Yeah, you need one. I have used a dedicated phono preamp with my AC200 and it works great.

Two recommendations for low cost / high quality phono stages that will complement your AC200. The iFi iPhono3 is great sounding and a bargain. On this side of the pond, the Schiit Mani is also a good buy. The knee in the cost-benefit curve is pretty low on phono stages these days. These mini phono preamps will put a lot of the older "golden age" preamps to shame and are dead quiet.

#1 G65, UHD722, Oppo UHD-205, BAT VK6200, Vandy Quatro, VCC5, VSM1, Swarm, Pass XP-25, VPI HW-19 Mk. 4, FR64fx, Koetsu Urushi, SOTA, MDC-800, Miyajima Shilabe, BS Node 2i
#2 AC200, M6, BS Node 2i
#3 DIY Tube Pre, Pass FW J2, Alesis ML9600, BS Node 2i, Direct DAC, PassDIY Pearl 2, Denon DP-70, Ort. SPU, Spendor SP-1, Magnepan LRS, VPE LDW, Pass SLOB