Upgrading an Audio-Technica AT-LP120-USB turntable

the upgrade is complete, awaiting some tests and cartridge swapping, i heard it with the 160 on it and WOW! the seperation is amazing now, distortion and background noise is much lower! pics and samples will be posted as soon as the tests are done!

Nick

How hard it is to replace the tone arm wire? I see where the tone arm wire is soldered to the PCB - but where does the other end go?

well, that depends a bit on your tonearm. (and how the wire is mounted and run)
I did it twice in the past.
On a Dual where it was surprisingly easy and a Eumig where it was much more complicated.

How hard it is to replace the tone arm wire? I see where the tone arm wire is soldered to the PCB - but where does the other end go?

When I upgraded the wire, I ran it from the tonearm straight to RCA jacks that I added to the back of the turntable; I bypassed the PCB and removed the preamp/ADC board altogether.

I'm still looking for the pictures I took during the upgrade, I don't remember where I put the files. When I find them, I'll post them.

It would be great to see those pictures

I have the hum issue with I'm assuming the preamp. Wouldn't another way to disable the preamp non destructively would be to just unplug the preamp's power cable and switch to phono? It looks like a passive trace to the output cables although with a couple of caps in the mix. Why not just add a mini toggle switch mounted on back to cut the power to the usb preamp board?

I did notice that the hum increases slightly the moment the cart is over the platter. The preamp is not under the cart in that position. There may be some other issues contributing.

Just thought I'd share my experience with the on-board pre-amp bypass mod:

When I initially bypassed the AT120's pre-amp, I was using an AT440MLA cartridge.  At the time, the only thing that was bypassed was the pre-amp itself (making the my mod look almost identical to the mod at the beginning of this topic, except not nearly as clean in the cable management department).  I immediately noticed an improvement in the treble response, and can say without reservation that the overall sound quality improved with this mod.  Also, there was no hum present, or any perceivable signal interference present at the time.

Unfortunately, my AT-440MLA suffered some unintentional damage (i.e. over-tightening), at which point I switched to the Denon 103R (a natural alternative, right? xD)
Ignoring the mis-match of the tonearm and cartridge issue (brought up by lshin80 earlier in this thread), I immediately noticed the presence of the dreaded "mains hum" (i.e. 60hz hum) in the sound.  After removing a DIY pre-amp from the mix (substituting for a Schiit Mani), the sound of the mains hum dropped slightly, but was still very present.  Moreover, the hum would increase nearly 20dB when the direct drive motor was on (not necessarily even spinning), and even higher when the cartridge was placed over the record.

I discovered (largely through trial and error) that the hum I was hearing was largely correlated to the AT120 direct-drive motor being on. In an effort to minimize the noise, here are the things I did (no particular order):

1) Completely bypassed all PCB boards that carried the cartridge signal.  That is, I soldered the tonearm cables so that they now go directly out to the step-up transformer (SUT).  I did this by de-soldering the EMF shielding and tonearm cables from their first PCB (i.e. the board with the traces), and routed them directly to two RCA connectors I added for the initial mod.  Note: I soldered the white and red wires to their respective posts, and solder the remaining green, blue, and black wires to the ground posts.  Also, I kept the EMF shielding around the tonearm cables and stretched it to cover them as much as I could.

2) Dramatically shortened my interconnects.  Originally, I was using 3' cheapo RCA cables out to the SUT.  In replacing these, I purchased two 6" Schiit RCA interconnects, and connected them between my RCA outs from the tonearm to the input side of the SUT.

3) Completely bypassed the grounding to the spring post with the cartridge ground wires (note the grounding to the spring post from the tonearm ground cables in the pictures provided by BSD2000).

4) (Optional) Although still connected in my configuration, you may be able to get rid of any kind of dedicated outbound ground wire altogether.  However, this will obviously be TOTALLY dependent on your own configuration.

Doing all of the above dropped my noise floor and mains hum below were it was even audible, and allowed me to hear why the Denon 103R is considered such a great cartridge.  Also, there is now no additional noise when the motor is turned on, nor when the cartridge is moved over the platter.

Caveat: I am bringing my signal (after pre-amping) into an Apogee Rosetta AD.  Setting the resolution to 24-bits and the sample rate to 48khz was the configuration I used with regards to the claims above. 

Hope this helps!

I keep looking through all my memory cards and on my drives and for the life of me, I can't find the photos I took when I swapped the cable to Cardas. I think what happened was the SD card that had the photos on it got wiped by accident and lost forever. 

As I recall, it wasn't that hard; I just removed the connector at the headshell, un-soldered the old wires, soldered on the Cardas cable and taped the new cable to the old and pulled it through the tonearm. I kept the Cardas cable tightly braided through the tonearm and I did fish it through the braided mesh on the bottom of the tonearm base (just as you mentioned) to keep the cable shielded as much as possible. The Cardas cable was terminated to two female RCA connectors on the back of the turntable with individual grounds, not shared like in the photo. The grounding lug was kept as it was, attached to the rest of the ground cables in a 'star' configuration. After completing the bypass, the PCB was no longer being used, so I removed it.

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The Cardas cable made a huge improvement in the overall clarity, giving music a more controlled and tighter sound. I highly recommend replacing the tonearm cable with Cardas - the improvement is quite dramatic for such a small monetary investment. 

As you mentioned, there was a slight bit of 60hz hum, but it was relatively benign; down around -60dB, which is barely audible once the music starts. Using a good quality interconnect can help reduce it even further. You mentioned about bypassing the ground to the spring - I may try that to see if it makes an improvement.

The only thing I found from when I did the wire upgrade was a few test recordings, which I can share if anyone is interested. I didn't do any recordings before the upgrade, only after is was completed. 

Caveat: I am bringing my signal (after pre-amping) into an Apogee Rosetta AD.  Setting the resolution to 24-bits and the sample rate to 48khz was the configuration I used with regards to the claims above.

I love the sound of Apogee Rosetta AD's; I have a 96K model myself.

I managed to find some of the pictures I took while doing the upgrade. 

If I was going to do it over, I would have ran the wires directly to the RCA jacks instead of to the PC board.

I managed to find some of the pictures I took while doing the upgrade. 

If I was going to do it over, I would have ran the wires directly to the RCA jacks instead of to the PC board.

It's never too late Thanks!