A guitarist friend of mine, in Switzerland, has an Ibanez effects matrix which allows him to route three guitars and a pedal steel through a selection off effects, then into a mid sixties Wallace, a late sixties Vox AC30, a Marshall 2 x 12 combo from the eighties and a Mesa Boogie - I'm not sure when that dates from. Sometimes the effects will be mixed with the instrument, sometimes fed to another amp, and should there be a breakdown it is the work of seconds to plug a guitar directly into an amp input - and this, of course means that each amp is grounded, no playing with safety constraints.
In the fullness of time I intend to have a feed going to the Leslie, for numbers that don't need the B3, but they've decided they want to be able to feed a mix of backing vocals in there, and until I know exactly what is required I can't do the drawings for the mechanics.
Two of the amps (the Wallace and the Mesa) react to the outputs of the matrix as if it were the instrument itself, but the other two get a hum - low level, and depends on the volume, turning down with the instrument, so probably not ground loop, as such. Change cables, or outputs of the matrix, and the problem always follows the amps, never anything else. So, I assume the amps are referencing to chassis rather than the input jacks, and there is enough ground current that, despite the fact that the jacks are metallic and not isolated from the chassis, some AC voltage might be generated by ground currents.
Has anyone else had an equivalent problem, and if so, short of changing the power transformer, has anyone found a not too complicated solution?
In the fullness of time I intend to have a feed going to the Leslie, for numbers that don't need the B3, but they've decided they want to be able to feed a mix of backing vocals in there, and until I know exactly what is required I can't do the drawings for the mechanics.
Two of the amps (the Wallace and the Mesa) react to the outputs of the matrix as if it were the instrument itself, but the other two get a hum - low level, and depends on the volume, turning down with the instrument, so probably not ground loop, as such. Change cables, or outputs of the matrix, and the problem always follows the amps, never anything else. So, I assume the amps are referencing to chassis rather than the input jacks, and there is enough ground current that, despite the fact that the jacks are metallic and not isolated from the chassis, some AC voltage might be generated by ground currents.
Has anyone else had an equivalent problem, and if so, short of changing the power transformer, has anyone found a not too complicated solution?
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Scrool down to 12/8/04 | A quicky - updated humfree splitter A/B/Y
You should be able to adapt the idea to your situation.
Scrool down to 12/8/04 | A quicky - updated humfree splitter A/B/Y
You should be able to adapt the idea to your situation.
Not a simple earth loop, despite there being an obvious path, as connecting the screen of the cable without the core does not cause a buzz. I suspect that the Ibanez EPP400 programmable patch has some kind of active output ground isolation - I am about to look for schematics, as the guy's just got back from the States and sent me the data.
Buffers and 1:1 transformers (actually, probably just the transformers as the patch has a <1k output impedance) was the first thing I thought, so the lack of quality here was probably due to adaptor cables - the transformers I had on hand were XLR connected (most of my gear is) so I slung together unbalancing leads, and gained many dBs of hum.
Thanks for the ideas.
Buffers and 1:1 transformers (actually, probably just the transformers as the patch has a <1k output impedance) was the first thing I thought, so the lack of quality here was probably due to adaptor cables - the transformers I had on hand were XLR connected (most of my gear is) so I slung together unbalancing leads, and gained many dBs of hum.
Thanks for the ideas.
Doesn't. Except that it drops the level, and the hum drops proportionally, and when you boost the gain for original level, it's back. If it weren't for the fact that some amps don't have it at all, I'd assume it was electronic noise on the active patcher.
Maybe it's just a difference in gain between the amps?
I think the thing to focus on is that there's no problem with 2 of the amps, so the others can be fixed.
I think the thing to focus on is that there's no problem with 2 of the amps, so the others can be fixed.
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