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Just upgraded my Integrated Amp - now here a HUM out of my LUMIN - HELP

I run two systems in my home - System one is in my family room - my old Krell 400 xi died last month. I replaced it with the new Krell Integrated amp the K300i - Everything is better - soundstage is larger - highs are clearer with no harshness, bass is amazing, and midrange vocals are so real Carly Simon vocals bring me to tears! My problem is I now have a very low level pulsating hum between tracks that I cannot eliminated. I have isolated this hum to my LUMIN when i input its feed into the Krell. The low level hum follows the RCA jacks as I move them from inputs S1 to S2 to S3 on the Krell. My DVD / CD player on this system does not have this issue - it is stone silent between tracks. The only ‘odd thing’ about my LUMIN RCA inputs is they are long - 15 feet. I have my LUMIN upstairs feeding my second system via the balanced outputs. This system runs with my older Krell S550i integrated amp. The sound is stone quiet between tracks - no HUM.

i am running the Krell K300i at a volume output of 65 ( volume runs from 0 to 100). I then control my actual volume via my I pad mini via the LUMIN app. My sound is amazing , but this HUM just bothers me. Do I need to ground the LUMIN D1? Both systems get their power via two separate FURMAN ELITE 15 Power Conditioners. I am out of options. Any help would be appreciated
tom8999
tom8999 OP
151 posts
 
Millercarbon- I am making progress - my HUM is getting less and less. All of my AC power cords have been moved away from the RCA interconnects at The back of the integrated amp. My Furman Power Conditioner is not contributing to the hum - I shut it off and just ran the LUMIN, and Integrated Amp but no hum reduction. My new RCA interconnects from Anticables from the LUMIN to the Krell k300i I think are the best investment I have made. I am now convinced I am fighting interference hum.

Thanks for the help.
millercarbon's avatar
millercarbon
12,531 posts
 
Okay so you've picked all the low hanging fruit and its nice and quiet. From here its an Easter egg hunt for what is probably mostly really bad RFI or EMI. Which are just different aspects of the same thing. RFI is radio frequency, EMI is more static sporadic. Hardly worth two terms but there you go.

Anyway the most likely culprits are electric motors, lights with dimmers or transformers like fluorescents and some LEDs, and even plain old connections. Can be just about anything. You got it down to a way lower level than my system though I can tell you that! I'd rather spend my time making it sound better than hunting stuff like this. Anyway there's some ideas if you want to go even further with it.
imhififan's avatar
imhififan
2,108 posts
 
My new RCA interconnects from Anticables from the LUMIN to the Krell k300i
My suggestion is try the Blue Jeans Cable LC-1 for better shielding.

https://www.bluejeanscable.com/store/audio/index.htm
flashbazbo's avatar
flashbazbo
12 posts
 
I’m a Chemist too! Good people...  I see two problems you have on the go. The 15 foot rca unbalanced is picking up noise as has been identified. That’s a long run for unbalanced rca cables in a possibly noise home environment. It seems you have minimized it as the other posts have suggested. Fluorescent lights and dimmers can be big contributors as mentioned. Keep the rca well away from ac cables. Well shielded cables can help as you have seen.  The second issue is “gain staging”. The lumin should be left a unity, or full volume in order to maximize the signal to noise ratio. Control you volume level at your preamp. This helps to further diminish the amount of noise in your signal.  The best would be to use the balanced Lumin outs for the long 15 foot run.
flashbazbo's avatar
flashbazbo
12 posts
 
I’m a Chemist too! Good people...  I see two problems you have on the go. The 15 foot rca unbalanced is picking up noise as has been identified. That’s a long run for unbalanced rca cables in a possibly noise home environment. It seems you have minimized it as the other posts have suggested. Fluorescent lights and dimmers can be big contributors as mentioned. Keep the rca well away from ac cables. Well shielded cables can help as you have seen.  The second issue is “gain staging”. The lumin should be left a unity, or full volume in order to maximize the signal to noise ratio. Control you volume level at your preamp. This helps to further diminish the amount of noise in your signal.  The best would be to use the balanced Lumin outs for the long 15 foot run.
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