How to use mono filters on stereo tracks

[Otolito]

Hi.

I have a mono plugin (4 band parametric eq, Ladspa) I want to use on a stereo track. The track must be "split" into two mono tracks and an instance of the plugin inserted into each one.

What I'm doing without success is:

Copy the stereo clip to another track

For the first track clip enable left channel only in clip properties (the waveform changes to show only the left channel)
For the second track's clip enable right channel only

Insert a patchbay filter on each track and set it so that the first track only outputs to the left and the second track only outputs to the right. (e.g. left to left and rights disconnected on first patchbay and lefts disconnected and right to right in second patchbay) At this point the two tracks together sound like the original stereo track, e.g. the split is complete.

Insert an empty rack filter on track 1 and put the equalizer plugin in the rack, or insert the equalizer and wrap it in a new rack. Then copy the rack to the second track by ctrl-dragging or clicking on "drag here to insert an instance of this rack" and dragging. (The idea is to put the rack on both tracks so that when I edit the EQ on either instance of the rack both tracks are affected)

Now, where do I go from here? I know this can be done. I know I must configure the inputs and outputs in the rack and the rack instance's properties but I'm not sure what the right settings are. I've tried a few things but I always end up getting mono and don't understand why.

It would be great if someone told me how this is done.

[mchoffmann]

Hi,
why not simply do a rack with 2 instances of your plug each connected with l/r audio output?

Regards
Marc

[Lutin mutin]

Hi !

When I am in a similar case of you (as I understand it), here under is what I do :
1. copy the stereo track in an other track (total of 2 tracks with the same audio stereo)
2. select the left part in one, and the right part to the other one (as you do it in your comments)
3. I render each track ==> track 1 now mono (was the left one) ; track 2 now mono (track was the right part) ;
4. If my plugin is a mono EQ (for exemple), I insert the EQ in track 1 and the same EQ in track 2
5. I adapt the settings of the EQ to each track. If I want the same "preset", I copy all the setting of the EQ track 1 to the EQ track 2 ;
6. I have in the master output, a stereo track... done !
7. Other solution : after point 5 above, I route the outputs of track 1 and track 2 not to the master, but to an other track, let say to track 3... and now, track 3 is stereo, and "corrected" with the mono EQ... done !

For me, this way has an easy workflow than doing something equivalent through a rack, because I have always directly access to the settings of the 2 EQ.

I hope this will help you...
... my 2 cents.

Best regards and good luck !

Lutin mutin.

[Otolito]

why not simply do a rack with 2 instances of your plug each connected with l/r audio output?

@mchoffman I'm not sure I understand you correctly. Do you mean I should connect the single output of the plugin to the rack's two outputs? I tried something like that but it didn't work (this resulted in stuff meant to be carried to only one channel being carried to both, hence becoming mono). If this is not what you meant would you mind describing the steps?

@Lutin if by "copy" you mean you set everything again manually on the second EQ to match the first, that's what I'm trying to avoid.

By the way, I just discovered there is an option in the plugin properties that allows it to copy the parameters of another. Seemed like what I wanted but when you change its parameters the other eq takes some time to copy its settings, which results in distracting stereo effects. I'd rather do it with a rack

[chico.co.uk]

Imagine the tracktion Reverb filters in this rack are two instances of your mono filter.

rackf.JPG

Connect up the left audio input in the rack to one plugin, the mono output of that plugin to the left output in the rack

Connect up the right audio input in the rack to the other plugin, the mono output of that plugin to the right output in the rack

So your left hand side goes through the top mono plugin, the right hand side goes through the bottom one

Drop this rack onto a stereo track, and tweak the mono plugins in the rack to taste

[Otolito]

"Drop this rack onto a stereo track, and tweak the mono plugins in the rack to taste"

So I have to edit each plugin settings individually? If so, I only want to edit one plugin while affecting both channels

[whyterabbyt]

"Drop this rack onto a stereo track, and tweak the mono plugins in the rack to taste"

So I have to edit each plugin settings individually? If so, I only want to edit one plugin while affecting both channels

Yes, but its not possible(*) to have one plugin's controls affect some other plugin's controls, even if that is a different instance of the same plugin.

(*) Not in Tracktion(**), in realtime(***).

(**) You could maybe do it do this sort of thing in a couple of other modular hosts eg Bidule with parameter linking.

(***)You could maybe cut and paste the automation lanes from one plugin to the other, parameter by parameter, after the fact, if its not in realtime. But you'd need to repeat that after any updates, or possibly write a macro to do the copying.

[chico.co.uk]

Suggest you find a stereo eq, because that's basically what you want to use. You're trying to make a square peg fit a round hole, and it's not obvious why. I assumed you wanted to eq the separate left and right channels differently. If you don't, just use a stereo eq plugin.

[Otolito]

I'm asking only because I know it can be done. Racks can be exploited to achieve this. I've seen it done, I just don't know how to do it myself

[lay it prodctions]

One question. Will this plugin when placed on a track make a audio clip that don't have a even volume on the left and right even on the output meter?
If so you are getting a mono signal.
You can check by putting a stereo clip on the track
and volume and pan fader before and after the mono plugin.
Now pan the one in the front left or right.
You should see a even signal on the level meter.

[Otolito]

One question. Will this plugin when placed on a make a audio clip that don't have a even volume on the left and right even on the output meter? If so you are getting a mono signal.

That's what happens if I just place the plugin on a stereo track. The output becomes mono. Also my attempts at configuring the rack result in mono.

[lay it prodctions]

Okay I get you. The image in the thread is the best way. If you want the left to mirror the right just set it to mirror the plugin. In the Plugin options.

[Otolito]

That's what I tried but it's not very nice cause it doesn't work in synch (the second plugin takes half a second to mirror the first) and two instances of the same plugin require more cpu.

[whyterabbyt]

I'm asking only because I know it can be done. Racks can be exploited to achieve this. I've seen it done, I just don't know how to do it myself

I really doubt it; AFAIK there's nothing in Tracktion, or in racks that allows one plugin's controls to affect a different instance of the same plugin.

It might be that what youve seen is two plugins set up to respond to the same MIDI controller, and that's controlling them both. If Tracktion even lets you do that, Im not sure.
And there are a very small number of plugins where they've been specially written so that multiple instances can control each other.

But I dont see how what you're describing can be done; there's no mechanism for routing parameter info between plugins.

[Otolito]

It might be that what youve seen is two plugins set up to respond to the same MIDI controller, and that's controlling them both.

Nope, this is not dependent on midi, but being able to do this would be awesome as well. In fact it was the first idea I thought of for my problem.

And there are a very small number of plugins where they've been specially written so that multiple instances can control each other

Yeah, like the one I'm using. But this one doesn't synchronize well when using it this way. In case you're on linux, do you know any other linux VST or ladspa plugins that can do this well? Maybe they work better than my 4 band parametric