The key hinge here is 'single instance'. Whatever Totalmix does, it cannot feed multiple signals to a single instance  with separate outs for each input, so whatever it merely appears to be doing, it is not a single instance.

SuperG
The key hinge here is 'single instance'. Whatever Totalmix does, it cannot feed multiple signals to a single instance  with separate outs for each input, so whatever it merely appears to be doing, it is not a single instance.

Totally agree. Sort of like unscrambling an egg.

SuperG
The key hinge here is 'single instance'. Whatever Totalmix does, it cannot feed multiple signals to a single instance  with separate outs for each input, so whatever it merely appears to be doing, it is not a single instance.

Did you read my post?
 
There don't need to be separate outs for each input. Only one of the 3 audio sources is playing at once, and only one of the audio destinations will be unmuted, so the fact that it all goes through 1 plugin and the same audio gets duplicated 3 ways is not a problem.

Kylotan

SuperG
The key hinge here is 'single instance'. Whatever Totalmix does, it cannot feed multiple signals to a single instance  with separate outs for each input, so whatever it merely appears to be doing, it is not a single instance.

Did you read my post?
 
There don't need to be separate outs for each input. Only one of the 3 audio sources is playing at once, and only one of the audio destinations will be unmuted, so the fact that it all goes through 1 plugin and the same audio gets duplicated 3 ways is not a problem.

Then all you need is a buss. 

I'll repeat myself:
"He could do the same thing via routing to a bus with Amplitube set as an insert - but then he doesn't get to have the 3 separate post-Amplitube fx bins and fader levels.
 
A workaround would be to have each track output to the single Amplitube bus, then that sends to 3 separate buses. But now he has to mentally tie his 3 input audio tracks to the 3 output buses. And his pre-Amplitube and post-Amplitube FX (if any) are in completely different places - an awkward workflow."

Bad post delete

Kylotan
I'll repeat myself:
"He could do the same thing via routing to a bus with Amplitube set as an insert - but then he doesn't get to have the 3 separate post-Amplitube fx bins and fader levels.
 
A workaround would be to have each track output to the single Amplitube bus, then that sends to 3 separate buses. But now he has to mentally tie his 3 input audio tracks to the 3 output buses. And his pre-Amplitube and post-Amplitube FX (if any) are in completely different places - an awkward workflow."

Just out to a buss and then export each track one after another. You get three different tracks but you will be able to control the fader on the buss for what volume you want for each.
 
Then import them into the project. If that is what you want.

Kylotan
The thing that has confused most people, because it was seemingly only mentioned in the first post, is that there is "only one track feeding per time". So the fact that all 3 tracks are getting the same audio back from Amplitube doesn't matter - 2 of the 3 tracks are muted/archived. No need for time-sliced demultiplexing. ;)

I didn't miss it and it didn't confuse me.  What I posted does exactly what he wants.

@ Kylotan - I don't believe the setup you have drawn is what he's describing, but extra credit for taking the effort to try and explain what you think it is he wants to do. It would be a simple matter for 200 bpm to simply post a screen shot of the Totalmix routing; why he hasn't is just one of this thread's many mysteries. 
 
But, the fact is none of us really knows what goal he wants to accomplish. Basically, he has stated what he thinks is a solution, and stated the solution is not possible within SONAR but is possible if you use Totalmix. However, he has not fully explained the problem the solution is supposed to solve. And I interpreted "only one track feeding per time" differently than you did. I thought he meant that he would only be auditioning one track at a time, but want to be able to switch instantly to a different track, and when he switched, what he would hear would be that track through AmpliTube, controlled by the track's output fader. But in that case, all you would need to do would be to set up three tracks, click the exclusive solo button, and drag Amplitube from one track's FX bin to another track's FX bin. However, it appears that if he were to do that, he ALSO wants the previous track he was listening to to be audible processed by AmpliTube. Maybe. Possibly. Hence Karyn's suggestion about freezing, which certainly appears to do what he wants, based on one of the many possible interpretations of what he wants. 
 
I think the main problem with your translation of 200 bpm's post is where you say "A workaround would be to have each track output to the single Amplitube bus, then that sends to 3 separate buses." But that would mean you would no longer have control over each individual track that went into AmpliTube, and he claimed very specifically that I was wrong to say it's impossible to extract three independent audio streams from a single instance of AmpliTube. He claimed that he could do this with Totalmix. I'm not familiar with the latest version of Totalmix, for all I know maybe it does do time-division multiplexing. That's how Gibson's interfaces for their high-tech guitars (like the FBX) derive individual string outputs from a single stereo cable, so why can't Totalmix? 
 
The issue may not be that he lacks a fundamental understanding of routing principles, he may lack a fundamental understanding of basic audio terms. So until he actually defines the problem he wants to solve instead of what the thinks would be a solution, and who knows whether it would be or not, any solution we offer is based purely on speculation about what his problem actually is. 
 
Meanwhile, I just want him to answer my question because if Totalmix actually does what he claims it does, an RME interface is going to have to be in my budget.

JohnnyV - the routing is not pointless under these 4 assumptions: (1) He wants to use a single instance of an effect (in this case Amplitube) shared across 3 tracks, (2) he's only going to have one track playing at a time, but wants to be able to switch between them quickly (eg. for comparison purposes), (3) he doesn't want to bounce Amplitube (because he's going to tweak it), and (4) he wants to be able to have 3 different post-Amplitube fader levels (or post-Amplitube FX, which he mentioned in his last post). Nobody else has suggested any way in which he can achieve this combination. Yes, it's the same mix in 3 cases, but he wants them passed through different faders on the way back in. If Amplitube was a piece of hardware he could do this with the External Insert.
 
John - I'm assuming he doesn't want to export anything because he is still trying to tweak the Amplitube settings to see what works. Perhaps he is trying 3 different mic-ed signals and seeing which works the best. Exporting or bouncing anything would happen later on, by which point this setup is redundant anyway.
 
Karyn - Well, maybe. You are presuming that he is in a position to bounce down or freeze all his Amplitube tracks. Perhaps he is not, and wants to leave it open so that it can be tweaked later, perhaps in the context of the mix. Nobody wants to be repeatedly re-bouncing every time they tweak a setting. But sure, if he doesn't know that Amplitube can be bounced down but he does just want 3 processed tracks each with a fader, maybe that is the way to approach it.
 
Anderton - You're right, he hasn't fully explained the problem, but he has sprinkled clues around, mostly in the first post ("I have three DI tracks for bass [..] only one track feeding per time)" - this means he doesn't need to split them out again) and the last post ("there is no way to add different post effects to that many->"one" track"). The simplest explanation to reconcile everything he's said is that he wants to have 3 tracks, each with their own audio, and in the FX bin, among other effects, is Amplitube. But to save memory he wants to share that instance.
 
"But in that case, all you would need to do would be to set up three tracks, click the exclusive solo button, and drag Amplitube from one track's FX bin to another track's FX bin." As I understand it, this would work, so no - you didn't understand him differently to me. I don't recall anybody suggesting this solution to him yet, though. (Plus, it's rather fiddly.)
 
"But that would mean you would no longer have control over each individual track that went into AmpliTube" - Why? There are still the 3 source tracks that feed into the bus. Plenty of control there. Not that I think this method would be good.
 
"he claimed very specifically that I was wrong to say it's impossible to extract three independent audio streams from a single instance of AmpliTube. He claimed that he could do this with Totalmix"
 
Actually, what he said was you're wrong to say he's not getting three separate audio streams through a single instance. You could take that as implying he gets 3 separate streams out, but it seems more logical that he means it as getting 3 separate audio streams into Amplitube and getting something out. The multiplexing issue is a distraction; if the intermediate plugin doesn't support multiple paths then it's going to be impossible, even if you have mux/demux at the ends. (Excepting the very rare case where each sample can be processed in isolation.)