For Noromance, I would agree with your idea. Just because I recently;y got a new TV (air) antenna that had a built-in filter for WiFi frequencies. IT cleared up a lot of degrading interference. I would also suggest that Philipm looks at his neighborhood to see if anyone has recently added an Illegal CB radio amp or even a HAM operator putting up something new. HAMS are almost ALWAYS agreeable to helping you find a resolution to any interference from their Radio station. EVEN if their equipment abides with the FCC laws. In days gone by the Phono cart itself was one of the biggest offenders acting like an antenna. I also liked the Ferrite rings idea. THat has stopped many offending signals. I have them everywhere and even MY OWN HAM equipment does not get in the way of quality sound from my stereo. If the tinfoil ides had some effect, THat is the first thing I would replace with High-grade shielded Cartridge wires. I really liked the answers here. Not so many people talking stupid or trash, but helpful responses. I will probably get blocked for saying something nice about the site.
Tube PHONO preamp interference - RFI, EMI, bad grounding?
Hello!
My tube phono is picking up interference most probably from the air. It's EAR yoshino 834p, using three 12AX7 tubes. It's sounds pretty amazing and I willing to try everything to keep it.
Here is a sample of the sound -
The rest of the setup is ARC LS16 mk1, Classe CA200, Chord Qutest, Technics SL1200 with Nagaoka MP200, Tannoys D700
I have tried many things already -
- grounding the phono to the preamp, grounding the phono to a socket, covering the phono with a pot, saucepan - no change
-plugging the phono preamp alone into an integrated (Bryston B60) and removing other stuff.
- the important part is I have taken the phono to two other places and it worked perfectly fine, even with the cheapes cables.
- I haven't had any problems with previous phono preamps which were all solid state.
- if I unplug the turntable the signal fades to about 50%
- if I try different RCA cables, there's not much of a change even they are shielded (audioquest mackenzie, supra etc.)
- the signal also fades when I grab the cables. Also works if I grab or squeeze the output cables.
- I have tried to wrap the cables into aluminum foil, I have noticed a difference but it's still unlistenable.
- I have tried pluging in a 5 meters long RCA output cable and walked with the phono preamp around the room. It's simply like carrying an antenna. Placing the phono on the floor helps but again, the interference is still present.
Do you have any suggestions what else to try? Is there some kind of grounding that would prevent the phono preamp acting like an antenna?
I haven't tried a new set of tubes yet.
I think the 12AX7 are simply too sensitive to all the mess in the air. The ARC LS16 preamp was catching the same signal very quietly when I took it's cover of.
Thanks!
Filip
Showing 3 responses by esarhaddon
It may NOT be HAM radio but HAMs have been using PACKET radio for many years. It was just one more place to look for a source of trouble. |
I'm sorry if I am beating a dead Horse. I feel you shouldn't have to sacrifice good quality sound. I must restate that you should look for the source after a reasonable effort to protect your equipment. In doing so I would first follow up on your failed effort of putting a pan over your equipment and actually try to build an impromptu 'faraday cage'. the theory isn't that hard and some light reading should provide you with some inexpensive solutions. Once you find where the noise is entering your system, you can research what type of source might create this type of spurious signal. Also though unlikely look into all of your equipment power supplies to see if you have a failed filter. Even a $1,000 power supply could have an occasional bad capacitor. |