The different grounding points have different resistance, which can mean return current flowing through them can develop a small electrical signal introduced in the audio devices being used. When audio signal cables such as stereo cables with RCA plugs used between an audio source and an amplifier, small currents may create voltage potentials that can be picked up as noise. Ground loop noise or hum is a common problem in many home stereo, auditorium, theater, or car stereo amplified systems due to having multiple paths with differing ground potential. Ground loop noise and hum also affect video systems, although in that case, the noise often appears as distortion in the video signal.Īny time multiple audio devices are connected with cables there exists a potential for ground loops. They work with line level audio signals via RCA or 3.5mm connectors between a stereo, AV receiver, or car head unit RCA audio outputs and an amplifier that share a common ground for power. When is a ground loop isolator recommended?Īn audio ground loop isolator is a type of noise filter used to prevent electrical noise or hum, picked up by audio signal cables along the ground conductor path, from being amplified.Is it bad to use a ground loop isolator in audio?.How much does a good quality ground loop noise isolator cost?.What to look for when buying one with better sound quality.Do ground loop isolators affect sound quality?.Do ground loop noise isolators always work?.No dead person ever enjoyed their stereo, perhaps their surviving spouse enjoyed it. The power amps all originally used 2 wire power cords, but now use 3 wire IEC power cords, and plug into approved 3 wire grounded power mains. above.Īll of the signal sources are designed to be safe with 2 wire power cords (UL, CSA, etc.). Pay attention to the spacing and orientation of the output transformer, versus the placement and orientation of the power transformer and B+ choke.ģ. Then the bottom of the RC network then connects to the chassis ground (serially in that order).Ģ. * Finally, the output tube g1 grid resistor ties to the bottom of the output tube self bias parallel RC network. * The output transformer secondary Common connects directly to the Chassis ground. That reduces the Input circuit hum ground loop. And, the input tube g1 Rg ties to the bottom of the input tube self bias RC network. The bottom of the self bias parallel RC network connects to the Chassis Ground (serially in that order). * The RCA input connector Return ties to the bottom of the input tube's self bias parallel RC network. The negative of the second filter cap, ties to the Chassis Ground (in that "serial" order). The negative of the first filter cap ties to the negative of the second filter cap. * The center tap of the B+ secondary connects to the negative of the first filter cap. I have never heard any hum from my loudspeakers, using these methods. Works for Single Ended, works for Push Pull. Using an 8 Ohm load resistor, and testing the power amp by itself: Use plenty of capacitance in the B+ supply. The vacuum tube B+ negative *, RCA input connector return *, and output transformer Common *, are eventually tied to the chassis ground. The IEC socket ground ties directly to the chassis. I use RCA to RCA shielded cables to connect the units together. Vacuum Tube Power amplifiers, with IEC 3 wire power cord (the only 3 wire power connection of all my audio system devices). Most of the time, I only connect one pair of RCA cable from one signal source to the power amplifier at one time (no multiple RCA cable hum loops). Turntable, with the turntable ground wire to the phono preamp ground screw.Īll of the above have 2 wire plugs, not 3 wire plugs. But I live in the US, and this works for me:
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