Hum
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| Posted on March 31, 2015 at 08:47:19 | ||
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Posts: 1800
Location: Omaha NE Joined: September 8, 2006 |
After trying in vain to modify a modern-production Audio Technica turntable to eliminate or at least greatly lessen hum I got to thinking. Why is the standard for turntable single-ended output? Why not balanced, using either XLR or two RCAs? Twin RCAs could be retrofit onto any turntable, as could XLRs. If twin RCAs were used each "hot" would carry one side, and the shield would be common ground. Phono preamps would have to be differential, but that's no big deal at all. BTW, on the Audio Technica turntable, after extensive experimentation we determined that the turntable, and not the cartridge or the preamp, was the culprit. We tried twisting AC leads, which surprisingly did nothing, and taking the leads from the tonearm straight out through high-quality RCA cables. Other experimentation revealed that the damn thing produced substantial hum even with the cartridge shorted at the cartridge. I think the culprit is the non-toroidal power transformer. Remoting the power supply might eliminate the hum, and using a toroidal would be a good idea, as well. This turntable appears to be of good quality until it's opened. The bottom plastic, and most of the weight comes from a thick steel plate in the bottom, not from the platter, which is nice light ringy aluminum.
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