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Amp FX Return Noise Problem

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Hi all. I have a Marshall DSL40c valve amp and I connected a send from my Helix to the amp's FX return. It's very noisy, hum, hiss and digital noise. I've tried all the usual ground loop stuff to no avail. I have a Kemper and this works fine with this amp. Setting line level or instrument level on the Helix sends makes no difference and I'm using an empty patch. Main outs have the same issue. Even with the Helix turned off the noise is still there. I suspect this is an impedance issue, there is a missmatch between the two and the amp input needs some additional matching and loading.

 

Any thoughts greatly appreciated! Thanks.

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Just to be clear....

 

With the Helix powered off, you are still hearing the noise from your Marshall when the Marshall's FX Return is connected to, either, the Helix's 1/4" FX Send or 1/4" Main Outs?

 

In the above scenario (with the Helix powered off), have you tried removing the Helix's AC power cord (from the main power strip or the Helix's AC port) to see if the noise persists?

 

After absolutely confirming that there is no Ground Loop (even with the Helix off and unplugged from the AC Mains) I would next suspect a faulty cable between the Helix and the Marshall.

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I've found the Helix is super ground hum prone.  I have to make doubly sure everything is on the same circuit with it.  Which is fine, but a thing.

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I've found the Helix is super ground hum prone.  I have to make doubly sure everything is on the same circuit with it.  Which is fine, but a thing.

A classic Ground Loop issue! Inconsistent (different) ground potentials of the different circuits. It's often easier to home run the electical runs than to undertake the burden of isolating the power feeds.

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Just to be clear....

With the Helix powered off, you are still hearing the noise from your Marshall when the Marshall's FX Return is connected to, either, the Helix's 1/4" FX Send or 1/4" Main Outs?

In the above scenario (with the Helix powered off), have you tried removing the Helix's AC power cord (from the main power strip or the Helix's AC port) to see if the noise?

After absolutely confirming that there is no Ground Loop (even with the Helix off and unplugged from the AC Mains) I would next suspect a faulty cable between the Helix and the Marshall.

Thanks for your help. I have a Keeley pedal compressor and I put it in series with the Helix and Marshall. I turned the compression setting to minimum and turned the gain control down, it got rid of the noise. I think I need to attenuate the input level of the Marshall, just turning down the patch volume makes the patch quieter but I think there's just too much gain on the Marshall return and its boosting up the noise floor of the Helix outputs. I figure it's a bit like turning up the amp to full and rolling back your guitar volume, not recommended. I'm Going to rig up a simple pot in a box, put it between the two and see what happens. I'll post the results!

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Look forward to you next update. Thanks for keep the Forum informed.

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I'll have to give this a shot.  I got quite a bit of noise running 4-cable method with my Carol-Ann Triptik.  I narrowed the problem down to something between the Helix 1/4" out and the Carol-Ann fx return.  Changing cables didn't help.  Swapped the Helix 1/4" out for fx send 3 and the noise disappeared.  

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On 2/14/2017 at 2:46 AM, DarrellM5 said:

I'll have to give this a shot.  I got quite a bit of noise running 4-cable method with my Carol-Ann Triptik.  I narrowed the problem down to something between the Helix 1/4" out and the Carol-Ann fx return.  Changing cables didn't help.  Swapped the Helix 1/4" out for fx send 3 and the noise disappeared.  

 

Hey DarrellM5

Thanks a bunch, you helped me solve the same problem !!! I'm so happy!

Cheers

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