Dual SVF Tuning

The system I used was to tune filter 1, then try to match filter 2 to it by the following steps

1. play the lowest note where you can still hear the tuning well
2. adjust the range until they’re in tune
3. play the highest note where you can still hear the tuning well
4. adjust the v/oct until they’re in tune
5. repeat 1-4 until it’s dialed in

Having said that, it’s probably easier to just use a guitar tuner or tuning plugin. I know I found a free tuning plugin before when I was tuning my x0xb0x. Although the above steps are probably still useful for getting them totally matched.

Also, if you can’t get filter 1 tuned to 1 octave to begin with you might have to replace a pair of resistors to get there. I had to do that with mine. I was all the way to one end of the trimmer and it was still a semitone short.

I just managed to tune my SVF but I found it a bit awkward so I thought I’d share my findings. Maybe it’s helpful in some way.

First of all I had to turn both v/oct pots all the way counter-clockwise for the best tracking, and even then both filters didn’t track the octaves perfectly. I don’t know how this can be, since the trimpot is of no use this way.

The tracking of the filters seems to depend a lot on the octave range, and thus changes when the cutoff is at a different value. I tuned my filters by setting one after the other at cutoff 63 and res 63. The modulation matrix I set:
1 note cv1 63

For the tuning I used a guitar tuner on my phone (Guitar toolkit for iphone has a really accurate tuner)

1: tuned the range of filter1 so that a C on my keyboard corresponded to a G1
2: tuned the range of filter2 to the same G1
3: set both filters to res 63 and tuned filter 1 to match filter 2 exactly by listing to the “beating” frequency

Because both filters have a slightly different tracking, and v/oct pots are both at the absolute minimum, there is a slight drift in notes along the octaves. It’s not bad an both filters definitely sound in unison.

To illustrate how the tracking changes when you have a different cutoff here is the final tuning of my filter1 at 2 different cutoff settings (one octave apart). You see that depending on the octave the tracking goes from perfect to really bad. I guess this is expected behavior.

cutoff @ 63:
g1 = +16
g2 = +16
g3 = +15
g4 = - 40

cutoff @ 75:
g1 = +70
g2 = +16
g3 = +14
g4 = + 8

The +/- values are cents detune

This behavior means that if you tune the filters one octave apart like that they only stay in tune for a limited range of frequencies. Somewhere below g2 and above g3 one of the filters will start to get some serious frequency drift if relation to the other.

I think I made the best of it, but let me know if I missed something.

Use 1 note cv1 32 and 2 note cv1 32 to get 1:1 tracking between both filters.

It’s pretty easy with Olivier’s technique.

Maybe someone can guide me through the steps with this as well.

1: Power Dual SVF

2: Press Switch 1 and Kill Osc 1

3: Press Switch one again and kill Osc 2

4: Press Switch 2 (filter) set cutoff to 64, resonance to 63, kill env and lfo. I hear a single tone. Range 1 and V/Oct control this tone.

5: press switch 4 (mod) set mod 1, note, cv1, 32. set mod 2, note, cv1, 32.

I only hear one tone. The second filter range and V/Oct do nothing.

What am I doing wrong?

I just want to send this to a friend in Frankfurt asap, if its here too long I will only keep it and rather it go to a friend who will use it. :greed:

wait. i think i found my problem. second filter page is inaccessible. gonna try some things.

filterboard set to svf in the options?

+1 > loderbast

Thank you folks! This was the problem.

I thought I only needed to do that when using a programmer with it.

So now I adjusting the trimmers following other threads and info to adjust the tuning.

Is there a way to just play the 2nd filter tone and not the the first?

Found it. Turn off res on first filter.

Ox80’s method actually got me to dial the trimmers in very close. Thanks for that!

Glad I could help :slight_smile: