CAL Alpha DAC - Cool Tubes?

This is a two part question. First, I recently purchased a CAL Alpha DAC with the 24/96 upgrade. I have found that I prefer the sound of a tube DAC and I am enjoying it very much. However, I've noticed that it is completely enclosed with no holes for ventilation and cooling. This is obviously by design, but I wonder if this is good for the tubes and internal components in general. I know that there are quite a few current and former owners out there and would welcome your comments. Second, I would appreciate any recommendations on tubes, tweaks, and such. I am currently running Mullards.


Do a search[Audio asylum and here] on the Alpha.I remember a lot of people thought they sounded better with top off.I have a Sigma II 24/96 and have always had top off.Easy for tube rolling too.
I left an Alpha running night and day for several years, with the cover on, and had no problems. The tubes might have deteriorated somewhat, but if they did I couldn't hear it.
Some owners believe the Alpha sounds better with the cover off. One unit listed on AudioGon in the past even had louvers stamped into it! The cover stays on mine so as to protect the internal components from dust. As for NOS tubes, Mullards (best bang for the buck) and Amperex Bugle Boys (best all around) have been my favorites thus far, especially the latter. '60's vintage Sylvanias were OK, too. If cost is a concern the Sovtek 12AX7LPS is a surprisingly good tube, especially given the cost. Very good extension on the top, but without the sterile sound of the rest of the Sovtek family. BTW, my Alpha does not have the 24/96 upgrade.
i keep the top on - have newver had a problem with tube life. here's a thought on tubes on the cheap - try some yugo el12ax7s. they are cheap and have a very transparent high end. very clean. i prefer them. i don't have the converted model (24/96). my unit has a standby switch. did they change this with the 24/96 upgrade?
Thanks everybody for the replys. It does seem strange to me to have tube equipment that is totally enclosed. I've thought about drilling some holes in the cover over the tubes, but would be a afraid of making the cover look like hell! I wonder if the eclosure is some kind of performance design?

Has anybody had any experience with tube dampers, isolation components, etc? I'm breaking in a LAT digital cable and associated equipment is a McIntosh MCD7008 changer, McIntosh MA6450 integrated amp and KEF 104/2 reference speakers.

Newbee- My upgraded 24/96 unit still has the standby switch.

You did ask originally ask about tweaks, didn't you? My Alpha sits on BDR cones and Those Things which cleans the sound up a bit. The top end gets a little fuzzy when they're removed. The original PC was replaced with a Synergistic Master Coupler. This added more "meat" to the sound; I believe the appropriate audiophile phrase is "it sounds more palpable". The Alpha is connected to a Delta transport with an Illuminati D-60 digital cable. Of the various digital cables tried it suited the system best. I've also tried mass loading, inner tubes, various wooden shelves, etc., but none of these seemed to add anything desireable.