Help With 60Hz Hum PLEASE
Jo3533, Great news! I am glad to hear the dreaded hum/buzz is finally gone. With that said,...... Curiosity killed the cat. Would you try one more test for me? Would you disconnect the wire that you connected to the Marantz chassis and instead connect it to the metal chassis of the Adcom amp. Post back the results. Jim |
Great news indeed, Joe! We provided some thoughts and leads, and you did an exemplary job of following up on them in a thorough manner, and taking them further. Truly a collaborative effort, on a difficult problem (as grounding and hum problems often are). Regarding the popping issue, all I can suggest is what I said in my post dated 2-7-16, which raised the possibility that it might be resolved by a firmware update, if one is available. As I indicated in that post, someone had reported elsewhere a few years ago that what sounds like the same problem was **introduced** by a firmware update. Which suggests the possibility that the issue may have been addressed in a subsequent update. Aside from that possibility, I would suspect that the popping is being caused by a hardware problem, perhaps a faulty capacitor or relay, or a diode associated with a relay. Enjoy! Best regards, -- Al |
Darn Cats......Why are they curious again? So, I was extremely hesitant to pull my rack out of my wall again to try this, but curiosity got the best of me also. However, I had a hunch what was going to happen, and that turned out to be correct. Grounding to the chassis of the amp the 60hz. buzz came back in full effect. I promptly changed it back and pushed my rack back into my wall where it will stay until I purchase my Oppo-105D. At which point I will also make a relay circuit to control the on/off cycle of some muffin fans I am running. (right now I have them on a switch I must turn on and off) Just in case you wanted to know. My next, and last, comports for a while will be the Oppo-105D (I have to save for a bit for this) and the Sony xbr75x850c (I have been saving for this, almost there!) Other than that I do not plan to do anything to the system for a good long while except enjoy it! |
Joe, (jo3533), Thanks for doing the test for me. Had I known you had to pull out the rack I would not not have asked you to try it. Thanks again. AL, Looking at the Adcom Amp schematic wiring diagram again, trying to figure out why when all the outer contacts of the RCA jacks of the 5 amps of the Adcom are connected together and then connected to the Marantz chassis by an extended wire, the hum/buzz is eliminated. Wiring diagram. Without the added wire connected to the Marantz chassis, (connected signal ground), to the signal grounds of the Adcom’s 5 separate amplifiers, the XLR cables/circuitry (either at the Marantz or the Adcom), the signal grounds of the two pieces of equipment are not connected together by the XLR cables alone. Am I right? So when the two pieces of equipment’s signal grounds were not bonded, connected, together, (by the added wire connection circuit), why was the sound, hum/buzz 60Hz? Jim |
Looking at the Adcom Amp schematic wiring diagram again, trying to figure out why when all the outer contacts of the RCA jacks of the 5 amps of the Adcom are connected together and then connected to the Marantz chassis by an extended wire, the hum/buzz is eliminated.Your guess is as good as mine, Jim. Although I'll add that if the modules in the Adcom conform to the photo you supplied (as opposed to the schematic), as we said earlier it would appear that the Adcom's analog ground (which is common with the ground sleeves of the RCA connectors) is connected to XLR pin 1 through a thermistor. And if that is the case then the solution Joe arrived at resulted in a reduction of the impedance between the Adcom's analog ground and the chassis of the Marantz Pre/Pro (which you had indicated is common with the signal ground of the Marantz), from whatever impedance the thermistor has during normal operation to essentially zero. The introduction of that more direct connection between the signal grounds of the two units would seem consistent with a reduction or elimination of hum, that might have been caused by small amounts of AC leakage to chassis in either component. In any event, considered purely from an intuitive standpoint it seems to me to be very plausible that what Joe did would result in a solution. Best regards, -- Al |
