The horrors of Ground Loop Isolators...!
Posted by: ChrisBathory on 20 May 2009
Hi All,
just had one of those moments where you fix a nasty problem you didn't quite realise you had, and the music flows!
When I first setup my cheap-as-chips AV system and integrated it to my naims I had loads of trouble with an earth loop. The result was a nasty hum at all volume levels - and the Naims sounded very flat and lifeless.
I discovered that you could get a Ground Loop Isolator - basically a pair of little transformers that you stick between a hifi and an AV system to cut the direct electrical connections - but let the signal through - thus killing the hum and restoring the performance of the Naims!
So a fiver later on ebay and hugely relief - it worked OK! - the hum disappeared and the AV stuff crashed and banged pretty much in all the right places... I was happy!
However I recently upgraded to a mid-range AV amp (getting HD codecs, ready for blu-ray). It has a fancy microphone and runs an analysis of the sounds from each speaker, to set levels and compensate for room shapes at various listening positions etc. All jolly impressive. But the results of its analysis bugged me 'cos it told me that the Naims were connected up out-of-phase (which I know they arent!) compared to the Denon-directly-connected speakers - and it also thought that I should set everything to be small speakers and let the sub do most of the work...
- not really what I was expecting given the 52-supercap-250-SBL stereo system coupled to the ProaAc Response 1SC's plugged into a £900 AV amp...
Last Sunday I found time for research and eventually came across some advice that suggested that some Ground Loop Isolators are wired up wrongly inside - as most are designed for in-car use, where the phase doesn't seem to matter as much (excluding recent Bentley's naturally
) - so I opened up my el-cheapo Isolator, dug my soldering iron out and reversed the connections.
The AV amp's analysis then reported that the Naims were in-phase (Wooopee! - and it predictably sounded a lot better!) - But it still said that I should set everything for small speakers
.
Did more research and found a site that said that for hifi's the cheapo Ground Loop Isolators shouldnt be used as they really are poor quality - and limit the signal in a nasty way. I bit the bullet and ordered the cheapest Ground Loop Isolator that wasnt aimed at car use! - slightly tricky, as there don't seem to be many available in the UK - anyhow I finally picked out a Xitel unit (about £30 including postage) from someplace on Amazon...
The Xitel turned up today - I plugged it in ...encouragingly the AV analysis programme now says that my naims are connected in-phase - and that I have big speakers!
-----and everything sounds MUCH better, Music dvd's actually engage me - obviously not like CD - but massively better than before!
Peter Gabriel's Growing Up was always marvellous (great pictures and OK sound) - and is now simply stunning!
So the moral is if it only costs a fiver, it'll probably sound that way !
...and I'm wondering if maybe I should've spent a little more...
Adam, I reckon there's a real niche here in the market for a cute NAIM-GLI - or perhaps some posh isolating input boards for NACs
Cheers!!!
Chris
just had one of those moments where you fix a nasty problem you didn't quite realise you had, and the music flows!
When I first setup my cheap-as-chips AV system and integrated it to my naims I had loads of trouble with an earth loop. The result was a nasty hum at all volume levels - and the Naims sounded very flat and lifeless.
I discovered that you could get a Ground Loop Isolator - basically a pair of little transformers that you stick between a hifi and an AV system to cut the direct electrical connections - but let the signal through - thus killing the hum and restoring the performance of the Naims!
So a fiver later on ebay and hugely relief - it worked OK! - the hum disappeared and the AV stuff crashed and banged pretty much in all the right places... I was happy!
However I recently upgraded to a mid-range AV amp (getting HD codecs, ready for blu-ray). It has a fancy microphone and runs an analysis of the sounds from each speaker, to set levels and compensate for room shapes at various listening positions etc. All jolly impressive. But the results of its analysis bugged me 'cos it told me that the Naims were connected up out-of-phase (which I know they arent!) compared to the Denon-directly-connected speakers - and it also thought that I should set everything to be small speakers and let the sub do most of the work...
- not really what I was expecting given the 52-supercap-250-SBL stereo system coupled to the ProaAc Response 1SC's plugged into a £900 AV amp...
Last Sunday I found time for research and eventually came across some advice that suggested that some Ground Loop Isolators are wired up wrongly inside - as most are designed for in-car use, where the phase doesn't seem to matter as much (excluding recent Bentley's naturally
) - so I opened up my el-cheapo Isolator, dug my soldering iron out and reversed the connections.The AV amp's analysis then reported that the Naims were in-phase (Wooopee! - and it predictably sounded a lot better!) - But it still said that I should set everything for small speakers
.Did more research and found a site that said that for hifi's the cheapo Ground Loop Isolators shouldnt be used as they really are poor quality - and limit the signal in a nasty way. I bit the bullet and ordered the cheapest Ground Loop Isolator that wasnt aimed at car use! - slightly tricky, as there don't seem to be many available in the UK - anyhow I finally picked out a Xitel unit (about £30 including postage) from someplace on Amazon...
The Xitel turned up today - I plugged it in ...encouragingly the AV analysis programme now says that my naims are connected in-phase - and that I have big speakers!
-----and everything sounds MUCH better, Music dvd's actually engage me - obviously not like CD - but massively better than before!
Peter Gabriel's Growing Up was always marvellous (great pictures and OK sound) - and is now simply stunning!
So the moral is if it only costs a fiver, it'll probably sound that way !
...and I'm wondering if maybe I should've spent a little more...
Adam, I reckon there's a real niche here in the market for a cute NAIM-GLI - or perhaps some posh isolating input boards for NACs
Cheers!!!
Chris
Hi Avole,
Good question - I did try disconnecting the sky+ dish connections as is suggested here on the forum occasionally - as if this fixed it I could've put in-line coax isolators in, but sadly no improvement.
The rest of the kit is all essential day-to-day and too difficult to isolate:
HDMI cable: dvd to AV amp;
S-Video cable: Sky+ to AV Amp;
HDMI cable: AV Amp to TV)
so I didnt try to track it any further
- over the last couple of years I have replaced the TV and DVD and the AV amp without affecting the hum at all
.
I also put in a dedicated spur to the AV kit from my dedicated HiFi fusebox - and again no change.
Good question - I did try disconnecting the sky+ dish connections as is suggested here on the forum occasionally - as if this fixed it I could've put in-line coax isolators in, but sadly no improvement.
The rest of the kit is all essential day-to-day and too difficult to isolate:
HDMI cable: dvd to AV amp;
S-Video cable: Sky+ to AV Amp;
HDMI cable: AV Amp to TV)
so I didnt try to track it any further
- over the last couple of years I have replaced the TV and DVD and the AV amp without affecting the hum at all
.I also put in a dedicated spur to the AV kit from my dedicated HiFi fusebox - and again no change.