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
Thanks, Jim (Jea48). Note, though, that the transformer coupled outputs shown on the schematic you linked to are the digital outputs, not the analog outputs which Lowrider is using.  Although that schematic is for the CD2, rather than the CD3 MkII he is using.

Regarding overload, the UV-1 doesn't appear to have an input overload point specified, but I'd be surprised if it couldn't handle 2.7 volts.  And even more so given that it provides a 6 dB input attenuator.  And in any event, if it were overloading I'm sure Lowrider, who is clearly a very perceptive listener, would have noticed the distortion that would have resulted.

Regarding Mr. Crump's statement, I would add that in the case of most power amplifiers, at least, one certainly does NOT want to attenuate everything above 60 Hz. As has been pointed out in past threads by Ralph/Atmasphere among several other members, since most power amplifiers draw current in narrow high amplitude spikes, rather than continuously throughout each period of the 60 Hz waveform, their AC supply needs to be provided in a manner that is not bandwidth limited below something on the order of tens of kHz. That requirement being one of the reasons upgraded power cords can often provide superior performance compared to stock power cords, for power amplifiers at least, because many of them provide significantly greater bandwidth than most stock power cords.

Also, I just Googled "inductance of Romex" and found a not necessarily authoritative post in a thread elsewhere stating that it is about 1.45 uH (micro-Henries) per foot.  That is indeed high, but for run lengths that are not particularly long I suppose is probably low enough to be compatible with the kinds of bandwidths Ralph refers to, perhaps depending on the particular amplifier.  While at the same time being high enough to provide significant attenuation of digital noise, which typically has a good deal of its frequency content in the MHz range and higher.  

Best regards,
-- Al
 
Thanks Jim. As with the CD2 only the digital outputs are transformer coupled. And I don’t see any issues with the unbalanced analog outputs Lowrider is using, or with using a Jensen transformer between those outputs and the preamp (assuming cable capacitance at the output of the transformer is kept low, which I believe he is doing).

Best regards,
-- Al

Al and jea48,
I really appreciate the time you've devoted to my situation.
I was out all day, but was able to take some measurements:

- continuity of RCA outer sleeve to metal chassis... reads OL
- continuity of each RCA center pin and pin 2 of XLR... OL
- continuity of RCA outer sleeve and pin 1 of XLR... 000.0

Al, I looked at the 20a dedicated AC line and it appears to be a 12/2 generic cable. I looked at the electrician's invoice from years ago and it is itemized as a Refrigerator line, dedicated 20a circuit.
If you recall, I had a thread where I asked for advise on the proper installation of a dedicated line. That's when I discovered that the electrician placed this wiring near the top of the circuit box and close to the furnace and appliances. So, when I add another line, I will need to have the box reconfigured.

And jea, thanks for the pic of the Cardas jumpers. I found them online and will order them.

- continuity of RCA outer sleeve to metal chassis... reads OL
- continuity of each RCA center pin and pin 2 of XLR... OL
- continuity of RCA outer sleeve and pin 1 of XLR... 000.0

- You said in an earlier post you checked for continuity from the ground pin of the power cord male plug to the metal chassis of the amp and the meter display read "OL"..., Open, no connection. Correct?

IF the RCA jack outer sleeve to the metal chassis reads OL then the signal ground is not connected to the chassis. You said in an earlier post the safety equipment grounding conductor of the power cord is not connected to the chassis either.

I will have to search the archives of AA for a post of Charles Hansen, owner of Ayre Acoustics, but that’s a no no. Something about capacitive feedback loops. Or something like that. At any rate I think it can add hum/buzz on the signal of the amp. (Without rereading all this thread, did you ever have the amp turned on without anything connected to the inputs of the amp? That thing should hum/buzz like crazy I would think. Especially if a ground cheater was used on the amp plug to wall receptacle.)

I am still confused why you measured 1 ohm of resistance, basically continuity, from the ground pin on the plug of the power cord to the outer sleeve of the RCA on the amp. That means the signal ground of the amp is connected to the equipment grounding conductor, wire, of the AC power cord.

You really need to address the problem/s with the amp first before you do anything else. You need to pull the top cover and see why the safety equipment ground of the power cord is not solidly connected to the metal chassis of the amp. Why it, the safety equipment ground wire, is some how connected to the signal ground. Both the signal ground and safety equipment should be connected to the metal chassis of the amp.

(Note: I see no user ground lift switch on the back rear panel of the amp for user preference.)