Apologies, I have not found the sysx file yet. I'm in the process of setting up a RAID1 array on my PC and I've swapped my archive disk out for now.
Apology number 2...this is a long post, but is the most helpful information I can post.
This is exactly what I went through to set up the unit with the Roadster.
Starting with a comletely blank patch on the GT-8 (NOTHING on, not even the noise suppressor), check your input levels on the GT-8 alone. You don't have to have any other cable connected to the unit other than your guitar for this. Check your levels with palm-muted E major chords...those usually register the loudest. Move through every stage of your level meter to make sure you're not getting any spikes along the way. The meter should never spike above 70%.
Now, start turning on your effects ONE AT A TIME TESTING ONLY ONE EFFECT AT A TIME. This is where you'll be able to find out the gain factors of each effect. For example, the Chorus effect has a rather high gain factor and in stock trim typically pegs out the meter of the block following the chorus. Go through each of your levels and meters to ensure that you've got unity gain throughout each effect block. Take note that you'll also want to organize your effects chain in the unit in the order you normally operate in, as each effect is cumulative (effect 1 in the chain will always be affected by effects 2, 3 and 4, and effect 4 will always depend on the levels it receives from effects 1, 2 and 3). This takes some time and it is not a simple 5 minute exercise. The time you take now will pay off, trust me.
After your levels are set and you've got as close to unity gain as possible across the board on the GT-8, you can now connect the unit to your amp. This is the method I recommend.
Starting with the Roadster, set your power levels and rectifier tracking the way you want. Remember to set turn the effects loop on. On the Roadster footswitch, move to channel 1, turn the effects loop on. The solo and reverb should be turned off. Set your voice switches (clean, fat, tweed, etc) for all channels and set your basic levels (the master output on the Roadster should be set at a reasonable level...it will have no effect on the level matching tests to follow).
Connect your guitar directly into the input of the amp and connect the GT-8 in the effects loop. DO NOT CONNECT THE EFFECTS SEND ON THE ROADSTER TO THE INPUT OF THE GT-8. You're not going to be running it that way anyway. Connect the effects send from the Roadster to the effects return on the GT-8 and connect the output (left channel) on the GT-8 to the effects return on the Roadster. Now, place the FX LOOP on the GT-8 where you want it in the effects chain (after any pre amps and overdrive/distortion effects, but before any delay, chorus or modulation effects). KEEP IN MIND THAT DURING THIS SETUP PROCESS ALL EFFECTS SHOULD STILL BE TURNED OFF ON THE UNIT.
You will now calibrate your levels (WARNING, YOU WILL BE ASKED TO TURN SOME KNOBS ON THE AMP). Move to the back of the Roadster and set the effects loop level to 50%. Again, with all effects TURNED OFF on the GT-8, turn on your meter and scroll all the way to the first effect block that falls after your effects return on the GT-8. Again, palm muted E major chords do the trick. Check your levels. Your levels should match...again, no more than 70% on the meter, but what you should really be shooting for is an exact match to what you saw on the meter when you connected directly to the input on the GT-8. Adjust your levels AT THE AMP to compensate (I'm sure you know this, but the level control on each channel controls the signal level at the effects send...the effects send level is a secondary control that controls global output at the effects send). Turn up the channel's level control if your meter shows a low reading and down if it shows a higher reading. DO NOT WORRY ABOUT THE VOLUME YOU ACTUALLY HEAR RIGHT NOW...you will deal with this later. If you are unhappy with the tone, that will come later as well. Right now we're just balancing levels.
Move through each channel and do the same thing as above.
Now the test...does your overall level match when you bypass the GT-8? Again, playing a simple chord, use the Effects Loop bypass switch on the Roadster foot controller. Play a chord and bypass the effects loop. Did you notice a difference in level? If the overall volume from the amp is lower when the effects loop is engaged, compensate by turning up the level control ON THE BACK OF THE GT-8. Do not adjust any volume levels in the effects block, just use the level control on the rear of the GT-8. Continue to adjust until your loop-engaged level matches your loop-bypassed level. Once you've got this, the rest is cake.
Re-test your levels by turning on effects ONE AT A TIME INDIVIDUALLY and checking your levels again with the meters. At this point, no matter what amp channel or effect you use, you should hear no difference in the volume coming from the speakers (you will hear a perceived volume difference with the higher gain channels, but the actual level the GT-8 reads will be the same). If everything still matches up, we can now move on to the preamp section.
You will now connect the GT-8 to the Roadster via 4 cable method.
Again, with all of your effects turned off on the GT-8, check your meter reading. Your levels should remain the same throughout each effect block. If you notice a huge change between your preamp effects and effects loop effects levels, go back through the effects loop level set up because you missed something somewhere.
Now, start going through your preamp effects turning on one at a time individually. What you should be aiming for, especially with any overdrive/distortion effects, is a gain boost, not a level boost. I know that typically, gain=volume increase, but that's not what we're aiming for here. Set your gain and level settings on the effects. Again, you should not get any level increase. With overdrive effects, you're looking for a perceived gain increase with no level change. Check your meters to make sure you're not changing any levels. The majority of this process is simply repeating what you did in the effects loop setup process. If you have any specific questions, let me know.
If you want a volume increase for solos or louder sections, use the solo feature on the amp. You should not use the GT-8 for any level increase as this will upset your gain balance in the unit. Now that all of your levels are set and balanced between the GT-8 and Roadster, you can start shaping your tones with the EQ on the Roadster. After your EQ is set, check your levels once again to make sure you did not upset your level balance. If you did, simply adjust using the level control on the amp channel that's affected. Your overall volume should now be controlled with the MASTER VOLUME ON THE AMP. Do not adjust any levels in the GT-8 or the effects send/channel level controls on the Roadster. Doing so will upset your level balance.
You should now have a nice INIT patch to base all of your Roadster patches on. Keep a blank, unchanged copy of this patch on bank 1 (copy it to all 4 patches just so you know you will have a backup - name the patch INIT-ROADSTER). I copied this same INIT patch and saved it to banks 1-20 on my unit. This way you've got a blank patch everywhere just in case. Now program your patches based on the effects you want. I typically operated in just one patch using the unit in manual mode, turning on and off effects as needed with the foot switches on the unit, but you can set up patches as needed with various effects combinations. If you really want to get fancy, pick up a GCX switcher and use the GT-8 to control it via MIDI for some real flexibility.
Troubleshooting
You will probably get a lot of noise just with the cable runs alone. Amplifying this noise with further gain from the GT-8 is a bad idea. Keep your levels low in the unit and compensate with the volume on the rear of the GT-8.
Ground Loops. You're going to have them. If the noise suppressor on the GT-8 can't handle it, or if you're getting some tone loss with the suppressor, cut some of the grounds in your cables. You will need to label the cables if you do this to make sure you reconnect them correctly. Here's the run down.
Guitar to GT-8 - ground should remain intact on both plugs
GT-8 to Roadster input - ground should remain intact on both plugs
Roadster effects send to GT-8 effects return - cut the ground on the GT-8 side
GT-8 output to Roadster effects return - cut the ground on the GT-8 side
Inductance noise. Keep the GT-8 power transformer as far away from the GT8 and your signal lines as possible. The transformer in this thing is a huge source of noise. Try to keep the power cable away from your signal cables as much as possible as well.
Tracking problems. If you have an effect in the GT-8 that starts freaking out (typically this happens on any pitch shifting or harmony effects), move that effect to the front of your signal chain before any other effects (IE, if you're using the pedal bend effect, you will need to move FX2 to the front of your signal chain within the GT-8). This should fix the problem. If it does not, try putting a mild compressor in the effects chain before FX2...this should make the effect track a little better.
This should do it. I'll continue to search for the sysx whenever I get my archive drive back in my PC. Hell, at this point I'm almost willing to take advantage of Guitar Center's return policy to get a unit home and set up the patch for you. I know this is a lot of reading, and hopefully it all made sense, but if you have any questions, let me know.
