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Left channel hum issue with new Luxman 507U on phono input


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Been loving this amp however I have a strange hum issue I'm hoping someone can assist me with on the left channel.

So what happens is if the turntable is the only input connected to the Lux then both channels are pretty much hum free however as soon as I add my dac (Schitt Gungnir) to any of the 4 RCA inputs I get a hum on the left channel (when the phono input is selected) which is even more prominent if I turn the dac on.

So far I have tried two different pairs of interconnects and every input to no avail. Any ideas? Would running a pair if balanced cables help?

This pic clearly shos the increased noise level on the left VU meter

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Edited by Tubularbells
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Is this something that has always happened or only just begun ?

Have you a different input you can connect to the RCA's e.g a CDP player? If not can you borrow one? Connect it in place of your Dac - is the hum still present or not?

If yes, then problem is most likely in amp.

If no, then go back to Dac and try with a brand new set of interconnects

Sent from my iPhone using Tapatalk

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Is this something that has always happened or only just begun ?

Have you a different input you can connect to the RCA's e.g a CDP player? If not can you borrow one? Connect it in place of your Dac - is the hum still present or not?

If yes, then problem is most likely in amp.

If no, then go back to Dac and try with a brand new set of interconnects

Sent from my iPhone using Tapatalk

 

 

Ok so I tried using the analog outs direct from the squeezbox bypassing the dac and the left channel hum remains. Already swapped for a different set of interconnects to no avail :(

 

Looks like an amp issue which is a bummer seeing that its 1 week old. Still cannot understand why only the left channel is affected as it it were a grounding issue (which is what this is pointing to) you would think both channels would be equally affected.

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Would seem logical. Often an earth issue affect one channel more than the other. Someone with better electrical / wiring knowledge would probably explain it

Sent from my iPhone using Tapatalk

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Guys your on the right track. Removing the power plug from the Shitt eliminates the hum altogether. I also tried plugging the Shitt into my isolation  transformer and the hum actually got a little worse. I then tried using a cheater plug (removing the earth) and the hum was slightly less audible however the VU meter remained the same indicating approx. 25db more noise in the left channel.

 

This is really frustrating.... :(

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  • 2 months later...

Slight update however still have not been able to resolve this issue. Turns out the AU version of the Lux does not have an earth pin on the power unlike the others built for our neighbours. The Schitt is earthed so there must be a potential difference running via the RCAs. Today I tried a pair of XLR cables to see if that eliminated the issue to no avail so I'm basically out of ideas unless anyone else can assist.

Kinda bums me that an amp retailing above $6k cannot accept two or more sources at once unless the power is physically removed fom those not being used during playback....

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If you're in NSW, then you're protected by pretty strong consumer laws. i.e. If there is a 'major' part or component at fault in the product, you have the right to demand a replacement unit and are not obliged to accept a repair.

Good luck with it and hope it all works out for you.

Tricky

Edited by Trickster
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Slight update however still have not been able to resolve this issue. Turns out the AU version of the Lux does not have an earth pin on the power unlike the others built for our neighbours. The Schitt is earthed so there must be a potential difference running via the RCAs. Today I tried a pair of XLR cables to see if that eliminated the issue to no avail so I'm basically out of ideas unless anyone else can assist.

Kinda bums me that an amp retailing above $6k cannot accept two or more sources at once unless the power is physically removed fom those not being used during playback....

Hey there...What do you mean by "earth pin removed"? From the cable? Or the IEC socket on the back of the amp? 

Edited by Stedes
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Oh FFS....Inexplicable why they would do that for Australian versions.

 

Ok just thinking out loud....

 

- What's the TT grounded to?

- Does the Luxman have a ground terminal at the back?

- Is the hum present when you connect the Schiit/SBT to any of the other inputs?

- Does the hum remain with the Schiit/SBT connected and the TT disconnected?

Edited by Stedes
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Ok... now turn everything on, and with the hum touch the schiit with one hand and the luxman ground point with the other....

 

My feeble brain is thinking this:

- TT grounds luxman. No PD there.

- When Schiit introduced there is a PD between that and the luxman due to the fact that there is no common ground between them

- If the hum goes away by touching (i.e. grounding) the two devices all you might need to do is that.

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Ok... now turn everything on, and with the hum touch the schiit with one hand and the luxman ground point with the other....

 

My feeble brain is thinking this:

- TT grounds luxman. No PD there.

- When Schiit introduced there is a PD between that and the luxman due to the fact that there is no common ground between them

- If the hum goes away by touching (i.e. grounding) the two devices all you might need to do is that.

Thanks tried this and has absolutely no effect. Only way to stop the hum is to either remove the power plug or RCA/XLR from the dac

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Bummer...it looks like the only way to resolve your problem is if the Luxman had the earth pin. I wonder whether this can be easily retrofitted...i.e. just by changing the IEC socket and making the relevant connections. However...I must agree with what one of the other members said previously. It's unacceptable for such a quality high end and very expensive product to have this "limitation". They should have thought of this before removing the pin so I think you should contact where you bought it from and request the to fix the problem.

 

Good luck with it all....it sucks....a whole lot.

 

PS...VU meters rule

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Yeah sure does hardly listen to the dac so having the power semi-permimently removed from the dac hasn't caused me a major inconvenience thus far however I'm keen to rectify the issue.

Is it possible to remove the ground on my XLR cables leaving only hot and neutral?

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