What does a tonearm contribute to the sound of a turntable?

Everything matters. With turntables its primarily speed stability and vibration control. With the tone arm its vibration control and preserving the delicate cartridge output signal. Either way because of the way the cartridge works any vibration at all is indistinguishable from the groove signal vibration and becomes a part of the signal. The perfect arm will be stiff, in order to preserve dynamics, and highly damped, in order to minimize harmonic vibrations smearing the signal.

The difference between arms is easy to hear. Improved dynamics and detail, greater instrumental character, on and on. But its due to a combination of things. Its bearing design, mount and arm tube materials, every single aspect of design and construction and materials really. An arm like my Origin Live Conqueror has a direct signal path. The phono leads are continuous without connections from the cartridge pins to the phono stage. Some other arms will have the leads terminate in RCA, you need an interconnect, which adds connections. And expense.

Some arms have VTA easily adjustable, some even on-the-fly (while playing). Precise VTA adjustment is crucial. Some arms make it a pain in the butt. Some make it all but impossible. Others make it a breeze.

Some arms just plain look nice. Some are a pleasure to use. These things matter. Don’t pretend they don’t! It hardly ever makes any sense to buy anything based on tech specs but you buy an arm that way I can just about guarantee you will regret it. I did. Bye-bye Graham. Love my Conqueror.

You will read tons of comments on this. You will learn next to nothing. Even from me. What you will learn from though, a lot, is if you fork over $40 and order a sheet of fo.Q tape off eBay. Then stick that stuff on your current turntable and arm. Don’t worry, it peels right off if you don’t want it. With this tape you will hear what I’m talking about. Basically for $40 you will begin to appreciate what is going on. And it will be money well spent because it will make what you already have sound so much better.

There’s other tweaks like this. Do them all now, learn, and it will help you appreciate and understand why its worth upgrading. Then when you do and move all this stuff over to the new rig, wow you will appreciate it all over again.

Thanks, Chuck. I'm digesting all the information at the moment. 

I replaced my ancient sumiko ft3 with a jelco 750 eb. One of the things I noticed after installing and calibrating was that I had to use a bit more volume with the jelco to get to the same levels as before with the sumiko. Why might this be?

The arm itself has little effect on volume. That is almost entirely down to cartridge output. The arm does however have wiring, and connections, and those could produce a small effect. A bigger effect though might be vibration control. Remember the signal you get is the sum total of all the vibrations- stylus, cantilever, cartridge, headhshell, arm tube, bearings, mount, arm board, base, plinth, platter, motor- all of it. Its not just the record. Its all added together. The better arms of course add a whole lot less.

Now virtually all these vibrations that are added by the cheaper arm, they are there but at such a low level as to be inaudible. In other words you would never listen and go wow that vibration, it really bugs me, I need a better arm. 

This is a huge mistake, yet people do it all the time. I don't need a conditioner my power is clean. I don't have a problem with this mess of tangled wires they sound just fine. On and on. Just because you don't hear a noise and go "Oh! There!" doesn't mean you don't have noise. It simply means the noise isn't distinct enough to be heard as noise.

So what happens instead, and what you could be hearing, is the Jelco is so much better it has dropped the noise floor to where you feel you need to turn the volume up a bit. Not saying that's what it is, just saying that's what it could be. Because it happens. Happens all the time.

Especially depending on how they achieve the better performance. There's a balance between stiffness, which preserves dynamics, and damping, which eliminates noise. Done together the music has even more presence and life and dynamics because the lower noise level has revealed more detail. But it can also be done with more damping, in which case it might still sound better but with not quite as much dynamism or life. 

What makes it hard to know is going from one arm to another changes a whole bunch of things at once. Not as much as changing a turntable and arm and cartridge, but still a lot. That's why you can learn so much with tweaks like fo.Q tape. With that you are changing just one tiny little thing at a time. You can even control where and how much. You can if you want use just one inch and move it around listening and learning which areas have the greatest effect- those are the areas vibrating the most.

What you will learn by the way if you try this is the whole damn thing is vibrating like you can't believe!