Solving my EMI/RFI problems

[BradC]

Hi,  

 

After lurking here for a while and giving up on the advice at another forum, I thought I would try asking about a problem that has been bothering me for some time.

 

I am having substantial problems with my cell phone pings being picked up by the headphone cable.  I am running a nuforce HDP and HD650s in case someone else has experience with the same problem and setup.

 

So I see a few options:

1) Shielded headphone cables. (Although the price scares me vs option 6)

 

2) Craft a EMI blocking filter (Perhaps with an inline Neutrix EMC series XLR pair or equivalent), or maybe a ferrite core? 

 

3) A magical audiophile solution I am not aware of. Preferably not involving taping brilliant pebbles to the cord.

 

4) Move the damn phone. This isn't my favourite option but I foresee the suggestion.

 

5) Listen to more industrial music so the GSM pings blend in to the audio.

 

6) Just get a new amp.  This would solve some of the other issues I have such as highish output impedance, a crap volume pot at low volumes. If I do go this route is a balanced drive amp my best bet or do some single ended systems have better RF rejection?

 

Thanks for any advice, or just reading this far if you have nothing to say.

Brad

[Riotvan]

Sounds to me your amp is not properly shielded. As for cables making your own is much more cost effective and you get to learn a new skill. Sommer cable peacock mkII is nice but maybe a bit heavy.

[grawk]

#4 is the only practical option, and is easily implemented.  You'd need a fully shielded headphone cable, which would have terrible handling characteristics, in order to solve a problem that is easily solved with picking a new spot for your phone.

[BradC]

Regarding the Sommer cables.  Thank you for the info Riotvan. They do look really nice (and I might just make a cable up with some for fun as it's very reasonably priced).  However, I think spiral shielding is generally not very effective in the high MHz range that cell phones occupy?  If I understand correctly, only foil shields have low transfer impedance (aka good shielding) at frequencies in the MHz range?

 

Grawk > I was worried that # 4 would be a popular choice, I do appreciate the KISS solution. However, continuing with my elevation of a first world problem to epic proportions. This is my workplace setup so I tend to leave my cell phone in my pocket as I get up and move around relatively frequently. At my desk my headphone cable seems to really like falling onto my lap and interacting with my cell phone in my pocket (maybe I should just make a shorter cable...).  So it is a teensy bit more inconvenient to move the phone than it sounds. I am suspicious that any cable shielding effective in the cell phone bands will result in an unwieldy cable as you mentioned (last thing I can imagine anyone wanting is some cat5 connected to their headphones)...

[postjack]

a tube amp should make the EMI noises more warm, mellow, and bassy. also try flats.

[grawk]

try putting your phone on one side of your desk, and everything else on the other.  I've found a couple of feet makes a huge difference

[nikongod]

1: The beyerdynamic T1 comes with a shielded cable. This seems like a good reason to sidegrade. 

 

2: You could try putting Ferite beads on the headphone cable. I suspect that the noise is getting in to the system through allllll sorts of methods though. Do you have shielded interconnects? 

 

3: Briliant pebbles. Those fuckers work good! Try em. (April fools!) Almost no "audiophile approved" gear or mods do anything to protect the system from RF - in fact many "audiophile approved solutions" seek to remove what little was there! 

 

4: Occams Razor? Costs nothing. Quite effective. More effective would be to just turn the phone off and enjoy the music. 

 

5: I'd rather just listen to the GSM noise, but to each his own. 

 

6: Why does high output impedance matter? Do you mean you want higher? I could get behind that. The HD650 respond nicely to an amp with highish to freakishly high (60ohms or up) output impedance. The OTL tube amps so many people lalalove with the HD650 start at 60ohms output impedance and go up from there quickly. 

 

Balanced cables do not block *high frequency* RF! In a balanced system, the balanced cable rejects low-frequency EMF (60hz hum) but the individual strands of the cable are physically too far apart to reject high frequency noise. For high frequency you need a shield. The shield works great at high frequency, but does nothing at 60hz - so we combine them to kill allllll sorts of noise.

 

You have not mentioned what sort of interconnects you have - you may find some improvement by switching to shielded interconnects, if you don't already have them. 

 

In the case of a headphone or speaker power-amplifier output, where the pickup of 60hz is not a problem (there is no amplification stage after this...) balanced "works" for completely different reasons which have basically nothing to do with noise rejection/pickup. 

[BradC]

6: Why does high output impedance matter? Do you mean you want higher? I could get behind that. The HD650 respond nicely to an amp with highish to freakishly high (60ohms or up) output impedance. The OTL tube amps so many people lalalove with the HD650 start at 60ohms output impedance and go up from there quickly. 

 

Balanced cables do not block *high frequency* RF! In a balanced system, the balanced cable rejects low-frequency EMF (60hz hum) but the individual strands of the cable are physically too far apart to reject high frequency noise. For high frequency you need a shield. The shield works great at high frequency, but does nothing at 60hz - so we combine them to kill allllll sorts of noise.

 

You have not mentioned what sort of interconnects you have - you may find some improvement by switching to shielded interconnects, if you don't already have them. 

 

In the case of a headphone or speaker power-amplifier output, where the pickup of 60hz is not a problem (there is no amplification stage after this...) balanced "works" for completely different reasons which have basically nothing to do with noise rejection/pickup. 

High output impedance is only really an issue when I want to listen to my IEMs or Momentums which sound kinda crappy without really low output impedance. For now I just use a hacked together voltage divider as the amp has more than enough power and I do love the sound when it's not buzzing....  On the other hand my HD650s sounds great off anything (I do like OTL tube amps..)

 

Thanks for the info on balance connections. It's nice to know they aren't the magic some people suggest so I don't waste money on an expensive upgrade with no benefits.  Particularly given the very impressive price tag on balanced headphone out amps.

 

The interconnects on my amp are a shielded USB (I don't remember the brand as it was cheap, but it is a foil + braid shield), and for RCAs I use Belden 1694A Blue Jeans RCAs. I have disconnected the RCAs and USB and the interference is still a problem through the headphone cable. I'm pretty sure the toslink isn't to blame, but perhaps it needs demagnatizing

 

 

5: I'd rather just listen to the GSM noise, but to each his own. 

This is far too accurate ->

 

try putting your phone on one side of your desk, and everything else on the other.  I've found a couple of feet makes a huge difference

True, even a couple inches make a big difference.... It's sad that after more years of university education than I care to admit, that the best solution is probably the simplest "stop being a lazy whinger and move the phone"  

[n_maher]

If you post one more time about understanding the solution to your non-problem and don't just do it I'm going to send you packing.  So far you're about as useful as the interference you're so intent on not eliminating.

[BradC]

If you post one more time about understanding the solution to your non-problem and don't just do it I'm going to send you packing.  So far you're about as useful as the interference you're so intent on not eliminating.

Sorry, the last thing I want to do is contaminate this forum with annoying noise from my end.  I do genuinely appreciated everyones feedback, and hope I haven't come across any other way.

 

I was hoping that this was something I could blame the amp for (and maybe solve all my problems with one purchase), or solve with a simple cable swap (I am not very well versed in the headphone cable market) or filter.  I guess I'll just chalk the lack of other people with this problem up to me being the only dumb ass that leaves their phone in their pocket near where their headphone cable sits at their desk.  I did test moving my phone around (hence the couple of inches comment, which is directly from testing based on grawks suggestion not a snide retort), was saved form a potential ill-informed investement in balanced gear by nikongod, and ordered some of that nice looking sommer peacock mk II cable that riotvan pointed out for a cable building project.

 

Anyway sorry for the interruption I'll be shutting up now.

 

Brad