built-in phono stages -- good idea?


It seems to me that the best location for a phono stage is at the tone arm wire end -- in the turntable. My thoughts:

This would bring the following benefits to its performance:
Elimination of the sensitive and susceptible phono cable
Reduction of the need for a balanced phono stage
Reduction of noise without the need for balanced design -- half of the battle is won already.

Both are significant advantages, I think. But this puts some limitations on the design of the phono stage:
Needs to be very compact solid state design, probably SMD. Access to loading options and mc/mm switching need to be thought out and accessible from rear or underneath. Again, both doable.


Why don’t we see this more often? Your thoughts?


Herman
gera
There is nothing stopping one for placing the phono amp right behind or below the table/arm/cartridge, with an uninterrupted run of internal arm wire from cartridge tags to RCA plugs going right into the phono amp jacks. That's how I and others do it. If you can get the phono amp close enough to the arm, the wire need be only 1/2 meter long.
An interesting idea, but difficult in execution. Ortofon went part of the way there on their early SPU cartridges building a transformer into the headshell. See the excerpt below from the Ortofon wedsite:

"Because of the very low impedance and the very low output, the first SPU cartridge, the SPU-GT, had a small transformer integrated with the cartridge units in the GM- housing, yielding about 7mVolt at 5cm/sec suitable for an MM input sockets with 50kOhm loading. "
Can't remember any single problem with separate phono stages i've been using for a long time for MM, MI or MC cartridges.  

What if you built-in phono stage is not good ? 

This would bring the following benefits to its performance:
Elimination of the sensitive and susceptible phono cable
Reduction of the need for a balanced phono stage
Reduction of noise without the need for balanced design -- half of the battle is won already.
Getting rid of the tonearm cable is good. But the location otherwise says nothing about operating balanced- if anything, you'll need it even more as the preamp is susceptible to noise from the phono motor, especially if single-ended. Plus you'd need to transmit the signal to the preamp, so it would be beneficial to have a balanced output too (I say too because a cartridge is a balanced source).