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BFR1957
(@bfr1957)
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26/03/2020 9:46 am  

I am having the same issue as the earlier posts. First, I’m a total neophyte with electricity. I paid a local shop to wire the lepai as I was not comfortable with soldering. The shop is a vintage audio and musical restoration and service shop so I’m confident all is well on that end. The 19V power supply from amazon came in with the larger jack, so we switched those out, and still have the oscillating noise. As mentioned in earlier posts, this becomes quite annoying when amplified. I tried the power supplies that parts express suggests with the Lepai to no avail. The audio shop tested the speaker’s with an analog power supply? And they are silent. I have read the posts and wonder if anyone can help me with this issue. Does a RCA ground loop work? But the main question is why are some people having this issue and not everyone. Is it possible that we did something wrong on our end? Thanks for the support and I hope to get these fired up soon.

Cheers

Bill R


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123Toid
(@123toid)
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26/03/2020 12:32 pm  

@bfr1957 That is a good question.  It sounds like you are having a ground loop issue.  Unfortunately, this is due to house wiring, so there is no way to know who will or will not experience it.  Typically you can get a ground loop isolator and it will take away the issue.  @cardinals1225 was having the same issue.  He provided some of the things he did here: https://toidsdiyaudio.com/community/official-dinas-build-log/dinas-amp-noise/#post-236 1"> https://toidsdiyaudio.com/community/official-dinas-build-log/dinas-amp-noise/#post-2361


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BFR1957
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26/03/2020 4:36 pm  

Yes it must be the house wiring. And probably pretty common  as  I have plugged them in at other residences with the same noise. Definitely sounds like “Power Noise” I have a recommendation for the Jensen Ci-2RR ISO max. Seems spendy, but I would assume the less expensive ones don’t do the job. Any thoughts on a brand? 

Cheers

Bill R

 


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123Toid
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27/03/2020 12:53 am  

@bfr1957

I might start with something cheaper jut to make sure that is the issue.  Although, a ground loop, as of now, has been the only noise related problem I have seen with these.  SO I do feel pretty confident this is the issue.  I haven't had to use a ground loop isolator, so I can't really recommend a particular one.  Maybe @tvor-Ceasar can.  

 


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TVOR-Ceasar
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27/03/2020 7:59 am  

Is it always there when you turn the amp on, or does it appear when you plug a source into the amp? This will tell us if it's a massive ground loop or something else.

I am going to assume that the wall cord is a 3 prong grounded cord. You can always try a 3 prong to 2 prong adapter, such as this, to remove the immediate earth ground, but at the cost of a small bit of safety. I say small because these power supplies usually have other safety features inside that isolate the mains power from the DC side. That will break one part of the ground loop, even though that should be done already inside the power supply.

At this point I'd need to see more of your setup, a description of the gear, how it's connected, and probably more questions to be answered along the way. 

You may need to make a few more posts before certain features become available to you, so don't worry if the forum fights you right now. It's a BOT protection thing.

-Charlie


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BFR1957
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27/03/2020 10:41 am  

Thank you for your assistance.

The noise, although very faint, is there when the amp is powered up. By faint I mean up must have your ear very close to the speaker, and have no ambient noise in the room. Certainly tolerable!. This happens at our home, the hostpital that my wife works in, and the shop where the amp was wired. Also using the 19V 4.7A or the 15V 4A power supply has no effect. I also tried the 2 prong adapter...still no effect.

The problem is when the system is connected. I have the same set up that Joentell used on his review. I’m coming out from a Mac computer via usb into the Modi 3, then the Loki, and the Vali 2. Out via RCA to each of the Lepai plate amps left channel. Lepai set to 2.1. When this is powered up the oscillating noise is amplified. Again thank for taking time to help

Bill


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TVOR-Ceasar
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27/03/2020 1:31 pm  

This is actually good and useful information. 👍 

From your description, I'd say the amp(s) is not the problem, rather the signal chain is the cause. There are multiple ways to zero in on the cause, but I'll relay my preference for such detective work.

Start with everything on. At the Mac, unplug the USB (it isn't on the front, is it? If so, move it to a port on the motherboard-on the back) and listen. If the noise is still there, shut down and unplug the Mac.

Move to the Modi and unplug the USB that went to the Mac, and if the noise is still present, shut down the Modi, listen, if noisy, unplug Modi from wall. If still noisy, unplug connecting cable to Loki.

Move to the Loki. If still noisy unplug cable from Modi, if noisy, shut down Loki, if still noisy, unplug Loki from wall. If still noisy, unplug cable from Vali.

Move to the Vali. Unplug the cable from the Loki, if noisy, shut down the Vali. If noisy, unplug from wall. If still noisy, unplug the RCA cables from the Vali.

At this point, all that should be connected to the amps is the RCA cables. If the noise is still there, it's those cables. I think you'll find the problem before you get that far.

If you find it gradually reducing as you go through the process, do the opposite direction, removing the Vali first, and so on then connecting up the next in line piece.

The reason for completely unplugging the hardware is to reduce any chance of other noise being introduced into the signal chain. If they are powered off and unplugged from the wall, that is completely removed from the equation.

Going over your setup, I think it may be that the Vali would most likely be the source of the problem. If it seems that way, try going from the Modi to the Vali to the Loki instead. You won't get the advantage of the Loki for headphones, but it'll work with the Lepai.

Happy sleuthing!

-Charlie


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BFR1957
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14/04/2020 8:34 pm  

I ended up using a ground loop isolator, with some success. Still that faint noise that I suspect is bad power, and the lepai plate amp. These are flipping amazing speakers that play and sound way above their size and cost. I wish I had the ability to design a crossover for these and get rid of the plate amp and the 12V variable power supply. I am  shocked at the low end that these produce. I have them in my office, which isn’t a large space 12X15, and they will chase my wife out of the room!!! genesis back in NY City off of the Lamb Lies Down on Broadway album will test most systems to their limits. Again these are beautiful speakers. Congratulations on your design, and I will keep a sharp eye out for more of your goodies!

Cheers

Bill

 


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TVOR-Ceasar
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14/04/2020 9:03 pm  

I see you have great taste in music. Lamb is a favorite in this house (extended - my oldest still assails the neighbors with lots of Genesis). As matter of fact, on my phone I have "From Genesis to Revelation" all the way up to "Calling All Stations". Plus lots of other Prog. 

If you disconnect everything from the plate amp, is the noise still there? If it is, would you be able to open it up and take a high quality photo of the section where the power supply comes in? I'd like to see if there's anything that can be done before you give up on it.

-Charlie


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Kingsanguine
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21/07/2020 12:41 am  

I have given up on my 60hz humming sound and I cant figure out whats causing it. It could be anything. Ive tried for several weeks now.

I have:

Audio Technica lp 140 turntable

ES07 baffle speakers

Schiit mani pre amp 

Schiit sys volume control

The ice power amp 

 

Atempts

I bought a ground loop isolator (ice cube xlr) (maybe this was the wrong ground loop isolator?) Still humming

I change out the ground wire size.

Still humming 

I plugged it in the same outlet and different outlets.

Still humming

Tried messing with the gain on the pre amp

Still hums

Bought a noise filter power strip

Still humming

The humming will only stop when I unplug the turntable.

For some reason I am not able to upload other pictures here. This is the only one I could get from my old photos posted of the mani and volume control.

15860383933563706587965153457691

 


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TVOR-Ceasar
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21/07/2020 10:44 am  

Well, you've traced it back to the turntable. "The humming will only stop when I unplug the turntable."

What did you unplug, the power cord or the RCAs or both? What happens if you unplug one but not the other?

Go to the jacks on the Mani that you used for the turntable and use a paperclip to touch the inside contact. Does it hum then? If it does but is very low, that "should be" okay enough. Your hand and the paper clip are acting like an antenna which will induce a slight hum in such a high gain stage. Now if you do that again but then touch the outer contact with your hand, any hum should diminish. Again, that is what should happen. 

If this plays out like I said, you'll have to investigate the turntable or the wires/cables from it. 

You should be able to open the turntable by either removing the top deck or a plate on the bottom. I don't know how AT makes them, so just be careful how you access the inside. 

Check to make sure the ground point in the back is actually connected to something, and while you're in there, touch a wire from the ground lug to the motor case (while the ground is connected to the preamp, of course 🙂 ) to see if that helps. 

At this point, you'd have to let me know what the results are in order to choose another path to ridding the noise.

 

**Typos fixed - damn phone does weird things to my typing. As I often say, "That's auto-incorrect for you!"

-Charlie


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Kingsanguine
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21/07/2020 1:53 pm  

The turntable plug has 3 prongs and when I unplug it. The humming sound stops. The turntable also has a ground going to the amp and the ice has a 3 prong plug. I think this is the issue causing the ground loop. Can I use a cheater plug on the turntable?

Can I use a cheater plug?


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TVOR-Ceasar
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21/07/2020 2:24 pm  

You can try something like them to see if it helps. They are certainly inexpensive enough that it doesn't hurt to have a few around. 

If that doesn't work, make sure you don't have your signal cables draped over / crossing the power cables (separation is the key). 

If that doesn't work, I'd say a bad ground on your turntable motor or bad wiring in the tonearm.

A short article that may help.

-Charlie


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123Toid
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21/07/2020 3:09 pm  

@kingsanguine

Something else I was jsut thinking about, that I don't remember us asking. Does your turntable have a switch to turn on and off a phono preamp?  One of my old ones had it under the turntable itself.  It could be possible you are sending a preamped signal to the preamp. The preamp on the turntable can also be calleb phono stage. 


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Kingsanguine
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21/07/2020 3:29 pm  

@123toid

No, the turntable just has 2 rca plugs and a ground.

Also hum amplifies when I touch the rca cables from the turntable to the pre amp.

Hum is still there even without the turntable plugged in but it is connected via rca and ground to amp.

I ended up plugging the cheater plug into the 3 prong turntable and into the power conditioner. The hum is almost completely gone. It still there when you crank up the volume but it's a lot more bearable to listen too now. I would say a 85% improvement. I hope the cheater plug in the power conditioner is okay to use?

 

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