Isolating Digital Noise, need help.
lowrider57 said: Al, What are the chances the ARC CDP is still over driving the L & R input stage of the preamp? Also look at the ARC CDP output section. Transformers are used. Does that mate well with the input section of the preamp? |
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 |
Al, I guess I must have been having one of my brain fart moments. Try this ARC CD3 MK2 schematic wiring diagram.
Jim |
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. |
