ikhuong Posted May 25, 2020 Share Posted May 25, 2020 (edited) Hi fellow SNAs, I have just got a Foxtel box and hook it my system and got a buzz/hum noise in my entire 5.1 system Telstra Coaxial <>Foxtel box <hdmi> Marantz Receiver with Center and rear speakers <RCA preout> Pre <XLR> Power amp <> Front Speaker When I unplugged RCA cables between Marantz receiver and pre, the hum noise has gone(center speaker powered by Marantz), I have just noticed and discovered that Marantz receiver has only 2 pin, no ground wire. Is this the reason to create a ground loop between Marantz (2 pins) and Preamp (3 pins) with the Coaxial signal as the catalyst ? How to treat them? I have called Telstra to send tech, they will charge $100 if issue is on me. Also how can the Marantz has no 3-pin power IEC and is still allowed to sell in AU ? (I bought from local distributor) Thanks for your help, Edited May 25, 2020 by ikhuong Link to comment Share on other sites More sharing options...
Steffen Posted May 25, 2020 Share Posted May 25, 2020 The Marantz is double-insulated, see the symbol on the back: It’s been designed to be connected without protective ground, which is usually a plus and a good defense against ground loops. That hum could come from a dodgy cable modem power supply, or via the coax cable itself. Does it go away when you unscrew the coax cable? 1 Link to comment Share on other sites More sharing options...
ikhuong Posted May 25, 2020 Author Share Posted May 25, 2020 33 minutes ago, Steffen said: The Marantz is double-insulated, see the symbol on the back: It’s been designed to be connected without protective ground, which is usually a plus and a good defense against ground loops. That hum could come from a dodgy cable modem power supply, or via the coax cable itself. Does it go away when you unscrew the coax cable? Yes, it goes away when I unplug coaxial but does not when I unplug Iq3 box power supply (it is DC in standalone psu) Link to comment Share on other sites More sharing options...
Kahuna Posted May 25, 2020 Share Posted May 25, 2020 I had a similar issue, this fixed it-- https://www.matchmaster.com.au/filters/19mm-tdtisol/ 1 1 Link to comment Share on other sites More sharing options...
StuDog78 Posted May 29, 2020 Share Posted May 29, 2020 You might check if the coaxes outer shielding is making good contact to the plugs outer ground potential. I have had a plug play up like that. 1 Link to comment Share on other sites More sharing options...
Kahuna Posted May 29, 2020 Share Posted May 29, 2020 https://www.ebay.com.au/itm/10-X-CATV-COAX-Cable-TV-Isolator-CS-4002-Foxtel-and-Telstra-NBN-approved-PCD-/153687240255 10 for $25! 1 Link to comment Share on other sites More sharing options...
ikhuong Posted May 29, 2020 Author Share Posted May 29, 2020 I called Telstra and they sent tech to install those boxes, no more hum noise now. thanks all, 1 Link to comment Share on other sites More sharing options...
ikhuong Posted May 29, 2020 Author Share Posted May 29, 2020 (edited) Apparently the Telstra phone support guy( it bet overseas call center) was BS and advised I should hire local electrician as hum noise is from my system and kept me waiting for escalating, 40 minutes wait, i started to get frustrated and i told straight to him , please stop Bs and cut the chase, send a technician to install an isolator , if it is not the issue, I will pay for the call out fee, then he started to arrange. the technician guy came, just did hear hum and went around building block to find the mdf box, installed isolator and said someone stole the isolator. I said i don’t really care, go back and charge Foxtel/Telstra now. Problem solved. just frustrated me that those are common issues, they know but still push back and BS to their customer, not very good customer service from Telstra and Foxtel, right? Edited May 29, 2020 by ikhuong Link to comment Share on other sites More sharing options...
mr_gray Posted June 2, 2020 Share Posted June 2, 2020 dealing with Telstra is terrible. I've had a couple of issues crop up which is fine but then resolving them means engaging with Telstra, an organisation that has attempted to prevent it being contacted. It is not just hyperbole either, I was without a mobile phone for two weeks through no fault of my own. I'm surprised you manage to extract a result out of them at all. So well done and thanks for the helpful tip that's come out of this thread. 1 Link to comment Share on other sites More sharing options...
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