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Any issue with stereo outs from FX Pedal to two different DI boxes?

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Re: Any issue with stereo outs from FX Pedal to two different DI boxes?

Postby Hugh Robjohns » Tue Jul 17, 2018 4:19 pm

The problem is not really whether the patchbay is balanced or not, it's that connecting unbalanced sources and destinations inevitably creates ground loops, and those loops get bigger and more complex and more bewildering as the patching chain between different devices gets longer and more complex.

If everything was balanced you wouldn't have a problem at all... but it's not. And even with a separate unbalanced patchbay for the pedals etc, at some point (and in your rig, several points!) you will need to patch between balanced and unbalanced gear anyway.

So, you will need to use balancing transformers and/or specially wired (pseudo-balanced) cables to isolate the grounds of specific items in the patch chain which are prone to creating ground loop issues.

Hence my earlier suggestion about patching via line transformer isolator boxes where necessary -- and having them wired to the patchbay for easy integration in the patching makes a lot of sense.

If you have a lot of unbalanced gear that you patch together, a dedicated unbalanced patchbay can make sense, as I also mentioned earlier, with just a couple of bal/unbal transformer boxes on tie lines to the balanced gear patchbay... But with your requirements to patch often between balanced an unbalanced gear I'm not sure that idea would actually help much.

In my own system, everything wired through the balanced patchbay appears as if it is balanced, either because it genuinely is, or because I've used a pseudo-balanced cable (for things like synth outputs), or line isolating transformers (for unbalanced inputs). And that allows me to patch easily without creating ground loops in the process.

In your situation, you're going to need to identify which items lead to ground loops, and then find ways to prevent that, either by using specially-wired cables as previously discussed, or patching through transformers, or whatever.

Battery-powered FX pedals can't create a ground loop on their own, but can be the conduit for a ground loop from the preceding and following equipment. And the same applies to class-II or double-insulated mains-powered equipment.

H
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Re: Any issue with stereo outs from FX Pedal to two different DI boxes?

Postby James Perrett » Tue Jul 17, 2018 8:32 pm

Hugh Robjohns wrote:Hence my earlier suggestion about patching via line transformer isolator boxes where necessary -- and having them wired to the patchbay for easy integration in the patching makes a lot of sense.

As I mentioned before, the preamp that seems to be causing the problem already has transformers on the input and output so there seems little point in adding more of them to the system. In this case it is purely a wiring issue.
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Re: Any issue with stereo outs from FX Pedal to two different DI boxes?

Postby Hugh Robjohns » Tue Jul 17, 2018 10:01 pm

I thought it was connection via the patchbay that was causing the problem... And I was discussing the general solution approaches... But certainly the OPs preamp is unusual in having transformers on both input and output and that should make life easier if suitably wired cables are employed (as you explained earlier). So in that specific case I agree that introducing additional transformer isolators is unnecessary.... But only if the OP applies the appropriate cable wiring.
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