Crackling sound when using a DAC

I also have a Museatex DAC and have the same experience, albiet mine happens more occasionally. I asked John Wright about the noise and he explained that the initial click you hear when the "CLock" indicator illuminates is caused by the DAC recognizing the signal and opening the output relay. In turn, the "crackle" that you sometimes hear from the speaker is the result of a tiny residual DC voltage that can be present until the servo catches up and nulls it out. This is normal and rather low in level, so it shouldn't pose a threat to your tweeters. However, if you're worried about it then just turn down the volume or hit the mute button when cueing up a disc.

pbawcutt,

Do you mean that the crackle doesn't happen when the DAC's optical digital input is used ("I have avoided this problem by switching the Museatex to optic settings, then switching back to Wire")? This sounds odd, because the phenomenon that I described is totally independent of what digital input is used. Like I said, a small crackle sound is normal, but in my experience it isn't as bad as what you're describing. Perhaps your amp's input sensitivity and/or your speakers' sensitivity is higher than mine, which is exacerbating the issue. However, I doubt this is the case given that there are many Museatex DACs in the field, and I've never heard of a "normal" unit behaving like this. I'd suggest three things:

1. Try using the DAC with a friend's CD player/transport, and see if the same problem occurs. This would at least rule out that it's related to the NAD's coax output.

2. It may turn out that your unit has a problem, like a bad servo circuit that's failing to null the DC properly. It's therefore a good idea to send John Wright an email. You'll find his contact info at www.museatex.com, and I've found him to be great to work with.

3. A properly functioning unit is going to exhibit the occasional mild crackle when the CLock engages. It's simply the nature of the beast. In the end, if it turns out there's nothing "broken" with the DAC but you just can't live with this issue, and turning down the volume when you change the disc is not a satisfactory solution, then perhaps this relationship wasn't meant to be.

Best of luck.

Hmmm. So to summarize, these are the two scenarios:

A)
-The DAC is configured to use the coaxial digital input
-You then put in a CD
-The CD player reads the TOC and outputs a signal
-The DAC recognizes the signal; CLock engages
-You get a sharp "crackle" from your speaker

B)
-The DAC is configured to use the optical digital input
-You then put in a CD
-The CD player reads the TOC and outputs a signal (the DAC doesn't receive the signal because it's not hooked up via the Toslink connection)
-You switch the DAC to the coaxial input
-The DAC recognizes the signal; CLock engages
-You get no "crackle"

It sounds strange because I would think that since the ouput relay and servo are engaged when the DAC receives the signal, then if they are the cause of the problem (i.e. they are faulty) it shouldn't make a difference whether you use method "A" or "B". One possibility is that there is a brief initial "burst" discharge from the NAD's digital output when it sends a signal, which goes away after it has a second or two to settle. Perhaps this is upsetting the DAC's receiver, and by switching the DAC's input off and then on a bit later, you are effectively giving the transport's digital output enough time to settle before engaging the DAC. Have you tried using the DAC with another transport? Have you used different DACs with the NAD? Again, I would encourage you to email John Wright for his thoughts.