GROUND LOOP ISOLATOR SCHEMATIC TRIAL
GROUND LOOP ISOLATOR SCHEMATIC TV

The +12 Trigger Out on the right side of the diagram is ground-referenced (see the 'Trigger Gnd' label). There's no ground connection at all on the signal labeled 'Trigger 0V', which would be better named as 'Trigger Input Return'. One thing that's important to notice is that the +12V trigger input is opto-isolated via the optocoupler U1. On the left side is the +12V trigger input.

GROUND LOOP ISOLATOR SCHEMATIC TRIAL

Given the complexity of the causes and effects in any specific installation, trial and error, and suggestions from others who have solved this sort of problem, are the natural way to address the problem.

Hum from trigger circuits is occasionally reported on this forum, but is not a common problem. This voltage becomes part of the analog signal.Īs you can imagine this source of hum signals varies with each piece of equipment, and is very dependent on how the the pieces of equipment at each end of the trigger connection are designed, and perhaps even other pieces of equipment in the system. The current from the trigger circuit induces a voltage in the section of conductor that is shared with the analog signal. Just as with the return conductor, the shield, in an RCA cable, the return audio signal is sharing a conductor with noise from the trigger circuit. This means that the analog signal ground may the same conductor with the trigger ground for part of the way back to the power supply. In equipment with AKM DAC IC's by design, the analog ground is connected to the digital ground at the DAC IC so connection of the trigger ground to either ground effectively connects the trigger ground to the analog ground. The combined ground is carried back to the power source. To avoid this complex routing often the trigger ground is connected effectively to the analog ground at a convenient location. In complex audio equipment this routing of the ground can be complicated since the power supply and remainder of the trigger circuit can be located on different circuit boards. Ideally the ground for the trigger circuit is routed as a separate ground that is not connected to other grounds (analog, digital, relay, etc), and returned to the source of power for the trigger circuit.

The trigger circuit can be an electrically noisy circuit, but this is not typically a problem for the proper functioning of the trigger circuit. The hum issue likely arises from how this ground wire is handled in the equipment involved in the circuit. This of course forms an electrical circuit. One wire carries the voltage to energize the receiving circuit and the other wire is the return, ground wire. The following text attempts to explain a possible source of the problem.Ī trigger circuit has two wires. O You may want to stop here and continue with the trial and error process that you've already started. If there is still a hum problem from speakers and the issue appears to be trigger circuits then the solution often is hit or miss, trial and error. Usually problems can be solved by reducing these differences. Obviously if these differences are low enough then then they don't cause a problem.

GROUND LOOP ISOLATOR SCHEMATIC TV

Unfortunately ground loop problems that involved the trigger circuits can be hit or miss to solve.Ĭertainly it is good to find and remove as many sources of the ground loop potential (voltage) differences, such a cable TV inputs, but ground potential differences between equipment will still remain. Do you think of any other device with trigger in/out that I can use as a 'bridge' between the Marantz and the NAD, instead of the Oppo?

Any ideas of what was causing the hum between the Marantz and the NAD (this did not happen with the Emo amp)? My concern is that every time I want to use the Marantz/Nad combo I need to involve the Oppo, which is not very efficient and I do not want the Oppo to be switched on unnecessarily. What has worked for me is to connect the trigger-out of the Marantz to the trigger-in of the Oppo, and then connect the trigger-out of the Oppo to the trigger-in of the NAD. With the Emotiva I did not have any hum at all I have tried different power outlets, no luck. I have connected a gauge cable between them to ground them, no luck. I have tried different 12v mono trigger cables and even 1 stereo cable, and the hum remains with all of them. If I connect the AVR to the NAD amp via 12v trigger I get a strong hum, even with the Marantz in stand-by. I have a Marantz 7013 AVR and I changed the Emotiva A300 power amp by a NAD C275 yesterday.

Ground loop isolator schematic