I recently purchased an ISP decimator G string 2 pedal and could not use it because it causes a very loud squealing or high pitched noise or a ground loop. I have a ONE Spot isolated power supply for my pedals so that shouldn’t be the issue. I called ISP assuming the problem was the pedal but after a few experiments they suggested we confirmed the pedal was fine. In one of the test ISP had me put a jumper from “guitar out” to “decimator in” and try that, and by bypassing the key on the pedal I was able to get the pedal to work however I was losing the Key functionality. The Key functionality of the ISP G string 2 is what makes that pedal the most effective noise gate pedal on the market. I then decided to try the Fortin Zuul noise gate pedal which also has a Key option. The Fortin pedal also had the exact same issue. The Fortin pedal also has a ground lift switch integrated, but moving the switch does not help at all. I reached out to Fryette for some assistance and they recommended that I get a PYLE phe300 hum eliminator. The Pyle device does indeed effectively kill the ground loop, unfortunately it also cuts the signal level by almost half.
It basically makes the guitar sound drastically different in the sense that it has less output. This makes the PYLE unusable in my rig. Any suggestions of how to correct this
Hi @Carlosabc819 welcome to the forum!
I don’t have direct experience with the PHE300 so hopefully someone from the community 
will chime in to help you. But I’d like to better understand the signal path you are describing with the PHE300.
Some general comments, all transformers have:
- Insertion loss: the volume coming out is a little less than the volume going in.
- Target input and output impedances.
To achieve low insertion loss, the winding resistances must be much smaller than the target input and output impedances. This makes me think that there is an impedance mismatch somewhere in your signal path.
I took a look at the PHE300 data sheet, but it does not give much information.
Are you stating that when using the PHE300, the front end of your amp receives half the signal?
Maybe a high-quality buffer pedal like an EQ could restore some of the gain, which would help to drive the amp a bit more. However, because I don’t fully understand your signal path, it’s hard to say.
So is the noise gate in the effets loop of the Power Station ?
I have a PS-100 and Zuul+ here.
Yes, just as recommended. Zuul is in the fx loop. Are you using your Zuul + in the fx loop but using the key after the guitar
No
I only use the 4 cable method in front of the amp. Overdrive, boost, distortion and fuzz in the loop of the Zuul+.
Got it, that’s probably why your not getting the issue. If you were to try an use it in the loop of the Fryette you’ll get the squeal
Next time I use the Power Station I will try the noise gate in the loop.
Curios about other people’s experience ?
Thanks @stephensawall for chiming in 
it’s great you have the same gear too.
Joe’s video helped me a lot to understand how to fix these issues.
@Carlosabc819 I think, you fixed the squeal but you are having low signal volume into the amp?
Do you think you could sketch your rig and upload it, just taking a photo of a piece of paper would be fine to understand how things are connected and powered.