Dual SVF 0.2 to 0.3 changes

Sorry if this has been covered but is there a changelog for the new rev board?

Also, the 0.3 sch on git doesnt open in eagle…

Strange, it works here. Which version of Eagle do you use?

What has changed:

  • Resistor values in the mixer and the cutoff CV scaling circuits. There’s also a 220k->330k change in the filter core to match the Anushri design.
  • PCB rerouting.
  • Added a pair of pads in the VCA circuits for a 2M resistor, for offsetting the VCA CV down and preventing bleed.

6.5.0 (tried 6.4.0 also)

Throws up a :

line 17638, column 6: redefinition of name ‘F2SW[0…2]’ in tag

error

I can open other sch files normally, weird.

Did you download RAW from the github?

I use the app so I just pull the whole repo but I know what your saying… It’s not that. I can open other schematics just fine, it doesnt like that one for some reason

It might be that there’s so bug in Eagle’s file format conversion code. Do the v0.2 files load correctly?

Nope, in fact I can open all sch files in that folder except those two.

@pichenettes:
Minor correction to the new build instructions Step 1: Capacitors
Add 1x 100pF ceramic capacitor (marked 100 = “10 with 0 extra zeros pF”) in position C7. This part is not polarized. It tunes the frequency of the DC/DC converter which generates the negative voltage for powering the analog section.

Should that read 10pF, not 100pF?

Fixed - this is 10pF as printed on the PCB indeed!

I was having the same problem opening the file in Eagle the other week via ZIP. The app on Windows8 was also not showing recent files in the Repo like the XT stuff, still shows v01 and no Midnight boards.

> The app on Windows8

I assume you mean github. You need to pull the XT branch.

Thanks for that, worked like a charm.

"What has changed:

Resistor values in the mixer and the cutoff CV scaling circuits. There’s also a 220k->330k change in the filter core to match the Anushri design.
PCB rerouting.
Added a pair of pads in the VCA circuits for a 2M resistor, for offsetting the VCA CV down and preventing bleed."

@pichenettes: Does this mean that the v0.2 board could be built up with the new values and perhaps adding that 2M resistor point-to-point to be at almost v0.3 specs? The only reason I ask is that I plan to build a SVF board in a while but don’t need the full Midnight kit and it looks like only the v0.2 is available as a bare PCB.

> Does this mean that the v0.2 board could be built up with the new values and perhaps adding that 2M resistor point-to-point to be at almost v0.3 specs?

Yes.

I have compared the PCBs (but not the schematics) and here are the changes in resistor values from dualSVFv0.2 to dualSVFv0.3. The X denotes components omitted from v0.3.

Questions:

  1. Should the resistors marked X be omitted?
  2. Should the capacitor marked X be omitted?
  3. Are the 3.6V zener diode values used in v0.3 critical or can 4.7V zeners be used as shown on the v0.2 PCB?
  4. Have I missed anything?

1) Not all, check the 100k / 68 carefully on the schematics.

2) Yes.

3) Change to 3.6V

@pichenettes: OK, please see attached - the 100k is omitted and C2 is replaced with a link, and the 68R replaced by 220R. Is that correct? Yes, it pays to check the schematics…

Looks good.

Hmmm, I have built a v0.2 dualSVF with the substitutions, omissions and links shown above, and it only sort of works. The second filter works fine in all modes, and self-oscillates at high resonance as expected. However the first filter doesn’t self-oscillate (although resonance adjustment does have an audible effect), and the cut-off frequency is very low, even with the range trimpot at its extreme (yes I tried both directions…). In fact, I thought filter 1 didn’t work at all (almost no sound from the standard patches) until I switched its mode to BP or HP. In fact, it clearly works, and in BP and HP modes is sounds exactly as it should (albeit no self-oscillation on high resonance), but the cut-off range is so low in LP mode that almost everything is filtered, even with the cut-off set at 127.

Any clues? Have I overlooked a substitution? I’ve been staring at the schematics for quite a while, but nothing jumps out at me.

Show us what you’ve built.