Ghostly Hum caused by Triamp 3 Panel Lighting

This one sounds a little surprising and I wonder if anyone has seen it before...

While I was setting up my newly purchased Triamp3 with a G-System (4-cable method) I could hear a ghostly hum at about 392Hz (the same frequency as a G played on the top E string of the guitar). After checking my cables and power I finally found that the ghostly hum went away when I turned the Triamp 3 panel brightness down to zero!  There’s still the usual (acceptable) levels of electronic noise but the ghostly hum has gone.

The hum can’t be heard when the G-Systen is not connected so it seems to be something to do with the Send-Return loop. I should also point out that the hum is not heard on any of my other amps, so it is a combination of the Triamp 3 panel lighting and connecting an FX system. The hum is also there when the FX loop is switched off, but disappears if I remove any cable connecting the G-System to the Triamp 3. Disconnecting the guitar cable from the G-System makes no difference.

The noise gate did mask the issue but the hum could still be heard when I played quietly, so wasn’t really a solution. The noise gate on the G-System worked better as there are more control options on the G-System noise gate. The Triamp 3 noise gate even at its softest still has a relatively hard cut-off. On the G-System I can select the dB level for cut-off.

Has anyone observed this before? It isn’t a showstopper for me with the head - and even seems somewhat amusing to me that a ghostly hum can be heard with the ghostly blue light. But if you know an easy fix that will let me keep the panel lights on when I use the head at home then that would be great. I’m hoping it won’t be an issue live as it would be nice to have them on for shows - and to see the (many) controls.

Not really a clue as to what is going on yet, the schematics don't seem to show the lighting so I can't see where it is being fed from and what else would affect it. However, the signal path selections in the Triamp seem to be made through opto-isolators in the signal path. If something starts to put noise onto their control voltages then you will get noise in the signal path. I'm intrigued and still looking.

Did you find anything? Where can I find these schematics?

My Triamp mk3 does the same with a Helix floor in 4cm. When I use the CC86...88 commands to change light settings, I notice the following:

- Increased light strength is more noise
- Increase "brightness"(maximum is white color) is more noise
- Color changes make no difference.

Any way to get less noise and still have the lighting?

I did do some more digging into this as it intrigued me but I couldn't come up with anything concrete given the lack of info out there and the fact that I don't possess a Triamp to tinker with.

I hate to admit it as it always causes a feeding frenzy of "buy buy buy" but the issue of ground loops comes into mind. These can be particularly bad when you use digital equipment. I know there will be some who will immediately scream "Voodoo Labs Pedal Power" and other expensive "solutions" but you are much better proving that it is a ground loop problem in the first place before you throw ridiculous amounts of money at a proposed solution. Then you should try to solve the ground loop at source rather than finding something you can throw money at which will just mask it.

Does this happen in all locations or just in a few with some giving no problem at all?

Do you have your Fx setup powered from the same mains socket as the amp? If not then try shifting both of them to a single mains distribution block and see if that helps.

Is it even possible to battery power the Fx box for a test as that should remove the issue completely? I actually run my own modest board from a Makita 18V 4Ah drill battery with a matching USB charger cap on it to which I have added a DC socket which feeds a cheap Chinese Caline PSU. Because I have sorted out my pedals properly to remove any problems in the first case the battery/cheap PSU setup is absolutely perfect in terms of all noise and it can run for weeks at a time between charges if I let it.

I run the Helix and Triamp from the same socket. There are other noises from the amp also, but the light doe add it's own noise.
Shutting the loop off makes no difference

I might try to see if there is a ground lift on the Helix or amp. Also I try to use 1 connection to the amp helps instead of the 4 cable method.

One point here is that a ground connection on the Triamp may have corroded slightly and now has a small resistance in it.  This is common in guitar amps as they are sometimes notoriously primitive in their design and the grounds for the different sections of the circuit can be established at a number of connection points on the chassis.  There is usually one main earthing point near the mains input socket, then there can be various grounds taken to the metalwork.  If any of these work loose through vibration or corrode slightly over time then a resistance is put into that section's ground line and any current taken to ground there will raise the 0V reference.  This looks to the circuitry like a false signal voltage and can add noise and other unwanted effects.  If you can identify any of these points and break them down, clean them and connect them back up it may help.  For anyone who doubts this because the metal chassis is such a good conductor, I have worked on sensitive recording equipment on large survey boats, (think North Sea Ferries), which use the ship's steel hull as an earth for the power supplies.  It isn't unusual to find that the ground level at opposite ends of the boat is 20V different or even more!!!  Needless to say this wreaks havoc in your delicate signals if you don't take steps to deal with it.  (The best starting point is to do all signal transfer on balanced lines but the grounding between equipment must also be worked out very carefully.)

(EDIT: Your Triamp is a Mk3 I know so it is unlikely to be as simple as that as its construction is very modern with multiple PCBs. However, the interconnects between the PCBs may exhibit this effect though I would not have thought it would be a problem. I'm stretching for reasons to suggest here! )

There is one other thing you could try if you have a spare signal cable around which you don't mind playing with and a bit of time to spare.  If you can solder neatly it will help too.

Ground loops occur in questionably designed or implemented equipment when there is the potential for two areas to have different ground reference levels.  If the Helix has say 0V as its signal ground reference as it should but, let's say, your Triamp has a very slightly higher signal reference voltage due to something internal, then when you connect them you are connecting the two different levels together.  Current will flow somewhere and that can mean noise.  This is made worse when you connect multiple signal cables between the two as you do for loop work.  In hifi, which has much more demanding noise requirements than guitar work, this is often addressed by disconnecting the ground connection at one end of all but one of the signal cables, or even running a dedicated ground wire between grounding screws on each unit.  Each signal cable is still screened because the outer of the cable is still connected to ground at one end which is all that is necessary.  All signals then get their ground reference via the one cable which is left with a ground line connected at both ends.  The system is still safe to you as you have not touched anything to do with the mains earthing setup (an absolute nono!) and each unit still has its own ground setup untouched.  The grounds are connected even if imperfectly so the signals should remain ok.  However, you have now broken the loop in ground terms so no circulating currents can occur.

As I said, if you have a cable spare you could disconnect the ground at one end and try that as one of a pair of loop cables.  The other cable must be as normal of course in order to share the same ground reference for both units.

I have just read that other people have had Helix problems with certain household electrical units connected to the mains nearby! It seems that some pieces of equipment can cause noise and buzzing in the Helix just by being on the same mains circuit. One guy even found it was a new piece of mains kit of his neighbours. Some Helix users are a bit dissatisfied with Line6's response to this problem which has been noted by a number of people.

Do you know anyone who has a mains conditioner unit to clean up the mains as it is fed to a piece of kit?

I have a Samson PB10pro (or something like that), which has a filter. I can try that.