I have gotten great support from serato, Albeit not always right away or with the answers I had hoped for.. but they always respond which isn't a lack of support.

I assume you tried adjusting the latency within SDJ's option screen, Replacing the USB cable, tried different USB ports and optimizing windows to run SDJ. I see you say you tried windows 7 & 10, was this with the same PC using dual boot or seperate PC'S?

Have you tried contacting Denon support? Perhaps it is a faulty unit?

I hate to ask at risk of sounding like a total douche, but why would you book gigs when you didn't know if your hardware would work up front?

I only hope you have back up gear to compensate.

Try another usb cable.

I have tried 3 different USB Cables, Denon have saidit is a Serato software issue, DJ Raven yes I have tried everything that you have mentioned. It was on two separate lap tops one with 7 & one with 10.

if it was just a problem with just one laptop then maybe fine but two different makes of laptop and two different windows then a software problem.

These gigs were booked 18mths ago and yes I have back up decks but after spending so much on the MCX8000 I had hoped that I could use it.

I totally understand that, However I don't see that it is necessarily an issue with SDJ. Could very well be an issue with the unit itself. Just saying.

serato.com

This thread is discussing the controller in question and a few users seem to be using it with SDJ with no problem. It could be that they are using Macs as there are a few reports of some issue using Windows related to dragging and dropping files. Perhaps your issue has been discussed there. I suggest reading through it if you haven't already done so.

I have just sat down uninstalled serato then re installed and no usb lights coming on, and the music sounds perfect coming out. Now to return the USB leads that i got today.

Not sure what you mean by "USB dip"…. If you mean USB distortion and/or latency then if can be a number of things…

1. Please make sure you have downloaded the latest Windows drivers off of Denon's website(denondj.com)
2. Make sure you have the latest FIRMWARE downloaded off Denon's website(denondj.com)
3. Start at 5ms USB latency in SDJ and if distortion creeps in then adjust to 10ms.
4. Adjust your MAX Screen Updates Per Second to 20 MAX in SDJ
5. Keep the Master volume in SDJ at halfway(12 0'clock)
6. If need be perform a Factory Default reset on the MCx8000 unit itself. (under the UTILITY menu)
7. If all else fails contact the Denon support team by phone or email. The MCx8000 is covered under a 3 year warranty as long as the controller was purchased by an authorized Denon DJ dealer.

Good luck and let me know if you need any addition help.

Thank you Chino,
I uninstalled & reinstalled with My laptop running Windows 7 and have managed to get that one working. My laptop running Windows 10 I have that at 20 and then with Denon connected that is at max and still get USB dip and the music sounds really bad. I am back to the supplier tomorrow. But thank you for your advice I have a copy of that with my laptop just in case it happens again.