Harvey66 Posted September 20, 2010 Posted September 20, 2010 I recently completed a sub build but now have a possible ground loop hum to eliminate. I say possible because last night I removed an earth pin from a power lead and used it to power the sub but the hum was still there?? It is present regardless of weather the sub is receiving a signal but disappears when the HT receiver is switched off (even when it is just in standby mode). The good folks at Audio Marketplace have recommended one of these http://www.altronics.com.au/index.asp?area=item&id=A2517 or this http://www.jensen-transformers.com/sub1rr.html Can anyone point me to a local supplier, is it likely to do the job?
Ernie1553552694 Posted September 20, 2010 Posted September 20, 2010 Take it to a tech. Lookup the thread: Fixing a hole.
Owen Y Posted September 20, 2010 Posted September 20, 2010 If the hum is still there when the device is 'lifted' from mains earth, then the problem does not appear to be an Earth Loop. Clarification please: The hum appeared only after a new sub(one?) was connected into the system (how connected?)? No other system alterations? Hum is often baffling & hard to eliminate... that's why Jensen et al sell those isolating txs. (Which break your IC signal chain grounds, I believe.)
Harvey66 Posted September 20, 2010 Author Posted September 20, 2010 Ernie - I'd like to exhaust all other possibilities first, the parts (Hypex plate amp - Shiva X2 driver) were bought new from Audio Marketplace, the guys there have been really helpfull but even with the above information still believe it is most likely a ground loop. Owen - Yes, new sub as above, no other system alterations, the sub is at at the rear of the room and I have installed an in wall cable with Canare coax which is quite long @ 15m.
Owen Y Posted September 20, 2010 Posted September 20, 2010 - Is the sub is connected to the amp or main spkrs? - Is the in wall Canare signal able in close proximity to the AC mains cabling? - Is the in-wall Canare shielded & is the shield connected to the signal -ve at either end? -Are there short ICs plugged into sockets at either end of the in-wall cable? O, does the in-wall cable exit walls ea end & run to the devices? - Did the hum occur only after the sub was installed?
Harvey66 Posted September 21, 2010 Author Posted September 21, 2010 - connected to the HT Amp - I was carefull to keep it away from mains cable up in the roof but it does exit at the back about 0.5m away from a power point and it would most likely cross this mains cable at some point inside the wall. I would have thought as the hum disappears when the HT receiver is switched off this is the most likely culprit? - yes, shielded and connected at both ends, would you recommend trying to disconnect the ground at sub end? - no short interconnects, I have pull through plates installed in the wall to minimize connections - no hum problems until the sub was hooked up
Ernie1553552694 Posted September 21, 2010 Posted September 21, 2010 It probably is the in-wall cable. Try another cable to check. If it is, then you may have to make alternative arrangements.
Owen Y Posted September 21, 2010 Posted September 21, 2010 Harvey;133674 wrote: - yes, shielded and connected at both ends, would you recommend trying to disconnect the ground at sub end? Yes, connect IC outer shield to plug -ve at source(amp) end only. Disconnect shield at the sub end.
Harvey66 Posted September 21, 2010 Author Posted September 21, 2010 Ok - thanks for your help guys - I'll have another play around tonite and report back. I've found that Bartons Sound in AK city are distributers for Jensen and seem to carry a bit of stock if anyone is interested.
Marantz Posted September 21, 2010 Posted September 21, 2010 Harvey;133656 wrote: I recently completed a sub build but now have a possible ground loop hum to eliminate. I say possible because last night I removed an earth pin from a power lead and used it to power the sub but the hum was still there?? It is present regardless of weather the sub is receiving a signal but disappears when the HT receiver is switched off (even when it is just in standby mode). The good folks at Audio Marketplace have recommended one of these http://www.altronics.com.au/index.asp?area=item&id=A2517 or this http://www.jensen-transformers.com/sub1rr.html Can anyone point me to a local supplier, is it likely to do the job? I use a Isomax CI-2RR between the av amp and stereo/power amp and it works well. The distributor is Barton and unfortunately these are not cheap.
Ernie1553552694 Posted September 21, 2010 Posted September 21, 2010 Thor Technologies have the Smart Hum Assassin. An appliance dedicated to, well, I think the title says it all. $2.5K list price. Popping down to your local tech or an Isomax CI-2RR might be more cost effective. Then again... http://www.thortechnologies.com.au/products/product/ha5-smart-hum-assassin/
Marantz Posted September 21, 2010 Posted September 21, 2010 The Isomax pricing isn't that bad in comparison to the Thor. Try Barton Sound Systems 09 373 2416. The Jensen Isomax CI-2RR was $375.70 + GST.
Ernie1553552694 Posted September 21, 2010 Posted September 21, 2010 It's good to get things in perspective. How do you find the Isomax on your system Marantz?
Marantz Posted September 21, 2010 Posted September 21, 2010 Ernie;133722 wrote: It's good to get things in perspective. How do you find the Isomax on your system Marantz? The Isomax works well! I initially had concerns if it would adversely affect the frequency spectrum but have been pleasantly surprised that all sounds as good as it should. The hum is not completely eliminated but at a level where it is no longer a nuisance.
pasdesignal Posted September 21, 2010 Posted September 21, 2010 Owen Y;133677 wrote: Yes, connect IC outer shield to plug -ve at source(amp) end only. Disconnect shield at the sub end. This is most likely the succesful thread to follow... you do NOT need more equipment to 'solve' issues like hum/ground loops. It just requires some good had drawn wiring diagrams, a bit of knowledge and some lateral thinking
Ernie1553552694 Posted September 21, 2010 Posted September 21, 2010 Some of us are not DIY übermensch.
aarond1553552714 Posted September 21, 2010 Posted September 21, 2010 Ernie;133725 wrote: Some of us are not DIY übermensch. wow, a multilingual post! I_like_crumpets would have to concede to that. Back on topic, I've got a bad hum / buzz problem also with the new valve amps - tried everything to resolve it, with no luck. Therefore I read this thread with interest also.
Harvey66 Posted September 21, 2010 Author Posted September 21, 2010 I removed the -ve from the sub end of the cable plugged it in turned it on and got a LOUD hum (note to self, next time you try this turn the volume down ) so no joy there it made the problem much worse. This is probably a good time to mention it isn't a loud hum I'm chasing but just loud enough to be audible and annoying. I tried another sub cable and no joy there either, made no difference. The guy I spoke to at Audio Marketplace seemed to think that the cheater plug not working shouldn't necessarily discount a ground loop and seems quite sure an isolating transformer will solve my problems. I don't mind using one if I have to but am willing to try any other suggestions.
Owen Y Posted September 21, 2010 Posted September 21, 2010 Harvey, Just to clarify... don't remove the signal -ve from the plug, remove the shield connection to the plug (at sub end). And, check the integrity of the solder joints at the amp end - +ve to +ve, -ve to -ve & shield to -ve. Sounds like something's not correct.
Harvey66 Posted September 21, 2010 Author Posted September 21, 2010 Oops, I always thought that when using coax for interconnect the shield was -ve as well. I'm prepared to second guess my soldering skills but given that the second cable I tried was off the shelf, wouldn't this mean the cable is not the issue?
Owen Y Posted September 21, 2010 Posted September 21, 2010 Harvey;133756 wrote: Oops, I always thought that when using coax for interconnect the shield was -ve as well. Oh I think are saying that you are using a cable with single centre conductor + signal return thru the outer shield... rather than a 'twisted pair' cable with 2 centre conductors + separate shield (technically much better)? Which Canare model? I'm prepared to second guess my soldering skills but given that the second cable I tried was off the shelf, wouldn't this mean the cable is not the issue? Depends on the cable design (as above) & its orientation if it is a separate shield type.
Owen Y Posted September 21, 2010 Posted September 21, 2010 PS. The Canare 'audio' quality cables are of the Twisted Pair or Quad type (separate shield). Not 'coax' with single centre conductor + shield. Sorry to labour this distinction, but this could still be your problem area.
Ernie1553552694 Posted September 21, 2010 Posted September 21, 2010 There's sub cables and there's coax. Although I doubt it is the cable when I presume you're running the other cable loose and not inside the wall cavity. Another way to defeat the hum may be by using wireless transmission.
Harvey66 Posted September 21, 2010 Author Posted September 21, 2010 I used Canare LV61S a single conductor coax, I thought it would be ok as it has been used by cable manufacturers in similar applications and bought it from Sandman Audio in Wellington told them exactly how it was going to be used, they said it was perfect for the job.:confused: The second cable I tried was 2 x 3m digital interconects plugged together using a female to female RCA connector, they are of good quality but use a single conducter cable as well.
Shane Hanify Posted September 21, 2010 Posted September 21, 2010 Gidday Harvey, just to throw a spanner into the mix - have you tried powering the sub from the same socket that feeds the AVR? Cheers, Shane.
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