![]() when connecting the cables you would have to remember to always connect the grounded Sync line first else you basicly have a connection with a floating ground which can damage e.g. In practice this method has numerous drawbacks - e.g. R, G, B lines leaving just the Sync ground as the ground connection between the two devices (in case anybody is wondering Sony PVM / BVM monitors and Scart RGB TV's are both common ground devices). So in theory one could cut the ground connections on e.g. In the case of my particular setup it seems that the ground loop is caused by the monitor being connected to the switch box by way of four RCA cables (R, G, B, Sync) each having a signal and a ground connection. I resolved this by opening up both ends of the cable and running the audio in a separate cable external to the scart cable.įor the Mega Drive I am using the official Sega RGB cable, but since mine is a Model 1 with no stereo sound via the AV connector I modded the console to get line out audio through a 3.5mm socket and then modified the official cable by tapping into the audio on the Scart plug and running that externally via a audio cable ending with a 3.5mm jack to connect to the audio on the console.Ī possible way to get rid of a ground loop is to break the additional ground connections which are creating the loop. It turned out that even though the cable had the audio lines screened that screening was inadequate. With the SNES, prior to getting the official Nintendo RGB cable I had some third party ebay one which induced a tremendous amount of noise into the audio. ![]() The hum or a part of it may also be down to the actual scart cable used to connect the console. One thing which doesn't work is leaving the audio ground unconnected / floating - barely audible audio and noise / buzzing so relentless it will give you an instantaneous headache. I guess if one wouldn't want to mod the actual switch box its possible just to make a cable going from 2 x RCA on the switchbox side to 2 x RCA or 3.5mm jack/socket and break and rewire / divert the ground connection in that cable so as to be able to connect the ground from an external device. If you want to keep things simple you could skip the switch part and just hardwire the socket for external audio ground and use the scart switch box RCA audio outs in case you want to revert to using the common ground for the audio.ĭefinitely worth giving it a try. ![]() Give your setup a test and see whether your setup is generating any buzzing / hum - its a pretty common occurance with the amount of different stuff all connected together and if needed give the above a try. when browsing folders on an Everdrive and also a lot of hum / buzz when the volume was cranked up pretty loud (mightly annoying) flicking the switch makes a world of difference. on a SNES, which was generating a high pitched whine at high volume e.g. into the RF jack of a SNES or Mega Drive and select the 'audio external ground' via the switch. You can then plug that 'audio external ground' into the input device generating the sound e.g. to one of the terminals I wired the common switch box ground and to the other a cable ending with a male RCA connector (but bear in mind that we are just interested in connecting the ground, not the signal part) for 'audio external ground'. adding a female 3.5mm stereo audio socket to the scart switch box, wiring the L and R channels to the switch box and the ground of that audio socket to the middle od a SPDT switch I’ve been going through the comments and remarks here (in particular ’ latest ones) and I’m wondering for a first test: if I place a 5R (or similar) resistor between the Daisy’s DGND and AGND, and share the AGND as common ground with the rest of my circuit (opamps etc), could this avoid a ground loop and alleviate the CPU whistle issue? A 15dB reduction would be nice, especially as I’m messing around with shimmer reverbs that tend to repeat, amplify and shift any input noise, making it rather noticable.Just in case anybody runs into a similar problem a workable DIY solution not involving any external isolators / eliminators, which I found to work was: My issue is that the current draw affects the ground hence adding noise in the opamp buffers.Īt the moment my DGND and AGND are connected. It’s definitely dependent on the sampling rate, can be shifted by reducing the block size but it’s still present (I’m usng a 78L05 to create a regulated 5V for my opamps but am not using a dc/dc isolator as is shown on the Petal schematic). I’m running into similar whistling noise issues with a Daisy Seed built into a guitar pedal format.
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