What's wrong with my Cal Delta/Sigma?

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...

Yohjixme: I am just fishing here, but the digital IC does effect the sound quite a bit (regardless of what the bits is bits crowd has to say about it). It could be the cable, but I kind of doubt it would make the sound awful, as you describe unless there is something wrong with it. I have tried some pretty cheap ones myself and though they did not sound great at all, they were still OK. My DAC (a Bel Canto) needs to be powered up a minimum of three days (a week is better) for the detail to shine through, otherwise it is a little muffled, but I am talking very little here and as the cheap cable went, it still sounds not great but OK. What you may want to try is to clean all of the RCA connectors (both male and female) and then reinstall the cabling (both the digital and analog IC's). It is advisable to power down when doing this, but it should just take a few minutes. If you do not have a special cleaner for this an inexpensive one is electricians grade Isopropyl alcohol (available at electronics stores and probably even Radio Shack), which should be above 99.95% pure and have no additives. I use a cotton T-shirt over a pointed wooden skewer to clean the insides of the male RCA's, but most anything small enough will work fine (I just don't use knife blades for fear of scratching the metal). Following this leave it powered up for a week and see what happens. This won't cost you much ($3 or so) and is good maintenance anyway. Dirty contacts can severely degrade the sound from my experience and even if this does not work at least you will have eliminated this possible cause of the poor sound. Also why you are at it you might as well clean the power cord and IEC contacts.

jk, sounds like you spent a very worthwhile $100 upgrading your sigma? I will definitely look into that. I got most of my muddiness out of my system, but it still sounds kind of sharp, like a "tinny" sound. And there is more hiss coming out of my speakers than compared to when I am using other sources. Perhaps your suggestions can amerliorate these symptoms. Thanks

Dekay, funny you should mention about poor contacts between interconnects. I took out all my cables and reinstalled them like an hour before I checked your post. And I would say 90% of the muddiness has magically dissapeared. I just got two pairs of emeralds, used, from ebay, and perhaps these cables were suffereing from static electricity, as jk mentioned regarding his tubes and other equipment that suffered from being transported. I haven't used any cleaning solutions, which reminds me of those XLO cleaning cloths they used to sell. But, by reconnecting my cables, I probably shaken off whatever debris that was causing my system to not funtion properly.
Thanks for your help.

Have you guys used any after market power cords? I am thinking about getting some PS audio mini lab cords for the dac and pre, since I heard the transport won't be affected by power cord upgrade.