Turntable versus tonearm versus cartridge: which is MOST important?

Whatever gets the signal off of the source is the most important piece. Nothing later in the line can add back in what was missed. 

The majority of the highly technical responses above lack practicality if one wants to avoid making a turntable system a many years long project.  There is definitely a sweet spot that "might" be achieved if just three vinyl system components, turntable, tonearm and cartridge, were were generally ranked by price/performance, and then, considered on a diminishing performance returns basis.  For example regarding the turntable piece, it makes sense to give Fieckert, Sota, Rega, Linn, etc their due when considering all the mechanical aspects of building a turntable.  There is no need for non-engineer audiophiles to be bothered with consideration for bearings, motors, and other build components....that is better left to the specialty manufacturers with proven track records.  

Furthermore, as a practical matter, it would be necessary to make the assumption that longstanding venerable brands which have achieved a consistent and positive reputation in the audiophile community, have earned that reputation as a result of ongoing technical innovation provided at a given price point.  Because of the combined electronic/mechanical nature of a turntable versus all other hifi system components, eliminating pricy esoteric fly-by-night manufacturers from consideration will weed out all but proven brands, while state-of-the-art technical leaps will be well represented by the established companies.

Yes, I wish an honest retailer was capable of taking a client's budget number to assemble a vinyl playback system, matching the turntable, tonearm and cartridge on the basis of price/performance and the diminishing performance returns analysis of each component.

As this is a Old Thread and recently received a Post claiming that a non-audiophile does not need to concern themselves with Bearings.

When it comes to a Platter Spindle Bearing, producing a TT, that has a Platter Spindle Bearing which will not show a Platter run off, is a feat of engineering to achieve. To achieve a Platter run off which will show a measurement that has a very low tolerance for a movement, will need certain type of skilled labour at the production work front to hone the tolerances required. This practice has the potential to add substantial cost to the end product. Hence the average TT producer is not going to show the accuracy of their products in relation to a run off measurement, the exposure of the inaccuracies in relation to a Zero run off, will not bear well and will hold them to ransom on QA issues, if they were to make claims of the fluctuations in measurements working within a particular dimension parameter.

It can also be heeded, that as a result of allowed production tolerances for parts being produced, one TT to another from the same Brand/Model can show quite substantial variation in Platter run off. I don't see Parts being discarded when they fall within a certain tolerance, but are maybe at the dimension parameters of the tolerances allowed for.

Take the above and add it to used TT's being purchased, the condition of the Platter Bearing is a unknown, and Platter run off measurements might be further increased to the New Supplied item. When using a used TT, this might be the least of ones concerns, and will only be of a concern when a condition such as a discovered eccentric rotation is corrected. It does not necessarily mean a TT has to have had a hard life  and a long usage have developed Eccentric Rotation, some TT's as a result of the design and materials used at interfaces can quickly develop a eccentric rotation after a short usage life.

There is not a speed control device in use, or to be produced, that can correct a speed fluctuation due to a eccentric rotation occurring. There is not a Isolation design, whether Built into a TT or a Off Board Ancillary, that will stop the transfer of energy to the Cart', that has been generated as a result of a Platter Bearing Interfaces not being optimised, even worse is when eccentric rotation is present. 

The True Rotation and Quietness of the Platter Bearing during rotations, is 'one' of the Critical Factors to be considered that enable a Cart' and the Tonearm to function in a optimised environment.

It is known Vinyl LP users are quite content to use a $10-$15K Cart'>Tonearm in conjunction with expensive devices to accurately control the TT's Speed, under the guise, the expense associated with the ancillaries in use are creating a optimised environment. I myself have used £6000+ Tonearm>Cart in a non optimised environment and can assure one that when the Bearing is improved toward a optimised environment the performance presented is Uplifted to the perception it can seem tangible. 

The use of expensive supporting ancillaries in a non-optimised environment (Non-True rotations of Platter Bearing/ Noise/Energy Transferred), is seemingly quite acceptable. It does seem that the Non-Optimisation of the Platter Bearing during operation, for many, is a lesser consideration, and the Brand/ Reputation of the supporting ancillaries in use are the focus that has the TT users priority. 

The Platter Bearing, Cart', Tonearm are a Engineering Trilogy and are as dependent on each to produce the best mechanical interfaces for optimised performance. 

TT's in most conditions met, are able to function to enable a replay of recorded  music. If this is all that is wanted that is fine, the idea of spending substantial sums on supporting ancillaries is best avoided. When substantial monies are being outlaid to add supporting ancillaries to the TT, from experience, it serves the whole of the mechanical interfaces for the best, if the function is optimised for all critical parts necessary to enable the replay to take place.       

@pindac , with the concentricity spec on records at +- 2 mm I would not worry about turntable runout. I think as long as rumble is low and speed accuracy is high you are in business. I certainly agree that per precision is always welcome and the way all three items interface is very important. The toughest part is isolating it from the rest of the world. 

I'm from the camp, "Garbage in Garbage out" So many people I know that listen to my system say, " wow! those speakers are great! " As far as I'm concerned although a well balanced chain contribute to the end result you hear, It's the cartridge, tonearm, turntable or cd transport DAC that contribute the most. .Another analogy, No matter how "good' the camera, film is, if you start with a ill focused lens,,,,,,,,then what will you get as a photo?