Archon FX Loop Noise?

METAL123

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May 31, 2020
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Alright so I've been dealing with this issue for a while now, and over time, have tried many things. So for some background, I have a PRS Archon 100w head (2015 model according to the serial number). The FX loop makes a kind of airy hissing sound. It is quite noticeable on lower volumes, however when it's cracked it's barely noticeable. To be clear, the FX loop does work, but with noise.

I have a quality isolated power supply (Strymon Ojai), and quality cables (D'Addario American Stage). I upgraded these thinking they were the root of the issue, and they only made a slight difference in regards to the noise.

When I run a cable between the send and return, I notice it's incredibly sensitive to interference. For example. if I move the cable to the right side of the head (closer to the input jack), it's pretty quiet, however when I move it closer to the left side (closer to the on/off switch), it makes quite a bit of noise.

If I keep the FX loop cables on the right side and introduce any pedals into the loop, they will all make noise (except for a few exceptions I'll get to in a moment). I have tried 2 delay pedals, a reverb, noise gate, etc.. all quality pedals too. I have tried running on 9 volts and through the power supply.. both have the same outcome.

One very bizarre thing is that when I run a Polytune or OD808 through the loop (just for the sake of testing), they don't make any noise when the pedals aren't activated. But as soon as they're activated, they instantly start making noise. This is not the case for the delays or reverbs though, even if they're not activated, they make noise in the loop. I can 100% confirm that there are no issues with any of the pedals, as they all work perfectly fine in front of the amp, and through a different setup.

My Archon is a 2015 model, and thus, should have the loop mod fix already done. PRS sent me the loop mod sheet that I brought to my tech to make sure the mod was indeed installed. And it was.

Also tried replacing the power tubes in the amp as well/and changing the FX loop driver tube. Didn't really do anything to solve the issue.

I don't know what else to try from here. Any advice would be greatly appreciated.
 
What I have noticed with the Archon is that the FX loop is pre-master volume.

This means the self noise of your effects chain is amplified at 100% of the power of the amplifier.

It seems like a less than ideal design, but there it is.

The only way I've been able to tame the noise for lower volume is to crank the master volume up on the amp and put a good active volume control (I use a Morley volume pedal) at the end of the effects loop to set the master volume.

Give it a go and let us know how it works for you!
 
What I have noticed with the Archon is that the FX loop is pre-master volume.

This means the self noise of your effects chain is amplified at 100% of the power of the amplifier.

It seems like a less than ideal design, but there it is.

The only way I've been able to tame the noise for lower volume is to crank the master volume up on the amp and put a good active volume control (I use a Morley volume pedal) at the end of the effects loop to set the master volume.

Give it a go and let us know how it works for you!
The odd thing though is why is there very minimal noise with just a patch cable between the send and return? And as soon as I introduce most pedals, it makes noise even when they're not activated. But certain pedals introduced that aren't activated (OD808 or Polytune) don't make noise when not activated, but as soon as I stomp on the switch they make the noise.
 
The odd thing though is why is there very minimal noise with just a patch cable between the send and return? And as soon as I introduce most pedals, it makes noise even when they're not activated. But certain pedals introduced that aren't activated (OD808 or Polytune) don't make noise when not activated, but as soon as I stomp on the switch they make the noise.
A Patch cable doesn't have any active electronics (normally) to induce self noise.

Any circuit that isn't perfectly shielded with a true bypass is going to make noise due to amplifiers (esp cheap ones in pedals) self noise.
 
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