(gcx) 2 amps + gsp1101 played by 1 gtr & reamp same time

[JohnClark]

Simplify the setup to find where the problems are coming from... removing the laptop all together removes the hiss, but does the laptop hiss if connected direct to an amplifier? Does it hiss if only the GCX Feedthru is inserted? Does it hiss if the first loop is added... on and on down the line.

I don't know what you mean by running the amps with no ground, so for now I will have to go with "no". Again here you first need to identify where any ground loop is before adding any ground lift or isolation transformers... simplify the setup, add the fixes that are needed and nothing else.

[Midicity]

The hiss was coming thru the radial tonebone jx2 I just introduced last night to compensate for rhe lack if gain in signal from the x amp and being split 3 times. When I push the boost button on the radial to disengage the boost feature alot of the hisss goes away and is the same as when plugged in the gtr input or feed thru at the front of the gcx. Should I get a clean boost or line driver instead or is the radial ok to use? The drag feature may be usefull but without the boost enabled it doesn't seem to give any more gain to sound the same as my guitar. When I use home depot ground lift adaptors on the amps power plug the hum almost goes away without these adaptors on either amp it hums big time even if one amp is turned off? I took the radial switchbone completely out of the mix to simplify also. Last question: how can I, or should I, permanently connect the copper wire I rigged connecting the cables jackets for return and out of each loop as you described? I can't close the outer metal jacket (screw completely closed) as if now. Thanks a million

[JohnClark]

Don't remove the ground connection from the power cable for the amplifiers! Never in this thread has it been suggested to do this. Removing the ground connection is potentially unsafe! If your setup buzzes with the power grounds in place then you again have to simplify the setup to identify where you should be routing the Hum Eliminators.

I cannot say what will replace the Tonebone and the more you ask these things the more I realize that I have next to no clue what your signal path is and why you are trying to do all this in one rig. The GCX is selecting the source that feeds inputs to the amplifiers... not once was there mention of the Switchbone. This is getting quite out of hand I think.

EDIT: Don't do it... it does not work in this situation!
Please read my post about the relabel "mod" on the GCX loops used to A/B the input source for the answer to not having to tie the sleeves together with wire.
EDIT: I wonder how much vacation time I have accrued?

[Midicity]

I only added the switchbone last night to see what it would do to improve the signal strength of the reamp signal. It is not in the signal chain anymore. The routing is exactly as you suggested. The gtr signal y corded into 3 gcx loops inputs and the reamp into the 3 gcx loops returns with the return and out of each channel cable sleeves connected with copper wire. I shoved the wire in between the thread and outer sleeve. Is the mod suggestion in another thread? I know you did not suggest the ground lift plugs. I Just tried that today after reading it on the net as a suggestion from another forum and from the Mesa boogie tech I spoke with.The Mesa tech said it will not harm the amp and is wideley used to get rid of ground hum but to only do it to one amp. It is hooked up as you suggest and has hum but not as bad as before adding the wire connecting the sleeves of the out and return of each respectives loop individually. Its not the normal amp noise but hum. I went thru every possible routing down to the simplest and most complex and all in between as suggested. I greatly appreciate your help and I think it's almost there but the amount of hum is abnormal and only there when using 2 amps together Going into the gcx and out of the back regardless of any of the wacky routing and was there before any of the new routing. Should I try the ebtech power plug type hum elminator on the amps power cable? The hum went down drastically when using the home depot 79 cent power adaptor that goes in as 3 plugs and comes out as 2 with a metal tab on it. When I take the gcx out of the picture and use the guitar into the switchbone into the 2 amps the hum goes away but only with the ground lift switch engaged. If the ground lift is not engaged I get the same hum as using the gcx which leads me to believe its in the 2 amp setup being grounded regardless of the gcx. I just replaced the Mesa with another Randall RM100 to see if it was the Mesa dual rectifier and the hum is the same until I plugged the home depot ground lift plug on it. Is the fact that I have unshielded copper wire connecting the jackets a contributing factor? Any advice is greatly appreciated. Thanks

[JohnClark]

The gtr signal y corded into 3 gcx loops inputs and the reamp into the 3 gcx loops returns with the return and out of each channel cable sleeves connected with copper wire. I shoved the wire in between the thread and outer sleeve. Is the mod suggestion in another thread?

EDIT: Don't bother, it does not work anyway!
This thread, Page 3, 8th post down from the top.
EDIT: How many times did I reference this trick?

I know you did not suggest the ground lift plugs. I Just tried that today after reading it on the net as a suggestion from another forum and from the Mesa boogie tech I spoke with.The Mesa tech said it will not harm the amp and is wideley used to get rid of ground hum but to only do it to one amp.

As long as you understand what you are doing when you are seemingly randomly lifting ground here and there. The warning is there because the potential for danger is present.

It is hooked up as you suggest and has hum but not as bad as before adding the wire connecting the sleeves of the out and return of each respectives loop individually. Its not the normal amp noise but hum. I went thru every possible routing down to the simplest and most complex and all in between as suggested. I greatly appreciate your help and I think it's almost there but the amount of hum is abnormal and only there when using 2 amps together Going into the gcx and out of the back regardless of any of the wacky routing and was there before any of the new routing. Should I try the ebtech power plug type hum elminator on the amps power cable? The hum went down drastically when using the home depot 79 cent power adaptor that goes in as 3 plugs and comes out as 2 with a metal tab on it. When I take the gcx out of the picture and use the guitar into the switchbone into the 2 amps the hum goes away but only with the ground lift switch engaged. If the ground lift is not engaged I get the same hum as using the gcx which leads me to believe its in the 2 amp setup being grounded regardless of the gcx. I just replaced the Mesa with another Randall RM100 to see if it was the Mesa dual rectifier and the hum is the same until I plugged the home depot ground lift plug on it. Is the fact that I have unshielded copper wire connecting the jackets a contributing factor? Any advice is greatly appreciated. Thanks

Classic ground loop. Connect your guitar to the GCX and then off to two amps... if there is buzz, try the multiple methods at your disposal to eliminate this buzz. Pay attention to any setup where you are lifting the power ground to any of your amplifiers! Carelessness here can be a bad thing!

The wire connecting the sleeves is a ground connection, there is no need to shield it.

[Midicity]

THE HUM IS MUCH MORE TOLERABLE NOW! Thanks alot for your patience and help.

One note. I was typing from my iphone on the day we were communicating on page 3 and I never saw the post about the mod until today. Apologies. I tried it as described and it did work but only if all the amps were on (the respective gcx loops were engaged. When one or more were not engaged the other signal was bareley audible and clean even though that amp was on the dirty channel. It could have been some wacky thing with my midi channels not being lined up on the gsp1101 but nevertheless I reverted back to the original routing and took some shielded copper 14 guage primary automotive wire and put it in between the sleeve and the threads and tightened as much as possible. I put a home depot ground lift plug on the amp on gcx 2 and the hum was drastically reduced to a managable level now in combination with your other suggestions. It now works as it should and without great amounts of hum. I am having Dave Friedman make me a 3 channel isolator for safe measure to run before each amps input. Thanks again. VERY VERY MUCH

[JohnClark]

EDIT: Warning! This does not work for this rig!
For the "mod" you probably missed the part about needing a dummy plug in the newly re-labeled Send jack... but that is because I forgot to include that necessary piece of info the first time and just now edited that post to include it!
Edit: The above is further proof that you cannot trust everything you read on the Internet!


If sticking with the wire method I would go ahead and solder the wire ends to the sleeve connection inside the plug and run the wire out the back of the plug with the cable.

[Midicity]

I will try it again. By dummy plugs do you mean just a plug end with no cable soldered? If so I have some laying around. Thanks

[JohnClark]

It seems I am just not thinking things through lately... you will need to stick with the wire connections on the source A/B loops. The "mod" works when only one loop is selecting between two sources, but it will not work correctly with your setup because of the three way split with common ground. Any single loop of this group that is not active will short the entire laptop signal to ground. Sorry for the confusion.

[Midicity]

I made 2 daisy chain cables and I as wondering if the thickness of the ground wire that goes from the return cable ground to the amps input cable ground matters in thickness? In other words will there be less hum with a thicker or thinner ground wire connection?

Last question LOL

Is it ok to run the reamp signal into the 3 loop returns via the daisy chain instead of going thru the face of the gcx first --out the back--then into the returns? It sounds the same pretty much and I dont get much hiss and alot of the hum is gone by going into the returns without first going into the front guitar in. Thanks for all your help and a great product.