Well, no good deed goes unpunished......
I took your advise and went to bond the di/o case to a hard ground and in doing so had to move the outboard power supply. When i did that all of a sudden the power supply output dropped to zero. Ouch.
Opened the power supply case and found that it contained only a toroidal transformer and a black cylindrical unmarked component that was (past tense) wired in series with the transformer output. This cylinder had at one point been hot glue down to prevent it from moving, but had come loose in shipping and the lead at one end had snapped of right even with the end of the cylinder. (it would have been too easy to break further up the pigtail so tat I had enough room to make a solder repair). The next morning I call the service folks at Boulder to ask what the cylinder was and how i could get a replacement. They informed me that since they did so many different mods they had no idea what it was, but if I sent it out to them they would give it a look. They thought it might be a Bybee Quantum filter, but could not be sure.
Not wanting to part with the unit for weeks, I started to do some reseach on my own. I looked at the Bybee web page and the cylinder did in fact look like one of the large Quantum filters.After looking up the physical and electrical specs on the Large QF, I did some measurements on the broken cylinder and determined to my satisfaction that it was in fact a Bybee. This was a good thing because other than filtering out noise the Bybee did not have an effect on the output voltags and current of the power supply and I could bypass it and temporarily wire the transformer output directly to the di/o power input so at least the DAC would be and running plug while I went out and got a new Bybee (which may take a while since like I said in another thread, with all of the changes that i made to my system over the past year, my toy money is kind of tapped out at the moment.)
Anyway, by the time I got everything rewired and back in the system it was too late to do any serious listening (and still be able to get out of bed for work in the morning
) So I just did a quick check to make sure everything was functioning as it should (it was
)and I will have to further evaluate both the sound without the Bybee and whether the ground bonding eliminated to di/o lockup problem.
I'll let you know what I find.