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Need some help with a Stereo Rig

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CanoCano Frets: 20
edited July 2021 in Amps

I've recently been playing through an Orange Terror Stamp and decided that I need to make the most of my Eccos' stereo output (as well the the Immerse Reverb) so I added an Orange Micro Dark and matching cab.

However I have this pulsing sound that starts whenever the Terror Stamp is powered up. Initally I was using a very cheap ABY from AliExpress but replaced that today with the Orange Amp Detonator with its buffered and isolated outputs. However it hasn't fixed the problem.

There's a quick video here of the sound, as well as the combos of having the amps on/off.

The signal chain is :

Input - Tuner - Drive Pedals - Orange ABY - Output to each Amp In - FX Send to Eccos (both amps) - Immerse - Outputs to FX Return on each amp.

I've tried the Phase button on the Orange Amp Detonator but that didn't get rid of the sound.

What am I doing wrong here? I've tried it with nothing in the FX loop and the sound is still there, but much quieter and coning from the opposite amp (Micro Dark)

I've also tried swapping the A and B on the ABY and the inputs/outputs on the FX pedals but there's no change either.

My pedals are all powered by a TrueTone 1 Spot CS6, all on isolated outputs.

Edited to add: I've just tried a bit more unplugging/plugging combos. It would seem that as soon as the FX loop of the Micro Dark is connected, the pulsing starts from the Terror Stamp.

Thanks for the help,

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  • tekbowtekbow Frets: 1459
    edited July 2021
    Sounds like a ground loop from running the two FX loops into the stereo FX maybe.

    Have you got any standalone isolation transformers? Like the ones from orchid?

    I'd try putting one right after the FX loop send of the amp making the noise and right before going into the FX.
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  • CanoCano Frets: 20
    Hi, I haven't got any isolation transformers but I'll look into that. I see Orchid have a dual unit for £38.

    Current plan is to relocate the setup to another room tonight to rule out EM interference from anything else in this room.

    Also Orange Support are looking at it, they thing the Terror Stamp may have a fault so we're seeing if they have a loaner unit to send out so I can swap that in/out with the other two and work out which (if any) is the issue.

    As solo mono amps both work perfectly, it just as soon as both are running through a stereo FX pedal, even with no power to the pedal, the pulsing hum starts.

    I'd read that Stereo rigs weren't simple, kinda understanding that now.
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  • CanoCano Frets: 20
    edited July 2021
    I think the issue is to do with the power supplies.

    I contacted Orange support and they suspect a fault in the Terror Stamp.

    However they're particularly interested in the Terror Stamp PSU, which got me thinking about the PSU that came with the used Micro Dark I just got. Spec wise it appears identical to the one I got with my new Terror Stamp (centre positive, 15v 2a) but it's not the same unit.

    So I've been testing the amps with no input connected, one stereo pedal connected into both loops BUT with no power to the pedal. With that, powering on the amps I get the pulse sound triggered by one amp.

    Then I swapped the amp power bricks....the pulsing moved to the other amp.

    I then unplugged both power bricks from the plugboard, plugged them both directly into the wall sockets, one at each end of the room. Same issue repeated.

    I then turned the power OFF at the wall for the Micro Dark's power supply but kept it plugged in....I still get the pulse when I power on the Terror Stamp. As soon at I remove the power jack from the Micro Dark OR unplug it from the wall the pulsing on the other amp stops. So it's something from the ground of the power supplies.

    I'm waiting to see what the feedback from Orange on this latest test will be.
    It may be that I need to get a new power brick for the Micro Dark which isn't exactly expensive and if that works and I can return the Amp Detonator then I'm quids in actually.
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  • tekbowtekbow Frets: 1459
    I'm going to have to read that a few times to fully absorb what you're saying, but it seems like you've been systematic about it and that's the best way to find an issue.

    I've got a dual amp WDDW rig and noise IS a pain to track down.

    I just moved house and have currently got a brand new ground loop I haven't found the source of.

    TBH, it doesn't Get past my gates, so I'm inclined to ignore it, but I've got a few prime suspects on past experience for what it might be
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  • CanoCano Frets: 20
    edited July 2021
    Ha, yeah I did copy paste that from a reply I posted elsewhere so It may have lost the formatting.

    Basically, as soon as the 2nd amp psu is connected the pulsing hum starts, even when the mains power to that psu is off.

    If I swap the psus between amps, the hum moves to the other amp. 

    Anyway, I've just ordered a new PSU from Orange and will see if the one that came with my new Terror Stamp, or the old Micro Dark is the issue. If all combinations of PSU continue to hum then I know it's one of the amps.
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  • CanoCano Frets: 20
    The new power supply just arrived and the hum appears to be gone.

    I'll get the whole board back together and try properly later (my kid's sleeping in the next room right now) but in my basic test of 2 amps, one pedal and no input.... Beautiful silence. 
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