Is it? Have a look at some of the EMC sites and look at power line communications....
I would be interested in why you think EMC is over stated, as in most electronics great lengths are gone too, to prevent both emission's and susceptibility.
I don't know about that.
My stereo became very noisy when I replaced my CRT computer monitor with a flat screen. Ferrites clamped at monitor and computer end of the cabling helped a fair bit but the normal inter-music silence was only fully restored (and more) when I got rid of the last unbalanced connection in my stereo.
RFI/EMI and all our "wireless" gear amount to a lot of interference.
I use twisted pair a lot.
Very little of my gear uses coax and then only the very short lengths of <1m i.e. 2' and 3'
All the rest uses twisted pair without any screen.
I don't get interference from my fridge/freezer motor. I don't get interference from my mobile phone. I don't get interference from my compact fluorescent light bulbs/LED light bulbs.
Unscreened Twisted Pair (UTP) connecting unbalanced equipment are excellent at line level in a domestic environment.
Just buy Allen Wright's Cable Cookbook. The book is not just opinion, there's research, physics and math involved. It's paid for itself a few times over.
Think it's around $65. Got it direct from Vacuum State Electronics' website.
They also have the parts to build some of the better cables.
Think it's around $65. Got it direct from Vacuum State Electronics' website.
They also have the parts to build some of the better cables.
Yeah, I know but one has to draw a line somewhere.
At least with speakers if I don't count my time I can get something substantially better than commercial offerings for the same cash.
And if I had anything more than a passing insight into amps I'd probably make my own too. May be not because it would save money but it seems that there might be lots of room to experiment and thus it could be rather interesting.
But with cables there is no gain to ones knowledge or financial base.
The two things in favour of making XLR or TRS cables is that a) it's a good way to practice soldering and b) it kills time if you have time to kill.
Interference has been a major problem for me. I've found the following to be helpful:
1. Battery-powered HP amp (not economical for speakers)
2. FET-type inputs (outputs never seem to be a problem)
3. EI and UI transformers
4. No coax (I used STP, or star quad, with shield as a chassis-connected shield)
I think 1 just breaks ground connections that become loop or dipole antennas, otherwise, and HPs happen to be more sensitive than speakers, on average. 2 has been well-known for longer than I've been alive. It doesn't tend to show itself in obvious noise, but by subtler distortion, not being fatiguing over time, making comparisons annoying to do (of course, FETs are no panacea, so I'm not a zealot about it). 3 has been observation from using unregulated wall warts (plain EI) and scavenged DVD player SMPSes (one split-bobbin EI, and one split-bobbin UI), having less problems with them than popular toroid-based supplies, then researching. I'm just starting to do it DIY from the wall (as in having some parts and plans, but not yet anything built). 4 was kind of a no-brainer, with SE coax sharing the high surface area shield with the signal.
A cable can be an antenna, or turn devices into antennas, but it's just one piece, and should not make or break RFI problems on its own (it would be nice if it did).
1. Battery-powered HP amp (not economical for speakers)
2. FET-type inputs (outputs never seem to be a problem)
3. EI and UI transformers
4. No coax (I used STP, or star quad, with shield as a chassis-connected shield)
I think 1 just breaks ground connections that become loop or dipole antennas, otherwise, and HPs happen to be more sensitive than speakers, on average. 2 has been well-known for longer than I've been alive. It doesn't tend to show itself in obvious noise, but by subtler distortion, not being fatiguing over time, making comparisons annoying to do (of course, FETs are no panacea, so I'm not a zealot about it). 3 has been observation from using unregulated wall warts (plain EI) and scavenged DVD player SMPSes (one split-bobbin EI, and one split-bobbin UI), having less problems with them than popular toroid-based supplies, then researching. I'm just starting to do it DIY from the wall (as in having some parts and plans, but not yet anything built). 4 was kind of a no-brainer, with SE coax sharing the high surface area shield with the signal.
A cable can be an antenna, or turn devices into antennas, but it's just one piece, and should not make or break RFI problems on its own (it would be nice if it did).
Last edited:
You hear it or you see it in testing equipment?
I'm open-minded to that RFI is not a distinct noise, rather some kind of signal convolution, just like, say, you don't hear distortion in the form of noise like an air-conditioner click or whirr in a vintage DAC chip, you can only detect the different sound character, it's wet like a lizard.
See this paper for Mhz frequency interference folded down into the listening levels — http://www.uemc.polito.it/papers/opampsusc_01.pdf
Last edited:
Still yet to get farther than a DMM. I'm probably going to pick up one of the Hantek 6022 scopes, soon, and start with properly snubbing my transformers, then work from there.
I'm sure whatever I've heard in these cases would be measurable, with the right equipment and know-how to make use of that equipment.
Sometimes it's obvious noises, like hearing noises from a GSM phone in another room, or, "garbly," low-amplitude noise with nearby wifi. I've turned whatever I had, or intended to have, into a radio receiver. Yay me. Nearby GSM phones, like on my hip, were a problem for quite awhile.
Sometimes it's clear, in the sense that something just isn't right, even without a distinct sound that can be picked out, and then after turning off enough switchers nearby, or the wifi router, it gets fixed. Not right doesn't always mean harsh, or grainy, either. If I'm listening to Alice in Chains or Garbage, and it sounds, say, "airy," or seems to have a wide soundstage, something is clearly up (sometimes, it's been a colored amplifier circuit, of course)
. When it's that obvious, even not clearly distinguished as separate noises, usually it's usually been a grounding problem, like bad ground connection, or a shield making a ground loop (sometimes even with a hum breaker), or noise being passed from the mains, where trying other receptacles often does the trick (or, a bit later, using cheap wall warts instead of toroidal transformers for power supplies). Up to around +12V, with low current needs, it's usually not too hard to swap in batteries as a sanity check, removing one of the ground paths. Not having the ability to objectively measure it, I just have to speculate to the nature of it. However, theory and measurements from others over decades leads me to think most of it's mainly been noise picked up either just getting mixed in and being unpleasant, causing oscillatory issues, and/or rectifying into nasty higher-order harmonics.Sometimes it's much more subtle, such that it's not obvious quickly, but a feeling after some time. With that, there's the obvious, "is this placebo?" question to be raised. FI, going mainly to FET-input opamps did not happen by any feat of golden ears, but after skimming Opamp Applications, reading the section on rectification sensitivity, then going back and finding that the opamps I couldn't manage to like were BJT, and most of those I did were JFET/BiFET, even though there should have been nothing wrong with the chips or the circuits they were put in. Then, after switching all over to JFET/BiFET input types, and being quite content, I noticed I could have my cell phone or notebook mere feet away, with no problems. But, that last realization didn't come until months later.
Of course there are going to be more ways to deal with it. Even that change would not do much good without also dealing with ground/shield issues, which sometimes involved the ICs, and having already gone to gain <5 everywhere. But with my limited knowledge and understanding, not having any better luck with commercial stuff compared to DIY, and not needing high voltage gain, it is an easy and relatively cheap way to go.
I grew up surrounded by Hams, so every thin wire being a possible antenna that can cause problems is nothing new to me
, though the transistors rectifying and modulating was, and I'm still learning theory and useful practice behind how various methods of picking up or rejecting unwanted noise works. I've sometimes found cables to make a big difference, but changing what terminated to what, and how*, ended up consistently making things better or worse, not any exotic designs, materials, or construction.* jcx's post #16, for instance, might explain why I consistently had coax issues, rather than just it being related to having the shield and signal ground tied together. I always used regular audio connectors, as did any prebuilt RCA cables I used, which use lugs of some kind, not the 360 degree connection that a crimp connector would give.
Speed of electricity flow (speed of current.)
"I've seen one way to directly measure the drift velocity of charges in a conductor. Connect metal electrodes to the ends of a large salt crystal (NaCl), then heat it to 700 degrees C and apply high voltage to the electrodes. At this temperature the salt becomes conductive, but as electrons flow through it they discolor the crystal, and a wave of darkness moves across the clear crystal"
"I've seen one way to directly measure the drift velocity of charges in a conductor. Connect metal electrodes to the ends of a large salt crystal (NaCl), then heat it to 700 degrees C and apply high voltage to the electrodes. At this temperature the salt becomes conductive, but as electrons flow through it they discolor the crystal, and a wave of darkness moves across the clear crystal"
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.