preamplifier Gallien Krueger 2000 CPL problem hiss, hum or other

[Andrex88]

hello everyone, I start by saying that I'm not an electronics expert but I really like it and I would like to give it a try to try and find a solution to the problem, practically the GK and a preamp that I connect to the marshall 9200 power amp and you hear a strong hiss that increases as the volume increases, both clean channel A and distorted channel B, both with guitar connected and not connected, I am attaching a video for now I have limited myself to trying to replace the components of the power supply stage because I thought they were the cause of the problem, the replaced components are circled in red, but the problem evidently persists not in the power supply stage. Thanks

https://www.youtube.com/watch?v=NVaa8qDghNc

[Arbutt]

Hi Do you have a scope?
If so i would suggest you trace the signal path. If you also make up a dmm probe with a croc clip , connect it to chassis/ground probe the signal path at different point seeing if the hum/hiss/noise goes away, then you can narrow down the area where its coming from
as its the noise is getting louder when you turn the vol/gain control . Its likely to be before that

also scope the LT rails to be sure
Post up the complete schematic