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I need some basic guidance.
My new integrated amp has a background buzz with all inputs. Level is volume setting dependent. It seems to be a higher pitch than a 60 cycle ground hum.
I traced it to the outboard power supply for my outboard phono stage. That was initially located on the shelf below the integrated in my equipment rack. Moving the PS out of the rack to the floor behind diminished the buzz but did not eliminate it. It's not convenient to move the PS further away so I assume additional shielding is the answer.
Now, are some metals better for shielding than others? One that is easily bendable is preferred. I've not tried aluminum foil but doubt that may help much.
So recommendations before I go shopping will be appreciated.
"The secret of life is honesty and fair dealing, if you can fake that you've got it made." Groucho
Thanks to all who offered suggestions.
I had unplugged the phono stage from the integrated amp which eliminated the noise and confirmed that was the source of the problem. As stated, moving the PS reduced the noise but did not eliminate it. For the next few days I left it unplugged, using other inputs, while I worked on tax preparation.
This morning I plugged it in again to test a couple of suggestions. But the buzz did not return, silence even with high volume settings. So the gremlin was mysteriously cured.
For those curious about the phono stage, it is a second generation JLTi. That is the plain box version made in Australia. A friend had written a favorable review for Positive Feedback which encouraged me to try one. Originally they recommended using a wall wart. However a friend with a strong electronics background disagreed and built an outboard regulated PS for me. That did provide improvements with increased dynamics and deeper, more substantial bass. I've since used it for several years without any issues. It is plugged into a Chang Lightspeed line conditioner, while the integrated amp plugs directly into a dedicated line outlet.
So who knows why? Electronics remains a mystery to me. ;^)
"The secret of life is honesty and fair dealing, if you can fake that you've got it made." Groucho
Glad to hear that the issue is resolved-
Electronic gremlins are funny creatures...
Happy Listening
Which power supply do you have for your outboard phono preamp? I believe it's a JLTi phono from your Profile but those had various power supply options including a budget 'wall wart'. If the power supply is switcher it can produce 'noise' higher than the 60-Hz AC mains. If it's a switcher, upgrading to a linear power supply might help.As for noise mitigation there are a few possible solutions including mu-metal shielding (a full mu-metal box) would be best. BUT, there could be radiated noise on the power supply DC cable that can be attenuated with a ferrite choke wrapped around the DC cord as it exits the power supply and one right near its output feeding into your phono preamp.
Open inputs to your integrated amp can be capped off with metal caps. If you're running unshielded interconnects (like twisted pair Kimber KCAG or similar) I would switch to shielded interconnects.
Not actually seeing or knowing more details about your setup it's hard to say but there are a few paths you can take.
Edits: 03/12/25
Putting a shield in place may work, but it may need to be grounded-
Another thread to pursue - as mentioned, is the PS grounded?, is it plugged into the same circuit as the integrated amp?- try having them in different circuits
lastly, try rotating the PS through different orientations-
while it has feet, and was built to be 'upright' in a stack of equipment, it may need to be on its side, or another orientation so that the radiation pattern is orthogonal to the integrated amp...
Happy Listening
If the buzz is not related to volume ... that is, it does not increase and decrease with volume, I would first suspect DC offset, which is making the toroidal transformer resonate.
good luck!!
I imagine that you've tried a cheater plug to drop the ground.
I had a low level buzz with one of my amps. The buzz was not like a ground hum, more like a low A/C buzz, but volume didn't change the level. I didn't worry about it because it was only audible if I put my head next to the speaker.
Anyway, I was told that the transformer needed to be cranked down or to isolate the transformer. When I put my head next to the amp, I could actually hear the same buzz. If you can hear a faint buzz from the PS when the amp is off, isolation might fix it. We used some rubber grommets.
-Rod
It may be more complicated than shielding. Think about the grounds first.
Is the power cord for the PS grounded through a three prong plug? Is the phono stage grounded with a three prong plug? Is the PS connected to the phono stage through a shielded cable and does the cable also run a positive and ground wire between them?
As you can see there are several routes for a ground loop. Ensure the power cables are plugged into the same outlet or power strip. Ensure that the RCA jack on the integrated is not grounded to the chassis, but at a ground buss with all the rest of the grounds in the amp. Try plugging and unplugging the interconnect to see if the noise is reduced.
If you do try shielding, you could try copper roof flashing available at the hardware store. Try grounding it to the chassis ground and disconnecting it from chassis ground.
I this it?
At one time they sold a sample pack of their products.
I used a sheet to shield a Grado Reference - The Reference.
It had a lot of hum until I put a piece of MuMetal inside
my Linn LP12.
Then dead silence.
nt
Open up your mind, in pours the trash. - Meat Puppets, 1987
I have a Sachs Model 2, but the problem is with an integrated amp.
So specific components are not so much the issue, I'm asking about proper shielding material.
"The secret of life is honesty and fair dealing, if you can fake that you've got it made." Groucho
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