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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!

ajnackman
ajnackman OP
68 posts
 

Well now I'm thoroughly confused. I must not have noticed on other records previously, but the woofer pulsing for the outer ~15% of the record is persistent on everything I'm playing ugh.

glennewdick's avatar
glennewdick
1,763 posts
 

From my experience the woofer pulsing is a feedback issue. have you added a subwoofer or moved the table closer to a corner of the room or the speaker? It could be set up if your cart is a lighter one on a heavy tone arm for example but from a quick look, I think your fine there. Maybe some one not behind a firewall can look it up to confirm.

ajnackman OP
68 posts
 

Turntable hasn’t shifted any. I do have a subwoofer but that pre-dates the cartridge swap. The only other change is a new phono preamp (sutherland little loco mkii). Would the pulsing change over the course of a record if it was a feedback issue? Thats what leads me to believe its an issue with the cart. On the record with the low frequency syth, the tonearm bounces slightly once every rotation and you get an audible sound I can only describe as "tshh". The more I look at the pulsing, it seems to occur once per record rotation across the board. Maybe its an alignment issue?

yogiboy's avatar
yogiboy
5,865 posts
 

 I hate to be the bearer of bad news but there is nothing that you can do to raise the resonance frequency with that arm and cartridge! BTW,  are you sure that the high 25 gram effective mass on that arm is the correct information?

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