This is the first post in our new “Question of the Week” series. Each Wednesday our Audio Solutions team will address a question they frequently receive and provide detailed steps to help you get the most out of your Audio-Technica gear. This week they discuss a problem that can result from improper turntable setup.
Question: The audio from my AT-LP120-USB turntable only plays on one channel. How do I fix this?
Answer: The most common cause of either no, intermittent, or distorted audio on one side of the AT-LP120-USB, AT-LP240-USB or AT-LP1240-USB turntables is improper calibration of the tonearm assembly prior to setting the vertical tracking force for the stylus (needle). This improper calibration causes the actual tracking force to be much heavier than what the stylus force gauge ring suggests and, thus, heavier than what the stylus assembly can handle. This excess tracking force typically causes the left channel to have no, intermittent or distorted audio. It is possible, however, for the right channel to be affected instead. Excessive downforce causes excessive deflection of the stylus cantilever. This excessive deflection causes the tiny magnets attached to the cantilever (there is one magnet for each stereo channel) to become misaligned with the corresponding pole pieces, which extend from corresponding coils inside the cartridge. The misalignment of the magnets results in no, intermittent or distorted audio on one side of the stereo signal.
Below we describe how to isolate the problem to the turntable or the stereo device it is connected to, how to properly calibrate the tonearm, and how to set the required tracking force. We’ve also provided a link to our YouTube video that walks you through the setup of the AT-LP120-USB turntable (with the currently supplied AT95E Cartridge). The video may also be used as a general guide for setting up the AT-LP240-USB and AT-LP1240-USB turntables as well.
AT-LP120-USB Turntable Setup Video
To isolate the problem to the turntable or the stereo, the first thing you need to do is swap the RCA plugs at the stereo amplifier or receiver to see if the problem moves with the swap or stays on the same channel. If the problem moves with the swap, the turntable is at fault. If it stays on the same channel, the problem is with the stereo. If it is, indeed, a problem with the turntable, check for proper operation of the cartridge/stylus assembly by lightly brushing the tip of the stylus assembly with a soft brush or the tip of your finger when the tonearm is sitting idle and clamped in the tonearm rest. If you hear the brushing noise on both the left and right channels, the turntable itself is operating properly. But there is, more than likely, an issue with the operation of the stylus assembly when the tonearm is down on the record.
Turn the power dial on the turntable to the off position. Next, confirm that the counterweight assembly is installed on the tonearm correctly. Stand in front of the turntable like you would to operate it and look at the counterweight assembly on the rear of the tonearm. The black stylus force gauge ring on the counterweight should be facing you. It is possible to install the counterweight assembly backwards, with the ring on the back side of the weight, facing the rear of the turntable. This makes it impossible to calibrate the arm and set the tracking force correctly, and can result in an excessive amount of downforce at the stylus/cantilever assembly.
After verifying that the counterweight assembly is installed correctly, rotate the entire counterweight assembly (NOT just the black stylus force gauge ring, which can turn independently of the weight) in a clockwise direction (to the right) until the zero on the ring lines up with the black centerline marked along the top of the tonearm. Confirm the position of the tonearm when the counterweight is set at zero. Is the arm floating perfectly level in the horizontal plane, parallel to the record surface and about 1/8 of an inch above the tonearm rest? Or is the cartridge end of the arm angled downward toward the record (or still sitting in the tonearm rest)? Or is the cartridge end angled upward toward the dustcover?
If the cartridge end of the tonearm is angled upward or downward, the arm has not been properly balanced and zeroed and will need to be rebalanced to float perfectly level. Begin by rotating the counterweight assembly in the appropriate direction: clockwise (to the right) to raise the cartridge end of the arm or counterclockwise (to the left) to lower it.
After balancing the arm, use the clamp on the rest to lock the arm in place. Rotate the black stylus force gauge ring (the ring ONLY, not the weight itself – the ring will turn independently of the weight) until the zero lines up with the black centerline marked along the top of the tonearm. Finally, to set the actual tracking force, rotate the entire counterweight assembly counterclockwise (to the left) until the desired tracking force (as indicted by the ring) aligns with the centerline on the arm. For the provided AT95E cartridge (green colored stylus assembly) the recommended tracking force is 2.0 grams.
If proper balancing of the tonearm and proper setting of the tracking force does not correct the audio problem, inspect the four pins in the tonearm socket that receives the headshell/cartridge assembly. All four pins should protrude roughly the same distance. If a pin does not appear to be protruding as far as the others, that pin may be hung up and not making adequate – or any – contact with the corresponding pin on the headshell. The pins are spring-loaded in the socket. Typically, depressing the pin with a small non-conductive tool such as a chopstick, toothpick or cotton swab will cause it to pop back out to the correct distance. You may need to depress the pin a few times to make this happen. Reinstall the headshell/cartridge assembly and hand-tighten the locking collar on the end of the tonearm till snug.
If neither the tonearm balance nor the socket pins is the problem, the stylus tip may be damaged or the cantilever may be askew or rotated. It is important that the turntable NOT be running (the platter should not be turning) while you are attempting to balance the tonearm. If you should inadvertently drop the arm onto the edge of the rotating platter, the stylus or cantilever could easily be damaged by the platter’s raised aluminum strobe dots.
We hope you found this advice helpful. Be sure to check back each Wednesday for a new “Question of Week.” And, remember, if you need assistance with your Audio-Technica gear, please contact our Audio Solutions Department. We are always happy to help!