Weird sound please help

I have a weird sound that happens while listening to records. the sound is a loud 'wump'. That is the best description I can give you for the sound itself. The equipment I am using is Manley neo classic 250s, Manley Steelhead, Genesis G5.3 speakers, a Brinkman Bardo turntable with a Origin Live Conqueror arm and I am currently using the ZYX 4d cartridge. I also use the steelhead as a preamp for my DAC if have never heard the 'wump' while listening to the DAC...

I have experienced the sound with my last speakers so I don't think it has anything to do with the speakers. I have a feeling it is the Steelhead but not sure why or what I should do.

the sound occurs most if I turn up the volume or if there is a loud musical passage. @ higher gain it happens more frequently. but it still happens at gain set at 55...now i am testing gain at 50 the lowest gain setting on the Steelhead.

If I turn up the volume using the Manley Remora (remote control) I will surely get the sound to take place within 30 seconds though not always...

What the hell is it and how do I correct it?

thanks for your imput; I appreciate it.

jb