Cartridge measurement - fluctuating signal

I am having difficulties in receiving accurate measurement signals from the cartridge.
Picoscope is set to AC, which does not make any difference. Also digital filter setting does not improve the situation.

Are there any ideas, how to remove low frequency rumble and wrap from the signal? (wihtout an active subsonic filter)

Many thanks for any ideas.

Michael
 
Member
Joined 2014
Paid Member
welcome to the foibles of analog. Under 20Hz there is all sorts of grot that can be of high enough level to appear to swamp the wanted signal. First biggie is the 0.55Hz eccentricity of the record (at 33 1/3 RPM). This can be reduced with accurate centering of the record. Next is the resonance of arm and cartrige at anything from 6Hz to 18Hz. Then you have various rumbles from motors and bearings. I've attached a picture from a 60s B&K technical paper which IIRC was recorded off a silent groove. what do you want the signal for as that might help suggestions for reducing the issue?
 

Attachments

  • b&K rumble.jpg
    b&K rumble.jpg
    63.8 KB · Views: 46
Indeed, I own already a collection of test records - each of them having advantages and disadvantages.
The sub-chassis swings at 4.5Hz and the tonearm resonance appears at 10Hz.
Thank you for that interesting graph. I am surprised about the off-center effect.

Anyhow, I accept that the low frequency response measured from the cartridge is irrelevant, as long as the resonances of sub-chassis, tonearm etc. do not overlap.
Therefore, measuring the higher frequency response above 1kHz will be sufficient for the interpretation. This allows also a flat high pass...

Best wishes
 
  • Like
Reactions: 1 user