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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

128x128filipm

Showing 3 responses by perkri

perkri
896 posts
 

Agree, that the DAC plugged into the Phono would appear to be like a TT at first glance, however, completely different grounding protocol, and completely different sensitivity to the outside world and interference. 
 

Which EAR-834P model is it?

perkri
896 posts
 

That’s a challenge, for sure.

Never heard any “noise” like that coming from my phono stage, or any other component for that matter.

Sounds like a radio that is trying to pick up a signal, that won’t tune.

And the beeps are odd.

As others have said, sounds like WiFi/router signal.

And as you’ve taken it elsewhere, and it works perfectly, it’s likely not a defective  phono stage. Adding the TT increases the noise, which makes sense as the cartridge will also pu the interference. 
 

Have you tried plugging another source, other than a TT, into the phono stage? Like your DAC (powered up, but with no signal/source of course…)

Just curious if that removes it. 
 

Sorry for your headache, must feel like you’re  chasing a ghost…

The EAR-834P box is a pretty solid brick of metal, which should help to shield the tubes from the interference?

Something is the source of that noise, I know you prefer to shield the gear, but hunting down the source might be an easier task.

perkri
896 posts
 

Thanks for letting me know what model.

Was wondering about  provisions for a MC cart.

Asking to see what else is inside the box that might be picking up the signal?

And the unit is solid state rectified, all three tubes are used in the signal path

Heres an obvious, and silly question, but are the tubes properly seated in the sockets? Could they have been jostled with all the moving about?

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