External FX Send & Return Bus Assignment Flexibility

I can see this is a request stretching back years in one form or another. The issue is we cannot assign two individual mono external FX instances as a combined stereo external FX instance using the same send/return bus device port routing. For years it’s been either/or, which kind of defeats the purpose of purchasing two identical hardware processors for the flexibility of using them as dual mono or stereo applications. For example, I have a stereo compressor configuration using two mono compressors, but I also want to assign each compressor as a mono FX instance:

The problem comes when I go to assign the send/return device ports, which are obviously the same ports used in the stereo configuration. When I select Output 5 for the first mono send bus:

I get this:
External FX 03

What’s required is the same functionality you’ve given to the Inputs buses, where I can use the same device ports in a stereo and mono configuration:

Surely, if this is possible, then giving the External FX tab the same functionality should also be possible. Please!! A workaround would be to split stereo stems into 2 L&R tracks and insert the respective L&R mono external FX instances, but that’s just ridiculous.

Please look into this for us. :pleading_face:


I do a similar but I only use 1 stereo external FX and 1 mono.
You don’t have to use 1xStereo and 2xMono, when you want to use it as stereo, just use stereo, then when you want to use mono, use stereo and move the i/o to another mono.
You can insert a stereo instance into a mono track and the device receives L channel. Sure you have to change i/o on the F4 page but it’s quick enough for me.

Hi Takashi-san! Thank you for sharing your workaround with me - I really appreciate it. :smile: Just to be sure, are you saying this is what you do?

I guess my point is we have to come up with workarounds for a workflow issue that’s been identified since Cubase 9. I know Steinberg can only address a finite number of issues at any one time; however, a 2-mono-1-stereo configuration that shares the same device ports should be a reasonably commonsense, and indeed commonplace, approach in a hybrid DAW/external hardware scenario. Why shared device ports work on some F4 audio routing tabs and not others is confusing; clearly it’s possible. I just want to set up my studio’s I/O routing and not have to change it depending on which project is open.

In the meantime, I’ll use your workaround!

Yes, that’s what I suggested.

I am not sure about having ability to assign the same port twice for external effects.

What do you expect to happen in your scenario when you have used mono instance 1, that shares Lch with stereo instance?

Sorry - it appears I wasn’t all that clear!

I’d like to have 2 mono instances and 1 stereo instance of the external compressors configured in the External FX tab at the one time. The current functionality only allows me to configure 2 mono instances or 1 stereo instance. I don’t want to keep swapping I/O device ports between the mono and stereo buses.

In terms of workflow, let’s say I’m working on a mix and currently I’m mixing top and bottom snare tracks. In this instance, I can insert the 2 mono external compressors, one for each track, dial in the compression, then print the tracks and remove the external compressor inserts. Now I want to insert the compressors on a stereo overheads track. As things stand right now, I have to go to the audio connections window and reassign the device ports from the 2 mono configurations to the stereo configuration before I can insert it into the overheads channel strip. However, if the stereo external compressor configuration was already set, I could go straight to compressing the overhead track without having to worry about device port reassignments. After printing the overheads, if I want to then apply external compression on a bass track, then, right now, I’d need to go back to the audio connections window and change the I/O configuration yet again. It’s not a streamlined workflow, and it’s not as if I’ll ever want to assign a stereo and mono configuration at the same time - it doesn’t make sense.

With all external fx inserts, re-amping and external instruments, etc., once I have the track dialled in the way I want it to sound, I print it as a second track so I can free up the fx/re-amp/ext instr bus for further application in my project.

I hope that clears it up.

Yeah, that makes sense.
My point was, e.g. when you have mono instances active for SD bottom and top, Cubendo somewhat needs to detect that and prevent you from inserting stereo instance elsewhere. This or similar behaviour is not currently implemented anywhere else. It’s new and for them perhaps an irregular thing to realize.
On top of that, I wish I can re-use external effects. Cubendo must be able to check if the external instances are activated or not. It could let us insert the same mono instance elsewhere if the first instance is deactivated. On unfreezing/enabling the track, it can again check if there is an active instance. If that’s the case, it can warn us that the external effect is in use and the new instance can be removed. Similar to the above, this is also new and irregular. But surely both are possible.

I am not sure if your use case is requested in the past, I requested the re-use case some years ago. Still hoping to see these.

I have stereo units that I would like to use as 2 independent mono sometime.
always a nightmare.
So I have
unit A set in stereo in external FX
unit A set in mono 1 in external FX
unit A set in mono 2 in external FX
when I want to use it in mono… i manually update the send returns in the control room window.
Very frustrating managment.
Same when you have a unit used in a track, you should be able to locate zoom to that track to remove it faster so you can add it on another track. (or have a “remove from tracks” function in the control room window.)
also frustrating.
Each time you open the control room window, all tree structure for send returns are minimised… drives me crazy.

Yes, we can. Here’s how to:

  1. Configure your two-channel external device as dual mono (no need for stereo configuration), e.g., an analog stereo compressor as two mono compressors;
  2. In the project window, if the audio track is mono, simply insert one mono instance of the device;
  3. If the audio track is stereo, insert both instances of the device in series AND have Insert 1 process L ch. and Insert 2 R ch. in Channel Settings > Inserts > Routing.
  4. Save it as a FX chain preset. Enjoy!
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Hey @Aivaras!

Thanks for responding - your solution is genius! I had never even looked at the Routing tab in the Channel Editor before, so learning something new about Cubase is a real bonus.

Seriously brilliant! :clap:t4: :tada:

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Go trick… but are you sure this is working ? I’m having strange issues… might be a mistake a make.
So I have a stereo compressor. If I create a stereo external FX. Using send 7&8 and return 7&8 all is working normal and fine . I can change send return level or bypass the fx in nuendo. Sound return from compressor working as expected.

Now I do your technic externFX 1 mono send 7 return 7 and externFX mono send 8 return 8. (it deactivates my stereo external fx of course)
I add those on insert 1 & 2 and set the routing :
1 : fx1 / direct out
2 : direct out / fx2
And now the sound from the compressor is all messed up… like a stereo problem.

The unit is ssl bus+ I see no reason why a stereo FX or 2 monos would sound different. There’s an MS compression option but still input L is L and R is R.
So I though maybe having FX1 and FX2 on different inserts might affect the delay and tried to do a “measure delay” on both inserts.
Now this I really don’t understand :
measure delay on FX1 gives 0ms (loud pick noise going to L send L return)
measure delay on FX2 gives. 0ms but… the routing I set above -from Channel settings / routing) automaticaly switches back from R to L !
so… I don’t know about dual mono to use a stereo unit. I would be happy for you guys to make sure it’s accurate and you don’t get phase somewhere becuase the bus+ in MS mode should give me a strong mono center if I push the M and lower the S but the M sounds very bad…
If I use a stereo FX insert (with same send return outputs) from my Audio connection External FX then this M is solid.

no idea what is going on… this is taking to much time anyway.
I think have the possibility to have external inserts as stereo or dual mono is important just like you can have inputs from your soundcard mono or combined in whatever configuration.
The software should be smart enough in case of external send to see if it’s already used or not. Also smart enough not to force us to have to remove the insert from other track but simply have them disabled (so we can switch from one to another without inserting FX.
this all thing need redesign.

It is not a trick or workaround. It is a normal working setup in Cubase.

I’m not sure I’m following you in this step. Look carefully at this screenshot and try reproducing the FX routing settings in Nuendo:

thanks yes this is exactly what I have.
I’ll try to make a video about it if I find some time.
No offense I call this workaround because I don’t see a reason why I would have to use 2 mono inserts for a stereo external unit.
or use a stereo insert and then be stuck and having to readjust the connections ins control room to insert 2 monos.
please try to “measure delay” on your insert 2 does the routing stays ?

Just post the screenshots for Audio Connections > External FX > Expand All and Channel Settings.

If you want to operate a stereo external unit, set its I/O as stereo (no workarounds involved). If you want to switch smoothly between stereo/dual-mono/mono configurations, use the dual mono setup (no workarounds involved).

I do remember there being an interaction between the two plug-ins in terms of measuring the delays which struck me as a bug (can’t test it now). Just measure the delay value with one plug-in and manually enter the same value in the other.

here is the settings for stereo external FX that works

And trying to use 2 mono channels but on a stereo unit my seetings are like this :

with this routing

this is a 5.1 session
but I did the same with stereo only.

Hi @Aivaras & @sgodzillat!

I think I see what you mean about measuring delay in this configuration being buggy. Here’s the configuration before measuring the delay figures:


Measuring the delay on the left (slot 1) produces the expected result, so all is good here:


But after measuring the delay on the right (slot 2), Cubase automatically switches the routing configuration of the right insert to the left channel:


I think I’ll just measure the delays at the start of a session on an empty stereo track to know they’re accurately configured - though the 0.02 ms difference in the above example is negligible - and just load the FX chain whenever I need it, which has the correct L/R routing configuration. It’s the ol’ Set and Forget!

I’m assuming you have to keep connecting/disconnecting the send/return buses when swapping between the stereo/dual-mono configurations. If that’s the case, it comes back to the reason for the feature request in the first place, which, it appears, is still an issue for stereo outboard gear.

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Adding 5.1 to the equation complicates testing, otherwise your I/O configuration looks correct. The only other obvious place that may cause a sonic difference between your stereo and dual-mono configurations that I can think of are the different settings in the external plug-ins themselves.

Make sure the settings in the plug-ins are the same: copy the delay and gain values of your currently disconnected stereo configuration from Audio Connections > External FX > Delay/Send Gain/Return Gain and paste them in the respective fields of the external plug-ins. With the delay and gain values in unison, your stereo and dual-mono configurations should sound identical.

Great report and in accord with my findings! Please, consider reposting it in a new thread as a bug report. It will catch the attention of the devs quicker that way.

No need to re-measure the delays. Cubase remembers the last setting between projects. In addition to the routing, the FX chain also saves the delay and gain values. It is indeed a set-and-forget situation. I run 28 channels of external gear in Cubase. It works. I don’t have to think about it.

I have a 0.001ms offset I’m trying to get rid off. It’s 50samples And clearly audible :stuck_out_tongue: (specially with a parallel fx) [EDIT] my bad i measured 1ms not 0.001ms :stuck_out_tongue: I got it all messed up. yeah 0.02 is not audible then.

Yes sorry for those screen capture. I did the same in a full and only stereo session and had same issue.

yes it’s 0 / 0 / 0 settings.

Are these values also what you have for the stereo configuration?