Richardkrebs,
On the one hand you say that the air bearing is rigid at audio frequencies, but now you speculate that the arm is prone to chatter due to "pressure irregularities". You also claim that the pressure irregularities are audible.
The two theories are mutually exclusive - they cannot both be true.
The ET2 has evolved from the 1st incarnation that utilized low pressure low flow bearing, then with the advent of customers using higher pressure pumps ( the WISA300 for example) Bruce redesigned the bearing for high pressure low flow air supplies. Bruce will also custom build for specific air pumps and provide advice on cartridge compatibility with each of the options.
It is abundantly clear that each bearing has an intended set of parameters with regard to pressure and flow. You have discarded the original ET manifold housing, discarded the decoupled counterweight, discarded the horizontal moving mass targets that the ET design is predicated upon, and may well be running a pump that is not optimised with your particular bearing. Unless you can provide some documented testing as Bruce does on his website, your comments can only be described as speculative at best.
On the one hand you say that the air bearing is rigid at audio frequencies, but now you speculate that the arm is prone to chatter due to "pressure irregularities". You also claim that the pressure irregularities are audible.
The two theories are mutually exclusive - they cannot both be true.
06-06-14: RichardkrebsYou do Bruce Thigpen a disservice.
If there are pulsations in the air stream this will be manifest as slightly different flow rates into the manifold and thus pressures seen by each of these holes and the flow rate thru them. This would cause the spindle to chatter.
06-04-14: RichardkrebsPlease advise what testing you have done that would confirm your theory. The ET2 manual clearly states that Bruce goes through a design process, supported by principles of physics and sound engineering, includes mathematical modeling, the production of prototypes and thorough documented testing before his products go to market. There is no speculation or guesswork involved.
Below is a copy of a mail I received from Bruce T many months ago.
The resonance of the air cavity is over 500Khz and does not manifest itself on the surface of the bearing, it is a well damped liquid bearing.
I used three measurement methods when developing the tonearm, accelerometers, strain gages, and the simplest and most effective was the use of a second tonearm to play parts of the tonearm under test while playing a record.
The ET2 has evolved from the 1st incarnation that utilized low pressure low flow bearing, then with the advent of customers using higher pressure pumps ( the WISA300 for example) Bruce redesigned the bearing for high pressure low flow air supplies. Bruce will also custom build for specific air pumps and provide advice on cartridge compatibility with each of the options.
It is abundantly clear that each bearing has an intended set of parameters with regard to pressure and flow. You have discarded the original ET manifold housing, discarded the decoupled counterweight, discarded the horizontal moving mass targets that the ET design is predicated upon, and may well be running a pump that is not optimised with your particular bearing. Unless you can provide some documented testing as Bruce does on his website, your comments can only be described as speculative at best.