Hum through speaker due to unconnected cable
Posted by: Marksnaim on 13 February 2017
I've just packed away a Nakamichi cassette deck after using it to listen to tapes of the 1981 BBC Radio 4 adaptation of the Lord of the Rings. Excellent by the way, one hell of a nostalgia trip and far more true to the books than the more recent cinema versions.. but I digress. I packed away the Nakamichi but left the interconnect attached to the tape input of the NAC282.
Between tracks on the LP12 I realised there was a fairly pronounced hum coming from the speakers that hadn't been there yesterday. Head scratching time and a bit of craning of the neck over the back of the cabinet didn't show anything obvious. The earth wire from the tonearm is correctly secured to the 282 earth (terrible hum if I connect it to the Superline earth) The earth wire was resting against the tape deck connector leads though so I disconnected them to pack away with the tape deck. Hum is now gone! That suprised me. Hum being induced by contact with a connector lead that isn't connected to a source.
Live and learn and just goes to show that a bit a care and attention and effort can't hurt.
Interesting - glad you've solved it but could you enlarge on the "tonearm earth connected to the 282" comment? I'm experiencing a hum issue with my Superline when the tone arm (SME) is connected to the Superline earth and when it isn't but I haven't tried extending the leads to the 282. Is that the recommended way to connect the earth (haven't seen that in the manual?). Any further info much appreciated!
Ground I think - I'll check tomorrow.
john s posted:Interesting - glad you've solved it but could you enlarge on the "tonearm earth connected to the 282" comment? I'm experiencing a hum issue with my Superline when the tone arm (SME) is connected to the Superline earth and when it isn't but I haven't tried extending the leads to the 282. Is that the recommended way to connect the earth (haven't seen that in the manual?). Any further info much appreciated!
I seem to recall a discussion about the best earthing points in the past on the forum. When I first got the superline I was powering it from the powered aux2 on the 282 and the tonearm earth lead was connected to the Superline earth and there were no hum issues. When I dropped in a Hicap2 to power the Superline I had a very prominent hum. Recalling the discussion I moved the tonearm earth to the 282 ground and the hum went away completely.
Thanks - that is pretty much the route I followed so I'll give that a try tomorrow, and check out the NDX earth switch position at the same time.
Marksnaim posted:john s posted:Interesting - glad you've solved it but could you enlarge on the "tonearm earth connected to the 282" comment? I'm experiencing a hum issue with my Superline when the tone arm (SME) is connected to the Superline earth and when it isn't but I haven't tried extending the leads to the 282. Is that the recommended way to connect the earth (haven't seen that in the manual?). Any further info much appreciated!
I seem to recall a discussion about the best earthing points in the past on the forum. When I first got the superline I was powering it from the powered aux2 on the 282 and the tonearm earth lead was connected to the Superline earth and there were no hum issues. When I dropped in a Hicap2 to power the Superline I had a very prominent hum. Recalling the discussion I moved the tonearm earth to the 282 ground and the hum went away completely.
Always nice to tune in, especially if the topic is featured about RF interference, or the Dreaded Hum!
Good work Mark, I've picked up some pointers from your post, thanks.
But this Guy, Arch, on Systems Pic's, have really inspired me: (16 likes)
ARCH7 MEMBER
2 DAYS AGO
""Hello group:
This is my favorite thread and I thought it was time to contribute. I purchased a new RP10 recently and thought it was a good time to rebuild the stacks and clean everything so here are some pics of the rebuild and final layout.
Left Stack: (top to bottom)
nDAC
CD5XS
Rega RP10 PSU
Middle Stack:
Rega RP10
282
Superline
Right Stack:
Supercap DR (Superline)
250.2 (non-DR)
Supercap (282), non-DR
Not pictured, S400 with NAC5 (shown going into wall, speakers are 90-degrees to the gear, on the opposite side of the room.
Mostly PowerLined, except NAPSC, and CD5XS which has a Cryo'd A/V Options cable.
The power distribution device is an Audience PDC. The power outlets are FIM (First in Music) feed by separate 20AMP circuits. The little black discs are VibraPods left over from a previous system and used here to lift power cables off the floor. We'll see how long they stay there.""
That's what I call, building a System from Ground Level!
16 likes, and growing!
Allante93!
Allante93 posted:Marksnaim posted:john s posted:Interesting - glad you've solved it but could you enlarge on the "tonearm earth connected to the 282" comment? I'm experiencing a hum issue with my Superline when the tone arm (SME) is connected to the Superline earth and when it isn't but I haven't tried extending the leads to the 282. Is that the recommended way to connect the earth (haven't seen that in the manual?). Any further info much appreciated!
I seem to recall a discussion about the best earthing points in the past on the forum. When I first got the superline I was powering it from the powered aux2 on the 282 and the tonearm earth lead was connected to the Superline earth and there were no hum issues. When I dropped in a Hicap2 to power the Superline I had a very prominent hum. Recalling the discussion I moved the tonearm earth to the 282 ground and the hum went away completely.
Always nice to tune in, especially if the topic is featured about RF interference, or the Dreaded Hum!
Good work Mark, I've picked up some pointers from your post, thanks.
But this Guy, Arch, on Systems Pic's, have really inspired me: (16 likes)
ARCH7 MEMBER
2 DAYS AGO
""Hello group:
This is my favorite thread and I thought it was time to contribute. I purchased a new RP10 recently and thought it was a good time to rebuild the stacks and clean everything so here are some pics of the rebuild and final layout.
Left Stack: (top to bottom)
nDAC
CD5XS
Rega RP10 PSU
Middle Stack:
Rega RP10
282
Superline
Right Stack:
Supercap DR (Superline)
250.2 (non-DR)
Supercap (282), non-DR
Not pictured, S400 with NAC5 (shown going into wall, speakers are 90-degrees to the gear, on the opposite side of the room.
Mostly PowerLined, except NAPSC, and CD5XS which has a Cryo'd A/V Options cable.
The power distribution device is an Audience PDC. The power outlets are FIM (First in Music) feed by separate 20AMP circuits. The little black discs are VibraPods left over from a previous system and used here to lift power cables off the floor. We'll see how long they stay there.""
That's what I call, building a System from Ground Level!
16 likes, and growing!
Allante93!
??
Marksnaim posted:[...] The earth wire from the tonearm is correctly secured to the 282 earth (terrible hum if I connect it to the Superline earth)
The earth wire from my tonearm is connected to my SN2, with another wire from the SN2 to my third party phono stage. The signal ground on my NDAC is set to "floating". Pretty similar to the OP's setup and no hum at all.
Oh well back to the drawing board. I've tried earthing both the cartridge phono connections and the arm earth to the 282, and then the cartridge earthed to the Superline and the Arm to the 282 9as per the SME manual) but there is still hum in both variations, very obvious after about 30% on the volume dial. NDX is set to floating but it doesn't make any difference set to chassis either (or switching off the NDX/XPS). I think tomorrow I'll strip down the whole system and start building up the analogue side only to see what happens. I've a sneaky feeling the connections on the SME lead might be the problem but I'm not sure yet. Happy days!
There is an earth point on the Gyrodec mounting block which earths the arm, and the SME cable has an earth point for that connection (the arm) and a further one for the phono plugs. I've tried not connecting one of these, or neither of them, but the hum is then a lot worse.
Yes it does....but I think the earth from the mounting board to the arm is good (from a quick continuity check). I take your point about the one earth issue - I was a bit surprised that leaving off two SME earth connections made the hum worse, which is why I thought maybe the cable was a problem. I'll take it off this afternoon and have a better check on that front.