Well, I dunno if the DS3400G is JR’s BEST tail servo for the t-rex but they seem to think enough of it to set suggested retail @ $119.99, of course they usually go for about 75 bucks. As far as specs go the JR is a little bit faster (by about 0.03 sec.(0.14 vs 0.11)) but the s9650 has a bit more torque (by about 8 oz-in (50 oz-in vs 42 oz-in)). The speed I can compensate for through linkage setup, limits and expo but, as we say in drag racing, “there is no replacement for displacement!” Or torque in this case. Not that the JR is a bad servo, I’ve got a 9650 here, and I’m still running the JR. Mostly because I’m too lazy to change it and the JR is a smaller servo which I kinda like.
OK then as far as flying the two, the JR is constantly trying to re-center itself so it buzzes constantly. There’s nothing wrong with that really, it just gets annoying while your listening for other things (I mean on the ground, if its buzzing during flight, I certainly can’t hear it). The 9650 centers itself and remains dead silent. I’m using a gy401 of course so maybe futaba just has it dialed in perfectly or maybe the lil JR is just searching for perfection in an unperfect world.
Because of the difference in torque, (…I guess, 8oz-in doesn’t seem like that much…) I can get the 9650 to whip the tail around instantly. It’s pretty obvious during even simple pirouettes. The JR seems cause a bit of a lag, then the heli builds up speed in a pirouette.
The JR also drifts just ever so slightly from time to time but I think it might be caused by radio noise coming off the CF frame. The 9650 though is just rock farking solid (once you’ve got your heli’s curves set up properly of course.)

After coming back from a cup of delicious (and nutritious) Starbucks coffee and reading through this it seems as if I’m in favor of the s9650! But honestly they’re both awesome servos. For me, it comes down to this, JR=75 bucks Futaba=54 bucks hmmmm…what could I do with 21 bucks…?[sm=50_50.gif] Buy 3 more cups of coffee!!! [sm=what_smile.gif]