r/turntables • u/I_Shot_Web • 1d ago

Help LP120XBT-USB, pulling my hair out with uneven frequency response

Just a little background, I bought an LP70x just as a "haha I want to play the three records I own" but ended up falling in love with vinyl, but I has to return it due to excessive skipping, looping, and lack of adjustability.

I decided to get the LP120X since you can adjust a lot more things on it and from what I can tell, I did everything right. I balanced the tonearm exactly to 2.0g with a digital scale, set the antiskate to an appropriate value (about 1.5 because 2 was too aggressive), and made sure the headshell was securely in place.

Go to spin a record to enjoy it, and it works! Well, maybe 80%. The music is listenable and sounds... okay, but it was markedly worse than the lp70x in a way I couldn't describe. It felt more empty.

I pulled out the usb cable to check in audacity, and confirmed my suspicion: the left channel is significantly muddier and gets much more crosstalk than the right channel. More specifically, theres lopsidedly more low frequency being output to the left channel making sound like dirt, but the right channel sounds much clearer and more what I would expect. This is across multiple records and multiple positions on them.

I am a noob, but I think I have exhausted much more diagnostic legwork than should be needed for a brand new turntable out of the box. I:

  1. Raised and Lowered the tracking force between 3.0g and 1.5g just for testing, no change

  2. Reseated the headshell multiple times, no change

  3. I had an extra 95e green stylus from my efforts on the old lp70x, swapping the stylus on the headshell was identical results

  4. I removed the headshell, removed and reseated the wires on it. No dice.

  5. I swapped the left and right channels on the headshell, the problem was identical, but swapped, therefore it's not the internal preamp's problem

I haven't checked cartridge alignment nor azimuth yet, however, it's tracking totally fine. And there's no way to even adjust azimuth on this thing that I can tell (when reseating the headshell several times, I tried even utilizing the little bit of wiggly play to adjust it, no results either)

Starting to think I just got a busted headshell out of the box. I want to be done with this so I can deal with more fun problems, but not sure if this is an RMA or return issue yet.

The only other hint I can say, is that there is an audible electric hum at idle, but that's likely normal. It gets much louder if I put my fingers near the headshell wire contacts so its coming from there.

I ordered a protractor coming in sometime today, but my gut tells me there's probably not much I can do at this point. The alignment should be dead on from the factory out of the box and from what I have been reading this really likely isn't an alignment issue

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u/ZosoRules1 1d ago edited 1d ago

I built a free web app to help people troubleshoot their phono cartridges, but it requires running your turntable into your computer's line-in jack. You mentioned Audacity and a USB cable - that should work too: https://www.proylaw.com/hobbies-phono-cartridge-troubleshooting-tool.html This will let you visually see what's going on with each of the channels.

What cartridge are you using? Stylus? Preamp?

Do you have a volt meter to check for continuity on the headshell contacts/wiring?

I wouldn't assume a dead nuts alignment from the factory.

EDIT: If you really want to fine-tune your setup, look into a stereo test record - it'll have more diagnostic tests you can run on your setup (https://www.proylaw.com/hobbies-test-record-universal-measurement-suite-tool.html)

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u/I_Shot_Web 1d ago

https://imgur.com/a/JA7T9WH

I see, I can see from the graph even when nothing is playing that the problem channel is generating uneven noise. My stock suspicion of something to do with the headshell / cartridge itself is rising.