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Isolating Digital Noise, need help.

I'm hearing noise from my ARC CDP thru my speakers presenting as a high frequency "whine" or "soft screeching." I need to isolate my digital from the AC line it shares with my analogue components. Running another dedicated line is not an option at this time.

I was wondering if a power strip with isolated receptacles, such as star-grounding, would be an alternative to a separate AC line.
As a test, I now have the CDP connected to a different outlet in my house and the noise thru my system is eliminated.

Would this type of power strip be an effective solution, and if so, I could use some recommendations. I have several layers of Blue Circle power conditioning, so I would need a strip with surge/EMF/RFI protection.
128x128lowrider57
jea48
4,281 posts
 

And I just thought of something. I bought my amp used from a HiFi dealer; it was his personal amp. Could he have lifted the ground for use in his system?

Another reason to pull the top cover off the amp for a look inside.

**NOTE: Naturally unplug the amp from the AC power. It would also be a good idea not to stick your fingers inside the amp for at least a half hour or so for the electrolytic caps in the DC power supply to bleed off, discharge. One hour if you really want to be safe.

Look at where the power cord enters the amp’s rear panel. Look for the green insulated equipment grounding conductor, wire, from the power cord. It should directly connect to the metal chassis of the amp. From your test measurements it does not. What I don’t understand though is, why, where, or how, it is still connected to the B- rail/signal ground of the amp. (Going by your test measurements.)

almarg's avatar
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almarg
9,670 posts
 
Good comments by Jim (Jea48).
As far as the readings I'm getting, do I need a better multi-meter?
Nothing that has been said so far suggests that to me.  See my comments from yesterday about how to try the jumpers if XLR pins 2 and 3 both measure open with respect to the RCA center pin, which now appears to be the case.

Best regards,
-- Al
 
lowrider57's avatar
lowrider57 OP
5,393 posts
 
Many thanks to both of you.
I've been ill for a while and going thru some treatment, so when I feel better I'll open up the amp. That's why I was looking for a quick fix with a power strip. Until then, I'll run my components off a 2nd outlet which eliminated the digital noise.

With your assistance, I now believe the amp may be the root cause of all the issues I'm having with my system. I'll update you once I'm able to pull the amp out for inspection.

Thanks again, Al and jea48. And btw, I ordered the Cardas shorting pins.
lowrider57's avatar
lowrider57 OP
5,393 posts
 
UPDATE...
I spoke to the owner/tech of the only authorized Sunfire service center regarding the grounding design of their amps. He said in a Sunfire amplifier that the chassis, power and signal ground are connected together.
  We discussed my ground-loop situation with the preamp and he said he would try to contact Bob Carver to find out the reason for this design and if it can be modified.

In the meantime, I found this on Pass Labs website...
In order to minimize ground loop issues Pass Labs never manufactures equipment with signal ground and chassis ground contiguous.
  By separating signal ground and safety grounds, connecting units together should never cause ground loop issues; however, not all manufacturers follow this line of thinking.

Regarding the noise produced by the CDP thru the power line, I purchased a Tripp Lite isolated power strip since it is intended for computers and digital devices.
http://www.amazon.com/gp/product/B0000513O4/ref=ask_ql_qh_dp_hza

My findings...
- Furman and Tripp Lite both plugged into Blue Circle conditioner.
- Atma-Sphere preamp w/ Audience PC plugged into Furman,
  CDP w/ Audience PC plugged into Tripp Lite.
The result was high-pitched noise was still present thru the system.

Next, I swapped preamp into Tripp Lite; CDP into Furman...
The result was high-pitched noise eliminated. Preamp is no longer using a cheater-plug, but there is low-level hum due to the amp.
I've been playing CDs for 3 days and there has been no noise from the CDP.
I don't understand why the digital noise is eliminated with the preamp in the Tripp Lite, but it works and CDP sounds smooth w/o the Jensen transformer.
jea48
4,281 posts
 


UPDATE...
I spoke to the owner/tech of the only authorized Sunfire service center regarding the grounding design of their amps. He said in a Sunfire amplifier that the chassis, power and signal ground are connected together.

But yours is not. Through your testing you found the chassis is not connected to either the safety equipment ground wire of the power cord or the power supply signal ground. What did the tech say when you told him that?

How about the shorting/connecting jumpers for the XLR connectors? Did you ask him if the amp needs them installed when using the amp with single ended RCA ICs?

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