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Contributor - Level 2

G-System Ground Loop Hum

Hello,

I just bought the Ebtech Hum Eliminator to get rid of the ground loop hum.
So I "isolated" the effect loop with this device. But there is still a slight hum.

I found out that the problem ist the cable from the G's Insert Send to the Amp Input.
A soon I use a Palmer PLI01 or similar here, the hum is gone, but tone suffers.

So I used a high quality balanced cable. No result, still hum.
Even my Monster cable won't work and one of my Planet Waves cable actually increases the hum.

Accidently, i took a cheap, short patch cable and suddenly hum is gone.

Although I use the G's brain in a small rack, this cable is way too short and so i was serarching my whole inventory for the perfect one. Worse luck I didn't found any.

So I took a 3 m unshielded speaker cable and- believe it or not - it works.

Laird !!! Whats wrong????


Knut
Tags (1)
Keybi Contributor - Level 2 2008-10-07

2008-10-07

G-System Ground Loop Hum

Hello,

I just bought the Ebtech Hum Eliminator to get rid of the ground loop hum.
So I "isolated" the effect loop with this device. But there is still a slight hum.

I found out that the problem ist the cable from the G's Insert Send to the Amp Input.
A soon I use a Palmer PLI01 or similar here, the hum is gone, but tone suffers.

So I used a high quality balanced cable. No result, still hum.
Even my Monster cable won't work and one of my Planet Waves cable actually increases the hum.

Accidently, i took a cheap, short patch cable and suddenly hum is gone.

Although I use the G's brain in a small rack, this cable is way too short and so i was serarching my whole inventory for the perfect one. Worse luck I didn't found any.

So I took a 3 m unshielded speaker cable and- believe it or not - it works.

Laird !!! Whats wrong????


Knut

Contributor - Level 2

Re: G-System Ground Loop Hum

Keybi wrote:
Hello,

I just bought the Ebtech Hum Eliminator to get rid of the ground loop hum.
So I "isolated" the effect loop with this device. But there is still a slight hum.

I found out that the problem ist the cable from the G's Insert Send to the Amp Input.
A soon I use a Palmer PLI01 or similar here, the hum is gone, but tone suffers.

So I used a high quality balanced cable. No result, still hum.
Even my Monster cable won't work and one of my Planet Waves cable actually increases the hum.

Accidently, i took a cheap, short patch cable and suddenly hum is gone.

Although I use the G's brain in a small rack, this cable is way too short and so i was serarching my whole inventory for the perfect one. Worse luck I didn't found any.

So I took a 3 m unshielded speaker cable and- believe it or not - it works.

Laird !!! Whats wrong????


Knut

You probably has a mild ground loop formed on the Insert Send --> Amp Input connection. The use of an unshielded cable meant that there was no shield through which a loop could form - since ground loops form with cable shields. The problem is your potential issue with other RF because of not having a shield. The cheapo cable probably also worked fine because the shield was so bad that a loop could not form there either.

Right now, you have the HE-2 in two places:
1) Between the amp send and the G Insert Return
2) Between the G Output and the amp return.

Try the following:
Rob the HE-2 channel from (1) above and instead use it between the insert send and the amp input. Use a balanced cable to connect the Amp Send directly to the G-System insert return so you have a pseudo-balanced circuit.

What happens then? (This may not be a complete solution - but what happens when you try this will tell us a lot about the nature of the RF issues in your system. And it MAY be a complete solution also.)



BTW - On my rig with the H&K Switchblade, I need transformer isolation for all 3 links between the G and the amp - so I have two HE-2s on that rig. (The last channel is used for output to a second power amp for stereo). All cables from the G to the HE-2s are balanced (I use a 4-channel, 20' TRS recording snake) and then I use VERY short (12") mono instrument cables between the amp and the HE-2s (except when I go stereo, where the other power amp needs a longer cable of course). On my clean channel, you can't tell the unit is on unless I am playing - even when the volume is at ear-damaging levels. When on high-gain channels, I get a whisper/hiss of thermal noise from the amp that is so low you have to listen for it even at high volumes. In NO case do I need any other noise reduction or a gate.
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