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Faraday cage for my TT?

dewdude

dewdude

High on resolution.
Hey guys,

I've got a new dilemma in my spinning, and its CRT hum (or a very bad ground I can't find).

I'm running a Grado Green...and I know Grados are prone to hum, but luckly it doesn't hum on my table (there's a big metal plate underthe platterwhere the cartridge travels). In fact, I know it hums with CRTs because if I turn my tv on, it gets very noisy.

The problem is my roommate in the next room plays a lot of Xbox 360 and refuses to use a flat panel...so his CRT is causing massive problems for me. I can't convince him to switch (even offered to buy him the flat panel). So I need other options.

I've considered getting some copper mesh and rigging sort of a faraday cage around it.

Does anyone think this will work? Does anyone have suggestions? I'm considering getting an Ortofon HOMC, but that's a few months off and I fear I might have the same problem.

Thanks,
-Jay
Sent from my SPH-M910 using Tapatalk
 
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Try using aluminum foil first...cheap and plentiful. I would put foil on the back wall behind his CRT screen and ground it in some way (alligator clips might be useful if you have them) and put another sheet on the other side of the wall behind your table....also grounding it...then you can work up to a full Faraday cage if you really need it.

Stupid question but have you tried moving the turntable to the other side of your room?
 
Either way, it would look pretty unsightly! I would try moving the table first, if that is at all a possibility....

If not... A potential quick fix for Grados I've heard about is to twist the headshell wires into a braid to help reject noise.

Grados always get the blame for noise, but interconnects and grounding issues can actually be to blame. Check to make sure your TT ground wire is properly grounded to the metal components of your tonearm and headshell with a continuity tester. Better quality interconnect cables might also reduce noise. If your cables are not replaceable, you might try snap-on rf chokes for your turntable interconnects and AC cords. Outlet strips with built-in rf filters are also available.

Another thought... Make sure your TT is connected to the same (properly grounded) outlet as your phono pre and amplification. That way, you will reduce the likelyhood of a ground loop in the system that could pipe in noise.
 
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As far as grounding...the preamp "stage" I'm using is grounded to center screw on outlet..and that's secured to the ground screw with the TT, that helped a ground loop I had. The shelf everything sits on is the metal rack shelves you see at home depot and such...each rack is grounded (as they're isolated from the legs by the plastic fricton fittings). http://dewdu.de/mediarack.jpg

The hum is clearly from his tv as when he's actually in class..there's no noise. I can move the turntable across the room...across the house...it picks up any crt...except in the basement on the RPTV...in 1080I mode its scan rate is in the inaudiable range...still...anywhere in the house causes the crt noise.

Whatever I do...I have to do it within the confines of the room...he doesn't let anyone screw with his stuff.

Ill likely try the foil trick...I did that a few years ago when my tv's HOT was failing and caused excessive hum on line level stuff...in fact some of my stuff still has foil on it.

I mostly just wish he'd accept a 25" lcd flat panel with HDMI input..it would solve my problems.

I guess when I get home ill play with grounding a bit more.

Sent from my SPH-M910 using Tapatalk
 
How about turning in the uncooperative roommate for a more cooperative:yes: seems to me that he likes causing problems:sigh:. Preston
 
G'day all, this is an interesting one. Ferrite 'clamp on' chokes placed on various leads including the turntable interconnects, may be effective here in reducing this noise interference pickup.

If you can find these inexpensively, they are definitely worth trying. Regards, Felix aka catman.
 
I should of mentioned the cables and interconnect on my PX3 require disassembly to change....and I'm not about to risk killing this thing to fix something I'm 99.99% sure is not the cause (they were fine till he moved in).

I sadly have no say in roommates...I can only hope with his negative and "everyone owes me" attitude gets him kicked out.

Ill have to play with things when I get home and see.

Sent from my SPH-M910 using Tapatalk
 
I would look at the power line and ground...

The interference is most likely being transmitted through one of those from his gear to yours....

First thing to try would be chokes/ferrite rings, after that it gets more expensive.... if you can plug your gear into a point that is on a seperate circuit that might work.

A 1:1 isolation transformer is one solution, or a true sine-wave regenerator.... some of the better uninterruptible power supplies do that - permanently regenerate the power ... hard bit is finding one that is quiet enough.

I really doubt that the interference is direct, so a faraday cage would be unlikely to help.

good luck

David

P.S. I have a similar problem whenever the aircon comes on - so it gets turned off when I am listening... and yes I tried chokes, and UPS... the UPS worked but its fan was too loud!
 
Homerx said:
Why so pro CRT. one of those "lag" folks. which Isn't even visible on a modern LCD
Click to expand...
It is very variable among people: I, for one, see it to the point of being disturbed at times, even on "fast" LCDs (the problem exists for any interactive application, not just FPS games). Not an excuse for the roommate's behaviour, but definitely an explanation.

I had the exact same problem as dewdude's once, and was able to show that it was direct EM induction from the CRT 2m away, definitely not mains-induced. Any other cartridge than Grado was trouble-free, so the solution was obvious ;) A trick that sometimes works though, is just trying to rotate the turntable: since magnetic fields are usually oriented and magnetic sensors are seldom omnidirectional, it may be possible to find an orientation that picks up less hum. Not at all guaranteed to work, but at least it is free, so I'd give it a try before changing the cartridge.
 
The larger problem in crts is the video upscaling and processing. My parents have a couple of LCD's, a cheap vizio and a good vizio. On HD content, the good vizio is doing so much processing there's a noticable delay between them on the same channel. He doesn't hate lcd pixel lag, he just had problems with the upscaling and video processing.

I feel somewhat stupid. Here's what I found out.

Even my CRT a mere 1m awaydoesnt cause hum THAT bad...and its a lot older than the CRT he's using.

When I removed that heavy machine...I discovered the AC cord had tangled with the audio cords. Untangled, more hum.

The source came from something I hadn't expected. Amongst the shufffling I accidently disconnected the audio line from my sound card, hum went away. I popped open the tiny USB sound device and discovered the coupling caps on the input side had leaked. Replaced them. Turns out the ultimate problem was the 5v line being proided over usb. I took a couple diodes and rigged up a very stable clean 5v supply.

No more hum.

Sent from my SPH-M910 using Tapatalk
 
dewdude said:
Hey guys,

I've got a new dilemma in my spinning, and its CRT hum (or a very bad ground I can't find).

I'm running a Grado Green...and I know Grados are prone to hum, but luckly it doesn't hum on my table (there's a big metal plate underthe platterwhere the cartridge travels). In fact, I know it hums with CRTs because if I turn my tv on, it gets very noisy.

The problem is my roommate in the next room plays a lot of Xbox 360 and refuses to use a flat panel...so his CRT is causing massive problems for me. I can't convince him to switch (even offered to buy him the flat panel). So I need other options.

I've considered getting some copper mesh and rigging sort of a faraday cage around it.

Does anyone think this will work? Does anyone have suggestions? I'm considering getting an Ortofon HOMC, but that's a few months off and I fear I might have the same problem.

Thanks,
-Jay
Sent from my SPH-M910 using Tapatalk
Click to expand...


If it is EMI coming from other sources.........TV...etc. Copper will not stop EMI. It will stop RFI though. Soft iron will soak up EMI......as what is probably the plate on your table you refer to. To stop EMI from getting into your room, you would need to sheet the whole room with MuMetal.........kinda pricey. Might make for a nice antenna for lighting as well.
 
dewdude said:
I feel somewhat stupid. Here's what I found out...
Click to expand...
Wow, that was really a tricky one! congratulations on fixing it :bigok:

BTW is there really no way to turn off all the processing on that LCD TV? It is supposed to be possible on every model now, a demo might be a good way to give your roommate some food for thought ;)
 
Another happy ending! :thmbs

And here I was about to offer to lend you my aluminum-foil-covered beanie. It must work really well, because when I wear it I never hear any government or alien brain-control voices. No doubt it would stop the TV voices, too. :yes: :D
 
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