If it is louder near the floor, could it be the source of interference is in your downstairs neighbor’s apartment? How many floors in your building?
Another thought, it might be worth investing or borrowing test gear that would allow you to positively identify what type of interference it is. For instance, if @theaudioamp is correct about it being a demodulation, perhaps an oscilloscope trace could prove that. just a thought.
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 oldrooney
I thought of that while I was writing my response, but surely this is it, right? [Famous last words.] I hope @filipm has it resolved, or another preamp, at least. He sure has hung in there where lesser men would have thrown in the towel by now. |
I’ve spent considerable time reading this thread, but it has been worthwhile. @atmasphere got the ball rolling on a solution, @budlite22 confirmed it, and @ejb14 moved things along, while @dpop chimed in too. It really was a drama proving that solutions grow quickly and surely when one starts by asking the right questions and answering them by proven tools and methods. Reminds me of a Sir Arthur Conan Doyle mystery, “Facts, Watson, we must have facts and reason shall lead us to a solution. What can we deduce from the facts before us?” Well done, all. I’m nearly as grateful as I’ sure @filipm is to finally have solved the mystery. And all I can say to @ahal1 is wow! I’ve got to get me one of those! (Where were you earlier?) |