

so i built Tim Escobedo's ms 20 clone with a lpf and a hpf....i thought i'd vary it a bit and add a series/parallel switch

here's a thing, in series fine.... but when i switch them in parallel linking both inputs and relevant outputs... sounds a bit rubbish.

do i need buffers at input and output stages for a parallel circuits to work properly?

[PRR]

> sounds a bit rubbish.

Not a clear description of the problem.

Two amplifier outputs connected together will usually fight each other. In this case, turn the output pots to 90% and they should mix smoothly.

In general(*), a low-pass and a high-pass summed together is "everything". So not sure what yoou are trying to accomplish?

(*) However two sharp lo-/hi-pass filters summed will usually have "oddness" at the cut frequency. Could be a big bump or deep null. Can even be multiple lumps and nulls.

[ashcat_lt]

In general(*), a low-pass and a high-pass summed together is "everything". So not sure what yoou are trying to accomplish?

Only if they're set to rolloff at the same frequency.  Otherwise you get either bandpass or notch, depending on where they are relative to one another.

[mwvm]

Indeed.

A notch filter sound.

A bandpass can be achieved in series.

Basically the sound is a muffled lpf sound in parallel. Neither frequency or resonance pots have much impact on the sound. Really odd.

Both circuits lpf and hpf aren't perfect but they are usable.  There is added noise in the circuit, especially modifying the cap value to get a better frequency range. So I've increased the voltage at relevant points instead. And I can't get the hpf to a frequency where it ll cutoff everything. If I mod it to do so it interacts with the lpf circuit. Especially the resonance.