Get the Kabusa filter. No need to have the cartridge play down in the subsonic region.
Phasemation Cartridge Compliance or Alignment Issue?
I think I may be having a compliance mismatch issue with the tonearm on my MoFi Ultradeck and my new Phasemation PP-300. I'm fairly new to selecting matching components in analog systems - the Ultrdeck had the mastertracker MM cartridge preinstalled. I had that cart for several years and noticed some degradation to the sound and looked to upgrade my setup with something new.
I've come across two records where I'm getting some distortion across the first song on a side. My speaker's woofers also pulse like they are trying to play a really low note. The record plays fine closer to the center.
Tracking down the mass of the MoFi tonearm was actually a challenge. From various threads that I've read online, the effective mass of the arm is different than what MoFi states in their specifications. Based on this thread, my assumption is that the effective mass of the arm is 25.14 grams.
https://forum.audiogon.com/discussions/cartridge-reccomendations-for-the-mofi-ultradeck
I was searching for a low compliance MC cartridge to match with this tonearm and came across the Phasemation PP-300 as an option. This cartridge has an effective mass of 11.1g and a compliance of 8.0x(e-6)cm/dynamic@100hz. Using an online calculator, i thought I wad made a good selection, however based on some research, I've since learned that you need to convert this figure to compliance at 10hz for proper evaluation and system matching (1.7x multiplier). Recalculating with the new figure yields a resonance of 7.0hz. Have I made a mistake going with this cartridge? Many of the records that I've played have no issues whatsoever. One of the poor performing records is a live recording and the other is an album with low frequency electronic synth sounds.
I set up the cartridge with a Dr. Feickert protractor. Looking closely at the cartridge, it appears that the headshell and cantilever are very slightly askew from each other. I aligned the cartridge to the headshell. Is it possible that a slight misalignment would make the low system resonance more problematic? I don't notice any skew to the image and both channels seem balanced to my ears but of course that is challenging to determine.
Is there anything that can be done to raise the resonance of the system to a more optimal value?
Any help or insight would be appreciated!
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The following is based on the assumption all electrical connections have been checked, the output sensitivity of the new cartridge is matched to the phono preamp to assure there is no overload/clipping, the preamp/cartridge Capacitance has been matched, and the only change is new cartridge. Then, potential root causes of woofer pulsation when playing vinyl records are, without limitation: 1 Warped Records, 2 Turntable Rumble, 3 Turntable Isolation (proximity from speakers, suspension adjustment, racking/platform), 4 Speaker to Stylus Feedback Loops, and 5 Tonearm Mass/Cartridge Compliiance Mismatch. From what you have stated 1 to 3 can be ruled out, and you correctly identified 5 as a possible root cause. Reinstall the original cartridge to see if this resolves the issue. Check compliance recommendations for your tone are and stack the recommendations against the cartridge specification. This should give you information to determine if 5 is the root cause. If the new cartridge is higher compliance compared to your older cartridge, then I would also experiment with 4 by repositioning the TT further from the speakers. While 3 is a remote probability, you may want to experiment with your TT suspension to see if that resolves the issue Distortion on only the outer record groves and not the inner groves is normally an alignment issue or an anti-skating issue. Double check both to the cartridge manual specifications. Rumble filters are an option, but, IMHO, I would avoid them. Good luck, John
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What @lewm said. Enjoy the music |
"Distortion on only the outer record groves and not the inner groves is normally an alignment issue or an anti-skating issue." First, the problem is woofer pumping, which can be a cause of distortion due to a controversial form of Doppler distortion, but not other kinds of distortion. Second, even when an overhung pivoted tonearm is perfectly aligned, there are only two null points on the LP surface. Everywhere else there is tracking angle error, but it is worst in the space between the innermost null point and the runout grooves. Misalignment is likely to worsen the alignment in that region more so than at the outer grooves. So I don't see why misalignment would necessarily make for outer groove distortion while inner grooves are relatively unaffected (but again, I am not sure the OP is hearing much distortion, just woofer pumping). Anti-skate is always a crap shoot, but by what mechanism does it cause woofer pumping? Anyway, we agree that rumble filters are to be avoided when possible, but in this case if you take a pragmatic approach, perhaps the rumble filter will alleviate the problem. |
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