Assuming the OP lives in the US, I think it's a bit too simple to blame his issue purely on bad grounding, if you listen to the recorded noise up above. First of all, there is an intermittent burst of 50Hz noise. In the US, we use 60Hz AC, and it's pretty well regulated at that frequency. Typical noise due to grounding issues is at 60Hz or 120Hz. Moreover, it's not intermittent; it's constant. This noise seems due to RFI or EMI from some outside source, though it's true that the susceptibility to the Interference could be related to a poor ground circuit somewhere. There are already a myriad of reasonable ideas for the source and what to do about it in this thread. I hope something works. I am now wondering about bad diodes inside the EAR or the ARC. I am also wondering what did happen or will happen when all the tubes are replaced, though that will not rule out a cold solder joint inside one or the other device.
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
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- 187 posts total
@lewm - an excellent point - I was assuming the OP was on 50Hz AC power, based on one of his previous statements in this thread, and the circular plugs in the powerstrip in one of the pics he posted. @filipm - are you on 50Hz AC or 60Hz AC power? (should have asked this question earlier.) I plotted the noise spectrum in Audacity, and the 50hz buzz/hum is constant throughout the entire recording at around -17db though it does have very short spikes to -13db intermittently (I think this is the intermittent bursts lewm is talking about). And then there is another spike of a range of frequencies every four seconds. From the Bottlehead trouble shooting guide: "Buzzy hum, like a bee - This usually means a lifted ground connection. " if a lifted ground, then where it is lifted is the question, but a cold solder joint is certainly possible, though I would have thought if so it would have shown itself when the EAR was used at an alternate location.
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@lewm @ejb14 I should have mentioned I live in Prague, Czech Republic. The voltage is 230V and the frequency is 50Hz. I posted it on a local forum but got quickly annoyed by the same jokes some people have been posting for the last two decades over and over. I was in Berlin yesterday and took my EAR along. It worked perfectly fine even with the cheapest power cord and the interconnects I was using here. I didn't get the tubes yet but I returned with an ARC REF150 power amp. What a beauty. Ejb, I'm now gonna read the article you have sent. Thanks. Exactly, if there was a lifted ground on the EAR, it would have been apparent at least at one of the locations I have been to. I wanna try to bring a small intergrated amp and plug it in on the hallway to eliminate the circuit in the apartment. Is there any test I can do inside the apartment? I invited an electrician and he said the power line should be fine.
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@filipm You could get an outlet tester from Amazon or a hardware store - one that would show open ground/earth would be important. Search Amazon for "outlet tester Prague" (or UK) - You can also use your DMM to test (google how to do it, lots of hits) - just be careful - and use just your right hand to place the probes - do not use both hands - if the outlet is not connected to ground, you don't want to become the ground. If you can, I would get an outlet tester. They are cheap and a great thing to have in this hobby. You likely want to test your power cords too for ground correctness. I've been in and tested many homes and apartments. Not all were wired correctly, even the newer ones. Check all outlets. |
Beautiful city Prague. If you are in an older building, you should get an electrician to verify the male earth pins in the building are in fact grounded. They may not be, or the grounding may be compromised with poor connectivity - corrosion etc. Also if both the EAR and ARC are grounded through the power cables, then when you connect the 2 units with an RCA cable then you have an earth loop - have you tried lifting the ground on the EAR ( making sure iit is grounded via the ARC by putting a multimeter across the 2 chassis.? |
- 187 posts total