Here are some more measurements of the V15V-SAS - this time mounted in a standard V15V body...
I have set all parameters as close as possible to original V15V OEM specifications - the intention is to compare these to measurements taken from an original V15VMR...
All measurements have been done at 255pf and 46k
Test record for spot measurements is CBS STR130 (THD measurements were done the old fashioned manual way)
Test record for LF sweeps is Denon XG7002 - the sweeps shown here have been adjusted using an EQ curve set manually based on the table provided with the record... I have made a seperate posting regarding the best way to use this record...
I felt that the SAS damper brush was possibly less effective than the original and wanted to measure and compare the SAS damper brush to the Shure damper brush (soon as I get around to measuring the Shure one as well...)
The TT this is being measured on is a JVC with a Servo Damping arm - so the measurements were taken at three differing styli pressures (1g, 1.25g, 1.5g) in all the permutations of no damping, brush damping, and arm damping... Hence the confusion of measurements.
Straight spot frequency response measurements from CBS STR130
Not a lot of difference between the various VTF's and damping methods...
THD measured using the same CBS STR130 recordings
Interesting that increased VTF provides reduced THD - but only in the 5k to 8k range everywhere else it is much the same...
Perhaps keeping the cantilever under a bit of added tension reduces skew/twist related distortion?
As I get through some more measurements using the same settings, I will also look at an aluminium cantilevered Jico eliptical for comparison (different cartridge body unfortunately... but I have not seen this variation in THD in that frequency range noted in relation to VTF before...)
These last two plots are from the same data, the first is a close up of the second, showing the arm/cartridge resonance area, and the specific impact of the two damping methods and the no-damping configurations.
In all cases except one I have used the default Q-Damping settings recomended by JVC (which is for Q dial to be set equal to VTF) - the one exception was the 1g VTF reading where I found the Q=1 setting to be underdamped, so I did a secondary reading at Q=1.5 (as shown).
Interesting that the main resonance appears to be at around 5Hz (4 to 6Hz) - this appears to indicate that the SAS VN5MR stylus has a much higher compliance than quoted by Jico. (Jico quoted me 13cu @ 100Hz)
Remembering that this is being recorded on a JVC QL-Y5F, the V15V is mounted on a standard Technics headshell (7.3g) - which (using lds EMC spreadsheet) results in an effective arm mass of 14.5g and a total effective mass of around 20g - indicating a compliance of over 35cu (!).
Looking at the impact of VTF and damping on the resonance...
1) increased VTF appears to drop the resonance by around 1db
2) the SAS damper brush drops the resonance by 9db at 1g VTF, and around 8db at 1.5g - so it is actually quite effective!
3) Servo arm "Q Damping" is slightly more effective at controlling the main resonance (4.5Hz) than the brush, but noticeably more effective at controlling the Secondary resonance zone at 5Hz to 7Hz. Unsurprisingly the two together do the best job.
Would the brush + Q equate to a higher setting of Q alone - I don't know... But my gut feeling is that they behave slightly differently - and may be complementary.
Which also raises the question of whether the brush + Q damping is overdamping the system...
4) Damping did not have a measurable impact on THD. (I may have to try and measure IMD to see whether there is an impact there...)
Bye for now