TT/Tonearm/cartridge interaction theory?

Here are my favorites:

http://www.audioasylum.com/audio/vinyl/messages/1240.html

http://www.deadwaxcafe.com/vzone/cartalign.asp#vta

http://www.walkeraudio.com/fine_tuning_your_turntable.htm

http://www.tnt-audio.com/sorgenti/vta_e.html

http://www.theanalogdept.com/tonearm_alignment.htm

It's really quite simple. You have a stick. At one end is a rock and at the other end is a magnet. The stick is physically held in place such that movement at the rock end is mirrored at the magnet end (think of a see-saw). Additionally, the magnet end of the stick is surrounded by thin wire metal coils. As the rock end of the stick is dragged through the undulations of the record disc it moves in both the horizontal and vertical planes. At the magnet end of the stick this movement generates a small electric current through the surrounding coils which is then carried via an interconnect cable to a phono preamp.

Based on this description, the purpose of tracking force is to keep the rock (stylus tip) in contact with the record groove walls and to keep the magnet centered within the surrounding coils. Cartridge manufacturers usually give a range for tracking force. It's a little like tire pressure in cars. Depending upon what type of ride you like, the roads you drive on and your driving style the "correct" tire pressure could be a the low or high end of the recommended range. Tracking force is ultimately set by ear.

See these links for detailed explanations of all the other factors (SRA, VTA, azimuth, tracking error, etc.) that effect cartridge setup and sound quality:

Walker Audio

Laura Dearborn/van den Hul

Good Sounds

Audiophilia

Audio & Music Bulletin

A particularly important aspect is matching the compliance of the cartridge with the effective mass of the tonearm. The compliance being the springiness of the cantilever on the cartridge.

Since we have a weight (tonearm+cartridge) riding on a spring with minimal damping (unless the tonearm bearings are shot) you have a resonant system, and the resonant frequency is affected by the mass and the springiness (compliance). It is good to keep the resonant frequency below that of the lowest frequency in the music (15Hz), but not too low where warps in the LP could excite it. 8-12 Hz is ideal.

It's all here....

http://www.theanalogdept.com/cartridge___arm_matching.htm

There's also an accurate easy to use (no formulas) compliance chart at:

www.cartridgedb.com

Does anyone know the physical difference (i.e. how they're measured) between dynamic compliance and static compliance, and whether you can use them interchangeably in calculating resonance values. For some reason, cartridge manufacturers only seem to spec one or the other.

Dear Nil: In all those links that other people posted you have almost the answer for your questions.

+++++ " What kind of tolerance on this right amount is tolerable without loosing too much of a signal and ... " +++++

The tolerance range ( up/down ) is the one that the manufacturer gives at the cartridge operation manual. Between that range you could " move " but you have to take in count all the others parameters that has relation with the VTF for stay right on target: """ I do some clue that the amount of signal that cartridge retrieves from grooves is miniscule...""""""

The next step and a very critical an important one is that that minuscule signal could be amplified with enough gain and with out distortion/noise/colorations an according to the RIAA eq. and that's means with a RIAA deviation no more than 0.05 db

Regards and enjoy the music.
Raul.

Thanks a lot. More material available than I thought. I will have to read thru all and digest.

The arm wand material is a consideration also. Steel, aluminum, and carbon fiber tube arm wand may have resonance characteristics of dragging a metal/hollowed tube on a rough surface. Solid or small diameter wooden arm wands have lesser resonace/ringing as metal tube. Wooden arm wand gives more natural music. Metal arm wand that was carefully tuned can provide accurate music. Surprisingly, the musical differences among arm wand materials are in tonality not in frequency ranges. All arm wand meterials extract all frequencies from the record. Different arm materials emphasis different area on the musical frequency spectrum. Wooden wand tends to sound warmer and more relaxed than metal wand.