Further troubleshooting using multimeter. Found that hum is almost eliminated when one probe is on case ground point and the other touches the exposed RCA of the preamp out. What kind of symptom would this lead toward?
Subwoofer Hum When Connected to Integrated Amp
Observed issue: 2 different active subwoofers have sustained hum when plugged in to integrated amp's preout RCA. One sub has the hum independent of where the subs gain knob is set, while the other sub has the hum in relation to the gain knob and it stops when the gain is set to 0.
Troubleshooting: Different outlets on different circuits, surge protectors, RCA cable swaps with shielded and unshielded and length varieties. Cheater plugs on both the subwoofers and amps. Using 2 different preamps (solid state and tube) does not introduce the hum, along with using speaker wire input to subs from the amp.
Noticed the hum exists after powering off and unplugging the power cord from the amp, but leaving the RCA connected to the sub. The hum pitch varies when I touch the front of the amp faceplate or the sides.
Equipment: Creek Evo50a integrated. One subwoofer uses a Yung SD300 amp, and the other is a Pioneer of unknown amp brand.
The Ask: What other troubleshooting steps or direction is recommended? My thoughts are isolated to the integrated amp, especially when the power was off and the varied hum pitch happened when I touched the case. Appreciate any input!
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