Okay - I was somewhat curious, i needed to satisfy myself that some of @guiltyrollmops’s findings were the same here, so i set up a little test
I’ll present the findings in a similar manner, this is not necessarily the full story, but it’s certainly a fascinating insight into the character of the A4 filter, and crucially a lesson into how to set it to be ‘neutral’-ish
Please note, this was looked at with no key tracking, normal default res ‘boost’ and for an audition/viewing friendly frequency 65Hz-ish
I fed the A4 a Nord Modular G1 signal with three different shapes for info, having been amazed by the influence of the filter (and variations) on the square - for the square there is a recommended ‘flat’ filter setting (25 res on LPF ) and a value which gives better visual correlation (a pulse width varied shape was thrown in as it wasn’t always easy to see where the duty cycle of the post filter square was) for the saw and tri i have added in a zero res setting to show just how much the filter will impact the waveform, so they’re both shown at 0,25,64 (where 64 gives a closer approximate visual representation of that wave at that frequency) (Note no filter key tracking)
Two identical signals were sent into the A4, one direct via Ext In roughly level matched to a signal pulled clean through the Oscillator Injection of Osc 1 (so the A4 oscillators are all off) with max amp level (ext in level lower)
Both pulled through OB/Live to a pair of waveform monitors running simultaneously on Left and Right respectively, that way you can view the source and the impact on the source in real time
Note this doesn’t tell the whole story and it may be a flawed analysis, but it’s an interesting insight nonetheless - those high res settings may colour the sound somewhat, especially in other frequencies, so this is a partial insight into a complex picture
The filters are certainly not transparent, it does indeed beg the question, could they be bypassed for an extra flavour of sound, it’d be interesting to see what shape the A4 sends out pre filter, i bet they are more ‘regular’ looking than we all assumed
I’m glad i caught this part of the discussion above, i missed most of it since it got revisited a week or so ago, interesting … i didn’t try with resonance boost off fwiw, but it’s clear that the filter pair are a big player in the overall sound
It’s fascinating to see the impact of varying the peak filter full range, it inverts the signal when you go from freqmin/res0 to freqmax/res0
Anyway - for all the figures, they are presented as a snapshot of the filter settings and the A4 inject via filter is the upper waveform, the lower waveform is the direct one via Ext in - both are sent through main output via OB (i was monitoring pre OB) - not sure if i should have been doing anything about the DC offset
It would have been better to include a spectroscope
Nord square
res 25
res 25 (reduced pulse width)
res 70 !
Nord saw
res 0
res 25
res 64
Nord tri
res 0
res 25
res 64
