Hi guys
I have a relatively complex setup involving a stereo guitar (split bass and treble strings),two amps, an Effect Gizmo (Full Stereo version), an Axe FX II and a Mini Line Mixer, all setup for dual four cable method. I am using humbuster cables (TS to TRS) for all Axe Fx outputs. All Gizmo connection are used in Mono with TS cables.
This a great sounding setup for the music i'm making (regardless of whether it seems complicated or strange etc), but there are several ground loops happening because of the nature of the setup. Please bare with me and see the attached diagram and description below:
Guitar with stereo output >> RJM Effect Gizmo >> 2 x Marshall Heads (on set for clean, the other for drive)
-The left pickup of the guitar goes into one amp, the right pickup into the other amp.
-The Gizmo loops are as follows:
1-4 Front fx for Amp L
5-8 Front fx for Amp R
9-10 Post fx for Amp L
11-12 Dry and Post fx for Amp R
The Axe II's grid is setup for normal 4CM with the FXL block inserted, but with a separate row for each guitar signal, and using VOL/PAN blocks to allocate only left or right signal to each row.
-The Gizmo also has a Drawmer dual noise gate in two of its loops (Loops 6 and 9) that allows me to duck one guitar signal whenever the other is playing, and to simply gate the other signal (Amp R signal is gated before it hits the amp, while Amp L is ducked post preamp in the amp's fx loop whenever Amp R plays). Note that the Gizmo sends a copy of the Amp R pickup to trigger the ducker. The Drawmer is balanced and i am using XLR to Jack leads.
Amp R's send also goes straight into a Boss NF1 Noise Gate before it hits Loop 9 In.
The dry preamp signals and their respective post fx are mixed in parallel with a Mini Line Mixer.
I dismantled everything and started from scratch to do some testing, and discovered the following:
-Guitar and 2 amps only is fine, which means the guitar itself is fine (but maybe more shielding would be a good idea?)
-Full rig without guitar plugged in gives ground loop hum
-Guitar and 2 amps plus Gizmo for front end only creates mild ground loop hum as soon as both Loops 1-4 and 5-8 are setup to send to both Amps' inputs, without any post Loops setup at all.
-As soon as i then setup the Axe II's front fx in Loop 4 of the Gizmo, i get very loud ground hum. In order to eliminate this hum i used a Behringer HD400, but i had to use it for both the send and return of Loop 4 alone, which suggests that the humbuster cable is ineffective here. However i then get a new hum to deal with when i setup the other Axe loop in Loop 8.
-Additional hum seems to be created when i plug both pickups into the rig, when the rig is fully setup
Also, i tried a slightly different setup where Amp L is only used as a power amp so i can use the Axe's preamp models with that amp. I don;t have a diagram for this yet but in a nutshell, the L pickup goes straight into the Axe II, then out to Loop 9 (Loop 10 is not used) and straight back into the Axe, then into Amp L's Return. This would be an ideal setup but i get an additional kind of ground loop in the form of a high pitched whistle, which might be some kind of additional feedback Loop.
To cut a long story short, do you think the solution is to use several ground lift cables to eliminate all these ground loops? Otherwise it looks like i would need several Behringer (or similar) Hum Destroyers. I would really appreciate any help!!!!!!
I have a relatively complex setup involving a stereo guitar (split bass and treble strings),two amps, an Effect Gizmo (Full Stereo version), an Axe FX II and a Mini Line Mixer, all setup for dual four cable method. I am using humbuster cables (TS to TRS) for all Axe Fx outputs. All Gizmo connection are used in Mono with TS cables.
This a great sounding setup for the music i'm making (regardless of whether it seems complicated or strange etc), but there are several ground loops happening because of the nature of the setup. Please bare with me and see the attached diagram and description below:
Guitar with stereo output >> RJM Effect Gizmo >> 2 x Marshall Heads (on set for clean, the other for drive)
-The left pickup of the guitar goes into one amp, the right pickup into the other amp.
-The Gizmo loops are as follows:
1-4 Front fx for Amp L
5-8 Front fx for Amp R
9-10 Post fx for Amp L
11-12 Dry and Post fx for Amp R
The Axe II's grid is setup for normal 4CM with the FXL block inserted, but with a separate row for each guitar signal, and using VOL/PAN blocks to allocate only left or right signal to each row.
-The Gizmo also has a Drawmer dual noise gate in two of its loops (Loops 6 and 9) that allows me to duck one guitar signal whenever the other is playing, and to simply gate the other signal (Amp R signal is gated before it hits the amp, while Amp L is ducked post preamp in the amp's fx loop whenever Amp R plays). Note that the Gizmo sends a copy of the Amp R pickup to trigger the ducker. The Drawmer is balanced and i am using XLR to Jack leads.
Amp R's send also goes straight into a Boss NF1 Noise Gate before it hits Loop 9 In.
The dry preamp signals and their respective post fx are mixed in parallel with a Mini Line Mixer.
I dismantled everything and started from scratch to do some testing, and discovered the following:
-Guitar and 2 amps only is fine, which means the guitar itself is fine (but maybe more shielding would be a good idea?)
-Full rig without guitar plugged in gives ground loop hum
-Guitar and 2 amps plus Gizmo for front end only creates mild ground loop hum as soon as both Loops 1-4 and 5-8 are setup to send to both Amps' inputs, without any post Loops setup at all.
-As soon as i then setup the Axe II's front fx in Loop 4 of the Gizmo, i get very loud ground hum. In order to eliminate this hum i used a Behringer HD400, but i had to use it for both the send and return of Loop 4 alone, which suggests that the humbuster cable is ineffective here. However i then get a new hum to deal with when i setup the other Axe loop in Loop 8.
-Additional hum seems to be created when i plug both pickups into the rig, when the rig is fully setup
Also, i tried a slightly different setup where Amp L is only used as a power amp so i can use the Axe's preamp models with that amp. I don;t have a diagram for this yet but in a nutshell, the L pickup goes straight into the Axe II, then out to Loop 9 (Loop 10 is not used) and straight back into the Axe, then into Amp L's Return. This would be an ideal setup but i get an additional kind of ground loop in the form of a high pitched whistle, which might be some kind of additional feedback Loop.
To cut a long story short, do you think the solution is to use several ground lift cables to eliminate all these ground loops? Otherwise it looks like i would need several Behringer (or similar) Hum Destroyers. I would really appreciate any help!!!!!!
