I've recently started using Satson - originally for its Console Emulation, but as it has VU meters for the channels, I've started to use those for Gain Staging.  I'm using only VST synths, and as I understand it, I get the output of the synth to hit approx 0 on the VU meter (it occasionally goes over) and then use channel fader for the out put volume per channel.  
 
I'm routing each channel to one of 4 busses, before it reaches the Master.    Here is where I am confused - the Satson Buss has VU meter, but no Gain knob.  I don't have anything to use on the Satson to up the gain, and most of the time its quite a bit below the 0 on the VU.  
 
Question:  Does it matter that the busses don't hover around 0, that they are lower?     And if I SHOULD get them to around 0, how do I do that (eg, use bus gain level to up it before it hits the Satson, then reduce the volume by same amount on the fader)?

It's not necessary for the sub-busses to hit 0 on the VU. You can pick any target you like as a reference, as long as it's not too far left of the center position (because VU meters get harder to read the further left of 0 you go). 
 
In fact, it's probably better to NOT hit 0 on a submix. When those busses get added together on the master, the level will likely increase, requiring your limiter to bring it all back down. 
 

Thanks Bit - yes, you are right, the sum of the busses puts things right back up again.  
 
Here is what the Satson manula says though ... as you can see, re the Busses, it says to set the volume to average around 0 (although it does not say how to do that, as there is no gain on the Satson buss).
 
As A Gain Staging Tool:
To get a good mix, start by leveling your tracks’ volume output:
1. Create a new mixing project
2. Insert Satson Channel on all tracks of your project as a first insert
3. Insert Satson Buss on all busses and the master track
4. Before leveling your tracks with the DAW fader and before inserting other plugins, use
Satson Gain control to level individual tracks to 0VU (VU meter near zero)
5. When you have leveled all your tracks to 0VU, do not touch Satson’s Gain control again
6. Start mixing as you usually do: Insert new plugins; adjust the volume levels using your
DAW’s fader tracks, etc. (Please remember point number 5)
Buss Volume Levels : As with individual tracks, set the volume level of your busses to
average around 0VU as well. While viewing Satson Buss’ VU Meter, adjust tracks that send
to the buss with your DAW fader (not Satson’s Channel Gain control. Remember point number 5
above!).
Master Track Volume Level: Use the same process as above for “master track” volume.
Adjust the busses’ DAW faders to level at 0VU on your master track or 2buss.

 
The meters are adjustable to -14db or -18db and this should be taken into consideration.  I've learned from discussions here to pick the reference according to need, then use meters at each stage and adjust each stage so the needles just touch 0 on the peaks.  Stick to your reference throughout and there won't be any problem when you reach the end.  This seems to be more or less was is being done here.
 
I'm not sure that using the Satson Channel and Buss emulators gives you enough meters to see each stage.  And I don't see how the signal could be low when it hits your buss if it's near zero in the track that feeds into it.  Especially if there's more than one track near zero feeding into your buss.  It should be too high, if anything.  Does the Satson Buss reduce level on its own ?
 
Meters like those from Klanghelm are easy to insert anywhere you want to see what's going on.

The Satson is not the way to go in order to set up good gain staging. A proper VU meter is better and also one that has many ref levels as well. eg -14 or -20 etc..It may also be altering the sound which is not desirable.
 
I get all the tracks hitting 0 dB VU. (rms) Also when Paul P says get the VU meters to touch 0 dB VU on the peaks what he is really saying is loudest part of the rms component is hitting 0 dB VU. Real short term peaks don't actually move the VU much at all. They slip through. Use your peak metering to monitor short term peaks. This can be confusing.
 
I manage to get buses to also be at the ref level but I meter the buses before the buss fader. I tend to adjust the buss faders down a little and you can still end up with a perfect mix with all the buses feeding the main mix buss as well and that should also be at the ref level.  When you do this well you wont bring on a clip light anywhere either!
 
Turn the SPL monitoring level in your room up!

Jeff Evans
Also when Paul P says get the VU meters to touch 0 dB VU on the peaks what he is really saying is loudest part of the rms component is hitting 0 dB VU. Real short term peaks don't actually move the VU much at all.

 
You're right Jeff, I should have been clearer in my choice of words since peak has a precise meaning.  They only 'look' like peaks on the meter,in reality I guess they're more like mountains.  So the summits of the 'rms' component.
 

Thanks for the replies.
 
Paul :   Re your comment "I don't see how the signal could be low when it hits your buss if it's near zero in the track that feeds into it.  Especially if there's more than one track near zero feeding into your buss.  It should be too high, if anything.  Does the Satson Buss reduce level on its own ?" ---- I get each track that feeds to a bus to hit 0VU as a max, but that is the first insert on the chain.    The actual channel faders output of the various tracks that feed into a bus are lower than Zero dbfs, to when the tracks hit the VU meter on the bus they are not as hot.

Jeff:When you say Satson is not a good tool to use - do you mean just the Klanghelm is better as a VU meter?    the analog console coloration the Satson puts on, can aos be turned off, so in that case it should be like using a VU meter without coloration.
 
Re your comment "I manage to get buses to also be at the ref level but I meter the buses before the buss fader. I tend to adjust the buss faders down a little and you can still end up with a perfect mix with all the buses feeding the main mix buss as well" ----- does that mean you will use the Klanghelm trim to boost the bus signal if its not getting up to 0VU, and then bring its output fader down?

I have got the Satson and yes it is good console emulator.  Although I have Mixbus now and for me that sounds quite different and better.  But it does mean complete export of stems and into another DAW.  For certain genres it is well worth it though as many here also agree. (All the VU's in Mixbus are calibrated to -14 which also happens to be my main ref level here for most work)
 
The VU should be OK in the Satson and it will certainly allow you to see rms levels pretty well.  It only has two references though so it is limited in the ref levels it can work at.  (It is nice to just switch into -20.  All I have to do is recalibrate my real VU's and drop everything incoming that is down 6 dB)  Also the ballistics of the meter may not be quite as real in the Satson as say the Klanghelm ballistics are.  I read a bit more into meter ballistics.  I have found virtual VU's move in many different ways compared to the real (quality) VU's. They are hard to beat as they move in such a beautiful manner.  The Klanghelm meter is surprisingly close!
 
I don't use the meter to add or subtract gain.  (That could be confusing. Some how gain magically appears in your staging) If all your track levels are at the rms reference level than it is always easy to get any buss to reach 0 dB VU as well. The balance of track faders feeding a buss determines this final buss level. If I find a buss is low in level eg say it is reaching consistently around -4 dB VU then I grab all the tracks feeding that buss as a group and increase their (track faders) level slightly and it usually does the trick.  I use the Presonus Faderport and it is excellent for fine tuning stuff like this.  If a buss level is reading -1 or -2, I tend to leave it.  Being fractionally low won't hurt.  This is level before the buss fader.  I fine tune buss faders as a group that are feeding the stereo buss.  They often end up close to unity or -1 to -2 dB as well.
 
I find I can get all my tracks sitting at say -14 dB VU (rms level), all my buses which contain various mixes of track groups at the ref level and the final stereo mix at ref level.  With care and fine balancing I find it is possible.  And at the same time all the mixes on the buses and the final stereo buss are perfect.
 
Ballistics comes into play.  A buss may appear as being over loud but it could be some wild VU needle swinging instead.  (eg one or more tracks has poor dynamic control hence making levels erratic)  A compressor set right will tame that wild swinging  (buss or at track level usually on one offender) and the needle starts to move much better.  It pumps up nicely to 0 dB VU but does not go over.  You only need mild compression and the ballistics settle right down and now the level has gone from wildly moving up to + 3 dB VU to a more fluid action easing up real nice and just hitting 0 db VU.  Dynamic control on buses is great because it can tame a whole bunch of tracks at once.  Removing un needed frequencies also helps to tame wild swinging needles.  The VU meter has a response to DC actually so it can show very low un heard frequencies.  And also very high frequencies that don't need to be there.
 
Think about when the mix on say a buss is right, the VU is now going to show you that lovely mix in the form of a smooth but dancy ballistic.  When a mix is wrong the needle does not move well at all.  I can tell that something is up.  You can almost mix using a VU.  After a while you learn how much to push each track fader up.  First one to about -4 db VU etc... As the other stuff comes into a mix at the right balance and level the VU just ends up hitting 0 dB VU and it is moving great.  On a stereo buss if your vocals are tool loud the VU will move a bit wrong and the level will be too high.  Once you settle vocal levels right down to the right spot then the VU is now showing you the music and the vocals together and it just starts looking about right.

Hi Jeff, thanks for the detailed reply.  I also got hold of the Klanghelm VU meter (8 EUR can't go wrong).   
 
I'm still not totally clear how to handle the busses - you say if the bus is low in level then you group all the tracks that feed the bus and increase their level.   This will now make them too loud in the mix, so is the aim then to drop the Group fader to compensate?    It sounds much easier simply to increase the Klanghelm Volume Control knob by a few db (or whatever it takes).  Is there something wrong in doing it that way- will the sound quality suffer?   Also, all my tracks feeding into each group are all over the place, so it would be very fiddly to find them, group them, and raise the overall level.  

It actually makes no difference in terms of fidelity whether you turn up the tracks going into the bus or increase volume at the bus itself. Either way, you're doing the same thing: multiplying the data by a constant multiplier. Do whichever method you are most comfortable with.
 
You could, however, make a mathematical case that it's not preferable to reduce track volumes and then make them up at the bus. That may be where Jeff was coming from.
 
Keep in mind that we're talking about levels going into the master bus, not the final post-limiter levels. If your levels going in are conservative, then you leave more options about how loud the final master will be. That can change depending on your final destination (broadcast, MP3, YouTube, DVD/CD) and you probably don't want separate mixes for each.