What's wrong with my Cal Delta/Sigma?

How long has it been powered up and what were you using as a source before? Might want to check the tubes in the DAC as well. Most of the tubes that I receive in the mail sound like crap for a couple of days (both signal and output) as they seem to be full of static electricity. The same goes for most anything else that has been shipped.

I was using a marantz 63se. The tubes should be operational and well burned in because I purchased this trans/dac from a private seller who's been using it for years, and they sounded fine when I demoed them on his system.

Replace the 12AX7 output tube with the low noise version from Cal Labs (~$40). Also, ditch the optical digital interconnect and get a high quality (preferably silver) unshielded .5M digital coaxial interconnect. Set the units aside of one another and not stacked. Do not use vibrapods. Make sure that you NEVER turn off the DAC other than to move / change connections / service the tube, etc.

Had this Combo for 8 years and have experimented much. This is what worked for connection to ARC LS-25 / VT-100.

Another good upgrade is to change the 3 connectors to the upgrade versions from CAL ($60). Don't attempt this on your own unless you are confident in soldering skills, electronic technician abilities, and are very careful. The unit must be totally disassembled, connectors desoldered from PC Board, new connectors mounted in the Bulkhead, and wires run from the new connection to the PC Card. Just another tip...