Please help with delay/echo

[Fusionshred]

I know delays have been covered here extensively but I have a specific issue I'm dealing with...

I've noticed that my Carl Martin DeLayla XL changes the tone when engaged. When I switch on the delay, it seams like there are more highs and the volume has an apparent very tiny boost. So if I set everything up with the desired tone, as soon as I need delay, it throws everything off.

Is this a known attribute of this pedal - or do I have a defective one? Either way, what natural sounding analog delay has true bypass (I don't use a lot of pedals or very long cables) and will preserve the original tone when the delay is activated?

Thanks in advance
Tom