Amplifier noise

[Kinetic]

I've been building clones since the beginning of the year; I've built about 10 functioning pedals so far.  When I'm testing/tweaking new builds, I usually test using a small solid state practice amp.  All of my pedals work fine on that (albeit only tested at low volumes).

My main amp is a tube amp (Peavey 5150 mk 1).  I usually have it set at a much higher volume for playing.  I have noticed that when I engage my clone pedals, pretty much all of them add a lot of noise.  I initially assumed it was something to do with my builds, but I tried a Boss pedal and it does exactly the same.  Somewhat strangely, one of my clone pedals (an MXR Blue Box) doesn't add any noise whatsoever, it's just the same as when bypassed.  The pedals which add noise are a variety of different types; delay, chorus, distortion, compressor, you name it.

The obvious thing to say here is that I need to get a noise gate, but I was curious as to whether there is an obvious reason why the Blue Box clone would be noise-free when all of my other pedals add significant noise?  They were all tested at the same time, using the same guitar, same amp settings, same cables etc.