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Thank's all of you for your answers.
With the jet lag, I answer you a bit late. You sleep when I walk up, and vis et versa

Michael, This unit seems to answer to my question. 3 bands instead of 2 for the Fishman (why not), small, available, it has probably a clean sound available for double bass.
Michael did you tried it ?
The Empress also is probably a very good unit, but bigger than the Broughton, and the weight is important for me. Got no car, travel by bus, tube, or foot.
To be honest, I never tried a box with only parametric EQ, I have a Headway 1 and the old Fishman Pro Platinium, the bulky one.
Reading your posts in Talkbass for a while, a lot of players seemed to say that this box is the box to have, this is what decide me to get one. Is it a good idea ? Some also sells it, so may be not.
Mainly, I think that that kind of box is very usefull to fight some frequencies that bother you and that you don't succed to fight with a fix or regular Eq. it is a complement to a regular Eq.
The Broughton seems a good available answer, and I will look at the Fishman if somebody find one for me. Thank's for all. Alain