TJIann Posted January 29, 2015 Share Posted January 29, 2015 (edited) So, I am trying out a PrimaLuna Prologue 5 poweramp. It's a direct substitution for my McIntosh MC2105. The issue is a 60 cycle hum in both speakers (Cornwall IIs) with preamp at no volume and makes listening at low volume unpleasant. The hum was not there with the McIntosh. This does not increase when raising the volume. It's not the tubes as I did some swaps/rolling to test that. So, assuming a ground loop issue. In your experience, what are top things to do to isolate this problem? Thanks for any insights.Tim Edited January 29, 2015 by TJIann 1 Quote Link to comment Share on other sites More sharing options...
russ69 Posted January 29, 2015 Share Posted January 29, 2015 It's a ground loop. Drop the ground on one piece of equipment. Just make sure that if you change anything make sure it's grounded before power up. 1 Quote Link to comment Share on other sites More sharing options...
eth2 Posted January 29, 2015 Share Posted January 29, 2015 Question: Why do power amps hum? Answer: Because hey don't know the words. 4 Quote Link to comment Share on other sites More sharing options...
Max2 Posted January 29, 2015 Share Posted January 29, 2015 Good luck knocking out the GL. I am interested in your comparison in sound from the 2105 to the Prima Luna setup. 1 Quote Link to comment Share on other sites More sharing options...
TJIann Posted January 29, 2015 Author Share Posted January 29, 2015 Yup, after playing around with moving the plug to other outlets, re-organizing cords, moving the amp away from other components, I tried using a 3 prong to 2 prong adaptor on the amp and it's as quiet as a mouse. I'm a little unsure if I like that fix, but neither my preamp or other components have 3 prong cords, so not sure what else to do. Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted January 29, 2015 Share Posted January 29, 2015 Try this for a permanent fix: https://community.klipsch.com/index.php?/topic/154152-cheap-fix-on-ground-loop/ Quote Link to comment Share on other sites More sharing options...
TJIann Posted January 29, 2015 Author Share Posted January 29, 2015 Try this for a permanent fix: https://community.klipsch.com/index.php?/topic/154152-cheap-fix-on-ground-loop/ Great thread and link. Thanks for sharing. Quote Link to comment Share on other sites More sharing options...
eth2 Posted January 29, 2015 Share Posted January 29, 2015 (edited) Yup, after playing around with moving the plug to other outlets, re-organizing cords, moving the amp away from other components, I tried using a 3 prong to 2 prong adaptor on the amp and it's as quiet as a mouse. I'm a little unsure if I like that fix, but neither my preamp or other components have 3 prong cords, so not sure what else to do. I spent months and hundreds of dollars searching for the hum in my mono blocks. We never found it but here is what I paid techs to do: 1. Look for dimmer switches. I f you have any, disable them from the house current. Any change? 2. Look for motors of any kind (refrigerator, microwaves, bathroom fans. 3, Try moving the amps to another part of the house. Any change? 4. Try disconnecting the cable TV line into the house. Any change? 5. Check the ground into the house. 6. Are there any ham radio operators near your house? 7. Using an AM radio (I forget the frequency it should be set at but someone on the Forum will know) see if you are picking up airborne interference. 8. Do you have florescent lights? Check to make sure you do not have a bad ballast. 9. You can try a line filter like a Furman. 10. Make sure your power cords are not crossing with your rca cables, speaker wires, etc. 11. Call the power company and see if there is a bad transformer or tap somewhere. Hope one of these is your problem Edited January 29, 2015 by eth2 Quote Link to comment Share on other sites More sharing options...
NOSValves Posted January 29, 2015 Share Posted January 29, 2015 This thread is sure to bring out the anal analyzing electrocution police in no time flat Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted January 29, 2015 Share Posted January 29, 2015 Not this again, lol. Quote Link to comment Share on other sites More sharing options...
paul79 Posted January 30, 2015 Share Posted January 30, 2015 (edited) Most common scenario for ground loop is the preamp to amp interconnect connection. If both the signal input of the amp and the signal output of the preamp are AC grounded, this in most cases, will cause a ground loop. Not always, and you could very well take the system to someone else's house and have no issue. Tis what it is. Just cheat the preamp and call it a day. If it were me, I would isolate the offending product using a cheater plug, and then snip the AC ground inside the unit (and insulate the end of the ground wire). If you do use a cheater plug, get a NEW one. (not liable for any fire damage, electrocution, injury, or death) Edited January 30, 2015 by paul79 Quote Link to comment Share on other sites More sharing options...
muel Posted January 30, 2015 Share Posted January 30, 2015 I snipped the black wire... now it's really quiet! DEAD quiet. 1 Quote Link to comment Share on other sites More sharing options...
mike stehr Posted January 30, 2015 Share Posted January 30, 2015 Topsy chose not to ground her audio gear... Quote Link to comment Share on other sites More sharing options...
Thaddeus Smith Posted January 30, 2015 Share Posted January 30, 2015 6. Are there any ham radio operators near your house? my listening room is a former HAM radio room, which is precisely why I don't have any ground loops. That equipment is just as sensitive, if not more so, and the previous owner went to great lengths to remove any potential issues, including a dedicated circuit physically isolated from the house. Quote Link to comment Share on other sites More sharing options...
babadono Posted January 30, 2015 Share Posted January 30, 2015 OP, so when only 1 piece of your gear has a power(earth) ground you have a ground loop? Quote Link to comment Share on other sites More sharing options...
TJIann Posted January 30, 2015 Author Share Posted January 30, 2015 OP, so when only 1 piece of your gear has a power(earth) ground you have a ground loop? There are more pieces connected to the preamp inckuding the subwoofer,phono pre, computer and another amp to drive surround speakers. A couple have grounded plugs. Quote Link to comment Share on other sites More sharing options...
russ69 Posted January 30, 2015 Share Posted January 30, 2015 When you have a 60hz hum, you have two or more grounds, lifting one is still safe. If you are paranoid make sure you pull the cheater plug when you make any changes and reconfirm you still have a group loop. I'm paranoid and don't like using a cheater plug but remember you are not lifting THE ground you are lifting an extra ground. 1 Quote Link to comment Share on other sites More sharing options...
NOSValves Posted January 30, 2015 Share Posted January 30, 2015 I snipped the black wire... now it's really quiet! DEAD quiet. Does is sound like the band is not playing in your room now Quote Link to comment Share on other sites More sharing options...
muel Posted January 30, 2015 Share Posted January 30, 2015 I snipped the black wire... now it's really quiet! DEAD quiet. Does is sound like the band is not playing in your room now Yeah, it's as if they just left the building. Very real and natural sounding though! Quote Link to comment Share on other sites More sharing options...
TJIann Posted January 30, 2015 Author Share Posted January 30, 2015 (edited) When you have a 60hz hum, you have two or more grounds, lifting one is still safe. If you are paranoid make sure you pull the cheater plug when you make any changes and reconfirm you still have a group loop. I'm paranoid and don't like using a cheater plug but remember you are not lifting THE ground you are lifting an extra ground. I'm leaning toward leaving the cheater plug on the power amp which plugs into a good power surge protector and conditioner with the other components, and then installing a GFCI outlet this weekend for added protection. Edited January 30, 2015 by TJIann Quote Link to comment Share on other sites More sharing options...
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