Would a ARC ph5 have enough gain for a Lyra Titan

The Titan i has a output of .5mv. The ARC PH5 has a gain of 57.5db. That results in an output of 375mv. You should be more than fine.

Yes, that's enough.

The gain of the ARC PH5 is pretty healthy, It's the 12db gain of the ARC Reference preamp that might be a problem.

I don't see a problem. There is a nifty formula from TAS which says that the needed gain = 20Log(V1/V2) where V1 is the voltage needed to drive the amp to a reasonable level (typically somewhere around 1.0 volts) and V2 is the cartridge output, in this case .5mv (=.0005v). Plug in the formula and you get a desired gain around 66db. If I understand the specs mentioned in the above posts, the gain would be additive, and 57.5 + 12 = 69 db, just fine. For comparison, I run a Benz MC20E2L (also a .5 mv mc cartridge) directly into my ARC SP-8 which has 60 db of gain in the phono stage, and at a good listening volume my pre-amp gain is right around 11:30-12:00, right where it is supposed to be, so in my experience (feeding fairly insensitive Maggies) 60 db gain is sufficient.

I tend to think that there's not enough gain in the system for the Titan. First, Lyra rates their cartridges at 5 cm/s versus the typical 3.54 cm/s. That would knock down the input to 0.35mv and with the 12 db from the ref 3, you would be outputing about 1V at full throttle. If that's enough, really depends on your amp, speakers and what type of music you listen to.

I personally don't like being in a position where my source does not have enough output to drive the amp to full output or beyond. I think dynamics get compromised otherwise. The typical input sensitivity in todays amp's is about 2V for full output. Some less, some more. In my setup with 66db of gain, I can drive a Atma-sphere MA-1 to a whopping 3 watts.

Amplifier power also plays a role. Big difference driving a 60 watter to half output versus a 450 watt beast.

The bottom line is that there is no definitive answer.