I have been using a Mackie 1202 VLZ until . . .

Hmmm... I use a 1402 VLZ and never thought to test it for coloration. It would be easy enough to set up an A/B test. I'll give it a shot later.

Even an SSL E-Console's going to color the sound--albeit, in a pleasant way. Your speakers color the sound. The result is the key. If you work on inferior gear and produce killer mixes, you're going to have other people grabbing the same gear wherever they can. I wouldn't read too much into that. For Mastering purposes, the most transparent gear is the thing to shoot for, unless the desire is to color the sound. Aside from that, using Sonar and a 1202VLZ will probably do less damage than dropping in some modeled plug-ins. 

Go fix the room, or fix the instruments, talent, mics, pre-amps, clocking, monitors etc. before you spend too much time on OP-AMPs inside a listen-back mixer.

Viamichael
My nephew the sound engineer told me to take it out of the mix because it was coloring the sound. I only use it to control the volume coming out of my Edirol FA-101 into the powered Mackie monitors. Boy, was he right. The sound was very boxy, probably caused my some midrange boost. Now I have to control the volume coming out of my computer so I don't blast the speakers and my tinnitus riddled ears. I don't like doing it this way, but until I get one of the passive single knob volume controls this will have to do.

Have any of you experienced this and if so do you have any suggestions on which monitor control boxes I should look into?

Hmmm... I picked up a new 1202VLZ almost twenty years ago for my garage band setup.  Never really noticed anything off with the mixer.  But maybe we weren't all that either.  I had more trouble with my PC and sound cards back then.
 
I usually kept my EQ's at Unity or below, as well as all of the gain knobs. I always thought it was pretty flat, unless someone monkeyed with the EQ or something.
 
I ran all of my hardware synths audio outs to the line ins #5-12 on the patchbay.  My buddies guitars and or mics were the only thing that ever went into the mic pre-amps.
 
I believe that I hooked up my M-Audio Delta 44 soundcard with 2 in/2 out mode using the Mackie tape in/out hookups, and then used the control room outs to my amp and speakers.  This little thing had more routing options than I could ever need, LOL!!!
 
I don't have it currently hooked up to do any a/b testing with, since I'm mostly playing in the box these days and all of my sound goes directly out to the monitors.
 
But you do raise an interesting question.  I wonder if that's why Cakewalk decided to add console emulation to the Pro Channel and sell it as a "feature"? 

Viamichael
There is a serious difference when the 1202VLZ is taken out of the equation.

I think something's not right with your test conditions or you particular 1202. I just spent an hour doing various blind A/B tests of parallel analog sends to my 1402 vs. a direct analog loopback, and I would gladly challenge anyone to consistently identify which is which. I tried both line level channel strip inputs with EQ's centered and Aux Returns that have no EQ, and got the same results.
 
I also found that phase-inverting one input canceled the other to approx. -30dB below the source signal level. What was left was probably due more to A/D/A conversion differences and non-linear phase shifts between channels on the MOTU than anything else. And fiddling with any EQ, either on the Mackie or a plugin in SONAR created an immediately obvious difference.
 
Based on this, I would have to agree with others that the coloration of your monitoring system and your room are going to be far more significant than anything a properly functioning Mackie is going to do when used as a simple attenuator between your interface and monitors.

Viamichael
I hear all your thoughts that most of you aren't buying this, yet you say that the monitors and the room effect the sound more. This thinking confuses the question. The monitors are the same and the room is the same. Nothing changed except to take the 1202 out of the equation. And, this was replicated in 2 completely different studios.

Maybe you are dealing with defective channel strip(s)?
 
To rule this out, try connecting your audio interface to the "Tape In" source.  There is no EQ on that one.
 
Then select only the Tape source, and center the Main Mix and/or Control Room knobs.  Any difference?

Looking at the current version of the 1202vlz, I see three sets of outputs that could be used as "monitor outs":
 
1) Main Outs on top.
2) XLR Main Left and Right in the rear.
3) Control Room Outs in the rear.
 
Not to mention the ALT and AUX outs...
 
I'd try all of them and see if there's a marked difference in the sound.

Viamichael
I hear all your thoughts that most of you aren't buying this, yet you say that the monitors and the room effect the sound more. This thinking confuses the question. The monitors are the same and the room is the same. Nothing changed except to take the 1202 out of the equation. And, this was replicated in 2 completely different studios.

Sorry, we were also working on limited information given. There's so many variances of people's hearing in the industry. Some can hear big differences between a $1,000 and $10,000 power cord, while others can't tell the difference between a set of NS-10's and Tannoys. There's just different levels of hearing. For a 1202VLZ, Greg Mackie, when he first designed these compact mixers touted how transparent and accurate they sounded. Simple age and wear of the mixer, bad connections, insufficient cabling, low power output from the power supply, or variances in output levels all contribute to differences in performance. For example, my 1202-VLZ is very transparent. But it's old, and at times, it can drop volume in the right channel until I power-cycle it. Fortunately, I can detect that condition quickly and remedy it.

Point-being, I do agree with those who suspect a faulty 1202-VLZ or the connections to and from it. If it makes a noticeable difference without the mixer, and it's affecting your mixes, it's bad.

Viamichael
I hear all your thoughts that most of you aren't buying this, yet you say that the monitors and the room effect the sound more. This thinking confuses the question. The monitors are the same and the room is the same. Nothing changed except to take the 1202 out of the equation. And, this was replicated in 2 completely different studios.

What I meant was that the mixing choices you make are going to be affected more by your choice of monitoring system and treatment of of the space in which you mix than inserting a mixer in the monitoring chain if that mixer is functioning properly.
 
I don't doubt that you're hearing a difference, and it may well be due to that particular Mackie having issues. I'm just answering the premise of your original question, "Have any of you experienced this", and the answer in my case is "no". Also, I didn't want you to write off your Mackie without looking into why it (or the way it's connected) colors the sound so noticeably.
 
 

Sorry, I have been away. The tape ins and outs performed the best. Yet, something wasn't quite right. Going directly from the Edirol FA-101 to my Mackie monitors I hear practically nothing with Sonar on full blast. I actually never did that before and I am shocked it is so quiet. So I replicated that scenario with the 1202's tape in and out. Boy, is it noisy. I always have heard a funny noise when I move the wireless mouse around (which, btw, is never recorded) but at full blast the 1202 is introducing all sorts of static. I have moved the 1202 away from the audio and video monitors to know avail and have also plugged it in on a different circuit. All my recording equipment runs on a dedicated circuit directly to the breaker box. Now I see my mouse noise is created by the 1202.

Psychologically, it is impossible for me to use the 1202. So noisy. But, this noise is not the same problem I initially had, that boxy sound which is an increase somewhere between 300hz and 600hz.