I connected each individual outputs of the rytm in my mixer in mono and the main L/R in stereo.
The sounds 3 to 8 looks like they are not send in the mixer, but I can ear them in stereo.
Other sounds are working well in mono.
My question is normally are they suppose to work in mono with others drums ??
I checked on the manual using output research but I found no informations 
Any informations may help me in my trouble !
I’m afraid I really don’t understand your question, but…
It sounds like you are sending your voices to both the main stereo mix and to the individual outs. In your kit settings, check the track routing. If you are using the individual outs, you (likely) don’t want to send these voices to the stereo mix.
I’m wondering if you are not separating the voices on the shared output individual outs
These individual outs are TRS (not balanced), but need to be split, use an insert cable e.g.
If you throw a mono cable here you’ll lose one voice
but I’m also unclear as to the question, just throwing this in
I’m sorry if I was not enough clear.
Yes I connected both in mono and stereo to see where came the problem.
Now I understand my mistake I was using a simple mono jack cable instead of a split cable I changed it but now it seems that delay and reverb of the rytm is not working in mono.
It works as it should - the FX are send FX, the individual outs are tapped pre-send - this is normal and there’s no way to improve this - see the diagram at the start of the manual - there’s only one FX block
Thank you for your time ! Now it’s clear in my mind ! 