Help with 2x SVF Preamp ala Alembic/Wal

[garfo]

Hello, I want to build two of these:http://www.musiker-board.de/attachments/f3-musik-instrumente-know-how//f75-e-gitarren-forum//f39-modifikation-technik-gitarrenbau-e-git//241993d1350756654-lemme-state-variable-filter-sounds-aufnahme-kleiner-test-state-variable-filter_diy-layout-neu.gif

The idea is that there are two, each one connected to one pick up.
So neck pickup will go to one SVF and Bridge pickup will go to another SVF.
Since these are active electronics, what is the best way of mixing the signals together?

I'm thinking several options, but I'm not sure what the best way would be:

1:Use the 10k volume pots from each channel as volume pots, or a blend 20k pot, and wire them in parallel into a single Master volume.
2: Replace the 10k volume pots with fixed resistors and use a buffered mix(buff n blend) and then use a master pot.

What would be the best way to avoid losing any signal

[PRR]

A schematic would be useful for thinking.

[mth5044]

ROG has a nice little schematic for a splitter (google ROG splitter). You could use the second half of it to actively mix the signals together with a blend pot. This circuit also has a phase switch so you could add phase reversal to your arsenal.

[garfo]

This is the layout http://www.musiker-board.de/attachments/f3-musik-instrumente-know-how//f75-e-gitarren-forum//f39-modifikation-technik-gitarrenbau-e-git//241993d1350756654-lemme-state-variable-filter-sounds-aufnahme-kleiner-test-state-variable-filter_diy-layout-neu.gif

A schematic would be useful for thinking.

[garfo]

Yeah, I need just the mixer part.Each low pass filter has an output impedance of less than 1k.My main doubt is if I should use a passive blend pot, or still use the blend pot but then buffer it.

ROG has a nice little schematic for a splitter (google ROG splitter). You could use the second half of it to actively mix the signals together with a blend pot. This circuit also has a phase switch so you could add phase reversal to your arsenal.

[mth5044]

I should have added the word blend to the ROG splitter and blend. You can use the blend section.

PRR is requesting a schematic not a layout - if you don't have one, you can make one from the layout.

[garfo]

Here's the schematic: http://forum.musikding.de/cpg/albums/userpics/17486/alembic-like-state-variable-filter-schematic.jpg
I'm not sure the input from the blender section is intended for low impedance devices, or is it!?If it is, it could be a good candidate.

[PRR]

> pots from each channel as volume pots, or a blend 20k pot, and wire them in parallel

If you parallel two wipers, they fight each other. Add mixing resistors. If you need a master it goes after the mix resistors, 10K will work.

[garfo]

If I use fixed resistors I cannot control how much I will want from one pickup or the other.My idea was really to be able to add a bit of one to the other.Lets say, I'll use mostly the bridge, but at some times I want to add a little bit of the neck pickup still having the bridge as the more open sound.As far as I know using a true Blend Pot I'm able to do this, or using two volume pots.Perhaps If I built a buffer between the blend and a master pot this "fight" would be solved!?

> pots from each channel as volume pots, or a blend 20k pot, and wire them in parallel

If you parallel two wipers, they fight each other. Add mixing resistors. If you need a master it goes after the mix resistors, 10K will work.

[slacker]

Look where Paul has added the resistors, they mix the signals from the wipers of both volume pots, so it does exactly what you want.

[garfo]

Ohhhhh, I ser, the same goes If I decide to use a blend(mn tapper) pot isntead of two volumes, right?

[slacker]

If you want a blend you can do it the same as this http://www.runoffgroove.com/splitter-blend.html remove the volume pots from your filters and add the blend pot instead, you could replace the 1M resistor after the blend pot with a volume pot if you wanted a master volume.

[garfo]

Ei Slacker, I've built it.I've mixed the signals after the preamp, not before.I ended using the 10k resistors as you suggested because the preamps were fighting each other on the blend center position.My question now is, is 10k enough?After I played them individually and mixed it feels like some high end has been removed.Should I increase the value of those resistors, or will that change nothing tone wise!?
By the way, I used a Bourns MN taper Blend pot and left the ground unconnected, that way both preamps sound much fuller.

If you want a blend you can do it the same as this http://www.runoffgroove.com/splitter-blend.html remove the volume pots from your filters and add the blend pot instead, you could replace the 1M resistor after the blend pot with a volume pot if you wanted a master volume.