Hi I've looked for assistance on this on AudioKarma but am still stumped. Hope someone here can help!
I'd originally heard a high pitched noise in all channels in my EICO HF-81, sounding a bit like Cell Phone interference of yore ... a faint squealing noise a bit like a dot matrix printer. I recorded the sound at a loud volume through the phono stage here https://www.dropbox.com/s/21uk4b2jc4kirxh/Interference.m4a?dl=0
Cleaned the pots/connections as advised and the problem still persists.
I've subsequently plugged in various solid state receivers including a Marantz 2230, Marantz 3330 + 140 preamp/amp, Pioneer SX 780 through different speakers, different power outlets and different rooms and am getting the same noises through all in varying degrees. The sound increases with turning up the volume, and listening in the preamp stages.
I've disconnected wi-fi routers, power strips and any lights that might be causing this but the problem persists. I live in an apartment building in NY. The problem started a few days ago and my neighbor has cited a strange noise in his clock radio - not sure if there's a relation. There are also somewhat new cell towers in the neighborhood but I can't imagine these are the issue.
Any other ideas to help diagnose?
I'd originally heard a high pitched noise in all channels in my EICO HF-81, sounding a bit like Cell Phone interference of yore ... a faint squealing noise a bit like a dot matrix printer. I recorded the sound at a loud volume through the phono stage here https://www.dropbox.com/s/21uk4b2jc4kirxh/Interference.m4a?dl=0
Cleaned the pots/connections as advised and the problem still persists.
I've subsequently plugged in various solid state receivers including a Marantz 2230, Marantz 3330 + 140 preamp/amp, Pioneer SX 780 through different speakers, different power outlets and different rooms and am getting the same noises through all in varying degrees. The sound increases with turning up the volume, and listening in the preamp stages.
I've disconnected wi-fi routers, power strips and any lights that might be causing this but the problem persists. I live in an apartment building in NY. The problem started a few days ago and my neighbor has cited a strange noise in his clock radio - not sure if there's a relation. There are also somewhat new cell towers in the neighborhood but I can't imagine these are the issue.
Any other ideas to help diagnose?
Yes, it's cell-phone...given your equipments sensitivity, cell-phone bleedover has always been an issue.
Check your computer, your "available" link ups to Wi-Fi service?, no doubt in such an urban environment your get some dozen or so "picked up" as a possible Wi-Fi connection..??? same thing, cell-phones are so predominant now, & the FCC has not really done their job in requiring some buffers in frequencies, nor really successfully dealt with cell-phone "contamination" of the airwaves, no doubt a "victim" of corporate pressure & influence.
BTW, I get it here somewhat regularly, I can tell when someones cell-phone "goes off".....in our house, the house next door, or whomever is "within range" of the sensitivities of my equipment.
You could always encase your domicile in a sort of haphazard Faraday cage???
---------------------------------------------------------------------Rick.....
Check your computer, your "available" link ups to Wi-Fi service?, no doubt in such an urban environment your get some dozen or so "picked up" as a possible Wi-Fi connection..??? same thing, cell-phones are so predominant now, & the FCC has not really done their job in requiring some buffers in frequencies, nor really successfully dealt with cell-phone "contamination" of the airwaves, no doubt a "victim" of corporate pressure & influence.
BTW, I get it here somewhat regularly, I can tell when someones cell-phone "goes off".....in our house, the house next door, or whomever is "within range" of the sensitivities of my equipment.
You could always encase your domicile in a sort of haphazard Faraday cage???
---------------------------------------------------------------------Rick.....
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An Eico HF81. Is that a kit amp of a bygone era from Allied Radio?
I wanted an Allied kit but never had the nerve to call long distance and work out the shipping cost in advance (way before internet ordering).
Long distance calls were an hour's pay back then, maybe more if you went on hold.
RF is everywhere. I admit my country trailer 1/3 mile from the road in rural New market has less interference than my city house in downtown Jeffersonville, 30 feet from a busy corner and 4 miles from the AM radio towers of the Kentuckiana area. Two blocks from a cellphone tower. My worst problem was a CB nut who drove by emitting continuous dogs barking out Dixie.
I've retrofitted amateuristically sheilded hifi equipment with RF protection, both my dynaco ST-120, and a Japanese kit disco mixer, the RA-88a. If the enclosure has a complete steel box, then the job involves fitting parts to keep RF from coming in the various holes like AC cord, speaker terminals, line input, etc. Speaker terminals get a "zobel network" and a series 15-20 turn coil parallel a 3 to 10 ohm resistor. Analog inputs get parallel ceramic caps to ground, 33 pf to start with, most recently 68 pf. Power input gets a iron core or toroidal choke series the AC and neutral, plus the type x cap after the fuse plus a pi filter. Most of the latter can be salvaged from dead PCAT power supplies, or dead late model LED televisions.
For more gory details, see this about the mixer: http://www.diyaudio.com/forums/anal...improving-disco-mixer-mid-fi-performance.html
My ST120 amp had an enclosed iron core power transformer, so the chokes weren't needed. Having it very close to the AC cord entrance made twisting the wires unnecessary. It had a ceramic cap across the output of the transformer already, so I didn't have to buy an X cap. (X caps are rated for line AC service, have a UL CE or VDE symbol on them and the rated line voltage).
Best of luck exterminating your RF problem.
I wanted an Allied kit but never had the nerve to call long distance and work out the shipping cost in advance (way before internet ordering).
Long distance calls were an hour's pay back then, maybe more if you went on hold.
RF is everywhere. I admit my country trailer 1/3 mile from the road in rural New market has less interference than my city house in downtown Jeffersonville, 30 feet from a busy corner and 4 miles from the AM radio towers of the Kentuckiana area. Two blocks from a cellphone tower. My worst problem was a CB nut who drove by emitting continuous dogs barking out Dixie.
I've retrofitted amateuristically sheilded hifi equipment with RF protection, both my dynaco ST-120, and a Japanese kit disco mixer, the RA-88a. If the enclosure has a complete steel box, then the job involves fitting parts to keep RF from coming in the various holes like AC cord, speaker terminals, line input, etc. Speaker terminals get a "zobel network" and a series 15-20 turn coil parallel a 3 to 10 ohm resistor. Analog inputs get parallel ceramic caps to ground, 33 pf to start with, most recently 68 pf. Power input gets a iron core or toroidal choke series the AC and neutral, plus the type x cap after the fuse plus a pi filter. Most of the latter can be salvaged from dead PCAT power supplies, or dead late model LED televisions.
For more gory details, see this about the mixer: http://www.diyaudio.com/forums/anal...improving-disco-mixer-mid-fi-performance.html
My ST120 amp had an enclosed iron core power transformer, so the chokes weren't needed. Having it very close to the AC cord entrance made twisting the wires unnecessary. It had a ceramic cap across the output of the transformer already, so I didn't have to buy an X cap. (X caps are rated for line AC service, have a UL CE or VDE symbol on them and the rated line voltage).
Best of luck exterminating your RF problem.
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As for interference, Jim Brown is the go-to expert!
Start with (but skip the parts aimed only at Ham radio):
"A Ham's Guide to RFI, Ferrites, Baluns, and Audio Interfacing"
http://www.audiosystemsgroup.com/RFI-Ham.pdf
about 50 more excellent papers:
Audio Systems Group, Inc. Publications
Start with (but skip the parts aimed only at Ham radio):
"A Ham's Guide to RFI, Ferrites, Baluns, and Audio Interfacing"
http://www.audiosystemsgroup.com/RFI-Ham.pdf
about 50 more excellent papers:
Audio Systems Group, Inc. Publications
thank you all. I have some reading and research to do.
I have also noticed that when I turn larger components on and off, such as my christmas tree lights or the CD player, there is a popping sound in the system - despite these appliances being on different outlets. Not sure if that reveals anything
I have also noticed that when I turn larger components on and off, such as my christmas tree lights or the CD player, there is a popping sound in the system - despite these appliances being on different outlets. Not sure if that reveals anything
This tells me you have a problem at the source . It/they are emitting emi. It is better to attenuate the emi at the source.
The second is that your equipment is sensitive to picking up emi.
Add passive filtering to all the cable pairs that enter your enclosure.
Ensure the enclosure is conducting and has small holes/slots.
A long slot lets in the same frequencies as a large diameter hole that has the same major dimension.
Use screened cable for the interconnects, where these are easily available. Screened mains leads and screened speaker leads are generally unavailable.
Sounds more like there's a ground loop in the system TBH. Seems it's "hearing" the mains rather better than you want. It could still be RF demodulation if the amp is sensitive to EMI, but then the problem would vary a lot among different amps. Cables have been checked already?
I'd start with a barebones system - e.g. just amplifier and CD player (with 2-conductor mains cord, I hope) - and check whether the problem is still present.
Possibly stupid question: Mains voltage is nice and stable? We had a brownout in the office once, voltage went down to about half of what it should be (so ~US levels). Most things continued working, but guess whose PC went out? Yep, mine, the only one without a universal (100-240VAC) power supply. Also, a halogen light and an MFC's fuser didn't take kindly to this kind of treatment.
I'd start with a barebones system - e.g. just amplifier and CD player (with 2-conductor mains cord, I hope) - and check whether the problem is still present.
Possibly stupid question: Mains voltage is nice and stable? We had a brownout in the office once, voltage went down to about half of what it should be (so ~US levels). Most things continued working, but guess whose PC went out? Yep, mine, the only one without a universal (100-240VAC) power supply. Also, a halogen light and an MFC's fuser didn't take kindly to this kind of treatment.
Sometimes, it's worth looking at the OP device. It's a stereo tube amp, dating from the late 1950s. Would you really expect modern performance standards and RF or any "F" immunity? Eico HF-81 - Manual - Stereo Integrated Tube Amplifier - HiFi Engine
I've put about $4 parts in my 1966 design Dynaco amp (ST-120) to achieve RF silence. I salvaged some of the parts from PCAT power supplies designed to last a year and be replaced. Another $10 in parts to update the circuitry to something with modern accuracy.
These 1959 devices had transformers connectors & cases designed to last 50 years. IMHO a little DIY work to update the design to cope with a time when everybody carries a UHF radio in their pocket, is worthwhile.
OTOH my Dynaco ST70 may sound better than an Eico HF-81 did.
There isn't much protection at all (just an RC lowpass filter after the input selector switch) and I doubt it does anything to keep UHF - microwave frequencies out. Yes, something can be done about bypassing the inputs to ground (if the chassis is actually grounded) with 220pF MLCC capacitors - but it must be right at the RCA input sockets, for starters. I suspect though, that the feedback from the output transformer secondary and speaker leads and mains power cord also will be a problem. It needs a bit of expertise or a good read of some docs on the topic. For a trial, I would pass the speaker leads a few times through ferrite balun rings there. The right grade ring can work wonders on problematic speaker leads.
Here's part of the schematic showing one of the bare-bones input preamps. The whole amp. is built on the tagstrips and tube sockets, with lots of long wires everywhere, in the 50's AM radio style.
Here's part of the schematic showing one of the bare-bones input preamps. The whole amp. is built on the tagstrips and tube sockets, with lots of long wires everywhere, in the 50's AM radio style.
Attachments
I bypass line inputs with a ceramic cap to analog ground, not the case ground. No, my 1966 design cases are not safety grounded either. Just through the RCA cables to the mixer/preamp case. With no children in the house and the amp against the wall under the organ bench, I'm not worried about it. The mixer case is grounded from turntable ground terminal through a green wire to the outlet strip (replacement AC plug) but whether or not the plug is installed doesn't affect hum or RF interferance.
As far as the speaker output, the engineering has been done. On 2-8 ohm speakers, 13 turns 14 ga around a AA battery with a 3-10 ohm resistor parallel between output and speaker terminal seems to be the standard treatment these days. My ST120 is dead silent with the 13 turns speaker wire out around the 3300 uf output cap, plus 1kohm series .1 uf across output banana jacks. And there is plenty of RF in this location.
My dynaco transformers right next to the input switch are keeping RF out well enough with only a .01 uf 1000 v ceramic cap across the output. I've paralleled the AC input with a 300 vac 15 mm (high joule rating) MOS surge supressor out of a VF motor drive, mounted on a cinch solder strip.
If the Eico transformer can't keep RF out, those toroids thrown away with your dead ATX switcher supply do a good job bucking RF on the DC supply lines in my RA-88a mixer. Just make sure the wire is fatter than required for the fuse rating of your amp. Actually one toroid is the 5 v winding of the ATX supply, with some turns removed to get it down to 21 turns like the input AC choke. This is very similar to the input filter arrangement in a Peavey CS800s amp switcher supply , or the AC input board in a modern LED display TV I salvaged last summer.
Those ferrite beads, I don't know how to buy them, but Ishida uses them on the 440 VAC 3 ph lines coming into the DC supplies of their $$$$$$ weighing machines. So they must be good at RF supression. I haven't salvaged one of those so no beads in my inventory.
As far as the speaker output, the engineering has been done. On 2-8 ohm speakers, 13 turns 14 ga around a AA battery with a 3-10 ohm resistor parallel between output and speaker terminal seems to be the standard treatment these days. My ST120 is dead silent with the 13 turns speaker wire out around the 3300 uf output cap, plus 1kohm series .1 uf across output banana jacks. And there is plenty of RF in this location.
My dynaco transformers right next to the input switch are keeping RF out well enough with only a .01 uf 1000 v ceramic cap across the output. I've paralleled the AC input with a 300 vac 15 mm (high joule rating) MOS surge supressor out of a VF motor drive, mounted on a cinch solder strip.
If the Eico transformer can't keep RF out, those toroids thrown away with your dead ATX switcher supply do a good job bucking RF on the DC supply lines in my RA-88a mixer. Just make sure the wire is fatter than required for the fuse rating of your amp. Actually one toroid is the 5 v winding of the ATX supply, with some turns removed to get it down to 21 turns like the input AC choke. This is very similar to the input filter arrangement in a Peavey CS800s amp switcher supply , or the AC input board in a modern LED display TV I salvaged last summer.
Those ferrite beads, I don't know how to buy them, but Ishida uses them on the 440 VAC 3 ph lines coming into the DC supplies of their $$$$$$ weighing machines. So they must be good at RF supression. I haven't salvaged one of those so no beads in my inventory.
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UPDATE here:
To note, this issue is occurring in a variety of different receivers, not just the Eico, although it is most prominent. This is also occurring in my more modern (though 70's models) marantz receivers and others.
I reached out to the FCC, however they cannot help with my consumer electronics: To the extent that the interference is caused by a design defect with your consumer electronics equipment, you might want to contact the manufacturers of the affected devices and request an appropriate shield and/or filtering device.
I sense that this is an electrical issue. I've installed shielded speaker cables and interconnects, as well as an isolating power strip and have had no luck with this issue. Does anyone believe installing a dedicated circuit in my apartment would cure this?
Reattaching a recording of the sound: https://www.dropbox.com/s/21uk4b2jc4kirxh/Interference.m4a?dl=0
I should note along with the intermittent noise on all channels (on different receivers), I am also hearing a high pitched whine on the phono stage.
To note, this issue is occurring in a variety of different receivers, not just the Eico, although it is most prominent. This is also occurring in my more modern (though 70's models) marantz receivers and others.
I reached out to the FCC, however they cannot help with my consumer electronics: To the extent that the interference is caused by a design defect with your consumer electronics equipment, you might want to contact the manufacturers of the affected devices and request an appropriate shield and/or filtering device.
I sense that this is an electrical issue. I've installed shielded speaker cables and interconnects, as well as an isolating power strip and have had no luck with this issue. Does anyone believe installing a dedicated circuit in my apartment would cure this?
Reattaching a recording of the sound: https://www.dropbox.com/s/21uk4b2jc4kirxh/Interference.m4a?dl=0
I should note along with the intermittent noise on all channels (on different receivers), I am also hearing a high pitched whine on the phono stage.
I should also note the issue is occurring in different rooms, with outlets on different breakers.
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